Machsupport Forum

Mach Discussion => General Mach Discussion => Topic started by: m4uk on February 27, 2013, 07:18:18 AM

Title: Motor Tuning
Post by: m4uk on February 27, 2013, 07:18:18 AM
Hi All
Hope somebody can help here. Have finally got my lathe working but accuracy is a real problem.
This lathe was set up by a UK company who had never done one before and are pretty much no help at all. So its down to me.

Lathe is an Optimum 320X930
According to the company who supplied it ,its 5mm thread ball screws on X & Z.
Z has 40 tooth pulley on the screw and 20 tooth on the motor, Stepper on Z is 8.2Nm 1:8 degree. Stepper on X is 1:8 degree 4.2Nm, they said that X  is directly connected, I can see a gear box but the motor is offset from the screw so I don't think it is direct, unless this setup is considered direct, I don't know.
Z has a belt between the screw pulley and the pulley on the motor shaft.

The engineer is Polish and speaks virtually no English so this is not easy at all. He also hasn't got a clue about inches and is a mm guy. I work in inches.
He worked out some step figures and we put them into the software, I'm currently measuring and changing numbers and getting nowhere fast.
I have a dial indicator on x and z, x is giving me a real problem as if I set the steps per, so it moves .1'' its perfect, however if I then move it .4'' its .002'' over.
I'm not sure Z is right either.
 Z .600'' cuts .606'' and X .500'' diameter cuts .484'' so it no way correct.
I have backlash turned off, mechanically everything seems solid though and the build is good.
Hoping somebody can point me in the right direction.
Thanks
Title: Re: Motor Tuning
Post by: Hood on February 27, 2013, 08:08:25 AM
Sent a reply to your PM a week or so ago asking for details of your machine, what issues you were having (as you never specified)  and to send your xml to my email address. You have provided the majority of the info I require here but would still like to see your xml so that I am not working blind.

Gearbox may not be good and introduce backlash, depends on the quality and type of gearbox.
By direct they could simply be meaning there is no reduction, ie  1:1
What make of drives do you have an what microstepping do you have them set to (if they are adjustable)

Hood
Title: Re: Motor Tuning
Post by: m4uk on February 27, 2013, 10:52:12 AM
Hi Hood

we worked a lot of it out and Brett helped also.

Ill send you the Lathe xml file via email.

The motors came from Optimum in Germany:

http://www.optimum-machines.com/products/cnc-pc-controls-complete-and-adapter-kit/complete-and-cnc-add-on-kit-for-turning/index.html

But I don't know the make. On the back the Z says Step Motor Bipolar, Step angle 1,8 Degrees 8,2Nm 6A Optimum Germany

The X is the same but with 4,2Nm

They don't seem to be adjustable. But i don't have a clue what to look for.

I currently have the following numbers in Motor Tuning:

Steps per X:  2580, Vel 15, Accsel 5.6983
Steps per Z: 4071, Vel 34.998, Accel 24.9343
Title: Re: Motor Tuning
Post by: Hood on February 27, 2013, 03:10:58 PM
Ok info you sent isnt much help as all I have been able to find is a German website for the stepper drives and there doesnt seem to be info.
However from the info provided above it would kind of seem like your stepper drives are half stepping.
If the info is correct then your steps per unit for Z would likely be 4064 and X 2032, so if you give them a try and let me know if its more accurate.
Hood
Title: Re: Motor Tuning
Post by: m4uk on February 27, 2013, 03:47:44 PM
Thanks for that.

I ran a cutting test and Z seems to be on the money, programmed .500'' on Z and got .500''. Not sure about X, programmed .500'' DIA and got .571''DIA. I did a G54 X0 test and it didn't look to center before the cut. I touched it to .888'' DIA and used that figure in the Part Zero DRO for X as normal.

