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General CNC Chat => Show"N"Tell ( Your Machines) => Topic started by: RICH on August 30, 2009, 09:45:01 PM

Title: CNC CONVERSION - 6" ATLAS LATHE
Post by: RICH on August 30, 2009, 09:45:01 PM
The following  posts in this thread will show how I am converting my 6” Atlas lathe for CNC use. I rebuilt this lathe a number of years ago and it is mint condition. One of the conversion criteria was to ability to return the lathe back to manual. I have a Sherline CNC lathe that is quite nice for making small parts, but, the need for something more robust and  yet small was desired.

There are a few things one needs to consider before doing a conversion. What kind of screws will be used and how will they be mounted.  Motor selection and associated mounting. 
I will making a lot of posts as i go along with the conversion. Hopefully there will be a little something for everyone.

RICH
Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: RICH on August 30, 2009, 09:47:07 PM
The following are just some preliminary considerations for the conversion.

MOTOR
Currently a ½ HP / 1725 motor is mounted for use. An option would be to use an existing VFD with a 1 HP DC motor. I will first try the AC motor since backgears can be easily engaged for threading and heavier work. It’s very desirable to have a constant spindle speed for threading. This was one of my dislikes with the Sherline lathe. Regular turning on the Sherline was not a problem, but the lack of HP at the spindle during threading left something to be desired. I will probably be making comparisons to the Sherline from time to time. You can calculate the HP requirements but the calc’s can be  somewhat subjective, and if the motor is marginal, you really don’t know how it will behave under load and the resulting small rpm changes. Here’s a look at some of the Atlas lathe speeds.

ATLAS LATHE SPEEDS
M pulley  S pulley  SPINDLE    BACK GEAR  APPROX
                                RPM            RPM                  RATIO
1                 4           410                55                      7.45 
2                 3           870                120                    7.25
3                 2           1435              195                    7.35
4                 1           2350              320                    7.35

When the backgears are in use there is a considerable increase on torque delivered to the spindle.
½ HP x 7.35 = 3.7 HP ( approx ) which is a significant HP increase ( > 12X ) as compared to the Sherline.
RICH
Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: RICH on August 30, 2009, 09:48:24 PM
BALL SCREWS

I already had ball screws. Both the ball screws are easily adjustable for backlash. The intent is to minimize the backlash ( you never have zero but you can try ). You can do all kinds of calculations for the ball screws, but practically speaking, experience on sizing and mounting  from past experience is all that is needed for this conversion.

The Z axis will use a 16mm diameter x 5MM ball screw. The X axis will use a 12mm diameter x 4mmm screw. You are somewhat limited on a conversion as to what will fit and yet the basic mechanical integrity for supporting them is very important.

One important criteria will be resolution ( just how small of an axis move can be made).
Steppers will be used since the existing controller is for steppers, is portable, and is used for other CNC machines. Here are a steps per unit calcs and a look at resolution:

Z Axis
5mm x 0.0394 mm/inch = .197” / revolution   ( 1/0.197 = 5.0761 PITCH )  along with a 2:1 pulley reduction
STEPPER   x  MICRO STEPS x SCREW PITCH x PULLEY REDUCTION = STEPS / UNIT
200 Steps / rev  X 10  X  5.0761 = 20304 STEPS / UNIT

RESOLUTION:  1/ 20304 = .00005”

Note that the mounting plate will be such that the pulley ratio can be changed as I may want
to increase the Z axis velocity later after testing.

X axis
4mm x 0.0394 mm/inch = .1576” / revolution   ( 1/0.1576 = 6.3452 PITCH )
STEPPER   x  MICRO STEPS x SCREW PITCH x PULLEY REDUCTION = STEPS / UNIT
200 Steps / rev  X 10  X  6.3452 = 12690 STEPS / UNIT

RESOLUTION:  1/ 12690 = .00007”

There are tradeoffs to made. I choose to do a 2:1 pulley reduction on the Z because I wanted more torque delivered while cutting threads. The X resolution is fine but doing a reduction makes the mounting somewhat more complex. Another consideration will be how much holding torque will be available. The Sherline never skipped when using 300 oz-in steppers and the steppers were direct mounted. I'll need to take a look at the speeds I will be running when doing heavier work along with threading considerations. 
RICH
Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: RICH on August 30, 2009, 09:49:42 PM
AXIS VELOCITY

 A preliminary desirable velocity for rapids is 60 IPM. The Sherline normally ran at 40 . I won’t know just what kind of rapid movement I will get until the conversion is done since a lot of things come into play such as the stiffness of the axis system,etc. Calculations can be done to see the affects of velocity and axis loading as they relate to stepper motor sizing. The following data will be used later on when I look at stepper motor information.

60 IPM= 1 INCH / SEC
1 IN/ SEC x  20304  STEPS / SEC = 20304 STEPS / SEC = PULSES PER SEC ( PPS )
IPM    PPS
60       20304
30       10152
20        6768
15        5076
10        3384
5          1692
2.75        930

Figure #1  is a comparison of spindle speeds to axis velocity and motor PPS when doing a ¼ - 20 - UNC thread. Note that the motor will need to turn twice as fast as the ball screw ( 2:1 pulley reduction ) so the PPS is double of what was given in the other table.
RPM     IPM     PPS
600       30         20304
400       20         13536
300       15         10152
200       10          6768
100         5          3384
55        2.75        1860
Attached is a graph of  the above. Note that as the RPM goes up the axis feed rate increases along with
 the required acceleration during threading.
RICH
Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: RICH on August 30, 2009, 09:51:57 PM
Figure #2 shows the decreasing stepper torque as speed / PPS is increased. Added to the motor curve is the RPM and IPM when threading for a ¼ - 20 thread. The graph is for the Z axis. Won’t know how much torque will actually be required until after installing and adjustment of the ballscrews are done. At least it’s obvious that with the back gears engaged, there will be enough motor torque to do the threading. Note that in using the SmoothStepper , velocity increases of 2X and greater were achieved on my other machines so speed is  will be increased relative to the torque. Also not that the motor curve is for a lower voltage than what will actually be supplied to the motor. Even though you have a motor curve, if the curve is not truly representative of your actual drive, current and voltage and wiring configuration, you can only use it as a guide for  anticipated performance. Knowledge from past experience really helps!

