cnc crashes when cutting 2D profiles in wood

[chrisobrien07]

Hi, this is my first post here so thanks in advance for your help

My set up details are follows
CNC machine: Ooznest Workbee. screw driven.
Makita router for a spindle (1/4 inch collet)

Bit : Melin Tool Carbide Square Nose End Mill,
2 Flutes,
75mm Overall Length,
6mm Cutting Diameter,
6mm Shank Diameter

stock : maple or sapele 690mm(7) Long 119mm(X) wide 25mm high(Z)

I am having trouble when cutting 2d profiles through the 25mm
The operation I am trying to carry out is a 2D profile cut through 25mm of stock.
when the bit gets to be about half way through (12mm out of 25) the vibration levels increase.
This then catches the workpiece pulling it out of its clamps and the rest is history....

I increased the clamping around the workbed but the same happened again....
I have attached a few images of the setup of the toolpath for reference
if anyone can help me solve this I would really appreciate it.
I will try send image of clamping set up and the machine

Thanks
Chris

[magicniner]

For such an issue video with sound would be the best data source.
Have you tried halving your depth of cut until you don't rip your work off it's clamps?
You should be able to stall your router and axes before your work comes away from it's clamps.
Regards,
Nick

[DaveL]

Hi,
I have a workbee but have not cut anything as big and 3D as that. Unfortunately the picture of the path I find unreadable, could you repost the path details as separate pictures?
Regards,

Dave

Sent from my Lenovo YT3-X50F using Tapatalk

[Voicecoil]

You might also find using a shorter cutter helps = less leverage on the spindle mount = everything's a bit more rigid.

[chrisobrien07]

thanks for the replies folks...

I have pdf'd the toolpath settings.. hopefully that helps their visibility.
Also two short videos of typical operation.
you can see the clamping from these two videos.

The makita runs from 10,000rpm at setting 1 ... to 30,000 rpm at setting 6

https://1drv.ms/f/s!AkB76_oAdtF_guh6jjgvQ9UHM5Atwg

I have not video at the moment of the 2D contour operation itself... these are just videos from recent pieces....
let me know what you think

[cropwell]

Couple of comments :-

That clamping looks a bit flimsy to me. Also it is a bit far out from the workpiece, so the downwards force from the wing nut looks about 25% of what you could get by having the effort (wing nut) nearer the load in this 3rd order lever clamp.

The bottom of the Z axis looks perilously close to the workpiece to me. Are you sure it isn't catching when you get to a deeper cut?

I also use double sided tape a lot to stop the workpiece shifting horizontally.

Cheers !

Rob-T

[magicniner]

Follow Rob's advice, all his observations are correct, he's being very gentle when he says your clamping looks a little flimsy, it ranks amongst the worst I've seen, don't muck about, get some metal clamps and use them properly.

You have a significant lack of rigidity for what you're trying to do, your roller ways combined with the low mass of your system are allowing the cutter to bounce around and move away from the work, because the deflection is greatest at the tip of the cutter the side of the cutter can engage the work avoided earlier, as your cut gets deeper the side of the cutter will grab the material avoided higher up the wall by earlier deflection.
Getting rid of the rollers running in channels and replacing them with good quality linear slides will give you some improvement but you may still come up short on mass and rigidity.

[Dave the woodworker]

May be I am a bit late on this one but a company called RatRig do an update package for the WorkBee.