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Post by markwisniowski on Mar 6, 2017 3:20:30 GMT
I noticed that I'm not getting perfect circles. I did a few tests and it seems like the circles are more like ovals. I've researched online and came back with either the bit is flexing or it's being caused by code. My feedrates during the tests where very conservative (12k rpm on spindle, feedrate, lead-ins and out along with ramps and finishing step set to 400, multiple passes set to 1mm).
I'm using the 2D Pocket operation in Fusion360 to make 22mm holes for bearings. The material I was using for the test was 6.65mm thick walnut. The bit is an 1/8" 2 flute flat end mill bit using the climb method. The material was clamped down and using double sided tape to keep it to the bed, it was very solid.
The results are not extremely bad, they "look" like perfect circles. But when I try to place a bearing into the hole it's off by ~1mm short on 2 sides making it more of an oval.
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Post by mrbigj on Mar 6, 2017 4:08:49 GMT
I noticed that I'm not getting perfect circles. I did a few tests and it seems like the circles are more like ovals. I've researched online and came back with either the bit is flexing or it's being caused by code. My feedrates during the tests where very conservative (12k rpm on spindle, feedrate, lead-ins and out along with ramps and finishing step set to 400, multiple passes set to 1mm). I'm using the 2D Pocket operation in Fusion360 to make 22mm holes for bearings. The material I was using for the test was 6.65mm thick walnut. The bit is an 1/8" 2 flute flat end mill bit using the climb method. The material was clamped down and using double sided tape to keep it to the bed, it was very solid. The results are not extremely bad, they "look" like perfect circles. But when I try to place a bearing into the hole it's off by ~1mm short on 2 sides making it more of an oval. Sorry Mark, I can't really speak to your software. I'm not using Fusion yet, still trying to learn it. I will say, I am using Easel and haven't had any issue. In Easel, I've cut 3" and 4" circles at 30 inches per minute feed, 9 inch per minute plunge, and 1/8 inch depth per pass. No issues at all. I'm still trying to get used to working in mm's, so I'm not sure what that works out to. Also, that is using a 2 flute straight bit. Easel is free and easy to use, perhaps try that and see if you get perfect circles and then you'll know if it's the software or not? Jason |
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Post by markwisniowski on Mar 6, 2017 4:51:32 GMT
Thanks Jason, I'm up for trying Easel for this test. Under Machine type, which do you pick in the drop down list?
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Post by Derek the Admin on Mar 6, 2017 5:08:20 GMT
Careful with Easel that you don't click the wrong thing and let it reflash your board. I don't use it, personally, but if I remember correctly you need to manually enter a comm port (open UGS first to see what your comm port is) after you click "Carve" to keep it from trying to get you to set up one of their machines.
This is most likely a hardware issue not a software issue. Your cuts are not that aggressive, so I think it's more of a square or plumb (or both) issue than flex. Flex can play a roll, but not to the extent you are experience:
I would program a big square, perhaps 200mm. Cut it out of a cheap material like MDF instead of your nice walnut. Before you pull it off the machine, write on it how it was oriented with a sharpie or pen. Now pull it off and examine it. Is there a taper to the piece? Meaning when you view it from the side does it have a slant or is it straight? If it has a slant then the cutter is out of plumb. This most likely results from the gantry rail being tilted forward or back. This is solved by taking a square and measuring the gantry rail for perpendicularity to the bed. If it needs adjustment then loosen the tap hole bolts on the X rail just enough to rotate it into position. You can also view it from the side to make sure the edge of your square lines up with the spindle itself.
Next actually measure the square of squareness. If, for example, you put the square on the top right of your cut out piece (as it was oriented on the machine) and you had an air gap between your square tool and the 200mm square you cut out, then that means you would need to pull the right side of the gantry rail forward just a bit. There is a little adjustment there for this purpose.
Also, you might want to check out "Fine tuning your machine" in the assembly forum. This is not going to help with the squareness stuff, but it talks about getting to the fine detail of steps/mm.
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Post by mrbigj on Mar 6, 2017 5:10:37 GMT
Careful with Easel that you don't click the wrong thing and let it reflash your board. I don't use it, personally, but if I remember correctly you need to manually enter a comm port (open UGS first to see what your comm port is) after you click "Carve" to keep it from trying to get you to set up one of their machines. This is most likely a hardware issue not a software issue. Your cuts are not that aggressive, so I think it's more of a square or plumb (or both) issue than flex. Flex can play a roll, but not to the extent you are experience: I would program a big square, perhaps 200mm. Cut it out of a cheap material like MDF instead of your nice walnut. Before you pull it off the machine, write on it how it was oriented with a sharpie or pen. Now pull it off and examine it. Is there a taper to the piece? Meaning when you view it from the side does it have a slant or is it straight? If it has a slant then the cutter is out of plumb. This most likely results from the gantry rail being tilted forward or back. This is solved by taking a square and measuring the gantry rail for perpendicularity to the bed. If it needs adjustment then loosen the tap hole bolts on the X rail just enough to rotate it into position. You can also view it from the side to make sure the edge of your square lines up with the spindle itself. Next actually measure the square of squareness. If, for example, you put the square on the top right of your cut out piece (as it was oriented on the machine) and you had an air gap between your square tool and the 200mm square you cut out, then that means you would need to pull the right side of the gantry rail forward just a bit. There is a little adjustment there for this purpose. Also, you might want to check out "Fine tuning your machine" in the assembly forum. This is not going to help with the squareness stuff, but it talks about getting to the fine detail of steps/mm. Derek, I don't let Easel interface with my board. I just design and then output gcode and download it to my machine, then open it with UGS Platform. J |
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Post by andrew on Mar 6, 2017 15:40:31 GMT
Mark, You should check out Easel if you're just learning. It's helped me a lot to understand some of the little things and makes it much less complicated than Fusion. It is limited in what it can do of course, but honestly I've used it for pretty much most everything I've done just for the sake of ease. As far as which machine to pick, like J said above, skip that part and just export the Gcode file and send it with UGS to your machine.