RICH
Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: RICH on August 30, 2009, 09:53:13 PM
 Just thought it would be helpful to provide some of the considerations from a technical point of   view relative to the conversion. 

Why steppers instead of servos? Well it was a rather easy decision as the controller I built has drives for steppers and is used for other machines. Here is a picture of the movable cart I use.

RICH
Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: RICH on August 30, 2009, 10:27:25 PM
Z AXIS BALL SCREW INSTALLATION

The first thing was to see if the ball screw would fit. I had a saddle from an old lathe that can be modified and thus no need for changes to the original. All the bosses were removed and some rough outside machining was done just to mount the nut and square things up. The carriage will have a housing on the front of it with two small hand wheels. The hand wheels will turn encoders for the Z and X axis. Things looked very close but looks like it will fit.  The screw was held in place parallel to the bed and Z axis and temporarily attached to the carriage. One hole was drill for the ball screw nut and alignment checked, and then the other hole was drilled.  In the figure #4 the ball was just rough aligned by using parallels at two ends to check the mounting holes. A little clearance is provided in the holes for later refinement when testing.
RICH
Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: RICH on August 30, 2009, 10:30:25 PM
I'll continue to post more as time goes on. Feel free to ask questions or comment.
RICH
Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: RICH on August 31, 2009, 07:11:11 AM
The attached pictures show the trust bering assembly being mounted.
Rich
Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: RICH on August 31, 2009, 07:13:18 AM
THRUST BEARING
Two back to back bearings are used top take axial thrust. The bearings sit inside the housing. The end of the screw will be tapped for a bolt. The bolt when tightened will push against the retainer and thus provide for a preload of the bearing thus eliminating any movement of the ball screw along the Z. An additional bearing will be placed at the tail end. No machining of this end of the screw is required. It was a real bitch to machine the screws for my mill as the hardening went way down below the bottom of the screw lands. No fun, and heating / annealing the screw was not a choice and grinding it wasn’t an option. Figure #11 shows the mounted bearing assembly.
Note that the retainer will have a number of set screws which will tighten against balls and not directly against the screw. You can get away with this for smaller loadings.
RICH
Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: budman68 on August 31, 2009, 10:36:25 AM
Great looking project, Rich, should be fun to watch -  :)

Dave
Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: RICH on September 02, 2009, 10:12:27 PM
Well the conversion continues.

     SADDLE WORK
 
            New bottom guide plates will need to be made due to the nut location. The contact surfaces and the spare saddle that touched the bed required re-machining to remove wear. The surfaces were made parallel and shiming would be the same for both sides. You really take your time on the machining along with stoning, grinding, or scraping of the surfaces will be required. You can’t screw this up or the x axis will no longer be run perpendicular to the z axis. The finished saddle resurfacing is shown in figure 12 along with the bottom guide plates which are made from tool steel.

Figure 13 shows the  new holes being drilled into the carriage for the guide plates. There is were a knee mill really comes in handy as I have al lot of room on my small mill. That tap extension ( you know the stuff you buy but never use ) just did the trick.
Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: RICH on September 02, 2009, 10:13:40 PM
       CHECKING THE SADDLE TO BED FIT

With the screw adjusted to the bed as before, the tail end will be worked on next.
Note the small clearance of the nut along the bed axis ( I said it was tight! ) in figure14.


The fit of the carriage is again checked and all is well, parallel, perpendicular, and size shims can be used an even shim can be used. The back of bed was cleaned up and the surface checked for square before making a back mounting block. Fortunately no machining or scraping was required.
See figure 15.
Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: RICH on September 02, 2009, 10:15:04 PM
Dimensions are taken and a drawing is made so the mounting of the ball screw bearing and stepper motor can be figured out. This is shown in figure 16.
RICH
Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: RICH on September 02, 2009, 10:16:29 PM
TAIL END BEARING INSTALLATION
A bearing will be provided for on the tail end of the Z axis. The bearing is mounted inside the mounting block and then the motor mounting plate is attached to it. Figure 17 just shows some rough work done on the plates before drilling and machining. All the plates are precision 6061 AL stock. Figure 18 shows the bearing just lightly tapped into the mounting block. A boring head was used to bore the hole into the mounting block.

Figure 19 shows the tail assembly mounted to the lathe. The block was temporarily attached to the lathe bed similar as was done at the spindle end. The saddle is mounted, shimmed and the ball screw turned by hand to set the location of the tail and spindle bearings. There should be no binding of the carriage over the full travel along the bed. That done, the tail and spindle bearing holders received alignment pins.
RICH
Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: RICH on September 02, 2009, 10:17:58 PM
         X AXIS BALL SCREW INSTALLATION
The x axis will receive a different ball screw as the carriage is rather limited in what it can provide for as shown in Figure 20. The carriage requires machining to open up the cavity such that the ball nut can travel inside the carriage. Sometimes post machining of a casting you remove internal stresses and the thing warps some. Hopefully this will not happen as the other surfaces of the carriage were already fine tuned for fit to the bed. Carbide end mills take care of cuttin thru the sand, stone and other crap in the casting.

Figure 21 show the carriage cavity ready to be machined. Set up is very important as there is not that much surplus material. You want the screw to travel parallel to the dovetailed ways in the carriage. You take you time. By the way before this is done details were drawn to see just what would be removed and how the trust and axial bearings would be mounted.

Figure 22 shows the completed machining with the ball screw laying in the cavity.
RICH
Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: RICH on September 03, 2009, 07:48:09 AM
CARRIAGE TOP SLIDE
In order to mount the ball nut to the slide a new one will be made. It’s more robust than the original slide and will also allow for customizing it for tool holders and mounting of other stuff onto the carriage. A chunk of fine grained cast iron will be machined to create it. Figure 23 shows the dovetails being cut and the holes being added. Take your time on the dovetails as you don’t get a second chance if you screw it up! Carbide cutters are the way to go as HS or even cobalt will dull very rapidly.

Figure 24 shows the qib being machined. The gib is made from precision ground steel ( will still need to regrind one side of it ). The jig makes easy for what would be an otherwise PITA job. The jig is something I made some time ago and is actually meant for the surface grinder. The gib needs to beveled on both sides  and also flats put one side at  an angle for the set screws. See figure 24.

