I have a shapeoko five Pro with a 2.2 kW spindle. I’m working on a three-quarter inch Baltic birch plywood project and wondering if anyone has found the maximum or has recommended feeds and speeds with a compression bit?
I have been running a 1/4” single flute compression cutter with a roughing pass at 22k rpm 105ipm .60 DOC .010 stock left over followed by a 150 IPM .12DOC and that works pretty well and is fairly fast. Noise is terrible. First cut leaves a rough finish but second is quite clean.
I was also running a 1/4” 2 flute at 22k rpm 180 IPM .6 DOC but it broke not long into that pass not sure if it was because of chip evacuation or tool load. Machine did not bog down.
At $50 per tool it’s an expensive endeavor to find the limits.
Does your project limit you to 1/4” bit? I would use a 1/2” bit if possible. Also your DOC is at 0.60, that’s over twice the dimension of the bit. Standard rule of thumb is DOC should be approximately 1/2 of the bit diameter. I stick to this on my Shaper Origin as well as new SO5.
Thanks for the explanation, I only mentioned the DOC/diameter based on your comment about a broken bit. I have not cut any plywood yet on my SO5 so I have much to learn.
Interesting, I have not seen a single flute compression cutter. The ones I have used have been 2 or 3 flute. Who was the manufacturer for that tool as well as the 2 flute you also tried? You only need to get depths of cut equal to the upcut portion of the compression bit. So you could lower the depth of cut a little to get the finish a bit better. With an ER20 collet I really like 3/8" diameter tooling when I can use it. Great balance between tool rigidity and forces needed to push it thru material.
The finish might be because of unsupported material if you’re cutting a large piece of material. If you’re cutting away from workholding, the material can vibrate like crazy. This is why larger industrial machines use vacuum workholding…the entirety of the material is being “held”. If I’m cutting a large piece of sheet material I have one of two strategies for the material in the middle that is harder to workhold.
A - If the design permits, I have pocketed slots I cut into the material in the middle. I cut those pockets first, with one file. I then slide in some TeezNutz and bolt down the material with large washers and cut the periphery. This has the additional benefit of removing the need for tabs for the periphery and I like anything that reduces my need to sand.
B - I will place some double sidded tape in the middle of the design on the hybrid bed slats. That will support the middle as well. Sometimes I can also leave off tabs for the periphery.
So the core question here is what are the max Feeds and Speed for a compression bit in Baltic Birch. Has anyone successfully gone faster than the recipe below?
You’ve already said the noise is terrible with this recipe (and I’m not surpised - it makes me cringe thinking about a .6 DOC at 105 ipm in plywood). When the noise is terrible, I slow it down or reduce DOC until the noise isn’t terrible. I’m just curious - Is this a one-time hobby project? Or are you doing production runs and selling this, thus the quest for speed?
I run 1/2” doc. 1/4” 2 flute compression 24k rpm 250 ipm in baltic. This won’t give you the best edge finish but I use this for roughing.
A very important part of. Compression bits. Especially in baltic. Is to never plunge into material. You always ramp in. Plunging over heats the bit immediately and it goes downhill from there. I use a 20 degree ramp Angle.
Yes the noise is terrible but it is with slow shallow cuts too. The internet is telling me all compression bits make a terrible noise?
Hobby project but the quest for speed comes from:
-minimal time to work on project and lots of cutting. Want to get it done
-knowledge for the future. Would like the next project and those thereafter to be cut efficiently
-quest for optimization. It’s no fun to be slow and steady, right?
Maybe this is a different topic but how do you bypass the 200ipm limit on the machine? If I could go 250 I’d probably do 2X 5/16 + 1X 1/8 finishing or something like that. It would also be nice of the travels were considerably faster than 200.
Makes sense. Nowhere for the chips to go. I’ve been doing angled and helical ramps and so far so good.
Cool thank you. They are set at 196IPM/5000mm/m. I will try speeding them up to 250. My next question was what is the limit so thanks for answering that