Any ideas?
Title: Re: Motor Tuning
Post by: Hood on February 27, 2013, 04:07:05 PM
I am not really familiar with the standard lathe screenset as I dont use it but if you can do the following, move the X axis so you will be taking a light cut and jog along and take the cut. Jog back and then measure and then enter that into the DRO. Now try a few more cuts and see if the DRO corresponds to the  dia being cut.
There may be some reduction in that gearbox.
Hood
Title: Re: Motor Tuning
Post by: m4uk on February 28, 2013, 04:06:44 AM
Hi Hood

Been on the phone with Optimum in Germany and they say that the X ball screws are 4mm, not 5mm as I was originally told. There looks to be a tiny line on the crest of each screw and they measure 4mm between those lines. Z ball screws measures 5mm between those lines. I hope this is  the error  as have been test cutting this morning and X is out by a mile.

Had it confirmed that they are 200 step motors but don't know a make. Gearing on X is 1:1 for sure.

Would you be able to generate a magic number with the new info?

Title: Re: Motor Tuning
Post by: Hood on February 28, 2013, 04:20:10 AM
Ok motor is 200 steps per rev then you have 1/2 stepping drives so thats 400 steps to turn the motor 1 rev. 1 rev is 4mm but you want to set your native units as imperial so that is 25.4/4 = 6.35 turns to move one inch. So 400 x 6.35 = 2540steps per inch.

Hood
Title: Re: Motor Tuning
Post by: m4uk on February 28, 2013, 06:15:20 AM
Much better thanks Hood but still a bit out.

I programmed .4989'' and got .4850'', so .0139'' (.353mm)  out on the diameter.

Is there anything I can do to get this more accurate. Could it be backlash that causes the inaccuracy?

Z seems to hold about .001''

Thanks very much for your time on this btw.
Title: Re: Motor Tuning
Post by: Hood on February 28, 2013, 07:13:51 AM
Could possibly be backlash, it would be quite a lot for a new machine but if there is indeed a gearbox involved then its possible.
You could easily test for it, what to do is set up a clock (Dial Indicator)  on the bed and put the point against the cross slide, put Mach into step mode of maybe 0.001" and jog onto the point a bit then zero the X DRO and then jog back in the 0.001 steps and as soon as the needle moves stop and look at the DRO in Mach and see how much it reads, that is your backlash, or twice your backlash for Dia mode.

Backlash could be in many places, could be screw, could be gearbox, could be bearings of screw or flex in mounting brackets or even gibs needing adjusted.
Hood
Title: Re: Motor Tuning
Post by: m4uk on February 28, 2013, 08:13:53 AM
Ok, did as you said.

Put a .001'' dial indicator on X and set it to zero. Set Jog Cycle to .0010'', first tap nothing, second tap dial indicator moved. DRO reads +0.0024'' so double that .0048''.

Does that sound right Hood?

Title: Re: Motor Tuning
Post by: Hood on February 28, 2013, 08:31:33 AM
Ok just to clarify. you jogged in one direction onto dial and then zeroed DRO in Mach before reversing?
If so then thats correct and your backlash is half of what you read in the DRO rather than double as you are in Dia mode in Mach I think.
So it sounds like backlash is not an issue.


If you could cut a dia of say 1 inch and measure then tell it to cut 0.9 inch and again measure and see what the difference is.
Hood
Title: Re: Motor Tuning
Post by: m4uk on February 28, 2013, 08:51:02 AM
Ok

I jogged onto the indicator so that it started moving a few places, then I stopped and zero'd the DRO. Then I jogged in reverse and stopped the minute the dial moved, in this case one tap with .001'' set and the DRO reads .0016''. So even less.

I am in DIA mode so thats .0008''.

I have some '' I can turn to say .900'' and then .800''

Cheers
Title: Re: Motor Tuning
Post by: Hood on February 28, 2013, 09:00:17 AM
Thats fine, just make sure you command to the 0.9 and measure what it cuts and then command to 0.8 and again measure.
Hood
Title: Re: Motor Tuning
Post by: m4uk on February 28, 2013, 09:45:34 AM
OK so I measured the OD of the stock and it came out at .995''

First pass was set to cut .900'', that measured .899'' to .900''

Second pass set to cut .800'', that measured .800'' to .8005''

Third pass set to cut .700'', that measured .698'' to .701''

Fourth pass set to cut .600'', that measured .600'' to .6005''

Fifth pass set to cut .500'', that measured .4995'' to .500''

All cuts based on the original diameter of .995'', so later cuts had lots of fresh air passes.

