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Post by macgyver03 on May 26, 2017 0:05:42 GMT
Guys,
I am thinking of getting a Bondtech BMG since I am going to try and start printing more flexible materials and want a little bit better extrusion control. While I was playing with the X Gantry file, I noticed there was a circular pattern that mirrored the belt clamps onto the rear of the gantry. I like this design better than the slider that is currently on the rear of the 1.1 gantry since my belts keep slipping out since the PLA has slowly deformed, but wanted to ask if anyone had tried this before I printed one and found out why Andrew suppressed it.
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Post by 3DprintedLife on May 26, 2017 1:20:46 GMT
Guys, I am thinking of getting a Bondtech BMG since I am going to try and start printing more flexible materials and want a little bit better extrusion control. While I was playing with the X Gantry file, I noticed there was a circular pattern that mirrored the belt clamps onto the rear of the gantry. I like this design better than the slider that is currently on the rear of the 1.1 gantry since my belts keep slipping out since the PLA has slowly deformed, but wanted to ask if anyone had tried this before I printed one and found out why Andrew suppressed it. Ahhh yes, so that was the old system which just had identical mounting on the front and back. It does work just fine, but this new method with the large sliding block allows you to equalize tension in both belts very easily, which is important in corexy gantries especially when using bushings instead of bearings! You can print out that old version and just be careful with belt adjustment, or a better option is to just use a tiny amount of superglue to glue the two parts of the belt clamp together around your belt. This will ensure the belt does not pull out even if the pla softens a bit! |
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Post by macgyver03 on May 30, 2017 11:59:11 GMT
I ended up super gluing the belt into a loop, but the bottom nut started pulling through the thin slider channel. This must be from me over tightening, since the core xy only pulls perpendicular to that bolt, but I was trying to think of how to prevent that. I'll print the new assembly using PETG in case the high temp prints I'm doing is softening it, but since the front clamps didn't have that issue I was going to use it if it worked.
Also, what is the school of thought behind balancing the tension on a core xy? I would understand if they were extremely unbalanced or using a servo or normal motor. However, the stepper driver current should flux as needed to get the movement and the defined magnet steps should be the same between both motors. This should mean that slight differences would torque the bushings a little and make one direction draw more current than the other, but if you moved the assembly easily be hand, I wouldn't think this torque wouldn't cause a problem. Does it have to do with microstepping, because the driver is using undefined positions to smooth the movement or am I missing something about the Gantry torque?
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Post by 3DprintedLife on May 30, 2017 15:39:32 GMT
Ah nice that will work, and yeah the bottom bolt does not need to be tightened too much, as long as the top two are snug it won't move!
The reason I have that feature is due to the fact that I have a corexy printer that uses bushings rather than bearings. While bearings can handle rotational loads, like if the gantry were slightly skewed due to one belt being tighter than the other, it would have no problem. With bushings though, you can get some nasty vibrations, rattling, and rough spots. By including this feature, it allows you to very easily ensure the belts have equal tension so that first of all you don't have a skewed gantry, and second so that I can continue using bushings in instead of bearings to reduce the noise and improve the speed of the printer!
That being said, as long as you are careful and ensure you get the belts equal and the gantry square, you wouldn't have a problem going with the old design that just uses the 4 belt mounts. It just requires a bit more work to get set up!
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Post by Bokke on Oct 5, 2019 21:00:01 GMT
Guys, I am thinking of getting a Bondtech BMG since I am going to try and start printing more flexible materials and want a little bit better extrusion control. While I was playing with the X Gantry file, I noticed there was a circular pattern that mirrored the belt clamps onto the rear of the gantry. I like this design better than the slider that is currently on the rear of the 1.1 gantry since my belts keep slipping out since the PLA has slowly deformed, but wanted to ask if anyone had tried this before I printed one and found out why Andrew suppressed it. Ahhh yes, so that was the old system which just had identical mounting on the front and back. It does work just fine, but this new method with the large sliding block allows you to equalize tension in both belts very easily, which is important in corexy gantries especially when using bushings instead of bearings! You can print out that old version and just be careful with belt adjustment, or a better option is to just use a tiny amount of superglue to glue the two parts of the belt clamp together around your belt. This will ensure the belt does not pull out even if the pla softens a bit! |
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Post by Bokke on Oct 5, 2019 21:04:07 GMT
Did anyone ever finish a BMG style gantry? I’d love to get my hand on stl file to print please.
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