The Shapeoko Forum • View topic - Problem with circles Thought this might have been your issue but if you're using Mach3 not really sure.
I'm scratching my head now. You just know it is something obvious!! Try, 20 lines say 4 inches long, in the Y axis. Then 20 lines in the X axis. 20 lines diagonally to the right, and the same to the left. Then use character C shape, the flip that shape horizontally. And finally 20 circles. It doesn't need to be deep to start with. Maybe have the depth increasing with each line? Give it a try.
First of all thanks to both you Jimmybuckets and GrayUK for sticking in this search for the problem with me, really appreciate it. GrayUK: those lines on X and Y should they be crossing each other? And should i use the C shape to make circles? Depth is that really an issue? im reproducing the same patterns with a marker stuck with zipties to the next of the spindle, so there is no force in play that is responsible for this? Or is the increasing depth for some other reason? (just me that doesnt understand )
Just single lines in one direction, and then in the other direction. You are looking for any deviation of those lines. The C shape is to create a curve in one direction, and then in the other. You can do it with a pen, but cutting will add the additional stress that may be needed.
backlash is the enemy! What is backlash? Detail of CNC machine tool backlash in ballscrews, bearings, gibs, and servo backlash.
Just rigged up my mpcnc again ( a 3d printed machine with pipes and bearings as linear guides) with the same electronics i use on the ox. The mpcnc moves flawless compared to what i can get out of the ox. Gotta say im getting dissapointed putting out all this money for this machine, and it cant even move a pen over paper in correct dimensions. How is this machine supposed to be able to mill anything?? (the mpcnc is 600x600 with gt2 belts and the ox is 750x750 ) This is the ox: And this is the mpcnc
I know how frustrating it can be. You are missing something and you will kick yourself when you find it. Are you using the identical set up for both? As in are they both being run on Mach3? Or are you running MPCNC on GRBL and OX on Mach? If it's the same then you have a mechanical issue.
No it doesn't come with double belt. And if it doesn't it should at least be able too draw correct with a ballpen.
If you don't have drive on both sides of your gantry that is your problem most likely. These aren't full list in the normal sense. They are more like 85% kits with some end user final finishing. But yeah it should have 2 drives on the gantry.
Is anyone else having problem cutting circles? https://www.google.com/url?sa=t&sou...vOQaSeQmA9w-aREBA&sig2=NohUKY5C4RrYJ9wzaKZW3Q I found this on CV angle settings.
Isnt this to compensate on mach3 issues, im using the same control box and same mach3, on both machines. One draws nice and the ox doesnt..
Racking is when one side of your gantry moves differently than the other side. Basicly one side gets ahead or behind the other side for any number or reasons. I am no expert when it comes. to the software side but your MPCNC is very light and has a much lower moving mass. When trying to change directions the OX has alot more mass to move around. Alot more area for deflection. I am just totally guessing since you seem to be positive it's not mechanical.
Daft question, but the second Y axis stepper has been mirrored in GRBL to run in reverse? I did mine by reversing the cables for one of the phases - but either way works.
Have you tried seeing how it looks climb vs conventional? And then tried doing one in one direction and the other in the other direction back to back?
Hello Tore! I seem to be having the same issue as you! Problem Engraving the Letter O or circles Were you able to resolve your problem? Please let me know as I am struggling in this area right now.
I stand by my original feeling that you have something that is loose or binding. Start on your z axis and move you way through each axis. Twist, push, pull to find where you might have something loose. Check the travel of your axis to see if there is any binding. Check your ball screws to see if you have one that could be bowed from having too much tension on it when you put the end caps on. I would check for loose things first, ball screws next and binding travel last.
Hi Jimmy! I put my ox hybrid together and noticed that circles do not align over single passes (like engraving). I took my machine completely apart, followed the Openbuilds assembly Youtube video and double checked every v wheel and bolt was tightened. I have moved from mechanical, to software, to now electrical.
I am starting to think that the 20x80 t slot rails are racking. Is there a way to prove this? Maybe marking a spot shared by both rails and running a program to observe their movement?
So if you cut a circle you are saying if you were to cut another right over the top you get different results? Racking would be if your moving gantry were to have one side get ahead or behind the other basically coming out of parallel. If your cuts are coming out 99.5% correct than you are most likely seeing a mechanical issue. Depending on how small a cut you are seeing these issues on. Don't take your machine apart and put it back together . There are going to be things that need tweaking and will solve some and create new issues when you pull it all apart. You machine will act differently when it is under load. You have forces that you can see pulling and pushing things around that don't happen when it's not plowing through material. I am no expert but I have been fooling around with building cnc routers since around 2000. Usually electronic or electrical will show up in a major way and know it right away...like a stepper being wired backwards or limit switch not being connected. The mechanical stuff is where l have spent most of my time fine tuning and finding my last bits of accuracy hiding. Maybe your x rails are not perfectly parallel and your vwheels are riding up a little on one side...pinion set screw not tight...stepper motor mount loose or motor loose in the mount...is your work piece moving it all in the x or y AND Z? Are the issues happening everywhere or just in one area on your machine? I could be wrong and I know how frustrating it can be but my experience is accuracy issues have almost always come down to mechanics.
Thanks for the reply Jimmy! When I cut a circle and then cut another circle in the exact same position, it will not deviate, not even a tiny bit. My brain is not interpreting the question that well.. but here goes! The workpiece is pine board. It is secured with x4 #12 screws into the sacrifical mdf board which is then bolted to an aluminum extruded base table. I am cutting it 1mm deep with my 1/8" engrave bit. The z depth is set in place. When I cut a circle, the ends do not align/meet up. If I repeat the circle in the same exact location, it will trace it perfectly with no change in shape. The issue happens everywhere. I've tried it in every corner/center but the pattern is identical. Yeah! It's frustrating! But it's nothing to fret over.