So it seems to be working. But I have not changed any settings.

I took shallower cuts of .005'' at a time, before I had been taking .010'' and gone from .995'' to .500'' in one cycle. Could that have been too much?
Title: Re: Motor Tuning
Post by: m4uk on February 28, 2013, 10:16:02 AM
Just did it in one pass and got .485'' instead of .500''

So why is it .015'' out when cut in a single pass, I used the shallower cuts too.
Title: Re: Motor Tuning
Post by: Hood on February 28, 2013, 10:18:48 AM
That sounds fairly good, the shallower cuts may be helping as you may have flex somewhere, cant really say what would be a good DOC for your lathe as I dont know how rigid it is but 5 thou does sound very shallow, I have 2 lathes here, the big one can take 10mm DOC if I want but usually stick to 2 or 3 mm DOC. The wee lathe which is based on a Myford ML10  I will take maybe 1mm DOC and it is fine.
Hood
Title: Re: Motor Tuning
Post by: Hood on February 28, 2013, 10:19:44 AM
Definitely sounds like flex somewhere.
Hood
Title: Re: Motor Tuning
Post by: m4uk on February 28, 2013, 10:21:46 AM
Hi Hood
Do you have any idea why its so far out when cut in a single pass?

With shallow cuts too.
Title: Re: Motor Tuning
Post by: Hood on February 28, 2013, 10:25:08 AM
Something is either loose or flexing with the extra cutting forces. You will  have to put the clock on various points and push/pull and see if you can find it.

Hood
Title: Re: Motor Tuning
Post by: m4uk on February 28, 2013, 11:51:20 AM
Just checked with the indicator. Against the Aloris tool post I can just about push .001'', thats measured off the tool holder, the tool is rock solid in the holder.

Cant push a thing on the slide against the ball screws. Everything else is rock solid.
Title: Re: Motor Tuning
Post by: m4uk on February 28, 2013, 12:28:09 PM
I'm taking .005'' cuts, thats .1269mm each cut so I don't understand how there can be too much pressure on the tool. I was taking .010'' cuts or .2539mm before, even then I cant see how there could be too much. I can just about push .001'' on the tool post against the indicator. Actually managed to rock the 750Kg lathe a little doing that.
If I command an X move of 1'' (.500'' as in Diameter mode), then the dial indicator runs out by .002'' under, ie it shows .498'' total movement.
Lets say that the .005'' (.1269mm) cut is causing the tool post to move by .004'', that would give a total of .494'', but I get .485'', another .009'' from somewhere.

.500'' diameter cuts to .485'', or .015'' out.

Is it possible that the software is causing this? As the tool is moved in and out through multiple passes the error gets larger and larger?

Why can it cut .100'' accurately with the same tool pressure, working down to .500''.
With .015'' error I should have seen .003'' on each of those passes. 
Title: Re: Motor Tuning
Post by: Hood on February 28, 2013, 01:15:30 PM
Cant see how it can be a software error as Mach is sending pulses out regardless of what distance you command.
Ok so can you do some tests with the clock against the toolpost. Command it to move so tip is in contact then zero the clock and then do a series of X axis move and see if each one corresponds. Then reverse these moves and see if clock goes back to the original position.
Hood
Title: Re: Motor Tuning
Post by: m4uk on February 28, 2013, 01:42:59 PM
Will do Hood
Title: Re: Motor Tuning
Post by: m4uk on February 28, 2013, 02:24:49 PM
OK I have a .001'' dial indicator, so each graduation is .001''

Moved into the indicator and set it to zero then did these moves away. I did .100'' moves so the hand on the indicator had to do a complete 360 movement.

x+.2 should be .100'', indcator reads .089''

x+.4 shoudl be .200'', indicator reads .1985''

x+.6 should be .300'', indicatoe reads .2985''

x+.8 shoudl be .400'', indicator reads .3988''

x+1. should be .500'', indicator reads .4991''

x@1.2 shoudl be .600'', indicator reads .5987''

Please bear in mind that I don't have any graduations within the .001'' marks so I was estimating the fourth digit.

