Missed steps, I think!!


Back again. After thinking I had a low power issue, I upgraded all software and settings to your recommendations, and changed the end mill I was using. All seemed to be working until yesterday when I tried to cut some 10mm hdpe. I was cutting at a feed of 15mm/s with a 3mm single flute endmill at 3mm per pass, 12k spindle.

As you can see from the pictures it seemed to be cutting perfectly with well defined chips, until the third pass of the final cut line, when suddenly it just went cutting across the whole piece.

On closer inspection of the wholes it did cut, there seemed to be a slight step to the left on the x axis.

Motors and drivers were not hot.

Any ideas what would cause this? Has I going too fast? Did I loose steps?



It could be so many things at this point. How big is you machine, what spindle, how far out is the z axis hanging? How far out is the bit hanging?

You want to move the work piece closer to the gantry, and the bit in as deep in the collet as possible.

Check your pulleys, are they all good? loose pulley will still work but causes steps like that.

The edges of that do not look very clean at all, I would say take it down to 2mm/pass and see how that looks. Just make a small test square and do some cuts.

The bit will run away if it bites off more than it can chew and, to me, from those pics, I think you might have been running it too hard. or you have a large or tall machine and there was some flex happening.

In my opinion, you are going too deep. Try to stick to 1-1.5 mm per pass and increase the speed to compensate. Especially with a 3mm bit, it’s not recommended to go too deep.

Also, check that your drivers are correcty set up, it’s possible that they don’t send enough current to your motors. Drivers should be slightly hot (but not too hot!!)

My machine is 3x3. Pulleys seem fine and everything seems rigid enough.

What would have caused it to suddenly take of in the wrong direction? Is that missing steps?

I’ll try going at 1mm pass. Should I keep feed at 15m/s? Should I use a finishing pass on hdpe?

Drivers are actually set for slightly higher amps at 0.8v. I’d say they were around body temperature.



P.S. I use shielded wire for my steppers, grounded at one end to the Ramps ground. When we say ground do we mean the negative of the ramps board? or to an earth supply?

Make sure your router is plumb. If the bit is canted when you get down to your last couple passes there might be enough of a slant to cause it to grab the full depth of the material you’re cutting. When it does that it can pull the bit into the material even more, which sets the whole thing off to the races. I’ve done that in half inch plywood.

Grounded is to earth.

Weird things can also happen when you ask for more speed than the firmware allows. Make sure the non-cutting movements aren’t trying to go too fast.

Never thought to check the router for plumb. Cheers

I’ll try keeping the feed at 15mm/s, but reduce pass to 1mm, and earth the stepper cables.

Hopefully next try will work better.