Figure 25 shows the semi finished slide with gib installed. A bearing support will be added onto the carriage for the ball screw bearing that you can see in the picture. Note that the slide is machined flat and square on all sides. Figure 26 shows the back side of the slide and you can see the ball nut laying in the carriage. A split attachment will screw onto the nut and also attach to the underside of the slide. That piece will be held via countersunk screws from the top of the slide as adjustment will be required when aligning the ball screw. Yep, you need to lay it all out!

RICH
Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: Overloaded on September 03, 2009, 08:03:18 AM
Looking good RICH !
Sure to be a nice addition to your collection.
How are you planning to cover/shield the Z screw ?
Russ
Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: RICH on September 03, 2009, 08:31:28 AM
Russ,
I am not sure, yet. Will add wipers to the ball screw but that dosn't cut it. Maybe bellows or hard covers  or a combination of both. Design yet to be done! At this point still have plenty of time to think of it.  ;)
Collection, ha....ha.... i need to get rid of stuff, as the shop is full.  ;D
 What did you do?
RICH
Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: Overloaded on September 03, 2009, 08:56:31 AM
Bring some of it to York, quality stuff goes for top dollar.
I'll come down and help you load up. :)
I put the Z screw behind the bed and covered its entire length with a sheet metal channel.
It was about a 20" lathe but I only CNC'd about 6" of the Z so the traveling guard never extends beyond the footprint of the machine.
Crude but CLEAN !
NO airguns allowed so it is impervious to debris.
Russ  8)

Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: RICH on September 04, 2009, 08:32:09 AM
Russ,
 A friend may have "Telescoping Spring Steel Covers" which will work great with the lathe.
I found them in McMaster -Carr and they are pricy , but, mine will be free.
I will post here when the time comes and also may try to make my own that are rmovable for kicks.
RICH
Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: RICH on September 06, 2009, 12:38:58 PM
X AXIS BEARINGS AND BALL SCREW NUT

Two bearings will be provided for the X axis taking axial thrust loads and eliminating play.
Figure 27 shows one side mounted after a drawing layout was made. The ball screw and nut was centered and made parallel to the cross slide as shown in figure 28. Dimensions are taken and used to design the ball screw holding nut. The internal threads were done manually on the lathe as a tight fitting metric thread was deisired. The ball body nut is actually used to check the thread and also used to form the thread.  Figure 29 and 30 show the fitting of the ball screw nut. Three set screws will keep the holding nut from turning. Figure 31 and 32 shows the finished holding nut relative to the carriage and it’s slide. Figure 33 is just a tapping holder which I made and use for small taps. The tap is held in the holder, internal bearings provide for nice finger “feel” of the tapping and allow the holder to be held by the chuck. Works like a charm and worth making as I have never broke a small tap yet ( even 0-80 or more ). Next steps will be to make up the other bearing block and mounting of the stepper motor to the carriage.
Oh well, more layout to be done.

RICH
Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: RICH on September 09, 2009, 04:45:44 PM
A little redesign of what was in the last post for the bearing. Just didn't like the bearing or assembly.
RICH
Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: RICH on September 12, 2009, 11:33:55 AM
JUST AN UPDATE ON THE CONVERSION
The ball screw was turned down on both sides. I used a chuck which uses 5C collets to hold the ball screw. Only went through 2 triple sided carbide inserts to machine down the screw. The screw hardening was at some 0.070” deep ( just a real PITA! ) on one side.

The motor mounting bracket was mounted to the carriage to confirm fit. The linear travel was tested to see if there was any binding post adjustment of the cross slide gibb and bearing preload. This was done by feel and manual turning the screw. The motor and ball screw were also aligned. I have dimensions on how to position everything thus very easy to do.

I figured I would do a preliminary check of the torque required to just move the axis. Only 11 oz-in is required. Figure #35 shows the torque gauge used for the check. It is very accurate gauge and comes in handy. Just one of those things that you get a bargain on over the years ( they are rather expensive! ).

Some trimming of the motor bracket was done along with providing access holes for the carriage gibb screws. I am waiting for bearings ordered.  A single bearing will be added on the motor side. So you don’t see one in Figure #36. Additionally the coupling will be replaced with a solid one since axial loading will
be very minor, if any at all, back into motor. The adjustable carriage and motor mount along with the screw bearing arrangement provide for precise coupling alignment.
 
I just had to know what the backlash would be. Steps per unit were calculated and slightly adjusted based on testing. Calculated was12690 and was adjusted to 12700. The adjusted steps per unit provided repeatable actual movements, both full and incrementally, when going in one direction over the full length of screw travel. Same for the opposite direction. The screw is a precision preloaded ground screw.
That done, backlash was checked ………..life will be good ……..only 0.0003”. So it seems that the x axis positioning can be used without any backlash compensation. I use a SmoothStepper and it doesn’t provide for backlash compensation in Mach. Backlash is a PITA when trying to cut threads  it doesn’t take much to screw up a small fine thread.  All starting to look promising, but,…….never know until you actually use the
lathe.

RICH
Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: RICH on September 14, 2009, 02:33:54 PM
Time to get back to working on the Z axis. Here are some picks.
Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: RICH on September 14, 2009, 02:36:56 PM
A long way to go but the hard stuff is somewhat out of the way.
It's starting to look like a CNC's lathe.
The next psoting will have some interesting info you may want to review for undestanding.

RICH
Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: Dan13 on September 14, 2009, 03:10:42 PM
Hi Rich,

A nice looking machine is starting to show up there :)

Thanks for all the updates and photos throughout the process - almost like a DIY manual ;)

Looks like the mechanical part is almost done... we'll see it coming alive soon :)

Daniel
Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: RICH on September 14, 2009, 04:30:31 PM
Z AXIS ADJUSTMENTS – BACKLASH  REMOVAL –BEARING PRELOAD

The Z axis components were adjusted by feel. The axis was turned using a makeshift handle attached to the screw. Now  we get into testing for refining of  the axis components. This may get a little long, but a lot of how to and description is included which may be of value to someone.

The Z axis calculated steps per unit and a basic velocity of 40 was used as rough motor tuning units in Mach. I just needed something so I could jog around using the controller. What I wanted to see is if the carriage is trying to lift or bind in any way. The Z axis ballscrew is not a precision ground screw such that the overall straightness meets a tolerance, but, that tolerance is not like a ground screw. The screw is anchored at the spindle end and the bearing at the tail end allows axial float ( just used for radial loading ) Slowly moving the carriage a slight adjustment of the ballscrew nut to saddle had to made. This was repeated until no movement ( of the carriage off the ways was happening – initially it was around .002” ).

