Messages

1971

General Mach Discussion / Re: THC moves on the Z axis...

« on: February 13, 2016, 11:55:40 AM »

I see what you are getting at - reducing Z max speed to increase THC rate ?

I can see that might be worthy of testing, will slow probing down a tad but whats a second here or there???

1972

General Mach Discussion / Re: Educational Sources???

« on: February 13, 2016, 11:50:59 AM »

Thanks
 

1973

General Mach Discussion / Re: THC moves on the Z axis...

« on: February 13, 2016, 11:50:17 AM »

So reduce speed again, increase acceleration and check it under THC control?

Back to 1500 again or compromise at 2000 maybe?

I can use the keyboard as THC inputs again and just flick the U/D keys.

1974

General Mach Discussion / Re: THC moves on the Z axis...

« on: February 13, 2016, 11:01:07 AM »

So i should put the speed back down and take advantage of lower motor speed but increase the acceleration rate?

Currently 3000mm/min and 3000mm/s/s

The speed in homing for Z only adjusts the final stage - the slow bit before contact, it was the first rapid stage that had the issues - like it missed to use acceleration sometimes.

1975

General Mach Discussion / Re: THC moves on the Z axis...

« on: February 13, 2016, 10:53:56 AM »

I have a total of 70mm Z travel, I wanted to keep it tight to help prevent wobble etc as it is usually cutting at near full extension.

A 4th axis or tube cutting was not a design consideration so adding one would be hard.

Yes I may have overstated the irrelevant part of backlash but with about 1.7kg on it, the z would have to get very stiff i think before it stopped responding to small moves due to backlash.

1976

General Mach Discussion / Re: THC moves on the Z axis...

« on: February 13, 2016, 10:16:11 AM »

luckily backlash is irrelevant as gravity will keep that in check for a plasma.

How long it lasts is anybodies guess

1977

General Mach Discussion / Re: THC moves on the Z axis...

« on: February 13, 2016, 08:58:12 AM »

Well I gave it 100 repeats of each test, I only used a travel 0f 55mm on Z as it trips at 65.

At 3000mm/min in motor tuning, it passed 100%, I started out at Z1 with a feeler gauge on a test plate and after each series it was back at Z1 perfectly.

I tried 4000 in tuning but it was not happy and stalled after two repeats.

So using the 75% of stall setting rule I put it back at 3000.

I did try a couple of simple test cuts and it ran fine, no skips in the G28.1 anyway, also left the THC rate where it was before so that is effectively doubled now I guess and still seems happy, or at least I could not see any sign of see-sawing on the Z axis in the cut.

Did not try G02/3 as not enough knowledge there yet

Now need some jobs to run.

Does not explain why a different screw made any difference though, the only other change was that the nut is now brass and not delrin, don't know yet if thats good or bad though.

1978

General Mach Discussion / Re: THC moves on the Z axis...

« on: February 13, 2016, 08:05:07 AM »

Going out  to try it now.....

1979

General Mach Discussion / Re: Educational Sources???

« on: February 13, 2016, 08:02:16 AM »

Thanks, bookmarked

1980

General Mach Discussion / Re: THC moves on the Z axis...

« on: February 13, 2016, 07:45:24 AM »

Sanity says i should cut the rate back down and take advantage of lower motor speed / higher torque etc, but I can ONLY make the fault appear when running code, not when manually jogging or using the MDI, I am fairly certain it has only ever done it when running G28.1.

I am guessing that it set at twice the rate and twice the pitch I am actually worse off - it was doing 1500mm/min on 2mm pitch now doing 3000mm/min on 4mm pitch.

I could split the difference and go to 2000mm/min maybe?

But why only stall when doing G28.1 and why only when running code?