Frayed edges on carves

Brand new to the x-carve. When I first started printing I had nice sharp edges. Like the first couple of letters. Since then everything is pretty sloppy. Followed the suggestion inside of easel to no avail. If someone could point me in the right direction to fine tune my machine it would be greatly appreciated. The “S” below was my first carve everything else came after.

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Seems like your tool is dull.
Maybe caused by overheating due to too high rpm?

I hope not. I’ve got the manual dewalt 611 what should my settings be for different cuts.

Also I used 2 bits. The first one cut the S above and one other letter pretty much without any issue and then started fraying and jumping. The second one frayed and jumped from the start. Both only jumped when the Y Axis was going away from me.

The bits I was using:
First one was a ball end upcut.
The second was a Fluted Carbide Upcut. (I think)
They were the only 1/4" that I have and they are currently the only ones that will work with the Dewalt. All my other bits are 1/8th inch.

I run a Dewalt also but set the speed at #4 it seems about right for most . I also picked a reducer Rocklen woodworking for my 1/8 bits

Downcut bits will reduce the amount of fraying. The only negative is chip (dust) removal.

after experimenting a lot, for mdf at least, I am using downcut 1/4" 2 flute at a speed setting of 1-2 with a feed rate of 70-85. Still doing more test to find the sweet spot, but at those speeds at a DOC of .05" has been coming out pretty nice.

Upcut will pull the material up which will result in the fraying. Downcut pushes the material down which will give a clean cut, but can give a little fray at the bottom if cutting through. To combat that, have a material below to cut a little into and it usually gives good results in my experience.

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What is the best bit for cutting through 1/8" to 1/4" plastic?

I’m going to try your suggestions. I’ve got about 40 bits and all of them are 1/8" so I’m going to have to get a reducer.

To my knowledge, the upcuts or downcuts should both reduce fraying. The downcut won’t do much/any better than the upcut. The downcut vs the upcut changes the surface tear out. The downcut is better for tear out because it ‘pushes’ the tearout down and into the wasteboard below, so that tearout is reduced on both surfaces. The shearing of the spiral should reduce fraying when using either upcut or downcut bits.
Also, ball end bits should mostly be used when doing 2.5/3 D cuts. They’re best for shaping the surface. When making flat cuts, they don’t do all that well.

I get that finger nails on blackboard feeling anytime someone mentions a reducer. For less than $20 you can get a real Dewalt 611 collet and save yourself a ton of headaches. .

Also, while mdf does ‘cut like butter’ as they say, as with plywood, the glue in it quickly dulls bits.

I don’t think anyone ever answered the best bit for plastic bit. Use a single flute compression bit. Micro100 has them.