To do that, in the Machine menu where it asks you what machine you have you will see an "advanced" button (right under the set up your machine button). click that and it will give you the option to "generate gcode". click that and when it's done another button to download the file will appear.
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Post by markwisniowski on Mar 10, 2017 17:22:57 GMT
Alright, I did my best to square-up the gantry and pushing and pulling forward and back but I'm still having the issue with these 22mm circles. In the picture below you can see my Fusion 360 sketch and the piece I cut out, also overlayed the sketch on top of the cut piece. You can clearly see how the circles are off.  Attachment DeletedCircle on the left using BORE operation in Climb mode, Middle circle is BORE operation in Conventional mode and circle on the right is CIRCULAR operation in climb mode... |
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Post by andrew on Mar 10, 2017 17:41:56 GMT
Seems like it's off enough that this wouldn't be an issue, but is there a possibility that tool deflection could cause this? Like going across the grain of a hard wood like that is deflecting the cutter a little bit? Have you tried it with a softer material? Or maybe using a larger bit diameter (like a 1/4 with a 1/4" shank) just to test and eliminate the deflection theory..
Or maybe strap a sharpie pen on there and run the program with a piece of paper to see if you get the same result.. Seems like that would confirm or eliminate the idea that something was flexing a little bit and causing the problem.
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Post by markwisniowski on Mar 10, 2017 18:00:10 GMT
Seems like it's off enough that this wouldn't be an issue, but is there a possibility that tool deflection could cause this? Like going across the grain of a hard wood like that is deflecting the cutter a little bit? Have you tried it with a softer material? Or maybe using a larger bit diameter (like a 1/4 with a 1/4" shank) just to test and eliminate the deflection theory.. Or maybe strap a sharpie pen on there and run the program with a piece of paper to see if you get the same result.. Seems like that would confirm or eliminate the idea that something was flexing a little bit and causing the problem. Thanks Andrew - 2 great ideas on how to tackle this, I'll try your suggestions! |
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Post by andrew on Mar 10, 2017 18:18:01 GMT
Seems like with a pen and paper there would be next to zero load on anything. If it draws the circle perfectly, then it has to be a flex issue somewhere when there is load on the cutter, if they are still out of round then it's got to be a software issue.. just a theory  |
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Post by Derek the Admin on Mar 10, 2017 18:51:23 GMT
Did you also check plumb of the router?
Two options here are to do the fine tuning procedures mentioned before to see if there is error in steps per 1mm that can be slightly adjusted.
You can also try to slow down the x and y acceleration in grbl under the $$ settings as a circle always has it changing direction.
What's your pitch on the boring op and step down on the circular?
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Post by markwisniowski on Mar 10, 2017 19:02:48 GMT
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Post by markwisniowski on Mar 10, 2017 19:03:37 GMT
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Post by Derek the Admin on Mar 10, 2017 22:54:20 GMT
I suspect not. Getting perfect circles can be tough as there are a multitude of factors involved. You settings so not look like they are going to cause deflection.
When checking the plumbness of the router you want to put a square on the bed and look down the direction of the Y axis. You won't actually put the square on the router, rather you will have the square a few inches in front, close one eye, and see if the body of the router in the background lines up. Do the same in the X direction. It's easier with a DWP611 router or spindle as they have good round bodies unlike the Colt for instance with some countour to the body.
How did the square cutout test described in a few replies previous to this one look?
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Post by aforww on Mar 10, 2017 23:02:04 GMT
Looking at the pictures it's pretty obvious to me its deviating most near the areas that would be the corners if it was a square. This tells me that while the machine is entering or exiting load along the X axis it's going off track. I would check belt tension (should sound like a tight rubber band when you pluck it), the spindle mount(can you rock it left to right and does the Z plate have any play in any direction. does the table itself have play if you grab it and move it around?), and tightness of the all the rails. I can pretty much guarantee that what you're seeing is a result of slop along the x or y rails or belt tension. Nothing should move around or have slop. The only movement in the machine should be along the axis as it is intended to.
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