Then the velocity was increased until it skipped at 120 IPM. The velocity was reduced and set at 80 IPM and no skipping happened. ( Just for info the X will do 200 IPM and is set at 100 and it only took 11 oz in to just move the axis ( 31 in oz with a new / different stepper installed ). The difference is the internal pole attract / detent. So we have an initial velocity that works, but, it is governed by how well things are aligned and associated torque required.

I will elaborate more in the refinement comments.

BACKLASH CHECK and REMOVAL
The steps per unit were confirmed. Now backlash was checked by moving one direction and then the other at different distances. The backlash was 0.012”…..

The bearing at the spindle end provides axial anchoring so any play between the outer rings must be removed. The ball nut is adjustable so that is another backlash point. Belt, motor quality, pulleys can play into this but the main two were noted first.

The bearings in the anchor end were re-shimmed. The bearings sit in a housing and the outer rings of he bearings are fixed by compressing them together via the mounting plate and the bearing housing. The inner ring of the bearings receives a preload by tightening a bolt into the screw.

Another back lash check was done, didn’t touch the rough ball nut adjustment, backlash now reduced to 0.008” and I know that the outer bearing rings are making contact. I then tighten the screw which adds the preload on the inner bearing rings. Another backlash check is made and it improves, but the steppers are skipping which indicates the bearing preload is too much. So I reduce it, the steppers don’t skip, and backlash is now at .004”.

Now the ball screw nut is progressively tightened until back lash comes down to around 0.001” and the motors are not skipping. Remember the carriage movement check done in the beginning. When all this stuff is tight there is not much give and alignment is very important. Not bad for a rough testing.

You will never have “0” backlash ( the X axis has 0.0003”) . Remember that lubrication needs to be between the moving components. So absolute “0” backlash is rather difficult to achieve if not impossible.
You can however do your best at each component of the axis train to eliminate it.

There is another part to these adjustments, since as you increase the loading on the bearings and ball screw nut, the torque required to move everything also can increase. So you need to play some to find a good combination.

TURNING TORQUE
Torque will be measured using the gauge shown in one of my other posts.
The torque to rotate the axis was measured and it took 80 in oz ( that’s a lot ). The belt was removed and the motor static detent torque was measured at 20 in oz. Can’t do anything about the motor so your left with 60 in oz. to try to reduce. A stated before the X axis has 21 in oz and one less bearing when measured.
The belt is replaced so I can jog the axis.
The ball nut preload was reduced / played with such that the backlash didn’t change. Then I further played with the anchor assembly preload again not causing an increase in backlash. That done the belt was removed and the torque measured. It’s now 35 in oz to just start to move the carriage. So the torque was refined rather easily and reduced almost in half. ( 60 down to 35 in oz). I would guess that at most the best I can reduce it is around 10 in oz.

The ball screw is not perfectly straight so when it turns you are putting a radial load into the bearings. I believe I can reduce required torque by adjusting the bearing mounted at the tail end of the lathe. That requires shimming the mounting plate and just takes some time fooling with it.

But for now, I know that I can almost eliminate  the backlash  (0.001” current on the Z ). Everything needs to be removed, but I just needed to confirm that all is within what I would like to accomplish before continuing on.

You say what’s the big thing about the torque readings?
Well if you can minimize the required torque for the axis without undue strain on the components keeping backlash within a desired tolerance, then you have a refined machine which will improve velocity and acceleration.

I will note that if you go back to the speeds, feeds, and torque that I was after, they have already been exceeded.
LIFE IS GOOD!

RICH
Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: RICH on September 14, 2009, 04:37:30 PM
Daniel,
Thanks.
Still a ways to go, guards, covers, re-machining the slide for whatever will be attached to it, box for the two encoders, etc.
Movement always seems to light up the fire in oneself.  :D
I forgot why folks go out and buy one!  ;)
RICH
Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: Dan13 on September 15, 2009, 12:48:52 AM
The ball screw is not perfectly straight so when it turns you are putting a radial load into the bearings. I believe I can reduce required torque by adjusting the bearing mounted at the tail end of the lathe. That requires shimming the mounting plate and just takes some time fooling with it.

Rich,

That is not good. If the screw is not perfectly straight it also means that the ball nut experiences radial loads, and that is really bad. Ball nuts are NOT designed to take radial forces. Subjecting them to this kind of load dramatically increases the wear and rapidly shortens their life.

Daniel
Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: RICH on September 15, 2009, 08:22:25 AM
Daniel,
The screw is like 0.004" out over 5 feet. It's small but when mounted such that it's made parallel to the lathe bed you sometimes see it since that tolerance can be in the short section used. There is some radial loading no matter what you do and you want to minimise it. The bearing support plates are made such that they can be adjusted for parallelism between the bearing supports. I fooled for some time with the mill as the ball screw was locked in, you find the spot that just works, but need to play around some to make it just so. Using the torque measurements is a great help as it shows you that what you have done is improving the mounting.
RICH
 
Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: RICH on September 17, 2009, 03:55:11 PM
This conversion may never end! But it is getting more fun now, since the bulk of the
main work is done. A third bearing was added to the X axis and whole bunch of holes were drilled into the X axis cross slide providing the ability to make adapter plates and special mounting for miscellaneous accessories to be used later on. Figure 44 shows one of the guards, and still need to make the others.
RICH
Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: RICH on September 17, 2009, 03:56:37 PM
There are numerous accessories already made and to be used for this lathe. It’s one of the reasons I never wanted to part with it. Figure 45 shows two different tool holders. The one on the right can rotate and is vertically adjustable. So a number of mounting blocks will be done over time. At least the small quick change on the left is ready to go.
RICH
Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: RICH on September 17, 2009, 03:58:00 PM
Here are some more accessories for the lathe. Note that both the three and four jaw
chucks have index’s. The three jaw chuck also has a vernier attachment ( not shown ) that can be used for finer indexing. The index band (magnified as shown in figure 50 ) is graduated in 1 degree steps on one side and then offset by 30 minutes on the other side. Additionally when using the vernier you can down to 5 minutes. When used with a high speed drill very small accurately placed holes can be done as shown in figure 51. The smallest holes in the piece are 0.010” in diameter. I placed a 0.010” drill in the test piece for reference. What is nice, is that you can do some fancy drilling with the finished turned piece left in the chuck and thus there is no need to do additional setups using a  sensitive drill press / mill / rotary table. Note that both radial and axial drilling is easily done. Yes, you can also then do some fancy pocketing, hole elongation, and scribing on the lathe. That is where an axis with almost zero backlash is important. If backlash is used you will snap a lot of the small end mills / tooling in a heart beat. As you can tell, the lathe will be used for small model work besides general turning functions.
RICH
Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: Sam on September 17, 2009, 05:28:28 PM
That's a pretty slick project you've got going on, Rich. I have enjoyed following your progress. Do you have a mill at home that you make your parts with? You do know, that were gonna need to see a video of it making chips when your done, don't you. Is your wife as enthusiastic about your machines as Simpsons wife is with his? Good job Rich, I'm looking forward to the next update.
Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: RICH on September 17, 2009, 06:15:16 PM
I trying to post a little for every one.

