Success! Mini Machining Center under Mach3 control - Video link

[simpson36]

Coolfox,

Some encoders have a separate 'index pulse' in addition to the regular incremental quadrature. My encoder has this, but the motor is geared down to the spindle, so I can't use it for indexing and therefor I added a separate photointerruptor to the degree wheel.

It is not neccessary to zero the machine after homing unless you are recutting a part that has already had indexed operations done to it, or if you want to use absolute azimuth locations. Another reason would be to have the DRO numbers be meaningful for monotoring purposes. The Mach manual describes the A axis as 'infinate', and I have taken it to the tens of millions, so I don't see a practical limit there, and if your Gcode utilizes only relative (incremental) moves, and a DRO showing rediculously huge numbers is not a problem, then you would not need to zero the A axis.

Fixture offset is unaffected by the A axis shenanigans . .  so far anyway.

My objective is to make a sort of 'mini machining center' and emulate as many of those funcitions as time and budget (and Mach3) allow. A combined spindle/indexer is, I think, the first and most important step, and I have that pretty much worked out. I've just been prototyping to test feasibility up to this point, but I'm satisfied now that the concept is proven out sufficiently to start designing a sturdy permanent head with reasonable quality ball bearings and alignment pins and table mounting. I'm going to have two gear ratios 3:1 and 2:1 to accomodate different materials and stock diameters.


EDIT: checked out your site. That is some seriously unique and beautiful jewelry!  I pray my wife never discovers your site . . .
 

[Hood]

Simpson,
 regarding the gearing and encoder Index, it may have been possible for you to utelise the pulley ratios in Mach so that the correct speed was shown. Probably not needed now as you have the interupter but just thought I would mention for your next build as it may save time or hassle.
Hood

Edit
 Just thinking again, dangerous I know
I think you are just using the parallel port so maybe the above info will be useless as chances are the index pulse from and encoder will be too short for the PP to see accurately, you could of course electronically lengthen the pulse but probably easier just to use the interupter after all.

[coolfox]

Simpson36,
From my experience. I have 1;1 ratio on the machines as if you use powerfull 1KW+ servo for the drive you normally wouldn't need more torque unless you want to cut 1.5mm deep cuts on tool steel 10mm diameter :-) my 2.2kW servo I have to limit torque 1/2 as it rip the 25mm wide AT10 cam belt in shreds then I accidentally start the locked spindle :-( .
You want to build a lathe headstock why not buy ready made one?
In regards of ball bearings have to say if you have time to make plane bearings it work better in spindle from experience of use Shaublin have double row roller on front and two angular on the back and cost of etch in £200+ compare to plane bronze taper bush bearings in Smart&Brown doesn't stand a chance in stiffness and precision you my say constant lubrication requite for plane bearings in Smart it organised with simple capillary effect felt pad inside bronze bush and not requite attention for weeks of constant use ( I have used it every day for 10 years and no wear on spindle or bearings noticeable!!!).
I'm planing to upload some photos, as would do maintenance ( want to respray it), of internal construction of headstock in the mean time you can have a look here usefull info http://www.lathes.co.uk/smartbrown/page3.html
Would you mind to share macros for your machine and sample of code (for that infamous screw :-)?
Kind regards
Ilia

[simpson36]

Hood,

I don't need to read the speed since there is an encoder on the motor. The issue is homing te axis. There are some symantics do deal with . .  the 'index pulse' is an ADDITIONAL once per rev pulse built into the encoder. I can't use that with the gearing , because Mach has no way to know the position of the spindle from the position of the motor. i.e. index pulse from the motor can mean the spindle is at 0, or 120, or 240 degrees. Mach would no know which, so I have to have a n index on the spindle itself (as far as I know, but you've enlightened me before).

You are correct about the form of the index pulse. It is not something that can be connected to the BOB in any simple fashion (I don't think) as it is a tiny ampitude square wave or something like that. If I could have used it, I would have already been pestering the electron guys for a how-to.

 

[simpson36]

Coolfox,
I agree with you completely, but you are on a different level. Many moons ago I had my own machine shop to develop prototypes and am familiar with the construction of machine tool spindles. 