Did X0 and the dial indicator was approx .0001'' short. Just a fraction under a complete return to zero by the indicator I have.
Title: Re: Motor Tuning
Post by: Hood on February 28, 2013, 02:45:29 PM
Ok so was your first move in the opposite direction from which you moved onto the clock to zero it?
Have you still got Mach kernel at 25KHz? (config menu then Ports and Pins) If you do then enable Sherline mode and restart Mach and see if that makes a difference.
Hood
Title: Re: Motor Tuning
Post by: m4uk on February 28, 2013, 02:53:39 PM
Moved into dial indicator and then set zero, all moves were done away from the indicator. Checking Pins bit now
Title: Re: Motor Tuning
Post by: m4uk on February 28, 2013, 02:55:12 PM
Kernel is runnin 25Khz and Sherline was already enabled.
Title: Re: Motor Tuning
Post by: m4uk on February 28, 2013, 02:59:00 PM
I had to move back into the dial indicator to get back to X0 though.
Title: Re: Motor Tuning
Post by: Hood on February 28, 2013, 03:05:27 PM
Ok all are relatively consistent give or take a few thou I think so you definitely have lost motion some place, especially as it is returning to zero or close to it.
Could be the bearings are not preloaded enough.
If you can get access to the end of the ballscrew place the clock on the saddle and the point against the end of the screw and jog the axis back and forth and see if there is movement in the screw.
Hood
Title: Re: Motor Tuning
Post by: m4uk on February 28, 2013, 03:06:54 PM
If its of any use a continuous move from x0 away from the indicator to x+1.2 reads .5990'' and when I move all the way back to X0 (into the indicator) its .0004'' short of returning to complete zero.

Did it again and got .5985'' and a complete return to zero as near as damn it when I moved back to X0.
Title: Re: Motor Tuning
Post by: Hood on February 28, 2013, 03:10:15 PM
Another test you can do to confirm it is lost motion is move onto clock and zero clock then go in the same direction with a commanded move and it should be close. If it is then you definitely have lost motion.
Hood
Title: Re: Motor Tuning
Post by: m4uk on February 28, 2013, 03:16:33 PM
Sorry don't understand that last one Hood.

Just put the indicator on the end of the screw with the cross slide set furthest away from me, set zero on the indicator and then did a SHIFT, Down Arrow, so quick jog towards me, the indicator moved and max run out looked to be .001'' more like .0008-9''. It ended run out at .001'' closest to me. if I jog it back away from me it goes back to zero at the far end.

Please explain the other test again and i will do it.
Title: Re: Motor Tuning
Post by: Hood on February 28, 2013, 03:40:46 PM
What I am saying is move onto the indicator and zero it then continue to move in the same direction as you moved onto it, I understood that you had moved onto the indicator the last time then backed off with your moves, maybe I misunderstood?
Hood
Title: Re: Motor Tuning
Post by: m4uk on February 28, 2013, 04:07:18 PM
Thanks hood I'll do that test tomorrow.  Can't I just start with the dial indicator touching and zeroed and then move forward and back
Title: Re: Motor Tuning
Post by: Hood on February 28, 2013, 04:34:50 PM
Yes that would do, the first move I think would be correct then moving back would show the error.
Hood
Title: Re: Motor Tuning
Post by: m4uk on March 01, 2013, 04:11:08 AM
Ok
I have done a number of test and hopefully they will generate some meaningful info.

First I set the .001'' per graduation dial indicator against the tool post, zeroed it and commanded the lathe to move forward, into the indicator 1'', I'm in diameter mode so x-2 was used. Moving in the dial indicator swings clockwise and out anti clockwise.
I then did X0 to get the lathe to move back, away from the dial indicator to the zero point.

I did this 10 times in and out.

