Messages

941

General Mach Discussion / Re: Backlash...

« on: November 01, 2016, 02:25:33 PM »

Tried a few different settings, I think it will be ok on the standard mill setup with 50% speed and 0.1s but on the high-speed setup its far too violent when doing V-Carve stuff as its hundreds of very short lines and it just sounds and looks rough on the old girl.

Will do an engraving test tomorrow and see how it is with the new thrust bearings in and the rebuilt Z drive.

942

General Mach Discussion / Re: Backlash...

« on: November 01, 2016, 10:26:55 AM »

Yes that would be the only way to guarantee zero backlash, but at speed its not so easy to do. The thing with gas springs or springs in general is that the force is not linear, only a portion in the middle of travel is reasonably linear.

943

General Mach Discussion / Re: Backlash...

« on: November 01, 2016, 09:40:19 AM »

Yes, this was caused my recent ePid fault query, i was trying some V-Carve engraving for the first time and i had the following error set a bit too tight.

So, whats best to do - I can't really reduce backlash anymore physically without spending stupid money on surgical grade ball-screws which is just not worth it on this machine. Is it best to leave BC off and live with it or leave it on with the risk that it will hammer the backlash worse than it is?

Or set a slow comp time maybe?

944

CS-Lab / IP-A and Servo drives, voltage matching...

« on: November 01, 2016, 09:18:13 AM »

Is it possible for some kind soul to explain if I have any issue here or not please...

I have 3000rpm AC servo motors and they are controlled by 10-0-10v from the IP-A as normal.

However, I have my motor tuning velocity set to 3000mm/min as its not a very big mill and pretty old.

With the lead-screws I have (inch) they are 5.08mm/rev and I have 2:1 belt reduction so I think the motor will never do more than 1181rpm ((3000/5.08)*2)

Does this matter or am i ok here - I'm finding confusing info about motor tuning and matching the control signal to the speed etc.

I cant change the belt drive reduction but I have found the setting parameter for the drives that reduces the motor speed per input volt.

Thanks

945

General Mach Discussion / Re: Backlash...

« on: November 01, 2016, 09:10:20 AM »

Thanks

I'll try it out on some code, do a test piece.

I've measured BL as good as i can, at three points on each axis, all axes show <0.1mm backlash at all points.

946

General Mach Discussion / Re: Backlash...

« on: November 01, 2016, 07:43:29 AM »

Here's one link...

https://youtu.be/A27nOkTFYDY

A bit long but skip to around 5:30


Dave

947

General Mach Discussion / Re: Backlash...

« on: November 01, 2016, 03:20:46 AM »

Thanks Rich,

I have re-read it and the reason for asking was that it goes against a couple of videos on the 'tube - nothing like a bit of confusion

Their idea was to go 100% speed and something 0.001seconds

I will have a play with it and see what makes a difference if anything

You can see taking the backlash out so i guess the controller is ok with it.

948

General Mach Discussion / Re: Backlash...

« on: October 31, 2016, 04:15:34 PM »

Whats teething with backlash compensation and the shuttle acceleration?

Is there a recommended setting for servos and a CSMIO controller?

Currently have it on 50% acceleration and 0.001 shuttle accel, but the shuttle thing does not seem to make much difference - what should it do?

All values are sub 0.1mm so its just a tiny but sharp knock when changing direction on jog, n to tried any code yet.

949

General Mach Discussion / Re: Backlash...

« on: October 30, 2016, 03:58:29 PM »

Replaced both sets of bearings on X & Y - got a great price from BearingBoys of £60 per pair of Nachi graded bearings.

Amazing difference, really quiet when doing rapids now, backlash is sub 0.1mm on each axis.

A little bit of compensation should get rid of that i think

950

General Mach Discussion / Re: Bridgeport Knee Mill Conversion?

« on: October 30, 2016, 12:45:21 PM »

That was a long day!

Stripped the head, cut away the small web of cast at the bottom of the quill slot, altered the screw connector by welding on a 13mm thick bar underneath, the end of the bar was milled to the curvature of the quill before stripping, fitted up, refitted the Z drive and shimmed the connector, power head back on, motor back on, encoder back on, tested.

The connector now has an extra 25mm of contact below the quill bolt which is a massive improvement over the first attempt, this makes a big difference to the twisting effect on the quill bolt and is now far more rigid in the downward direction which is what matters.

Total backlash is now down from 0.6mm+ to 0.1mm and I also discovered that most of that backlash is caused by the BK screw block not clamping the screw correctly - this was always there but never spotted it before. I will strip that block and see whats wrong with it - either crap bearings or sleeves too short and the nut not reaching properly.

I don't think this one is getting any stiffer (ooh err!)