Have two mill's, one CNC'd which is a converted Atlas knee mill  (you can find pictures of it on the Show N Tell ) and a manual import mill drill that i beat the poop out of.
What is interesting is that you have all this CNC stuff and for the most part of this conversion you end up doing it manualy because it's a design / mill / drill, turn a piece......... work as i go kind of thing.....very little cnc work.  Now once done all ,of the machining could be optimized and CNC used more.  ;)

You may get a video since a friend has a desire for creating one for other things to.  :)

My bride of 34 years has her side of the basement and i got my shop on the other side.  I stay out her Kitchen (http://en.wikipedia.org/wiki/Vance_Miller) and she stays out of my shop. There are certain nuptual agreements that are made in your vow's which never should be infringed on. It's just a matter of respect. She does Tai Bow  ( can kick the poop out of you! ) and i make metal chips.
You know like, honey, when we get married you do realise that i will still go hunting for one week's vacation in the mountains, of course you are welcome to come and joint the boys, but it is not really required on your part. It's a guy thing like you getting together with the gal's once a year!  >:D

RICH

RICH
Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: RICH on September 17, 2009, 09:10:34 PM
Z AXIS BALL SCREW  PROTECTION

I looked at a number of different bellows that you can buy which encase the screw. The metal ones as shown on a piece of screw in the picture are expensive and act as a spring. Didn't care for rubber bellows ones as they just won't hold up. Telescoping tubing requires installation on the screw before the screw is mounted. I realy wanted something that can be removed and mounted very easly. Screw wipers will mounted in back of the carriage and on both ends of it and there ball nut adjusting screws i need to get to. A shower curtain rod cover can rap around the screw and i quess you can make your owne slinky type.

I decided to give the homebrew telescoping angle covers shown in the picture a go. Easy to install and remove. Don't know how they will act during a high Z rapid move. I guess we will find out.

The MPG may get mounted to the carriage or off to the side at the tailstock end of the lathe. The one shown is just for comcept. The future new one will have a smaller box, and yes, actual wheels. The most natural mounting is on the cariage but mounted near the tail wouldn't be too bad either. Usualy i use the MPG while also looking in the microscope. You want to feel comfortable and instinctively operate them just as if it were a manual lathe.

They call this thinking "conceptual design" especialy when using high tech things like  tape and clamps.

Any simple ideas out there on the covers, give a reply!
RICH

 
Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: RICH on September 20, 2009, 11:41:01 PM
Just a little update on the conversion. The pictures show the X and Z axis ball screw covers done and attached. The telescoping Z ones work great and are made from Al angle while the X axis was bent and then welded. Shouldn’t have any debris getting on the screws. What is not apparent is that the carriage drilling was completed and that to install the gibs on the operator side of the carriage the Z axis needed to be removed. So all was taken apart and put back together, realigned, gibs shimmed just so for a nice slide of the carriage, etc. The Z now only takes 16 in oz ( with out motor attached ) to just start movement. That gave me an extra 40 IPM to the Z max velocity.

The X travels within 0.0005” perpendicular to the Z axis over it’s 4” travel. Remember that the carriage was re-machined where it sits on the ways. The chuck ( a set thru ) was re-checked holding a ground rod in it and centers to within 0.001” . The Z run out is within 0.0015” /  8”away from the chuck. So I will just leave the chuck as is. Just ran the spindle at different speeds (  from low to high rpm ) for about four hours since the lathe was not used since new bearings were installed a long time ago.

X axis backlash is 0.0003” and the Z is 0.001”. Trying to bring the Z backlash done just a little required
to much preload on the anchor bearing and the ball screw nut. You can’t get zero!

Still need to make a new pulley cover for the head stock and wipers for the Z axis. Also need to make and mount the index disc for threading and get the limit switches installed. The other stuff for accessories will
come over time.

Since the lathe is basically checked out and usable as is, maybe I will just try it out for kicks.
Lot of work ……but also a lot of satisfaction!

RICH
Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: RICH on September 23, 2009, 11:39:17 PM
If your following this thread nothing new other than i am making chips as i test out the machine some.
So far all the conversion meets expectations and it sure is nice to not to have to deal with backlash.
Waiting for some hall sensors ( to be tried for as a threading index source ) and then willl try threading.
Will post as time goes on.
RICH
Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: RICH on September 24, 2009, 11:26:14 PM
I have been playing with the converted lathe using the wizards to do basic things like cutting down shafts, ball ends etc  and she's got accuracy and repeatablity.

Figured i would rig up something quick and dirty to try some threading ( waiting for a hall sensor ). Just quickly mounted a small disc with a single slot as shown in the picture. I couldn't use any regular chucks so used a small one which has a MT to fit the lathe spinde as shown in the picture #1.

Picture #2 & 3 was my first thread, 5/16- 24 cut at 402 rpm. The rpm would  occasionialy flicker between 401 and 402 rpm. Measured rpm to displayed rpm was within 1 rpm.  One thing for sure, there is no slow down of the spindle!  What a difference as compared to using my punny Sherline lathe. The thread pitch diameter only varied 2 thousands across the length of the thread.

After cutting some finer threads, i tried a 3/8-20 as shown in picture #4. It was cut at 863 rpm / 43 ipm and .008" cuts. All was fine up until the next to last pass when the little chucks MT came loose outof the spindle. Result was a chewed up thread! No spindle slow down at all and at that speed not much time to hit the Estop! Oh well, i quess I'll just waite to test out some of the larger / deeper threads using a regular chuck.