1. X-2, dial was short of 1'' by .002''
X0, dial was short of returning to zero by .0005''

2. X-2, dial was short by .002''
X0, dial was short of returning to zero by .0004''

3. X-2, dial was short by .002''
X0, dial was short of returning to zero by .0004''

4. X-2, dial was short by .002''
X0, dial was short of returning to zero by .0004''

5. X-2, dial was short by .002''
X0, dial was short of returning to zero by .0005''

6. X-2, dial was short by .002''
X0, dial was short of returning to zero by .0004''

7. X-2, dial was short by .002''
X0, dial was short of returning to zero by .0004''

8. X-2, dial was short by .002''
X0, dial was short of returning to zero by .0005''

9. X-2, dial was short by .002''
X0, dial was short of returning to zero by .0005''

10. X-2, dial was short by .002''
X0, dial was short of returning to zero by .0005''

I then re zeroed everything and got the lathe to move into the dial indicator and back out by .500'', so X-1 was used, then X0. I did this 6 times.

1. X-1, dial was short of .500'' by .001''
X0, dial was short of zero by .0001''

2. X-1, dial was short by .001''
X0, dial was short of zero by .0002''

3. X-1, dial was short by .001''
X0, dial was short of zero by .0001''

4. X-1, dial was short of .500'' by .001''
X0, dial was short of zero by .0001''

5. X-1, dial was short by .001''
X0, dial was short of zero by .0002''

6. X-1, dial was short by .001''
X0, dial was short of zero by .0001''

I then reset everything and got the lathe to move into the indicator by .500'' and then do another move into the dial indicator by .500'', so doing 2 moves totaling 1'' and then moving away back to zero. So X-1, X-2, X0. I did this 5 times.

1. X-1, dial was short of .005'' by .0012''
X-2, dial was short of 1'' by .0022''
X0, dial returned to zero.

2. X-1 dial was short by ,0012''
X-2, dial was short by .0024''
X0, dial was over zero by .0001''

3. X-1, dial was short by .0012''
X-2, dial was short by .0022''
X0, dial was over zero by .0001''

4. X-1, dial was short by .0014''
X-2, dial was short by .0025''
X0, dial was over zero by .0001''

5. X-1, dial was short by .0012''
X-2, dial was short by .0023''
X0, dial was over zero by .0001''

I also did a series of .001'' moves into the indicator adding up to 1'' total movement, the indicator was short  by .0012'', the same as one complete move.

Title: Re: Motor Tuning
Post by: Hood on March 01, 2013, 05:16:41 AM
OK things are just getting confused here or at least I am. Can you do one test for me :)
Place the clock onto the saddle and have the point towards the toolpost, jog onto the point and zero the clock. Go to Tab screen and set it to step jog mode and set a value in the increment size, lets say 0.1 then going in the same direction do a step jog move and read clock, do another still in same direction then another, assuming your DTI has enough travel. Then reverse and step jog back to zero again.

Hood
Title: Re: Motor Tuning
Post by: m4uk on March 01, 2013, 05:25:23 AM
Just tried something else.

Set the dial indicator up against the x axis so I could measure forward movement.

Put some 1'' stock in the chuck and set the X Part Zero to 1'', touched X against the edge of the stock and set zero in Mach 3. Also set zero on the dial indicator at this point too.

Now I use the command G54 X0 and the tool tip moved forward to the centre of the stock. Dial indicator shows that it is short (or oversized) by .0035'', not brilliant but still couldn't account for the dreadful inaccuracy I'm getting.

Next I measure the stock and its actually not 1'' its .995'', so I reset the fixture table, put .995'' into X Part Zero, touch X against the stock again and zero Mach, I also zero the dial indicator again like before. Now I command G54 X0 to position the tool tip at the centre of the stock, dial indicator now reads .005'' short !!!!

Reset everything and do just a normal X-1 command and the tool tip moves to the centre of the stock with only .0015'' short.

So what I have discovered is that the G54 X0 command adds another .002'' error to the movement with a 1'' diameter stock (total .0035'') and another .0035'' error if the stock is .995'' DIA (.005'' total).

Nevertheless these errors are all short of commanded diameter and therefore the stock would be oversize when cut. I end up with .015'' undersized stock after cuts.

