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Sled vibration when cutting causeing chatter marks

I have a vibration when cutting with my machine. It really bounces the chains even. I did several changes to my setup all at once. There are several factors that might be causing it and Im not sure where to start. I have added the HDPE to the bottom of the sled for less friction but it has not helped.

  1. I have upgraded the z axis to the Meticulous Z axis. I have the router clamped down with plywood clamps and pipe clamps. I originally thought this was the problem but I can not get the clamps any tighter. The router seems very secure.
  2. Im using GC 1.27
  3. Im using a 2 inch vacuum hose. With a 5hp 12 gallon shop vac. It seems like this is making a lot of suction to the surface which could be causing some grab. When I shut off the vacuum it seems like the stutter/ vibration is some what less.
  4. I added some weight to the sled. Maybe if I added more it would help. I have pushed down on the sled as its cutting and it seems to take a little bit of the vibration out.

For the most part the sled cuts well. There is a chatter mark on pieces but nothing a little sanding cant take out. I would just like to come up with a solution to the problem.

if you don’t have the bit in the wood or the machine moving does it still
vibrate?

if you move the sled, but don’t lower the router to cut does it still vibrate?

How sharp is the bit? if it’s having trouble cutting that could cause this sort
of vibration.

Is this a single flute cutter? Are you using an upcut, downcut or straight flute bit? If it is downcut you may be able to slow the feed and improve your finish.

If it’s bouncing it could be the weight of you sled or frame angel. Can you send us some pictures of your set up?

Thank you

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Here are some photos of my setup

I have used both new up cut double fluted and down cut double fluted. They both have the same vibration. The down cut is more pronounced than the up cut but the chatter marks persist in both.

as I asked before:
do you get the vibration when the motor is running and the sled not moving?
do you get the vibration when the motor is running and the sled is moving?
or do you only get the vibration when cutting?

can you get a short video of the problem so we can see what’s happening?

Also, what is your cutting depth per pass? And, what feed rate are you using? That is, are you trying to take larger chunks of wood out faster than the bit can handle?

Sorry I was waiting to reply until I could get too the machine. There is a vibration just in travel with the bit up. They are new cutters as well. I’m also using a counter weight system and I think that’s part of my problem too. The pullies are too small causing the jerking I think. This morning before I left the house I put a bungee on for chain slack tension. That improved travel vibration but I did not get a chance to cut anything. I’ll post a video after I get home from work.

This should not matter, but the fact that you have vibration without cutting
lets us eliminate a lot of possibilities.

do you have vibration moving with the router off?

one possibility is that your chains are stiff and need to be lubricated.

David Lang

I general will cut in steps of .15 inches max. Rpm at 12. I usually run at Max feed rate. Which is like 30 or something idk. That being said I have been getting vibration at .05 of an inch.

I’ll lubricate the chains tonight. Any recommendations on lubricant?

I’ve seen something like this when I didn’t have my chains adjusted parallel to the surface. The chains weren’t meshing with the sprockets smoothly. I adjusted the height of the ring on my sled and that smoothed it out in my case.

It’s really hard to tell from the photos, but what’s the angle of the frame? It looks fairly vertical…

The chains should be parallel to cutting surface? I did adjust the ring due to the new z axis changing the center of gravity. I also moved the motors so the gears are in plane with the ring.

I don’t know the angle off hand but it’s the standard wood frame design. Bolt together frame it might be called?

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That’s what it looks like (bolt together) but it just seemed like it was at a very vertical angle in the photo. I think the standard design calls for ~15 degree tilt-back (we don’t know what the optimal angle is) but I think people have found issues at 10 degrees… If its too vertical, then there’s nothing pushing the router bit into the workpiece and that could cause chattering.

I might need to adjust the ring more. The maticulous z axis really pushes the center of gravity away from the surface. I’m also not using the stock z axis motor which is a tiny bit heavier.

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If the ring height needs to stay tall then moving the top bar might be the answer. It’s pretty important for the chains to be parallel with the surface.

Edit

I also moved the motors so the gears are in plane with the ring.

Sorry, I missed that, sounds like you’re already set up right.

Update:
I oiled the chains and adjusted the ring. Travel vibration is gone but vibration returns at cutting depth of. 6 of an inch. I think fine tuning the ring placement and planeing the chains perfectly will solve the vibration problem completely. Finding time to do it is the first step.

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