I am using a  SS and of course i have  no need for backlash compensation now. Additionaly, believe spindle slowdown will no longer be an issue. Hey, small lathe but running with the big dogs now!  It will be interesting to see how long threads and multiple threading goes. I'll waite for the sensor to be installed first.

RICH
Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: Dan13 on September 25, 2009, 01:19:41 AM
Ha..ha... What a difference to a Sherline ;) 

What's the practical backlash you've got?

Daniel
Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: RICH on September 25, 2009, 06:01:33 AM
Daniel,
I had the Sherline tweaked quite well, or maybe better said, after lots of testing i knew how to get the most out of it. Being fair to Sherline, it's still a nice little lathe for making small parts.

Practical backlash on the converted Atlas is zero.  The x axis is 0.0003 to .0004" and the Z is slightly under 0.001".
Just using code generated by the wizards, like turning down a  shaft to dimension i was able to get within or better than the X axis backlash. The backlash is a real PITA if your doing threads, not only fine 0-80 but also deeper
threads like 20 or 13. On the small threads, a few thou makes or breaks a usable thread while on the deeper threading 2 thou can create a spindle slowdown, force you to use flank threading, etc. Even though a lot of effort by Art  and testing by users to make the threading cycle work with spindle slow down, there is no comparison if it doesn't happen in the first place.

The intent of this conversion was to build a lathe that could do fine precision work but also be able to do larger work. To that end the goal was achieved.

I still have a number of refinements to make the accessories usable and a fair amount of testing to gain experience
using the new toy.  I guess if I had to do it all over, I should have CNC'd the Atlas a long time ago. If you read the postings, it is obvious i knew what i was after and wanted.

RICH

 

 
Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: Dan13 on September 25, 2009, 08:13:48 AM
Rich,

Obviously looks like you achieved your main goal. Well done!

Like you said, it's a lot easier when you know exactly what you want.

May I ask, how much money did it turn to you?

Daniel
Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: RICH on September 25, 2009, 08:47:58 AM
"May I ask, how much money did it turn to you?"

Not sure what your asking?

RICH
Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: Dan13 on September 25, 2009, 08:58:04 AM
Reading it again, I am not sure myself what I typed there :D

Wanted to ask how much money have you spent on it so far?

Daniel
Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: RICH on September 25, 2009, 09:44:53 AM
I had most all the "stuff" to do the conversion. So just a few miscleaneous things needed to be purchased. Say around $140 so far. 
RICH
Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: RICH on September 26, 2009, 10:07:09 PM
INDEX PULSE – MOUNTING / USING A HALLS SENSOR
Got the index pulse all working. I used a Hall sensor instead of a slotted disc.
Readout is dead on from the 53 – 2400 rpm of the lathe and doesn’t vary. Components amount to a rare earth magnet which is was super glued to a gear inside the spindle housing. The sensor ( SMC D-F7NC )
was mounted onto a steel strip and attached to the casing. The sensor actually has two sensors in it and only one was used. The sensor also has an indicating light to show when it is triggering making for easy alignment and visual confirmation other than using the diagnostics. The sensor components and mounting are shown in figure # 55.

What was really nice was that it could be mounted in close quarters. I didn’t have many options for
mounting a disc and this did the trick. The sensor works from 5 to 24 volt and I already had the wiring inside the controller setup for a 5 volt supply which saved some rewiring. Why did I use this particular
sensor? Well, as a friend pointed out, look in your “junk box” because we have a few of them ( always like to have a spare part !) and there they were. A little guidance from another friend on the pull up resistor and life is good. I didn’t check the generated pulse with an o’scope so I can’t say how good it is, but frankly,
it works, and that’s what is important.

In the last post I showed a ruined ½ - 20 thread. Now I can use the proper chuck and test out some heavier
threading. The ½-20 was again tried ( 863 RPM / 43 IPM and .006” cuts) and was done with ease. I tried a few more threads to build the confidence level up and all was fine.

Picture # 55 & 56 show the results for a ¾-13. It was cut at 115 RPM using flank cutting ( 15 degree ),
.010” first pass / then .003” passes / and I spring pass. The steppers have a lot of torque at that speed and in back gearing the motor has plenty of torque. This is a rather deep sharp vee thread ( 0.0662” )
so the cutting is rather heavy. The RPM / feedrate never changed. The resultant threads pitch and profile
is very good. An increase in RPM and lighter cuts along with a few spring cuts would probably improve finish. But I was interested in timing, rpm and cutting ability.

The next tests will be with longer threading to see if the lead is going to change over the length.
This is a problem that plagues a number of folks when doing threading. Stay tuned!

RICH   
Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: Chaoticone on September 27, 2009, 12:05:56 AM
Very nice Rich!    :)

Brett
Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: Dan13 on September 27, 2009, 12:54:15 AM
Rich,

Looks like a prefect thread, but did you had chatter when you cut it? That's how it looks to me.

Daniel

Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: RICH on September 27, 2009, 09:24:29 AM
Daniel,
The material is AL 6061. No chatter, but i did have that "crackling sound" at times which indicates that the
chip was breaking and there was work hardening of the material.  The tool is somewhat hung in front of the carriage
so you get some flex of the carriage. ( moment about the carriage Z axis, so whatever play is in the gibs was happening under load) You could see the tool  ( top part and tool mounting slide ) spring down, but again i wanted to see what she would do. I wanted to see if the belt would slip or rpm  or feed rate would change.

There is a fair amount of force when doing this thread. I  have broken a 3/8" diameter  diameter boring bars when doing a 1-8 thread on the 11" manual lathe. I would guess that the tangental force is 100 to 150# ( which is a lot for a little lathe ). Put that load on small part of you toe and you would really feel pain!

The little sherline would never be able to what the converted lathe did. Alll you need is a little backlash
say .002" in the Z, and making a cut it could be 0.005" instead of .003" and you would have disaster as the load
really increases.

Threading is a real true test of the lathe as you need to have accuracy, repeatablity, torque, and overall a good system.
Loads from cutting  are transmitted back into the components of the system. A good example from, a design point of view , would be how many and what size set screws should be put into the collar that acts as a retainer for  preloading of the Z anchor bearing.  Or notice that i deliberately didn't put any screw holes into the top carriage slide where the
tool gets anchored as it is rather thin in section, but, i can bridge across the slide with an adapter piece or plate.