I can only presume that the Turning wizard i am using that came with the software is doing something too.
Title: Re: Motor Tuning
Post by: Hood on March 01, 2013, 05:44:11 AM
What version of Mach are you using?
Hood
Title: Re: Motor Tuning
Post by: m4uk on March 01, 2013, 05:52:17 AM
OK did that test.
Im moving forward against the dial indicator in X in steps of .010'', these are halved on the dial indicator as in DIA mode.

I moved 5 steps of .010'' forward and 5 back, so from 0 to .050'' and back to 0 again.

Here are the measurements for each tap od .010''

forward movement of .010''  moved .0045'' on indicator, so .0005'' short of .0050'
forward movement of .010'' (.020'')  moved .0095'' on indicator, so .0005'' short of .010''
forward movement of .010'' (.030'') moved .0140'' on indicator, so .001'' short of .015'
forward movement of .010'' (.040'') moved .0195'' on indicator, so .0005'' short of .020''
forward movement of .010''  (.050'') moved .0241'' on indicator, so .0009'' short of .0250''

I then reversed the taps to move X away from the dial indicator

backward .010'' (.040''), dial reads .0200'', spot on half.
Backward .010'' (.030''), dial reads .0149'', so .0001'' short of half .0150''
backwards .010'' (.020''), dial reads .0102'', so .0002'' over half .010''
backwards .010'' (.010''), dial reads .0050, so spot on half again.
backwards .010'' (return to zero), dial reads 0.
Title: Re: Motor Tuning
Post by: m4uk on March 01, 2013, 05:53:30 AM
Mach is version R3.043.066
Title: Re: Motor Tuning
Post by: Hood on March 01, 2013, 05:56:32 AM
Ok I would suggest you try 057 version you will find it on the ftp site. There have been issues with 066 and 067 versions especially with Turn but I am not saying that is your issue but worth a try.
The other thing I can thing of is change the X Step pins active state.

To find the ftp site go to Downloads tab at the top here then to Mach3 then you will see it says for older versions click here.

Hood
Title: Re: Motor Tuning
Post by: m4uk on March 01, 2013, 06:06:30 AM
Hi Hood

Just turned Exact Stop on, as we had it set to Constant Velocity and an X-1 move error has gone from being .0015'' short to .0008'' short. Nearly halved it just with that option. Will download latest version. Is there a way to keep all the settings we have right now?
Title: Re: Motor Tuning
Post by: Hood on March 01, 2013, 06:11:01 AM
CV should not make the slightest bit of difference with a single axis move but it could be 066 version, will be very interested to know ;)
Hood
Title: Re: Motor Tuning
Post by: m4uk on March 01, 2013, 06:20:59 AM
Got 57 installed but it wont let me do an x-1, says 'Cannot do G1 with zero feedrate'

Title: Re: Motor Tuning
Post by: Hood on March 01, 2013, 06:28:11 AM
You are in G95 mode, feed per rev, change to G94, feed per min from MDI and it should work.
Hood
Title: Re: Motor Tuning
Post by: m4uk on March 01, 2013, 06:34:40 AM
Gave it a feed value and its happy now. An X-1 move with Exact stop enabled gives an error reading of .0018'', so worse than version 66
Constant Velocity gives an X-1 error of .001'' better (not as good as version 66). Will see what the G54 commands do now.
Title: Re: Motor Tuning
Post by: RICH on March 01, 2013, 06:38:22 AM
Once you gat the steps per unit set based on calculating or using Mach to set them you then measure to confirm that they are correct.
Rather straight forward but then there is usualy some error that one finds .........that sillly few thou. So i will call it the refinement part of finding the steps per unit.
A lot of things come into play when looking, accounting, and thus adjusting for the small inaccuracies.

Chances are that MAch or the software are not the culprits for the inaccuracies. As stated before, Mach gives the commanded instructions for the move and the axis will move as instructed.

It is fruitless to addrress backlash until you have rationalized out the refined steps per unit. You will have backlash, it can't be zero, just a matter of how much.
The refinement of the steps per unit requires that the user be very meticulous in whatever measurement they make and use. Said a different way the simple question is .....What did you measure?

