My circles are not round

[tag0110]

I have a shark HD. The circle pocket is cut useing a .25 EM at 30 IPM and .09 depth and step over. The pocket measures 1.466 up & down, but 1.496 side to side. I have tried changing the pocket cut to offset, raster, climb, conv. it always cuts not round. Thanks in advance for any suggestions.


Andy

[baby15]

I have a shark HD. The circle pocket is cut useing a .25 EM at 30 IPM and .09 depth and step over. The pocket measures 1.466 up & down, but 1.496 side to side. I have tried changing the pocket cut to offset, raster, climb, conv. it always cuts not round. Thanks in advance for any suggestions.


Andy

you might try to level router with some wood shims

[tonydude]

You can tell by looking at the circles that your router is not Parallel to the bed of the shark. Put a square against an endmill in the router and shim behind the router mount till it's parallel to the bed of the shark. Mine was off about 1/8''

Tony

[tag0110]

I had to add a .02 shim under the front side of the router clamp to make it perpendicular to the table. I ran the program with the exact same result (less lines to sand out though). Any other suggestions?


Andy

[milo30]

Have you tried creating another file to cut a circle and see if you get the same results? I would try that before searching for other problems if you haven't already.

[drueth]

tag0110

I would check two things Are all the screws that connect the drive motors to the worm drives tight. The Y drive would be my first one to check. You most likely have to remove one deck plate to be able to get your hand in there. With the controller on you should not have play in any worm drives. useing only two finger can you turn the drive shaft does it have play in it.

Your speed and depth of cut should not be a problem but if you turn the wood 90 deg. so the grain is running side to side does the cut still show the problem is in the Y direction and ok in the X. I have done many test cuts in 2x4 and have found some of the wood grain can cause some problems. The wood looks like pine and I would not expect a problem with the pine?

[BillK]

Looking very closely at your cut as you can see in the attached photo you don't have a true circle but a circle with flat lines at the top and the bottom.

Did you use the circle command in the software to create the circle? Or did you use bitmap trace for it? Click on the circle in you program with the node tool and if you see multiple nodes you don't truly have a circle. The Gcode should also show that.

[tag0110]

Bill,
My circle was created using the circle feature in vcarve, it has 4 nodes. The g code also has 4 G03's (clockwise circle points).
I included the tap file if someone would like to run it and see what they get. It starts on center with a .25 EM, and a 4"tall x 7"wide piece of wood.

Drueth,
I have made test cuts in cedar, aspen & pine with the grain going in both directions. I need to cut 2 projects out before I can take my table apart, but this will be the next thing I try.

Milo,
I have tried a couple different circles, all different sizes, with the same result. I remember a couple months back doing a profile cut-out that was not round.


thanks
Andy

[rungemach]

Hello Andy

I cut your file in my machine in solid pvc, and get two circles with measurements that vary from 1.646 to 1.648 or about two thousandths out of round worst case across the two pockets. That is pretty consistent with what my router will hold. I cut a 1.5 test pocket and that came out 1.492 with the particular bit I was using, so the tool is about .004 under the .250 nominal.

That would give me a true size of around 1.655 or so for your diameters on your pockets. is this anywhere close to what your design diameter was in vcarve.?

I am running mach3 on a modified shark, so my test circle was run with the mach3 post processor, not the shark version.

At any rate , it shows the error in diameters is not built into your gcode. it is a machine issue.
Your depth and feed rates are not unreasonably fast.
Since the x and y are giving you different sizes, I would suspect things like loose lead screw couplers, worn lead screw nuts, overall backlash (loose bearings)on either those axis, router loose in mount, etc. Do squares cut on your machine vary in size also?

tap file run in pvc stock, mach3

[tag0110]

I found a loose lead screw for the Y axis. Now my holes are almost perfect (about .002 off) I wonder how long it has been loose. Should I locktite this screw? The tap file I posted should have pockets at 1.65

Thanks again
Andy