This thread is about more than just here's the conversion. In the beginning there were posts about initial considerations
on components. I didn't take it to any high level of engnineering, but as a designer, the engineering stuff is of interest
to me. I may go into some calc's just for the fun and educational part for some. Then it went into each system and how it was done.

Sorry for rambling on but trying to add some perspective to the conversion.
RICH
Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: RICH on September 28, 2009, 12:01:44 AM
THREADING CHECK – LONGER THREADING
Mach3 version 3.042.27 and using a SmoothStepper.

For checking of how longer threading is functioning in Mach ( or my lathe ? ) a microscope was attached to the carriage for viewing and measurements.
The tube was finished down to a .7500” diameter, then the surface was colored blue with a permanent marker. A very pointed sharp tool ( no radius ) was used to scribe the lines on the shaft as it was cut.
The threading was as follows:
PITCH:  0.050”  and 29 degree angle ( basically there is no step change in the Gcode for Z as it just cutting radial)
PASSES: 60 @ 0.0001”
TOTAL DEPTH OF CUT: 0.003”
RPM: 402 / 20 IPM
Picture #57, 58 show the setup and scribed material after the threading cycle.

Now it is quite obvious that the pitch is changing as the threading is progressively getting longer.
I guess that has not been fixed yet in MACH! On the starting end of the thread there are five cuts in a space
0.005”, then in the middle there are 5 cuts in 0.011”, and at the end of the 2” thread there are 5 cuts
in 0.019”. This is shown in picture #60 and then enlarged to show the cutting grooves at the end of the threading as shown on picture #61.

Each groove measured 0.003” deep ( I have .0003” backlash in the X ) but the widening / changing of pitch is not do to the Z mechanically ( I have 0.0006 to 0.0008” backlash in the Z ). The rpm is not changing.
The steps per unit a correct.

In the last post a ¾-13 x ¾” long thread was cut and there were no lead problems. If this thread was
cut was 2” long only ¾” or  maybe 1” would have been usable. I didn’t get any X & Z combination moves,
but, as shown in the pictures, somewhere in the threading cycle there is still something causing a change in the Z such that one bigger cut is “always” done somewhere in  the cycle. On a punny lathe the thread may be ruined but on bigger machine you would just have a wider cut and may not even notice that quirk!

More threading tests need to be done but did notice that the affect is not as pronounced as in a smaller
thread. Maybe Mach4 will have have it fixed, but until then, there are still problems with threading on the lathe.
 
Till next time…….keep the threading short,
RICH
Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: WoodyCam on September 28, 2009, 07:11:34 AM
Hi Rich,

Correct me if I am wrong, but I thought Art had spent quite some time looking into this and found that some PC's have timing issues in the way Mach3 spits out Z movement for threading?

What happened with all that work? Did version .29 implement a different means of generating timing that overcame this issue? It may be worth trying version .29 just in case. Change log doesn't list it.

On my ORAC I have a really old, but seemingly good NEC 1Ghz PC and using the parallel port, single index and version .23 (I think) and I get no variation in pitch that I can measure, certainly up to 100mm length. Lines up with a rule perfectly the whole length and functions as a thread. Lucky perhaps. Deep cuts though are a no-no on that version, otherwise the X axis goes crazy (but never the Z for me). I've not tried vn 29 yet as I don't seem to have the timing issues.

Woody.

Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: RICH on September 28, 2009, 09:05:18 AM
The work kind of stopped as there was only Chip and I trying some things out that Art was testing.
It was difficult testing to do. I just posted in Problems Threading on the Lathe thread, so you may want to follow along in that thread. The combination Z X move that your seeing has been around a long time, it is a bear to really
see / define the actual movements when it happens. Haven't tried lastest versions and don't really know if there are any threading changes in them.
RICH
Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: BarryB on September 28, 2009, 01:19:42 PM
Does this sort of problem affect all things done with Mach 3, or just threading?  It looks like a major problem to me...
Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: RICH on September 28, 2009, 01:59:22 PM
BarryB,
Just the threading from what i know of.
RICH
Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: RICH on September 29, 2009, 05:17:25 PM
Figured i would post this as it's a nice option for a conversion. Yes they come in an
assortment of colors. Even pink if that's your fancy, but the colored ones cost more.  ;D
RICH
Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: Tweakie.CNC on October 01, 2009, 03:23:59 AM
Very neat. It is often the simplest of ideas that are the best.

Tweakie.
Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: RICH on October 03, 2009, 10:59:36 PM
Hi All,
The lathe is working great, but a sore spot was my computer.  I have never recomended a specific computer in any of my postings. I finaly broke down and had one put together. The company said it would work with me and put a solid computer together for running Mach. If it didn't satisfy the driver test, then components would be changed unitil it worked as I wanted. So off we went for a 1/2 hour lunch, returned and it was put together!
Good price, unbeatable service, with an absolute guarentee you could't beat!
Like, if the mother board was the problem  they would change it out, processor, and any component, with the cost only changing if the component cost more!

I need to get back to the company ( they have been around a long time and i have purchased pc's from them before)
and confirm that all is well. Then i will modify this post with their info.

The PC is solid. Here are some basics:
- Asus motherboard - M2N68-AM SE2
- 2 GIG Ram
- AMD  64X2 Dual Core Processor 5200+ 2.7 Ghz
- Asus graphics Card - EN9600GSO
- Rosewill PCI pp card - RC302

The pc will run my steppers at the same speeds as the SS. The PPS in the driver test will only change by 1 at 25khz and maybe 4 at 100 khz. Single line  with no bumps and you can play with the mouse and it dosen't screw it up.

This is the pc i am using for the threading tests if you have been following that thread.

RICH
Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: RICH on December 17, 2009, 01:15:45 PM
Got side tracked for a while and back to making and testing out some of the assessories for the lathe. Here are some pictures of the drilling / milling  attachment that will be used on the lathe.

FIGURE 1&2 shows  the drill in a holder and the adapter plate. Setup is quick as no shimming is required. The base can be attached to the carrage on the X, Z axis or even on an angle. Machining can be done via a coded program or manualy by using the MPG's. The drill and not shown matching collet model were modified to remove axial play. Figure 3 shows additonal air driven grinders ( made by Dotco and Ingersoll Rand ) some of which  have an adjustment for speed. So rpm range is up to 60,000 rpm. The same holder is used for all of them just that an adapter is reguired for use of the air driven ones in the holder.

