CNC Tuning

[ssgtbair]

I've finally completed construction on my JGRO and am at the tuning stage. I'm running a Xylotex kit with 425oz motors. I'm using an Ubuntu box with EMC2 and have successfully traveled each axis the full range of motion.

The problem arises when I try to run some G-Code and it tries to move multiple axis at once and it bind up. Does anyone know of any good tuning threads here on the forums? I've done some searching but my Google skills are failing me. Otherwise, any suggestions on trouble shooting? I'm a relative newbie in the area.

Thanks.

[ssgtbair]

Changing my step mode to 1/8 steps (the Xylotex board appears to be defaulted to this and I didn't feel like opening it up to change it) and reducing my ipm to .3 and acceleration to around 20 and it appears to work.

Haven't actually cut anything so that is today's project. Then I will get started fine tuning the axis. Right now my x axis is about a quarter of an inch off level. Hopefully I have enough play in my rails to adjust it out.

[voltsandbolts]

How's the tuning going? And how do you like emc 2?

[ssgtbair]

Well, the EMC side of things has gone well. I have settings that seem to work or did until I started to adjust my machine to try to get it level.

My problem is that the farther right I go on the machine the deeper my cut gets. I adjusted my adjustment blocks up on one side and down on the other on the long axis and the same on the short axis but still didn't get it quite level.

In the process I tightened things up on the gantry too much and as I move to one side it start missing steps when routing. So today's project is to loosen things up and if necessary (and if my problem extends pretty much the same across the bed) shim the bed to adjust out the problem. Otherwise I may just put a piece of MDF over the entire bed and mill it to be perpendicular to the cutter.

[ssgtbair]

So, I ran the StepConfig Wizard for EMC to check if I was losing steps and I don't appear to be in that test. I did however update my latency and re-ran the file without changing my machine setup at all and discovered that my problem was much less pronounced. Over six passes over the pattern I lost about 1/4 of an inch in steps on my short axis (for me on my machine it is X) Previously I lost about 2 1/2" in three passes. So I'll give it another shot with perhaps an even higher latency setting and see how it goes.

[ssgtbair]

On a related front, I'm using 1/2" 10 single start and my ipm rate is awful. I may try 1/2" 8 2 start to increase my rate. Unless someone recommends 1/2" 10 five start.

From my elementry understanding of the 425oz motors I'm using is that they produce higher torque at lower RPMs which make them ideal for the multi start. Not sure if an inch per two rotations will be ideal though. Gonna cost me a pretty penny for the rod and new anti-backlash nuts though.

[ssgtbair]

I'm still having issues, albiet smaller. On my x axis (same as before) i'm losing about 1/16" over 6 passes which results in the entire piece being skewed. Losing all of the steps in the same direction so I'm not sure what is going on. Seems that latency issues would cause problems on more than one axis and more than one direction.

Any ideas?

[TommieK]

If you can get Ger21 to answer it would be good. But in the mean time you might try slowing down your speed and acceleration about one-fourth and see if that helps at all. When I was using 1/4-20 stainless I lost steps when trying to go too fast. Hope this might help a little. Tom