Just a few thoughts that come to mind:
- The indicator is not calibrated or repeatable or not placed well for the measurement
- The ball screw is not linear
-  Coupling has backalsh ( if solid one not a problem but if anything else can affect the reading / repeatabillity)
- Thrust bearing loading ( and this can apply to the stepper motor itself especicialy if directly coupled to the screw)
- Any axis component inaccuracy ie; belt tension, gearing, bearing., etc)
- The motor itself in how well it will microstep.

 All of the above come into the refinement and one needs to know what is causing the error and what if anything can be done about it.
Some are easy and some are a real bear to isolate.

FWIW, back to the side ...........,
RICH






 

 
Title: Re: Motor Tuning
Post by: Hood on March 01, 2013, 06:40:44 AM
Ok sorry I misread your previous post, was for some reason thinking you said no spindle feedback message ;D

Hood
Title: Re: Motor Tuning
Post by: m4uk on March 01, 2013, 07:13:14 AM
Set stock diameter to 1'' and touched X to side of stock and then set zero in Mach, also set zero with dial indicator.

Did a G54 X0 and the dial reads .002'' under. So 66 version is .0035'' under with that command and 57 is .002'' under. Better

Now set stock DIA to .995 and touched X, did a G54 X0 and the dial reads .0045'' short, so better than version 66 of .005'' but not by much.

if I do individual steps of .100'' so G54 X+.9, G54 X+.8 etc... and work my way in, then each is bang on correct.

Cutting test:




Title: Re: Motor Tuning
Post by: m4uk on March 01, 2013, 07:25:52 AM
Please explain to me how one command gives an error of .0015'' and another gives an error of .0045''.

Or why changing the stock diameter causes the error to change from .0035'' to .0045'', because I can repeat these all day long.

Or how taking .0005'' cuts on a 1'' stock down to .500'' ends up being .485'', out by .015''

Do any of the measurements I have provided look like I have loads of slop in the mechanics, please tell me because I cant work this out.
Title: Re: Motor Tuning
Post by: Hood on March 01, 2013, 07:44:03 AM
I am unsure why you are having to call a G54, it may be something to do with the standard lathe screenset, Rich may be able to answer that?
I would have thought you were in G54 anyway so calling it would have no effect.
I also do not understand what you mean by changing the stock diameter? If setting the X DRO to a value then that is you changing the offset (G54 unless you have called some other offset) not changing the stock dia. Maybe I am just misunderstanding what you are meaning.
Hood
Title: Re: Motor Tuning
Post by: m4uk on March 01, 2013, 08:56:35 AM
Just discovered that he jumper on X motor driver was set to 3A and should be 6A, have changed it and am testing again.
Title: Re: Motor Tuning
Post by: m4uk on March 01, 2013, 09:25:08 AM
Just turned .489'' after asking .500''.

The guy who set up the lathe did not set the jumper on the X card correct.  >:( >:( >:( >:(

So much of my time wasted and yours Hood.

Thanks for all your help on this. There are a few niggles to iron out yet but its working a lot better.

Title: Re: Motor Tuning
Post by: Hood on March 01, 2013, 09:56:51 AM
Good to hear :)
  BTW I would stick with 057 ;)

Hood
Title: Re: Motor Tuning
Post by: m4uk on March 01, 2013, 05:54:57 PM
I have a slightly different problem now. :(
Could not get NSF turn to work in version 57 or the other turn wizard to show any part shape display so had no option but to go back to 66.
On two occasions now the machine has come to the end of a cutting pass, withdrawn the tool but rather than move in + to restart the cut the it has started from the position it was at and cut further down the stock. Somebody said that the rapids could be too fast and the code thinks it has returned to the beginning but in fact has not moved at all. Please can somebody advise me what to do, I have reduced z velocity from 35 to 30, is there a guideline for this at all please.
Title: Re: Motor Tuning
Post by: Hood on March 08, 2013, 01:08:32 PM
Does indeed sound like you may be stalling  but you should hear that easily? does the motor aqueal when it happens?
Hood