Figure 4,5  shows how the drill is alligned. A piece with a precision reamed hole is mounted in the chuck or collet. Using a extended eye relief microscope,  MPG's are used to allign the ground pin into the hole. The slightest movement of the pin can be detected. You can see .001" easily. The axis is then moved into the reamed hole some .5" deep.

RICH
Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: RICH on December 17, 2009, 01:18:12 PM
Been experimenting  drilling holes. Manualy using the MPG's,  G83 canned cycle and some macro's. Good allignment, just the right pecking, and quality

drills are mandatory for accurate drilling and hole size. You will break a small drill in a heart beat if things are not right.
Feeds( F.01 TO F1) can be increased once a starter hole is accomplished.
A 0.020" drill is shown against a 0.001" feeler gauge in Figure #1.

Figure #2  shows ( 12 equaly spaced 0.020" holes into a .375"  diameter piece. The manual indexing band on the chuck ( Fig 3 ) was used and each division

is 1 degree. I have a veneer that can be used to bring it down ot 5 minutes of an angle.But in the future ...never ends.... a stepper will be used to rotate the

spindle. Figure 4 shows two mounting options i am considering. A removable bracket along with a spindle adapter will provide quick setup and removal.
 
At 200 steps / unit and 10us, resolution would be 10.8 minutes, or if i use the stepper with a precison 10:1 gear box ( no backlash in it ) then resolution

goes to 1 minute.
1 MINUTE = 0.0003" @ 1" distance
So if the you can hold the drilling location to 0.001" @ say .25", that would be equal to approx
13 minutes. To eliminate rotation inaccuracy the geared unit should be used.

RICH
Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: BClemens on December 17, 2009, 01:49:52 PM
Really nice! I have an old Atlas 6" that my Dad gave me when I was about 12 years old. Years ago I made a quick change gearbox for it...if these conversions were going on then maybe I wouldn't have had to make all those gears! I still use it now and then. I sold a 12" one (I could kick myself now) that would have made a nice CNC conversion. Hindsight!

Great documentation of the conversion!!!!

Bill C.
Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: RICH on December 23, 2009, 08:00:54 AM
This picture shows the mounting of a stepper which is used for indexing of the spindel.
The stepper is mounted out of the way and just removing one screw in the based allows
for easy belt removal. Setup needs to be easy. The spindle pulley is mounted onto an expandable mandrel
and then just tightening one screw expands the mandrel and locks it to the spindle bore.
Not much of a reduction via the pulleys so steps per degree is only 7.04 which is not desireable.
But I wanted to see how usable and easy the setup would be. Need to order some belts and pulleys so
the stepper with the gear reducer can be mounted.

So now i can experiment using the rotary feature for drilling and milling along  the Z  and X axis.

RICH
Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: Dan13 on December 23, 2009, 09:55:47 AM
Looks good Rich! What kind of work are you intending to perform on this lathe requiring indexing?

Daniel
Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: RICH on December 23, 2009, 11:43:56 AM
Dan,
Will not do any "heavy drilling or milling".
Example: Say I turn a tapered profile and it has a flange on the top of it. Without removing it from the lathe i will be able to flute part of the tapered section, drill around and into the face of the flange. So  I am combining some of the features that you would normaly do using an rotary table on the mill. Additionaly i can do engraving around  the piece. Save a lot of time.

Since the lathes axis are very accurate i can do some realy nice peck drilling of small holes ( thank's to Melee's macros he just posted). I have not tried profiling using Copy cat on the lathe yet,but, again combining some things will just make makiing some of the small parts for a model so much easier and less time consuming.
I can easily swap my drives axis cables around and manipulate the Gcode.

It all depends on what i am going to do.
I don't know how my barrel for the 629 will prfofile out, but should be interesting.  I want to minimise some of the hand work.

Hope that gives you an idea of use,
RICH

BTW, You realy should have the A setup so you get a nice ratio which is divisible by 360 evenly. May need to make my owne pulleys and not use the 10:1 gear reducer.

Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: Dan13 on December 23, 2009, 02:18:32 PM
Ah... forgot you had that nice milling attachment :) Is it a self made spindle you attached to the electric motor?

Daniel
Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: RICH on December 30, 2009, 05:58:25 PM
Here is an upgraded indexer for the lathe. Mounts same as the stepper i mounted to try indexing out ( easly installed or removed).
I modified a gear reducer ( from the junk box ) so that the stepper was directly mounted to it. Total reduction is 135:1 which provides for 750 steps per degree. So positioning is more accurate than i can drill or mill and have the ability to run linearly at very slow feed rates to over  80 IPM with adequate torque / power for what i will do. Don't need to use backlash compensation and the DRO displays even numbers ( not 359.9875 or something for 360 degrees). Need to order a few timing belts and just drill a few holes in the base.
Till I start doing some fancy milling around a cyclinder on the lathe,
RICH
Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: bloomingtonmike on November 24, 2013, 01:27:18 PM
Blast from the past. I am interested in doing a 618 conversion to CNC.
Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: BOB FINLEY on June 16, 2014, 05:08:54 PM
Hi Rich
Can you do multipass threading. In that way each pass is only removing a small amount of material.
Bob Finley
Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: RICH on June 16, 2014, 05:15:49 PM
Bob,
Yes Mach can do multipass threading. I can also do other kinds of threading. Have a look at Threading on The Lathe which you will find in Members Doc's for detailed info about lathe threading.

RICH
Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: starrtraveler on March 01, 2015, 06:54:43 AM
Hey Rich...nice toys and impressive job on the Lathe CNC upgrade.  I've been learning and searching for info about upgrading my Atlas 6" to CNC and came across your postings.  Any chance you still have the source for your ball screws with the narrow profile ball nuts?  Only ones I've found so far are the big flanged type.  Thanks again for your inspiring project here.  Maybe while yer at it...where did you source your grey iron plate? 

~Wade
Title: Re: CNC CONVERSION - 6" ATLAS LATHE
Post by: RICH on March 01, 2015, 02:01:04 PM
Wade,

The X axis ball screw is made by Steinmeyer. The Z axis ball screw is from Techno Inc.
Get ready to shell out some money, so price around.

The fine grain cast iron was picked a long time ago from an individual and only a few pieces. Wish I bought more.

RICH