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aarongough
07-11-2011, 01:51 PM
Hey all!
I bought Vectric Cut2D a few days ago and have been having a weird problem with it...

If I create a square that is 4"x4" and then create an outside profile toolpath for it, the square consistently comes out at 3.95"x3.95".

I'm cutting MDF and I initially thought this was something to do with the material, but upon double checking any pockets cut are the right size to a tolerance of about .004

If I create an inside profile toolpath for the same 4"x4" square I get a cutout that is 4.05"x4.05"...

I'm really not sure why this would be happening, the tool setup is correct and I can't seem to see any other problems. The fact that the pockets are the right size is the weirdest part...

Anyone have any idea about what might be going on?

ger21
07-11-2011, 07:10 PM
Tool deflection or machine flex, maybe? Try cutting in the opposite direction and see if the size changes?

Also, let me see the code for a 4" square.

aarongough
07-11-2011, 07:15 PM
Tool deflection or machine flex, maybe? Try cutting in the opposite direction and see if the size changes?

Also, let me see the code for a 4" square.

Thanks for the response Gerry.

I also thought it might be something like tool deflection... But in that case I would expect to see the same deflection in pocketing toolpaths as well, and so far I have not been.

I'll copy in the generated G-Code when I get home tonight.

Tony Mac
07-12-2011, 08:11 AM
Hey all!

If I create a square that is 4"x4" and then create an outside profile toolpath for it, the square consistently comes out at 3.95"x3.95".

If I create an inside profile toolpath for the same 4"x4" square I get a cutout that is 4.05"x4.05"...

Anyone have any idea about what might be going on?

Hello Aaron,

Could the cutter be slightly larger than the diameter specified in the software?

For example, if the actual cutter diameter is 0.050” larger than the dia specified in the software. When cutting around the outside of the vector, the result would be to overcut by 0.025” on each side of the 4” x 4” square when run on the machine = 3.950” x 3.950” undersize by 0.050”

When cutting the internal pocket inside the vector, the tool would also overcut by 0.025” per side = 4.050” x 4.050” oversize by 0.050”

Spindle run-out could also be another reason for the overcutting??

Maybe machine along a line and measure the width of the groove to see if this matches the diameter of the cutter.

Tony

aarongough
07-12-2011, 10:56 AM
Gerry & Tony: Thanks for your responses.

I did a series of test cuts this morning to see if I could work out what the issue is. I've attached a photo of the cuts and the measurements I took from them.

The issue looks to be a combination runout & deflection. I hadn't realized exactly how much flex was in my router... (Luckily I can hand off the blame for that as it was built from a kit)

A slot cut using a .125" endmill measures at ~.140", which I would attribute mainly to runout given that my spindle is a Dremel. There is also tool deflection visible when the cut changes from plunging to XY movement. I measured the deflection at ~0.038"

So I assume I can compensate for the runout to an extent by setting the tool width to equal the measured slot width, however I am confused by the fact that the circular pocket cut is within tolerance at .505"

The tool deflection is starkly illustrated in the attached image by the difference between the two halves of the slot at the top of the image. One side was milled conventionally and the other was climb milled.

Any tips you guys have for compensating for the shortcomings of this machine would be great. I'm part way through the build of a new machine to replace this one, but I had anticipated using this machine to make parts, which now looks like it may be not such a great idea.

Thanks again!
-Aaron

aarongough
07-12-2011, 11:17 PM
So I've spent the afternoon making test cuts with different paramters to see if I can find the sweet spot for this machine and material.

The test cuts in the photo above were made with a .08" DOC @ 12 ipm. That may sound slow but remember I have a *very* flexy machine...

After numerous test cuts I have managed to get a near perfect result with these settings: 0.015" DOC @ 42ipm. I also adjusted the tool diameter to match the diameter that I measured from test cuts which was .143" (from a .125" endmill! Talk about runout.)

With these settings I am able to get profile cuts to within .001" of the expected size, which is good enough for the work I'm doing.

The much smaller Depth Of Cut also seems to completely remove the tool deflection I was experiencing earlier.

Pockets are another matter though as they are consistently turning out .02" undersized. Compensating by making the pocket in the CAD drawing .02" oversized yields a result to within .001" tolerance, but seems a little hacky.

If anyone has a suggestions about possible causes of the undersized pockets I would love to hear them!

Ron Dunn
07-12-2011, 11:34 PM
aarongough, is that a Dremel 300? The runout sounds awfully like my experience.

I found that 30-40ipm (depending on wood type) and .04" DOC was right for me.

aarongough
07-13-2011, 01:14 AM
aarongough, is that a Dremel 300? The runout sounds awfully like my experience.

I found that 30-40ipm (depending on wood type) and .04" DOC was right for me.

Hey Ron!

I'm using a Dremel 4000, but obviously it isn't great either. I'm looking forward to upgrading to a Bosch Colt on my upcoming machine, that's for sure!

kiwichris
07-15-2011, 06:39 AM
One thing I found with my Dremel was packing out the bearings in the casing helped the runout/slop/wobbles quite a bit.

I thought it was bearing runout, but it turned out the bearings were fine, but the upper one was actually moving around inside the case. Mine is a 395

Something easy to check anyway...

aarongough
07-15-2011, 09:02 AM
One thing I found with my Dremel was packing out the bearings in the casing helped the runout/slop/wobbles quite a bit.

I thought it was bearing runout, but it turned out the bearings were fine, but the upper one was actually moving around inside the case. Mine is a 395

Something easy to check anyway...

Thanks for the tip! I will definitely check that out.

I'm already part-way through the build of a better machine that will use a Bosch Colt as a spindle, so hopefully that will help get me away from these problems in the future.