Cutting in fits and starts - not smooth at all

So I just spent the last few weeks upgrading my Maslow to have a C-Beam z-axis, with a 800w spindle instead of a router. My test cut in thin stuff went pretty well, so I started on the big project I’ve had my eye on for a while.

However, it’s not cutting smoothly at all; see this video:

I’ve tried adjusting the spindle speed; it doesn’t seem to help at all. I’ve also lowered the feed rate a lot to try and fix another issue, but I think the fix was something else, so I don’t think I’m cutting too fast.

Any idea what could be causing this?

It looks like your spindle is twisting in the mount and that deflection is taking large material chunks as it springs back into place rather than smoothly chipping the wood as it moves along. Is there room to drop the spindle mount down closer to the work area so you get less side-to-side motion of the spindle as it cuts? or maybe add a second mount down closer to the workpiece so it won’t twist?

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That’s a good point; I had noticed that deflection, but I wasn’t sure I could do anything about it. I’ll try to move the spindle “up” in its mount, I can move it a good inch or two. I hope that does it.

I think @Orob is right. I would also look into trying shallower depths of cut. I would start off really small like 1mm per pass and gradually increase until things stop feeling good.

Thanks, I’ll have to try that as well. Although going through 3/4" plywood 1mm at a time will take a while! Hopefully I can get it up to 3-4mm with Orob’s suggestions.

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I too think that mount integrity is the root cause. I agree about shifting the router. I would move it up inside the mount then adjust the C-beam plate closer to the sled (if room allows).

I’d also consider replacing that square block of wood with a block of alloy if you could find one and someone who can bore the holes through it for you.

Stick with it, you’ll get there - I can reasonably comfortably mill 20mm deep plywood in a single pass at 700mm/minute now, albeit with a slightly bigger (850W) router and a 1/2" bit.

Believe me, I would if I could! I got as far a designing that block in CAD and got some quotes; they were not cheap…

One thing I’ll probably do, though, is moving the C-beam up on the sled and making that adapter block thinner. I have a piece of thick aluminium plate I can probably use for this; I’d be able to drill it myself.

Main drawback is that I won’t be able to use other (larger) routers. I liked to have that option, but I probably won’t end up using it…

Just a thought, but maybe you could use 2 or 3 pieces of that plate and layer them up to make it thicker? If you can drill one then you can drill three :wink:

Oooh that is painfully to watch! I went through similar situation and it was caused by flex in z-axis for me. I ended up making mounts out of hardwood and having the mounts as far top and bottom on router body as possible.

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