I would love to use specific purpose machine spindle bearings, but the cost is way out of line with a hobby level toy sized machine. Even angular contact bearings would be a bit of overkill for the amount of stress I can actually put on them with the miniscule power that I have available. I also know that preloading deep groove ball bearings is not proper, but that's how these little mills are set up and installing some decent ABC3 sealed bearings ($100 worth of spindle bearings in a $500 machine) is as far as I think is reasonable for an upgrade. I have to stick with what I can fit in my very crowded garage with my wife's classic Vette (which is not going outside), and what I can spend on a hobby and not end up living in said garage (we have no dog house). I've already passed double what I said I was going to spend on the CNC conversion. This is not a good strategy for getting my favorite cookies.   

This is all the motor I have to work with for the 4th axis power:
http://www.homeshopcnc.com/servo2.html

This equipment will never see production levels nor will it be called upon for precision work (.0005 and closer). Those are the parameters for the project.

Yes, I would share the macros and other stuff, but it would not be useful unless you had the same setup as I have.

[coolfox]

Ok, point taken. I won't be pestering you no more :-)
The code and macros I want to have a look as a sample with info to think about and may be cut few corners :-)
I just was looking through my stuff and came across spindle just like you described deep groove sealed bearings 6203RS screw shaft M19X1.3mm cans say for sure may be imperial for the chuck or else with 15degree looks like for ER 16 or similar collet other end is 15.85mm diameter 21mm long hoke through 8.5mm
center height 65mm clamps on 60mm wide dove tail with I also have I used this for grinding once 5 years ego :-)
Interested?

[Bloy]

Yes, I would share the macros and other stuff, but it would not be useful unless you had the same setup as I have.

Hi simpson36,
   I think your setup is great!  I'm intermiittantly building a similar system also using a cheap spindexer...
I've never actually written macros on my own, but have modified a few.....
  Seeing your macros and learning how you integrated your moves, axis swaps, and homing would be highly benficial ..... I think..
  I've often only dreamed/ponderd of doing just what you have done....
So, if you wouldn't mind, I like to see your macros....


Thanks,
John (Bloy)

[simpson36]

Coolfox, You're not pestering me. I enjoy conversations and debates on topics that interest me. There is always something new to learn. That's one of the enjoyable aspects, second only to actually designing and building stuff.

Thanks for the spindle offer, but I want something that is reproducible . .  i.e. something that someone could make for themselves if they chose to follow the project and duplicate it.

Coolfox and Bloy, I'm definitely interested in starting a thread on the programming/control aspects of an combination indexer/spindle.

The macros I've written so far are just the basics to get things working.  I'm going to want to talk to the Viper drive thru the serial port, and get Mach to adapt based on the data  . . . . . that should be an interesting challenge. Hopfully enough to lure Hood and Vmax or some of the other Mach programming gurus into the discussion.


Question is, where to start the thread. General Mach Discussion, Mach Programming, or Show and tell.

[Hood]

Hood,

I don't need to read the speed since there is an encoder on the motor. The issue is homing te axis. There are some symantics do deal with . .  the 'index pulse' is an ADDITIONAL once per rev pulse built into the encoder. I can't use that with the gearing , because Mach has no way to know the position of the spindle from the position of the motor. i.e. index pulse from the motor can mean the spindle is at 0, or 120, or 240 degrees. Mach would no know which, so I have to have a n index on the spindle itself (as far as I know, but you've enlightened me before).

You are correct about the form of the index pulse. It is not something that can be connected to the BOB in any simple fashion (I don't think) as it is a tiny ampitude square wave or something like that. If I could have used it, I would have already been pestering the electron guys for a how-to.

 

Ah sorry, was not reading your previous reply correctly, was thinking you had fitted the opto for an index pulse, should have remembered it was as a home switch

[Bloy]

Hi everyone,

After much study and work and help from this forum and other resources, I have my servo powered 4th axis up and running. It does everything I wanted it to do.

In the current arrangement, the mill spindle stays active and still functions as normal.

http://www.youtube.com/watch?v=2KNit__LJE4

For now, some interesting programming is needed along with a custom macro to do the thread passes, but in time, I think Mach3 will have features to make this much better.

I don't plan to make aluminum bolts from round stock. The part just demonstrates the various functions I wanted to get working.

I just can't get over your video.  it's so neat!
  I want to apply this to my router to accomplish custom threaded dowels, or spirals, along with the other variations in the piece form you demonstrate(hex head in your case) ..all done in single code file.     That's why I am so interested in your "basic" (as you say) macro coding.
 ....gotta play catch-up....been doing other things while my machines were covered with sheets for way too long a period.