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Joining Drive Belts

Posted by wayland 
Joining Drive Belts
April 08, 2010 07:05PM
I'm looking at drive belts mcmaster-carr ( [www.mcmaster.com] ) and they seem to sell them pretty cheaply by the foot, plus I may need odd lengths for my cobbled-together repstrap. How do you think I could join the ends of a belt to make it into a loop?
Re: Joining Drive Belts
April 08, 2010 08:15PM
A good place to go is a shoe repair vender in your town.

Strip the top off 1, the bottom off the other.

Just have them put 3 stitches in the vallies of the two ends. This is the same lay companies that have a lot of conveyeors do it, they just have the stitcher in their shop.

Re: Joining Drive Belts
April 08, 2010 08:37PM
There was an "official" way to do that when the darwin design needed a continuous belt for it's Z axis. As I recall, it involved superglue, shaving parts of the belt, and a jig to insure the tooth spacing stayed the same. I don't know what the reliability was, it seems to me that the superglue would be too brittle for that sort of use, and something like flexible yet strong like "shoe goo" would work better. Having never actually done it, my opinion on the subject is suspect at best.

I'm sure you can find all sorts of details if you go looking, but I'm too lazy to do that much work right now. "Darwin belt jig" might find it...

I'm building it with Baling Wire
Re: Joining Drive Belts
April 08, 2010 10:23PM
wait, so drive belts are two easily separated layers?

do you think I could sew them myself?

edit: oh, or do you mean cut top off one and bottom off the other with respect to the z-axis? or the y-axis? assuming the belt is parallel to the x-axis.

Edited 2 time(s). Last edit at 04/08/2010 10:35PM by wayland.
Re: Joining Drive Belts
April 09, 2010 10:42AM
This has some info on how the Darwin belt was spliced:


Re: Joining Drive Belts
April 09, 2010 03:09PM
You don't necessarily have to have the belt jig. I have used vises, c-clamps, visegrips, and hemostats to glue belts together over the years. You just have to make sure that belt lines up straight when you clamp it.

The best glue that I have found is the E6000 flexible glue put out by Eclectic Products. It is strong and flexible - but it has to cure overnight and has a strong odor while curing.

You can stitch your own belt together with a strong needle, pliers to push the needle through the kevlar, and heavy thread or fishing line. It's difficult to do with a narrow belt, but it can be done.

If you don't need the belt to run in a continuous loop, you can also just overlap them and put a heavy staple (like a carpet staple from a staple gun) through the overlap.
Re: Joining Drive Belts
April 09, 2010 04:11PM

I will try some of these on scrap and report back when I order the belts.
Re: Joining Drive Belts
April 11, 2010 03:13PM
I've built two Darwins with the shaving and gluing technique, using a jig made out of polymorph plastic. The belts have held up fine (one is almost 2 years old now, and still printing), but due to the teeth spacing not being perfect, the belts sometimes skip under loading. It means I have to re-level the bed on the Darwins every once in a while, but hasn't been a serious problem.

On the Mendel, I just bought a continuous belt of the correct size - works a lot better.

Re: Joining Drive Belts
April 14, 2010 01:24PM
The way to get by the tooth spacing without a jig is to first make your cuts very carefully and then second use a scrap piece of belt to line up the teeth before clamping. Glue doesn't stick well to neoprene so that scrap piece will peel off easily once everything is dry.
Re: Joining Drive Belts
May 01, 2010 02:49PM
> of a belt to make it into a loop?

You need no full loop. In cnc, belt never goes so far. Just use wire spring to connect start with end.
Re: Joining Drive Belts
May 04, 2010 03:18PM
I'm just guessing about the design, but my guess is he needs a long belt loop to run a z-axis plate up and down. Since it is a repstrap, it's the quick and dirty way to do it.
Re: Joining Drive Belts
May 04, 2010 03:28PM
At least one full loop is require for mendel design. As you indicate, this is the Z axis.

A loop makes it easy on the other axes (using the ingenious clothespin spring gimmick), but as full cyclic motion is not required, can be accomplished with linear belt segments and other tension strategies.
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