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Timing Belts / Pulleys

Discussion in 'CNC IN THE HOME SHOP' started by cjones6108, Sep 5, 2017.

  1. cjones6108

    cjones6108 United States Iron Registered Member

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    So far I've been thinking direct-drive for the conversion of my PM-932M, but I really like JBolt's implementation with timing belts for space-saving. From what I've been reading, timing belts introduce another point for backlash, but there are trade-offs with everything.

    What's the thinking on the type of belts -- I see on McMaster-Carr they come in various "weights", from XL (Extra Light) through H (Heavy) to HTD (High-Torque Drive). I've ordered the same stepper motors as JBolt used on his conversion (2 Nema 34 1600 oz.in and 1 Nema 42 I forget the torque). The L series belts come 1/2" wide and up while the H series start at 3/4" wide, and the stock ones start fairly long while the L ones can come somewhat shorter. None of them are terribly expensive. I'm looking at ball screws that are nominal 5/8" (approx. 16mm), which would need to be turned down to 1/2" , which is the size of the L-series pulley , whereas the H-series pulley starts at 5/8" diam. Do you think the L-series belt would be heavy enough for these motors?
     
  2. cs900

    cs900 United States maker of chips Active Member

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    Hey,
    so first off let me say, I love mcmaster...but....they are kinda pricey and selection is limited for pulleys and belts. you may want to check out SDP-SI. You'll find a much better selection there. They also have some great documentation to help you size your belt correctly.

    so that said, I don't believe that a properly designed timing belt system will induce noticeable backlash. You can get fiber reinforced belt that have nearly no stretch to them and with modern tooth shapes you get no backlash at the tooth itself.
     
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  3. jbolt

    jbolt United States Active User H-M Supporter-Premium

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    I got my belts and pulleys from Stock Drive Products. They are the GT2 5mm pitch series for 15mm wide belts. The belts are neoprene with fiberglass cords. I'll see if I can dig up the part numbers.
     
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  4. cjones6108

    cjones6108 United States Iron Registered Member

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    Thanks.

    I really like your implementation. I've been looking at the photos you posted; tell me: All the parts that you milled, did you do that with aluminum? What was the thickness of that plate you used early on, in the photo shown coated with Dykem? And then some chunks of fairly large square or rectangular bar stock -- Do you recall the dimensions? I'm just trying to get an idea of what kind and how much stock to buy.

    caj
     
  5. jbolt

    jbolt United States Active User H-M Supporter-Premium

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    All of the motor mounts are aluminum. If you have a CAD program I can send you my 3D CAD files to get dimensions from. I have the files in Solidworks and Parasolid. PM me your email.

    Sent from my SM-G955U using Tapatalk
     
  6. jbolt

    jbolt United States Active User H-M Supporter-Premium

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