[mgandy]

I have had my router going for about a week now and have cut a couple of simple shapes with it. This morning I tried to cut out something a little more complex. Not a very good idea. I will describe what is happening first. Doing a simple move to check my steps works perfect, If i tell it to go 1" it goes 1.00". Great. Next cut out a square or circle again perfect ( or good enough for wood ). Then cut out something that is going to take a while, Not great. I wrote the macro that it describes in the config guide that follows:
F1000
G20 G90
M98 P1234 L10
M30
O1234
G1 X20
G1 X0
M99

After the 10 moves the X axis will come up 0.011 short from zero, So I thought to double it. After 20 moves of 20" it comes up 0.022 short of zero and it doubles again after 40 moves. I have a moving gantry type (4'X8') with the 1200oz motors and the 72vDC supply from keling driven by 203Vs on both the x and Y axis. THe kernal speed is 35000. I have also tried the backlash function but that doesn't seem to work either. The same is happening with the Y axis also. The only difference is that is starts out as being 0.015 over with 10 moves of 20" and doubles with 20 moves then doubles again with 40.
I someone could help of have any ideas I would appreciate it.

[ger21]

What's your dir pulse width? And is the direction pin set to active high, or active low? Changing it might fix the problem.

[mgandy]

I made a couple of screens shots of how my settings are now.

[mgandy]

Lets try again

[Jack000]

couple of things to try
- slow it down and see if the problem goes away
- repeat the 1.00" experiment, but let it go back and forth a few times

the computer might not be generating enough steps to accommodate the speed of the stepper (or may not be fast enough to accommodate the pulse settings). Anyways, just a wild guess. I had that problem due to the high tpi leadscrew I used.

[mgandy]

I'm about to pull my hair out. I reinstalled mach and did my driver test. Everything shows good. The auto function that sets the steps per inch states my new value should be 1818.896532. Ok. So in my motor tuning on the X axis the steps are set to 1818.896532, max speed is 120, Step uS is 0 and dir is 0. I open the jog screen and set the cycle jog step to 1.0. Next I zero the caliper mounted to my X axis. I make 4 moves in the + dir on the X axis and come out with the following: 0.995, 2.014, 3.034,and 4.055. I zeroed it again and made 4 more moves in the - dir and had these values: -0.995, -2.012, -3.031, and -4.047. I have checked everything I know. Could this be a drive problem (203V) or a motor problem (KL34H2120-42-8A). My pc has 2.5 GHz pentiium and 2 GB of memory. The only software that has been installed on it is Windows XP and all of the updates and Mach3. The kernal speed is also set to 25000.

[Lemo]

Set the velocity and acceleration way down for the axis in question in motor tuning and try again. You might be issuing to many steps in to short of a time for the poor guy...
Lemo

[ger21]

I open the jog screen and set the cycle jog step to 1.0. Next I zero the caliper mounted to my X axis. I make 4 moves in the + dir on the X axis and come out with the following: 0.995, 2.014, 3.034,and 4.055. I zeroed it again and made 4 more moves in the - dir and had these values: -0.995, -2.012, -3.031, and -4.047. .

Does the DRO read 1, 2, 3, and 4, and then -1, -2, -3, and -4? If it does, then try it in a different area of your machine. Could be that the screws has some pitch errors.

And this is not the same issue that you're first post had.

[mgandy]

Yes, the DRO reads correctly. I am using rack and pinion on the X and Y axis.

[ger21]

Looks like you could possibly have some backlash, causing the first move to be short. Then you're steps/inch are off a little, causing it to go a little too far on each move. Just a guess.

[mgandy]

I hooked up my o'scope to the step and common on the 203V and ran it. Should I be getting 25KHz. I am only getting 3.3KHz and 5.5V at 120 ipm which is the max on the motor tuning. I will post pics of my setup later today. Thanks for the help so far. I am also using the C11 from CNC4PC. Should I try to go directly from the PC to the drives?

[mgandy]

Back again. I have been trying to set the steps per unit using the button on the settings page. I have a caliper on the axis and I zero it. I tell mac to move 2" and the DRO says it moved 2". In fact it only moved 1.980. I put that in when it asks. I move the x in the negative dir a little bit then zero my caliper again. I repeat the function but this time it goes over by 0.016. Every time I set it it is different. It never really goes the distance I set it to.

[ger21]

I move the x in the negative dir a little bit then zero my caliper again.

You need to move back positive again. If you have backlash, you need to take it up before you measure.

Don't use the automated function, just calculate the steps yourself. If you tell it to move 2" and it moves 1.98, multiply (1.98/2) x your steps per inch.

[mgandy]

Is there any way to measure backlash or do I just guess?