[Wildkard]

Hey all,

I finally got my custom sized 24x24 standard router going over the last coupe of weeks but I have been having some weird lost steps problem I can't seem to track down. The machine uses the standard linear motion system, but the Pro R&P drives, as well as the DiY nema 23 kit and an ESS. It is currently running off of my laptop, 1800mhz proc, 4gigs of ram, fully updated win 10, and I have as much background stuff shut down as I can. Getting no errors or anything.

When I first got the machine up and running as was playing with it to get used to how everything works as this is my first CNC machine it ran great. Then I had to take the gantry back off as I hadn't installed the sweepers. I ordered t-bolts instead of t-nuts and they interfered thought I could do without the sweepers, but that was wrong so I ground the down so they didn't interfere anymore. After I got it back together and squared up good I went to flatten the table top, but about halfway through, 20-25mins, I started to have a problem where everytime the Yaxis (this is the axis the gantry moves on for how I have it set up, slaved with the A) would start moving again when it came around the corner in the spiral the whole gantry would jerk like it had gotten out of square and was forcing itself back in.

After some playing I figured out that it was probably the Y motor losing steps as after it would jerk if I slowly went back towards 0 the gantry would hit the soft limit before it actually got to the end of the gantry, and the A side was always a bit ahead of the Y. At first I thought maybe it was the Gecko getting hot as it was pretty hot to the touch but not enough to burn you, I put a fan on it and let it sit to cool off but it didn't help. Then I decided to check the pulleys on the motors to make sure they were tight, they were and locktighted, no signs that they had been slipping. My motors have a flat spot on one side of the shaft and i made sure that one of the set screws was on that flat. The belts were also tight. When I had them disconnected I found out thtat the gantry was incredibly hard to slide, I think I over clamped the bearing slides when I reattached the gantry, so I loosened them up and readjusted everything and it rolls good, maybe 10lbs at most to move the gantry back and forth.

This seemed to fix the problem, I could jog it back and forth over and over again, and was able to restart the table surfacing run and finish it with no problems.

that was a week or so ago, I spent the last week making jigs and prototypes of the things I am making out of .070 phenolic sheet, had no problems, machine cut great. Today I went to make my first full run making 9 of one type at a time, they are 6.5x8 in rectangles with rounded corners and some holes drilled in them, nothing fancy. About halfway through the run I started losing steps again, the gecko was warm but not really screaming hot. I disconnected the motors the gantry still moves nice and free, and everything is nice and tight. So I started thing maybe there is a problem with the one of the Gecko drivers.

I zeroed my x-axis, and setup a dial indicator and zeroed it as well, then jogged the x back and forth its whole run about 30 times and then went back to zero and it was spot on. I swapped the x and the z motors to make sure the z was working as well and got the same results, so now I am pretty sure that the ports that the x and z are attached to are good, so I swap the x with the y, and the z with the a. Still got the binding on the y axis, and the x and z axis both work flawlessly.

At this point I was really stumped, I went and checked the motor tuning to make sure that the y and a were set to the same accel and steps per. The only thin I haven't really done is swap the motors themselves around. What is weird though is that as of when I left the shop I can zero the axes, and jog the y down to the other end and almost every time before I get back to zero it will bind, and if it doesn't happen the first trip it will within a handful every time. Thing is it wasn't doing this all week and I have probably jogged the thing back and forth a couple of hundred times during that week, checking fixtures and such.

[dgage]

Contact CNCRP as they know their stuff in general but especially their machines. They should be able to help you identify the problem pretty quickly I would assume.

As I was reading I was wondering if it could be something with a cable or loose connection. By chance did you switch all of the cables around when you were trying the different motors on different axes? Did you try pushing in all of the connections to make sure they are tight, I assume you probably did? But definitely contact CNCRP and then if you do find out, please follow up in this thread so others can learn. Good luck.

[Wildkard]

I sent this same story to the guys at cncrp with thier online form.

