Ridges in cut where tabs are

I’m cutting out some beefier Y plates out of 3/4" MDF for my lowrider V2 in case I ever wind up taking it apart again. It make some unpleasant sounds when cutting not sure if I’m pushing the machine too hard or if it’s normal. The cut took 16 minutes… running a double flute mill with RPM set at max with the fusion 360 calculated settings… not seeing or smelling any burning.

Anyways… I see ridges in the outside edge where the retractions happened for the tabs at the bottom even though I did a second finishing pass. Not sure what is going on or how to eliminate it. I’m thinking maybe do a first pass and leave 1mm then finish the rest?






You should always use a finishing pass (10-20% diameter), it lets you cut faster and then hone it into tolerance. You should not have that bad of an edge, MDF fresh off a cut for me needs very little post processing. Two flute max RPM you were pushing it really hard. I highly suggest a single flute. You could save some time and use far fewer tabs.

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Thanks… that’s helpful. I did some more experimenting.

Seems I was assuming Fusion 360 was changing settings based on RPM but it all works backwards from the chip loading. So, if you want the same chip loading for a different RPM, you need to make note of the chip loading, change the RPM which updates the chip loading, then change the chip loading back to the value you wanted and it will update the feed rate.

It varies on what I google but for MDF you want about 0.1 mm per tooth … at the feed rates I was using it was more like 0.02. I tried turning the RPM down to 16000 which is still only 0.03 but the X belt or stepper started skipping. While the bit was probably more than happy at those rates it introduces more forces than the little dewalt and lowrider can take.

So… to reduce the force I did shallower passes… 5mm at a time with a 1mm finishing pass and fewer tabs. It increased the time to from 16 to 25 minutes but it sounded way less hard on the machine and the result is nicer to look at. The mill was not even warm at all when it was done. I am still getting little grooves by the tabs but they are not as deep. I have some single flute bits on order. I think once those arrive and if I up the feedrate by 60% and do faster shallower passes I should be at 0.1mm per tooth.

That would put me at about 1600 mm/min feedrate. How does that compare with what you do?


Have a look at a few of my recent videos to compare what you are running. I have a calc and numbers I prefer on the basics page. I suggest using estlcam until you find some decent numbers that work for your machine. Fusion’s CAM is extremely complicated and can really be the issue here.

1mm finishing pass seems pretty high to me.

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I forgot about that page… great stuff.

Looks like I am running 5 times the depth of cut at twice the speed you are… I will try dialing it back before my router explodes. I’m all done with the MDF for now but next job I’ll use your settings then the one after that with my calculated one and compare. I’m so deep into fusion at this point the only way is forward. Maybe I’ll write up a little summary after I get it all figured out.