Messages

1

Show"N"Tell ( Your Machines) / Re: CZ300 Chinese Lathe conversion

« on: October 15, 2013, 04:17:37 PM »

Sorry if this seems repetitive to others but it's exciting for me !

I made a decent attempt at getting a good quality video of the thread cutting up closer and increased spindle speed to 800RPM.

http://youtu.be/9zn0O0JOqHA

CS

2

General Mach Discussion / Re: MPG Step size mystery

« on: October 14, 2013, 07:33:25 AM »

Hi Hood

Unfortunately the step/velocity mode is more like an encoder following mode while the step/multistep mode performs individual steps with accel decel on each step making it very 'steppy'

Thanks for the respose !

CS

3

General Mach Discussion / MPG Step size mystery

« on: October 14, 2013, 04:48:30 AM »

Hi All

I've only been playing with MACH3 for a short time now so please forgive me if this is documented somewhere I haven't found yet.

The problem I'm having is that the step size I get in step/velocity mode is independant of the step size set in the MPG jogging panel and seems to be 100x the resolution/min increment for that axis.

I've been unable to find anywhere that sets this multiple (x100) hence I'm confused.

The step or multistep modes work just as expected with the step size being that selected in the MPG step size box.


Is this adjustable ?

CS

4

General Mach Discussion / Re: Lathe servo spindle setup/cal issue

« on: October 13, 2013, 07:10:34 AM »

Thanks Hood !

Worked as you suggested, all sorted now with spindle speed and resolution spot on.

CS

5

Show"N"Tell ( Your Machines) / Re: CZ300 Chinese Lathe conversion

« on: October 13, 2013, 07:08:36 AM »

I was making a part today out of steel in this lathe and was drilling a 16mm hole at about 300RPM and noticed how much better it was with this setup than the old open loop induction motor.

I also tried cutting a thread for the first time with this lathe afte CNC conversion under MACH3 and it was great !

http://youtu.be/PrUnIrXUnOM

Pitch and diameter were spot on, however I may have made a mistake in setting the infeed angle to zero since as the cuts got deeper the surface finish suffered a little since it was cutting symmetrically on both sides of the tool. Anyway it worked as hoped and I'm very happy with how easy it was in the end.
I used the built in 'simple threading' wizard.

CS

6

General Mach Discussion / Re: Lathe servo spindle setup/cal issue

« on: October 12, 2013, 07:23:20 AM »

Hi Hood

I think that I've got everything as you've described except for the two max speeds being the same.

Would be odd if that is the issue but will give it go tomorrow.

Thanks

CS

7

General Mach Discussion / Lathe servo spindle setup/cal issue

« on: October 11, 2013, 07:42:35 PM »

So I now have my lathe with servo spindle running in some fashion although there is an issue I can't resolve in the way I would expect or that makes sense. Iam running an ESS and the latest version of MACH3 and all drives are running in step and direction command interface.

So when I configure this servo to operate as a rotary axis with the steps per unit I calculate, all works well. The servo is setup to accept 8192 steps per revolution with the appropriate 'electronic gear ratio' to compensate for the 40:56 reduction of the timing pulleys. So no problems there !

However, when setup as a spindle in MACH3 I cannot use the same steps per unit. I guess that I don't really understand what this value means. So rather than using 8192 counts/rev (I have assumed this is what it means ie counts per rev) I have to used approximately 9000 counts per rev to get the actual spindle to the correct speed.

So in summary, the whole system works fine when the servo spindle is setup as a rotary axis ie counts per unit all work as expected etc. There seems to be something wrong or I'm doing something wrong when setting up to run as a spindle....

Also, I have tried running the spindle cal tool and when I press cal, the spindle gets stopped immediately.

Any help most appreciated !

CS

8

Show"N"Tell ( Your Machines) / Re: CZ300 Chinese Lathe conversion

« on: October 11, 2013, 04:09:48 PM »

Hi Zafar

Yes in terms of power the motor is oversized but in terms of torque and inertia match it is about right.

If the servo was only for turning and not indexing then I guess a 3hp motor would be more suitable.

Even so the main reason I'm using it is because I already had it 

Regarding it being C axis, you're absolutely correct, not sure how I screwed that up !

CS

9

Show"N"Tell ( Your Machines) / Re: CZ300 Chinese Lathe conversion

« on: October 11, 2013, 07:21:19 AM »

A few videos of it running although it is still not quite finished :

Running in 'indexer' mode ie spindle running as A-Axis and pretending there is a spindle mounted on the toolpost.

http://youtu.be/fLNduamJI2s

First run under CNC, note spindle speed & feedrates are all wrong

http://youtu.be/DhYdeFltGbU

Very early video of servo spindle under direct control of the amplifier ie not under Mach3 control.

http://youtu.be/BHnfT_Vr-9M

CS

10

Show"N"Tell ( Your Machines) / Re: CZ300 Chinese Lathe conversion

« on: October 10, 2013, 08:22:18 PM »

Some more pictures of the build process :

Cross Slide modifications were significant and tricky since there was barely enough room to fit the ball nut (cylindrical).

A 5200 bearing (back to back angular contact) was chosen as the bidirectional thrust and radial load bearing. Since this was large in OD than the original bore would handle and I needed room for locknuts etc, the crosslide base/carriage top needed to be bored out. Since the original cast iron material was lacking on the bottom side, I had to weld some material in place prior to boring. This ended up being a block of mild steel and welded in place using some high nickel content 'weldall' rods after heating the whole assembly to about 200degC.

Unfortunately there was a little warpage of the carriage top surface (approx 100um) and this needed to be flattened out. In the end I did this with some stones and an aluminium block and lapping paste.

There is also a radial support "anti-whip" bearing on the far end of the screw since I do spin it up to 3000 RPM or so.

After all that, the cross slide works a treat with low clearance (gib done up nice and snug) and the axis seems to repeat within a few micron or less under servo control so couldn't be happier.

Unfortunately I'm still pondering where to put the limit switches which is the next task for this part of the machine.

CS