Belt size: what should I choose?
Posted by Regicide
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Belt size: what should I choose? October 14, 2020 01:19PM |
Registered: 5 years ago Posts: 23 |
I'm currently working on the design of my future 3d printer, and I'm ready to start building. My build is basically a complete part replacement of an Anet A6, along with a substantial print size increase (up to 400x400x500 or 600). The print head is going to be a dual Titan direct drive Chimera, and I'm wondering what belt size I should use for such a whopper of a head. I'll be using compact and powerful motors, but I'm still going to have a hefty build. My question is: what size belts should I be using?
Obviously, with such a large print space I want to keep print times fast. However, I also want the accuracy that comes with a direct drive system. Strength of frame shouldn't be a problem, I'm going with big old aluminum extrusions anchored to the wall. However, I'm worried that if I try to go up to any sort of high speeds with this I'm going to run into problems with the belt slipping. I'm going to be using toothed pulleys and Gates parts, but do I need to go bigger than 6 mm, maybe 9 or even 12?
Also, does anyone have suggestions for alternate extruder setups? I want at least one direct drive extruder so that I can keep my prints looking nice, and also because I want to experiment with using this for high quality small prints (swapping out the ac bed for a dc 200mm, maybe? I'll keep you posted.) However, if you can convince me that hybrid is better or there's a better way than Chimera: for example, the Itty Bitty Double extruder, then I might not need a bigger belt after all.
Thanks in advance for your help!
Obviously, with such a large print space I want to keep print times fast. However, I also want the accuracy that comes with a direct drive system. Strength of frame shouldn't be a problem, I'm going with big old aluminum extrusions anchored to the wall. However, I'm worried that if I try to go up to any sort of high speeds with this I'm going to run into problems with the belt slipping. I'm going to be using toothed pulleys and Gates parts, but do I need to go bigger than 6 mm, maybe 9 or even 12?
Also, does anyone have suggestions for alternate extruder setups? I want at least one direct drive extruder so that I can keep my prints looking nice, and also because I want to experiment with using this for high quality small prints (swapping out the ac bed for a dc 200mm, maybe? I'll keep you posted.) However, if you can convince me that hybrid is better or there's a better way than Chimera: for example, the Itty Bitty Double extruder, then I might not need a bigger belt after all.
Thanks in advance for your help!
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Re: Belt size: what should I choose? October 14, 2020 01:42PM |
Admin Registered: 12 years ago Posts: 3,096 |
Sounds like 6mm will still be enough. My personal experience with belts is that you want to go wider when the belts get really long. But comparing this to a CoreXY setup which gets very long belt paths even when the build volume only increases a little bit, I think you'll be safe with 6mm still. My main concern would be belt stretch. Also keep in mind, wider belts have more friction, taxing your stepper drivers more and adding even more weight to the axis. Of course the added weight it almost nothing when compared to getting a bigger printbed.
Why does swapping the AC for a DC bed have to be done in order to get 'high quality prints'? I don't think you need this. One big bed should be fine. Just build your machine mechanically sound and there's no need for making it swappable.
http://www.marinusdebeer.nl/
Why does swapping the AC for a DC bed have to be done in order to get 'high quality prints'? I don't think you need this. One big bed should be fine. Just build your machine mechanically sound and there's no need for making it swappable.
http://www.marinusdebeer.nl/
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Re: Belt size: what should I choose? October 16, 2020 07:18PM |
Registered: 5 years ago Posts: 23 |
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Re: Belt size: what should I choose? October 17, 2020 10:00AM |
Registered: 12 years ago Posts: 5,798 |
Toothed belts don't slip unless there's something seriously wrong with the positioning of the motors and pulleys.
Wider belts will stretch less than narrower belts, but 6 mm is probably wide enough. If you're not sure, go to 9 mm. Going wider than 9 or 10 mm will be a problem because it's hard to find pulleys for belts wider than that.
The problem with the toothed pulleys for GT2 belt is that they have tiny little bearings that wear out quickly. It's much better to used ball bearings as pulleys with larger diameter and bore and most importantly, bigger balls, to get long life. You can either twist the belts so that the smooth back side of the belt contacts pulley surfaces or you can use large diameter pulleys and let the teeth contact them. There is a Gates white paper that recommends that the minimum smooth pulley diameter should be equivalent of a 40 tooth pulley, and that a minimum of 9 teeth should contact the surface at one time. Pulleys bend the belts 90 degrees in corexy mechanisms, so if 9 teeth are on the pulley, it would have to be a 36 tooth pulley. So a 40 tooth pulley diameter will meet both requirements. A 40 tooth pulley would be approximately 25 mm in diameter (=40 x 2 / pi). It happens that F608 skate wheel bearings, which are manufactured by the millions and available cheaply, everywhere, are 22 mm in diameter, very close to the Gates recommended diameter. Two of them stacked will accommodate 9 mm wide belt. I have used stacked F608 bearings in two printers with great results. The teeth contacting the smooth surfaces of the pulleys do not create any defects in the prints.
The only complaint there is to make about the F608 bearings is that they are heavy, and is the 8 mm bolt that will be used for the axle. If you want to keep mass down and still use quality pulleys, try stacked F625 bearings and 6 mm belts. They are only 16 mm diameter, so you may want to put a twist in each belt to keep the back sides of the belts against the pulleys.
Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
Wider belts will stretch less than narrower belts, but 6 mm is probably wide enough. If you're not sure, go to 9 mm. Going wider than 9 or 10 mm will be a problem because it's hard to find pulleys for belts wider than that.
The problem with the toothed pulleys for GT2 belt is that they have tiny little bearings that wear out quickly. It's much better to used ball bearings as pulleys with larger diameter and bore and most importantly, bigger balls, to get long life. You can either twist the belts so that the smooth back side of the belt contacts pulley surfaces or you can use large diameter pulleys and let the teeth contact them. There is a Gates white paper that recommends that the minimum smooth pulley diameter should be equivalent of a 40 tooth pulley, and that a minimum of 9 teeth should contact the surface at one time. Pulleys bend the belts 90 degrees in corexy mechanisms, so if 9 teeth are on the pulley, it would have to be a 36 tooth pulley. So a 40 tooth pulley diameter will meet both requirements. A 40 tooth pulley would be approximately 25 mm in diameter (=40 x 2 / pi). It happens that F608 skate wheel bearings, which are manufactured by the millions and available cheaply, everywhere, are 22 mm in diameter, very close to the Gates recommended diameter. Two of them stacked will accommodate 9 mm wide belt. I have used stacked F608 bearings in two printers with great results. The teeth contacting the smooth surfaces of the pulleys do not create any defects in the prints.
The only complaint there is to make about the F608 bearings is that they are heavy, and is the 8 mm bolt that will be used for the axle. If you want to keep mass down and still use quality pulleys, try stacked F625 bearings and 6 mm belts. They are only 16 mm diameter, so you may want to put a twist in each belt to keep the back sides of the belts against the pulleys.
Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
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