As for the cables, they are definitely tight, they have double screw binding posts on each end to prevent them from coming loose.

[dgage]

Did you try switching the cables? A bad cable, especially with the machine vibrations, could have intermittent signal issues.

[Wildkard]

What a wierd issue, I talked with coiry at CRP yesterday, he thought it might be a heat issue with the gecko, so he had me try it out that afternoon after it had had all night to cool down. It was still doing it, so I thought it might be one of the motors doing it since regardless of which ports on the gecko they are plugged in to it was always the A axis that was losing steps. So I swapped the A and Y motors, leaving the cables alone, i.e. still driving the same axis just a different motor. And the damn thing stopped doing it, I ran it through the same cut in the air 6 times, only stopping in between to bring the axes back to 0 to check for lost steps, not a one.

So at this point it seems to have been fixed, we will see in a couple of days when the bit I snapped when trying to diagnose it the other night gets it's replacement in lol.

- - - Updated - - -

What a wierd issue, I talked with coiry at CRP yesterday, he thought it might be a heat issue with the gecko, so he had me try it out that afternoon after it had had all night to cool down. It was still doing it, so I thought it might be one of the motors doing it since regardless of which ports on the gecko they are plugged in to it was always the A axis that was losing steps. So I swapped the A and Y motors, leaving the cables alone, i.e. still driving the same axis just a different motor. And the damn thing stopped doing it, I ran it through the same cut in the air 6 times, only stopping in between to bring the axes back to 0 to check for lost steps, not a one.

So at this point it seems to have been fixed, we will see in a couple of days when the bit I snapped when trying to diagnose it the other night gets it's replacement in lol.

[Wildkard]

Ok, happened again, I have more info and a question.

Is it possible for dust build up on the rails to cause a problem liek this?

I ask becasue after I got my new bit in and installed a heatsink and fans on my gecko I have cut 2 sets of these parts and abunch of other minor things flawlessly. But ever since the last time it messed up I have been using my shop vac hose held near the bit to keep dust down in the shop and I wasnt before. Even with the vac and the rail sweepers I get this buildup of compressed saw dust on the rails over time. I had been gonna wait to make my dust shoe after I got some time to figure out how to cut acrylic correctly, but decided to make one out of mdf temporarily. I was in the middle of that cut when it messed up. I had been using the vac to keep the dust down but it got clogged and things built up pretty badly while I got it cleared. I noticed the cuts were off right after I got back to vaccing.

I stopped the machine and looked for obvious issues, and my uncle asked if maybe the dust buildup could be causing it. So I scraped the dust build up off the rails and it started working correctly again.

[LeeWay]

With dust build up, you are effectively adding thickness to the rails. This could certainly cause problems.
My plasma cutter uses the older style drives with skate bearings on fat bar.
I do some welding on the table too sometimes and I have seen a bit of spatter on the rail stall the gantry out before.
Now my usual start up consists of jogging the gantry to the far end and then homing. This lets me know my flat gantry rails are clear.

[ger21]

Is it possible for dust build up on the rails to cause a problem like this?

Yes. The dust maes the bearings to tight, and can cause them to stick or bind on the rail.

[Wildkard]

Well, had another hiccup today, machine had been running great since i got the dust collection hooked up and the rails/bearing all cleaned up. Was amazing how much smoother the gantry slid on its rails after I got it all cleaned up.

This time I didn;t even notice it happen during cutting as it didn't get bad enough to bind up, I just noticed that the later few pieces were undersized and the one edge was closer to the line of holes than it should have been as I was taking them off the table. And unlike earlier times the machine worked perfectly during jogging.

Is it possible that my speed and depth of cut requires more motor torque than my 420 oz-in motors can provide? I am using data from gwizard, 1/8 3 flute up cut ZrN coated end mill, .28 depth at 85ipm. I tried to look around for info about cutting forces but couldn't find any good information.