Hi Guyz, Does anyone know how to get a perfect circle cut ? I mainly have issues with small sub 1" circles they come out slightly out of round and I have tried everything including axis recalibration to setting my segments to 50 and they just dont look nice.... I dont know if it is a mach thing because they look awesome in sketchup but when they cut they look close but not.
I was thinking there is a super fine tuning required to get the best mix between axis and I am not sure if anyone has ever had this issue.
Thanks for any advice in the matter

John

 

I would try cutting some squares of 1 or 2 inches and then measuring them. It will at least let you know that each axis is cutting the proper distance. Another thing to consider is the constant velocity setting in Mach. I don't use Mach but Mark explained where to set it in a post somewhere.

Just so you know if you are using .918 or later of the script setting the segments doesn't have any impact on the gcode. The g2/3 codes will be the same but it generates one line for every segment. The only thing increasing the number of segments will do is add lines to the gcode output file.

 

Humm I may be experiencing this as well. Unfortunately I've been much too lazy to trouble shoot. I will look into my similar issue soon now that I know it’s not just me, and I’m running EMC. I was cutting a circle with a plunge cut in the dead center and it's about 1/4 inch off. Other tiny circles have turned out, out of round, as well. I believed the problem to be with a bent shaft on one of my pressure rollers combined with a very fast X travel speed. Never actaully went back to check the code to be sure / messed with speeds / fixed known issues.

 

Tim, Thank you for the input... I am using 921 on this plane and we spoke before of the tabs being oversized so I have been exploding the curves and end up with the code not allowing for your great smooth transition on the arcs, all the other parts with slight arcs show the color change in the code and cut perfect... Is it because I explode these curves and there is a bug between the two?

Erik, its great to know I am not the only one !!! Like you I am making little support ring plates about 1/2" with a plunge in the middle for my 1mm carbon rod and Yes, I am getting the slightly out of round circles. My camera needs charging so I will post some pics later. My y axis was off about 1/64" and that did help a bit but they still come out oblong and my drag holes cuts look like stop signs, they are about 1/4" ... Maybe I am just being to critical
Thanks for all your help as well!!

Also guys, what would cause one notched tab set at 3mm to cut right and the other one to cut larger maybe 3.5-4mm. Everything else on this wing is beautiful!!

John

 

John, have you tried setting your acceleration and velocity to identical values for the x and y axes? I'm just thinking out loud, but maybe it could be a problem with the axes going out of sync?

Si.

 

Hi Si, that is what I was thinking as well. I had Mark navigate my computer and set things up as he had them and all the corner cuts are perfect. there doesnt seem to be a sync issue with the axis but Im not sure that certain commands dont require different settings! I know we will figure this out as a team!!! I wll post some pics later when my camera batt is charged!!

John

 

Awesome Mark, I know we were talking about this once before and you had mentioned doing the select segments... There is just so much to retain LOL!! I am going to go back and redo the wing and see if I can get the curves back!! Also I did have my Y axis off by 1/64" and that made the circles look very good but not perfect also when I do tiny 1/4" drag holes at the tail of select surfaces they look like tiny stop signs at best!! Thank you so much for the input now I can go end redo this wing Good luck with the concrete today!!!!

John

 

Sketchup attaches extra data to arcs like the start and end angle, radius, and circle center. Once you explode an arc it throws all that info away. When it comes time to mark the edge for cutting there is no arc data left to retrieve and so the G2/3 codes can't be generated and the code falls back to creating straight lines just as they are displayed in SU.

We could write a bunch of code to try and look for arcs and recalculate the data but I think it would be just as harmful as helpful. Sometimes you might want to cut out a bunch of little stop signs and then we would end up with another mode to maintain in the tools. I don't really feel it is worth the development effort when just redrawing the arc fixes the issue.

 

Yes, Tim I agree and went ahead and did this, I also found another problem when I erased the arc there were a couple of unwanted lines under the other lines which were causing a slot to cut a couple mm wider
Do you think it is even possible to get 1/4" circle to look perfect? The reason for my original concern is I work with my buddys plotter and this is also and x-y machine and they are perfect, of course the cutting device is a razor blade


John