Easy way to tension the Z belt

Assembly questions and answers for the Shapeoko 3 CNC Mill
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CastIrony
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Easy way to tension the Z belt

Post by CastIrony » Tue Jul 26, 2016 7:16 am

While rebuilding my Z axis carriage, I decided to do a better job of tensioning the Z belt, since it was always much looser than the other belts on my machine. After a bunch of pulling, lifting, fastening, and unfastening, I had a really good idea.

Just loosen the Z motor bolts, and shove a wooden door shim in between the motors from both sides:
IMG_2595 2.jpg
IMG_2595 2.jpg (166.89 KiB) Viewed 2601 times
Then tighten the Z motor bolts, and remove the shims. I had to use a hammer to get them out, but you might be able to just wiggle them free.

These shims are cheap and easy to find, I think my hardware store sells a pack of a dozen for $2.
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WillAdams
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Re: Easy way to tension the Z belt

Post by WillAdams » Tue Jul 26, 2016 10:21 am

Yeah, I had to use a small pry bar on mine, and I worried about bending the motor shaft.

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twforeman
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Re: Easy way to tension the Z belt

Post by twforeman » Tue Jul 26, 2016 12:47 pm

This is how I tension mine too. Works a treet.
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LTEPM
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Re: Easy way to tension the Z belt

Post by LTEPM » Tue Jul 26, 2016 5:30 pm

I use wedges to tighten my X axis as well, leave them in place, then tension the Z axis motor the same way.

hatallica
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Re: Easy way to tension the Z belt

Post by hatallica » Sun Sep 18, 2016 3:07 am

Major kudos, CastIrony! This saved me tons of grief on Friday. In the middle of running a few projects, the Z axis just gave up and barely skimmed the surface. Thankfully, I still had a few shims in my tool closet (my wife - God bless her soul - used most of them as paint stirrers).

Ten minutes later, I was back to making a pile of oak chips. Cheers!
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KAScnc
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Re: Easy way to tension the Z belt

Post by KAScnc » Fri Sep 30, 2016 12:30 am

Some reason my belt was already tight with the stepper in the lowest position. I had to loosen the two 15mm spacers to gain enough slack to get the belt over the top pulley. Once everything was routed correctly, I tightened those two spacers which tensioned the belt without having to raise the stepper.

CastIrony
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Re: Easy way to tension the Z belt

Post by CastIrony » Fri Sep 30, 2016 4:30 pm

KAScnc wrote:Some reason my belt was already tight with the stepper in the lowest position. I had to loosen the two 15mm spacers to gain enough slack to get the belt over the top pulley. Once everything was routed correctly, I tightened those two spacers which tensioned the belt without having to raise the stepper.
Do you have the old or new style Z carriage plate? The old one was a little bit more adjustable, which might explain that.
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KAScnc
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Re: Easy way to tension the Z belt

Post by KAScnc » Fri Sep 30, 2016 9:39 pm

CastIrony wrote:
KAScnc wrote:Some reason my belt was already tight with the stepper in the lowest position. I had to loosen the two 15mm spacers to gain enough slack to get the belt over the top pulley. Once everything was routed correctly, I tightened those two spacers which tensioned the belt without having to raise the stepper.
Do you have the old or new style Z carriage plate? The old one was a little bit more adjustable, which might explain that.

Hmm, I'll assume it was the original style. It was the spark fun edition purchased Dec 2015. I just got the upgraded (front) Z-Plate few days ago.

Image



What I don't have is that adjustment screw on the back plate that puts tension on the z-belt pictured here.
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WillAdams
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Re: Easy way to tension the Z belt

Post by WillAdams » Fri Sep 30, 2016 10:29 pm

Pick up a stainless steel SHCS at your local hardware store.
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KAScnc
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Re: Easy way to tension the Z belt

Post by KAScnc » Fri Sep 30, 2016 10:43 pm

WillAdams wrote:Pick up a stainless steel SHCS at your local hardware store.

That would be sort of obvious if the plate had an adjustable slot for the bottom guide pulley and a threaded bung welded to the plate for that steel SHCS tension screw. :D

Maybe this is a Sparkfun thing?

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