Problems with unpredictable behavior/cuts

Our robotics team was trying to use the Carvey through Easel to cut out a gearbox when we started running into some serious problems. We were cutting the part out of 7/8" thick delrin. Part of the way through the machine started making a lot of vibrations and really loud noises.

Our initial thought was that the machine was making a final finish pass on the thick material, which was putting too much strain on the machine. After vacuuming away the extra material and looking closer we could see erratic cuts going through the entire thickness of the material.

We decided to rerun the file the next day in a piece of 0.5" birch plywood, thinking that perhaps the thickness of the material was the problem and to see if the problems had resolved themselves. We got most of the way through the cut when suddenly the machine started making erratic cuts. I am not sure if the cuts were completely erratic, or just the part offset by about an inch.

I have run some other simple parts in between the first and second tries, as well as afterwards. Is it possible the machine lost some steps somewhere? If it did, it was off by about an inch. Is there any maintenance or cleaning I should be doing to the Carvey other than vacuuming out the chips inside the machine?


After a little more research I am thinking that maybe the problems with the thick material caused the Y-axis belt to get stretched out. Perhaps this is causing the unpredictable behavior. Any thoughts? I will inspect the belt later today and report back?

The belt looked fine and seemed properly tensioned so this does not seem like the problem. I will try again in plywood.

@CharlesChretien1 What type of cut were you doing? What type / size bit were you using?

The bit was a 1/8" 1 flute spiral upcut from the starter end mill set. The part was made up of several circles in a row to hold bearings (created with the replicator app in Easel) and then an outline cut for the block with tabs to hold it in. Everything was cut out to full depth.

The first time we ran into problems as it was cutting the first circle. At first we thought we bottomed out the bit and the collar had run into the material. When we ran again, through the same circle we realized there was clearance and that wasn’t the problem. The next time through it was working hard through the finishing pass of the circles, but doing OK. Then it got most of the way through the outline and decided to jog in the Y direction (as it was making a cut in the X direction) and dig into the material at almost full depth, therefore causing a lot of noise and vibration, at which point we paused the machine. It did somethign similar when we were cutting out of wood, but the problem never occurred in the same location of the part which leads me to believe it is a hardware issue.


@CharlesChretien1 So your bits do have depth collars on them? The 1/8th bit in my starter set measures 18mm from the cutting tip. If you’re cutting a depth of 7/8th, that collar would definitely interfere.

My Carvey was a little loose. If I held on to the right and left ends of the X carriage I could rotate it up and down (moving the bit towards and away from me almost 3mm).

I fixed this by using a 2.5mm allen key to take off the 4 screws on each side of the X end, then removed and re-installed one at a time each of the 2 setscrews underneath on each side. While out I added blue locktite to each setscrew. After this the Z axis is a lot more rigid and there aren’t the same cut defects on inner pockets where the machine plunges.