Hard time figuring this out

[andyb]

Ok Guys,
I need help on this. My brain is fried. I am cutting a 6"x6" piece of .25 acrylic with a .1875 pocket that is .125 deep for a customer. See the attached pic. I'm using an Onsrud 63-510 bit for acrylic. Here is the problem. The 6"x6" cuts out dead on the pocket cuts .125 deep but the pocket does not cut the content width of .1875. The pocket on side A down the X cuts .164 wide, the side D down the Y cuts .169 wide, the side B cuts .168 wide and side C side cuts .175 wide.

Now I can see if the piece cut out the wrong size that I may have a machine problem but like I said it cuts dead on. So why is the pocket cutting out 4 different widths. One other thing is that I move the material around the table and zeroed the X and Y there then cut a sample. I have cut six sample and the problem is content.

Andy B.

[RoutnAbout]

Hi andy,
After looking at the tool specs, I wouldn't think the tool is flexing, but its possible.

After adding up your geometry, your pocket should be .188 wide on all 4 sides.
After subtracting your measurments of the pocket width, leaves a difference between 0.019" and 0.024" divided by 2 (for inside and outside for pocket1 toolpath) equals 0.012" and 0.0095".

Acrylic is a funny thing to machine. I'd try running the toolpath a second time without moving the material or changing the toolpath, hoping it'll clean the sides up.

You might also plunge a sample hole in a scrap piece to make sure your tool is cutting the diameter marked.

[mezalick]

Your gantry may not be parallel to the spoil board.
Just a thought.
Michael

[andyb]

Don,
I have also tried to run an inside profile of the pocketed area and am getting the same results. With the outside cut being dead on I would have thought that would solve the problem but it didn't.

Michael,
I'll check that out. Thanks.

Andy B.

[RoutnAbout]

On the inside profile of the pocket, you might try reversing the direction of the toolpath.
Other than that I don't know what it could be....
Let us know if you figure it out.
Good luck

[Bob_S]

Andy
This may be a dumb question, but have you gone back and checked the spacing of the vectors with the software. I had one a few weeks ago that I had bumped a vector by accident and never noticed it into I ran the final cut. It was off a lot so it was easy to spot but I'm sure I've done it before and it's been only off a few thousandths

[andyb]

Don,
I haven't tried to reverse the cut. One other thing I'm going to try is to reduce the step-over. I have seen one other time were the changing the step-over fix a problem.

Bob,
No question is a dumb question but yes. That was one of the first things that I did.

Andy B.

[esteeme1]

Hi Andy,

Did you try running the same file a second time on top of the first cut? If so did the bit cut in the same position? What are the second measurements? This sounds like a backlash issue. What happens if you cut an outside profile only not a pocket? Is the square perfect to the selected vectors?

[andyb]

Jim,
I have already created the profile toolpath and is cuts along the same inside and outside line as the pocket, so no change to the measurements. I'm beginning to wonder if it is something in the file itself.

Andy B.

[esteeme1]

What hapens if you cut it a second time?

[andyb]

Jim,
The same results. That is what is making me think the file. The only thing that I haven't done is recreated the file. The original file was a DXF created by the customer that I imported into Aspire.

Andy B.

[esteeme1]

Are the vectors grouped? If so I would ungroup them and use the centering object/vector tool to center one within the other Even beter just offset the vector to the selected pocket thickness.....of course I know you know just jabbering now.

[andyb]

Jim,
They are ungrouped and centered. I even offset both the inside and outside vector to make sure that they were the .1875 all the way around. Like I said I did the profile as you mentioned in an earlier post. If the outside is cutting the correct 6x6 for the cutout a profile on the pocketed vectors should give the correct cutout widths but it is not. That is what is weird about this.

I have several things that I have to try. Production is limiting my testing right now.

Andy B.