Messages

1

General Mach Discussion / Re: strange step loss.

« on: January 26, 2010, 02:07:24 PM »

I still haven't been able to try with a desktop. I ran the road runner program 5 times. The end result was a discrepancy in the x and y movements. Each run ended up with the exact same discrepancy about 0.3mm ,+- the variables of my home switches (about 0.002mm). I am thinking that the next step for me is to get a smooth stepper and run from usb. With my motor test, there is a perfectly straight line, except for an odd bump of 1/8 inch. However on the far right hand side, just visible before the far edge of the box there is an occasional large spike. Maybe 1/2 inch above and below the line. The test comes back as a pass but maybe I am on to something here. Does the smooth stepper require the same sort of computer control from mach, or is it more like a standard setup where the computers processor just sends out standard usb serial info for the smooth stepper to decode.
Bazza

2

General Mach Discussion / Re: strange step loss.

« on: January 25, 2010, 05:33:24 PM »

Unfortunately not. I do have a motherboard and a couple of ods and ends that I might try and cobble together.
Bazza

3

General Mach Discussion / Re: strange step loss.

« on: January 25, 2010, 05:16:32 PM »

So some more info. I have tried sherline mode, I have tried running drives at 250mm per min with acc of 1. Still the same. I have repeated it over and over and the amount of lost steps are near enough to be exactly the same. So I tried swapping z and y drives by pin selection. Exactly the same. This counts out my mill. I tried adjusting the voltage to the first buffer chip on the parallel port input. I tried it at 5v. 4.5v. 4v. 3.5v and 3 volts. By doing this I would be varying the required input high signal. If the problem was that the computer was not always sending a good enough signal the amount of lost steps would change as the hysteresis of the Schmidt buffer chip changed. However the discrepancy was exactly the same.So I have to figure its in Mach3. Or still in the computer. Any ideas?
Bazza

4

General Mach Discussion / Re: strange step loss.

« on: January 24, 2010, 01:42:00 PM »

Hollydog, I read your posts on engraving at an angle. Tell me was your original 2 boards usb or parallel?
Bazza.

5

General Mach Discussion / Re: strange step loss.

« on: January 24, 2010, 01:30:07 PM »

Ok to answer a few questions. Yes I am using stepper. Without the motor attached to the z it does not drop.It is however easier to turn the screw down than up. I tried with a heap of rubber bands on it to support it with no effect. I then discounted that as being a problem as when I reversed the motor wiring and software direction, the step losses followed the software and lost its steps on the upstroke. I will reduce the acc and try that. I think I did already try it at 1 with no effect but will try again.I am running pulses at 5, I will try sherline mode. Whats the difference with sherline mode?
Bazza

6

General Mach Discussion / Re: strange step loss.

« on: January 24, 2010, 12:19:18 AM »

I have tried both, one is better than the other. Can someone explain the difference between the 2 and its accumulated effect
Thanks Bazza

7

General Mach Discussion / strange step loss.

« on: January 23, 2010, 11:12:37 PM »

I have constructed a new mill and have come across a strange problem. My z drive has been losing steps. It was losing them in the negative way and the bit just gets deeper. I tried slowing the drive down. I am running at 300mm per min with an acc of 6.8. still the same. I swapped a motor from my y to the z. Still the same. Now if I swap the wiring on the z, so it is set up to run the opposite direction then set motor outputs to be "dir low active" unchecked. I then loose steps on the up stroke. So I wrote some code, g01 z0, g01 z-30, g01 z-35, g01 z-30, g01 z-35 etc till I had 100 up and 100 down movements. Then went back to zero and was within .002mm so no lost steps. I cant see it being a motor problem as I changed it. I cant see it being a mechanical problem as when its wired in reverse then sent fwd with software the step loss follows the software. What am I missing. I am using a dell laptop d610 that is exclusively for the mill. The motor tests are great. I am using univelop 4/5 axis drivers. The particular code that is giving me problems is a converted jpeg, so there is tons of minute z movement.There's a total of 30,000 lines of code. About 50% of the lines have a z directive in them. After the program runs the z drive is out by about 6mm or some 3700 steps. Some of this movement is smaller than my resolution. I presume that if the command is less than the resolution then there is just no movement. I also presume that mach keeps tally of the numbers though and still calculates them into the next line. Is that correct? What should I try next?
Many thanks Bazza.