SH 350 skipping steps or software related...?

[Arjen Abbestee]

If only my controller had an ethernet connection. But I have to make do with USB...

[Arjen Abbestee]

And the problem is back...
It seemed to be gone after my software downgrade, but today I notice a difference between two items that should be identical. So I did the test again running the file from the machine. Where the last time it seemed the mistakes were identical, now there are major differences with each run. So it is either something mechanical after all, or the controller and/or stepper drivers are on a rampage. But if the steppers are off it seems to me I would have to see hickups along the path where the steppers misses steps. But the paths are all smooth, just not in the place they should be.
I did some speed tests, it appears the faster I cut, the better the result. At 100 mm/sec I don't see any mistakes, at 4 mm/sec it's off by millimeters. Shouldn't a mechanical problem manifest itself more at higher speeds?
In the pictures the lower left corner is the same for both layers. In the close up, the shorter one is wrong. But in that one the total hight is the same. So it's more like it added steps than missing them.
The pictures are from different cuts. As you can see, one has a large mistake in the x-axes, the other in the y-axis.

I'm lost...

pic1.jpgpic2.jpg

[Kev Williams]

I wonder if you have a bad wire like I did-

The stepper motors on my Triumph come with a wired plug, and the wires are about 3' long, which is about 3' too short to run thru the drag chain and down into electric hell where the other ends connect to the stepper drivers. I'm assuming many machines are the same way, and the fix is to simply butt splice additional wiring on. The problem, at least on my machine, is the butt splice was in the middle of the drag chain, where it looped up at about 17" down the Y axis. Wire bends easy enough, but the soldered ends don't...

Here's where the splice is in my Y drag chain...
chain3.jpg


-here's where the bend got really tight-
.dragchainwires.jpg

This is the broken ground wire--
brokenwire.jpg

and after my repair..
Xwires.jpg

--my machine started out like yours, a bobble here and there, although mine was usually during engraving when moving from one spot to another. Most of the time the machine was fine, but during troubleshooting I finally realized the problem always happened around the 17"-down area. The wire would seem to connect okay until it hit that tight bend. Anyway, it's been perfect since I fixed that wire!

You might do some testing, you can just use paper, fill the table with paper and run at the lowest power you can and mark (or cut) the paper. That shape in your last picture, copy that into a matrix of 15 across and 10 down (or whatever fits), then run them all, first at the speed where it messes up the most, then faster, etc... if the errors occur, check if they're confined to one area of the table- my problems occurred whenever the Y axis got more than 17" down, but stopped messing up at about 20" down, and would happen ANYWHERE across the 51" of X axis. are That's when I thought 'bad wire'. I then found that if I grabbed the Y drag chain and shook it while the machine was working, the stepper would go nuts! But mine was real bad by then.

This may or may not be your problem, but if you have spliced wires in your chain, chances are good...

[Arjen Abbestee]

My machine is not that big (50x30 cm work area) so I don't expect spliced cables. But of course it cannot hurt to check. Your symptoms are different though. In my case the fault happens all over the bed, not only in a specific area. I'll try wiggling the wires during operation to see if this will invoke mistakes.

Thanks,

A

[Arjen Abbestee]

Checked the wires, no problems there. To rule everything out I took the whole machine apart (except for the XY stage itself). That was the only way to reach the gears on the Y-axis. The gears turned out to have no set screw at all, they are simply clamped to the motor axis. But no play anywhere.
While I had the XY-stage out of the machine, I took out the belts and put them back in reverse. So the part of the belt that used to run over the smooth wheel now runs over the toothed pulley.
Put everything back together again. Took some time to re-align all mirrors etc, and than it was time for the test. So far so good. No errors and as a bonus it cuts better than before. Fingers crossed, hopefully the belts were worn and caused the errors. New ones are ordered.
Does not explain why changing the software seemed to solve the problem at first, but there may be some logic as to why the error was more severe at lower speeds.
Anyway, if this caused the problem, its solved. If not, I'll be back...

Thanks to all,

A