User avatar

Options

Inconsistent cut depth (not levelling-related)

Hi! I noticed on some pocket cuts that the actual cut depth on neighbouring paths can vary by as much as 0.6mm - my only theory is that this is caused by the head flexing when cutting towards one path in one direction and the neighbouring one in the opposing one, but the difference seems extremely large, which is worrying me a bit, and is forcing me to do a lot of cleanup

Some details

  • 1500x1500 machine, mafell router head
  • these pockets are along the Y axis, but the same issue occurs when cutting in Y direction
  • These particular ones were cut with a 6mm 2 flute downcut endmill, at about 12k rpm, 2000 mm/min, 3mm depth of cut, in birch ply
  • stepover was quite conservative (about 3mm)

I’m also having problems with chatter and vibration in the router head - I’ll make a separate post about that, but mentioning it here as I wouldn’t be surprised if the problems are related

Block Image

Block Image

Answer this question I have this problem too

Is this a good question?

Yes No
Score 0
Add a comment

4 Answers

Filter by:
Most Helpful Newest Oldest
Most Helpful Answer
User avatar

Options

Hi Rob,

Thanks for your question.

For your speeds and feeds, I would say the RPM is a little low. I would increase it to 18k rpm and see if that helps.

Also, 3mm pass depth could be a little deep for birch ply. Have you thought about doing 3mm pass depths, but on the last pass, reduce it to 1mm so you can get the bottom as good as possible?

Thanks!

Was this answer helpful?

Yes No
Score 1
Add a comment
User avatar

Options

Hi Rob,

Ok does the endmill you are using give a recommended RPM or just a chip load? I just based my value on Amana Tool datasheets and found an endmill that sounded similar to the one you were using.

I think 3mm could be fine for hogging, but I would reduce it for a finishing path.

Thanks

Was this answer helpful?

Yes No
Score 1

Comments:

It is an amana one, I actually haven’t been able to find exact numbers for their metric endmills, so I’ve been going off the 1/4 inch one and just using the formulas.

Their datasheets indeed all assume 18k rpm, but that’s for 4500mm/min at up to 6mm DOC (and obviously assuming a very beefy industrial machine). I’m finding it quite tricky to toe the line between taking chips that are too thin and overloading the tool, but I do think my assumptions are skewed towards the latter because of how aggressive all the values in the datasheets are.

I’ll try out higher RPM combined with a gentler finishing pass later this week. I did actually try this with a similar upcut endmill before and still got a lot of vibration and chatter (to the point where i had to stop the cut), but I think I need to go back and test a bit more systematically.

by

@kirberich Hi Rob, I see, we always stick to their stated RPM regardless of chip load. The datasheets are very aggressive, so just tone down the pass depth, and try to keep the feedrate higher so you do not rub.

by

Add a comment
User avatar

Options

I did see that most posted numbers for RPM on the workbee are much higher than expected - the cutter I’m using has a recommended chip load of .12mm, which results in a theoretical rpm of ~8300 at 2000mm/min - I already reduced the chip load to 0.08mm to account for the fact that the workbee isn’t the most rigid machine, but 18k would mean a chip load of 0.05mm, which to me sounds like getting close to the tool just rubbing - but maybe my expectations are off here, I’m still quite new to this!

If you have some guidelines on how far you generally derate endmills for the workbee, it’d be quite useful to know!

The cut depth is an interesting one though - i didn’t think 3mm with a 6mm endmill would be pushing it, but I’ll try with a gentler finishing pass and see if that makes a difference!

Was this answer helpful?

Yes No
Score 0
Add a comment
User avatar

Options

Hi Rob, I’m having the same issue with similar setup. Did you get this ironed out in the end? Thanks

Was this answer helpful?

Yes No
Score 0

Comments:

I did fix it somewhat - with a combination of adjusting my expectations, and attaching a huge square aluminium extrusion to the back of the X axis.

I've updated to a Onefinity since my post, but even that machine still starts chattering when using a 2-flute endmill, all these machines just aren't very rigid. But there's two things that helped make the workbee much more reliable for me:

1) I bought a large (I think 150x150mm?) aluminium box section, screwed it to the back of the X axis (this won't work on a stock workbee because of the rollers, you'd need a linear rail upgrade). This reduced twisting on X significantly.

2) Only use single-flute endmills - the workbee cannot cut fast enough to make two flute endmills work well, the chipload has to be so low they burn up, or the cut has to be too light for compression endmills. With a single-flute compression endmill I've been able to take 4-5mm initial passes on plywood without too much chatter or deformation.

by

Hi @stucks,

We're sorry to hear you're having similar issues. We appreciate the tips provided by Rob, but if in any case the issue continues, we highly recommend reaching out to us for technical support at https://ooznest.co.uk/help/.

Hope to get this sorted out for you soon!

by

Add a comment

Add your answer

Author avatar Rob Kirberich will be eternally grateful.
View Statistics:

Past 24 Hours: 0

Past 7 Days: 0

Past 30 Days: 3

All Time: 165