Z Axis belt - too much slack

Assembly questions and answers for the Shapeoko 3 CNC Mill
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DannyBoyNYC
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Z Axis belt - too much slack

Post by DannyBoyNYC » Wed May 06, 2015 1:09 pm

Hi there. New to Shapeoko and CNC so please be gentle!

So far so good. I have got to the point where I am tensioning the belts and all is well except for the z-axis belt.
Image

Is this supposed to be this way or should I be looking for a solution?

Perhaps the 6mm flanged bearing at the bottom could stand to be increased to the 8x22x7mm flanged bearings used elsewhere.

Has any one else noticed this? What was your solution?

Thanks!

WillAdams
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Re: Z Axis belt - too much slack

Post by WillAdams » Wed May 06, 2015 1:38 pm

There was one other report of this or something like to it: http://www.shapeoko.com/forum/viewtopic.php?f=37&t=6044

The belt for the Z-axis is a newish configuration (I.C. had been selling various belted Z-axis upgrades for a while though), and I'm still trying to wrap my mind around it.

First, loosen the motor and slide it to the bottom.

Then try loosening the other belt connection points and see if you can nudge them a bit in their holes and then retighten them --- hopefully that will take up enough of the slack when you tighten them to allow you to tighten the belt by sliding the motor up.

The idea of standardizing the bearings is an interesting one --- it would be nice to eliminate yet another part --- not sure if it'd represent clearance issues though.
Shapeoko 3XL #0006 w/ Carbide Compact Router w/0.125″ and ¼″ Carbide 3D precision collets

DannyBoyNYC
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Joined: Sat Mar 07, 2015 5:16 pm
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Re: Z Axis belt - too much slack

Post by DannyBoyNYC » Wed May 06, 2015 2:12 pm

Thanks Will - I did not notice the other post. Nice to know I'm not alone. I'll try the recommendations and get back with my findings.

This looks to be a very robust machine and I'm looking forward to running a hello world test sometime this week!

WillAdams
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Re: Z Axis belt - too much slack

Post by WillAdams » Wed May 06, 2015 3:23 pm

One other thing (grasping at straws) --- perhaps the boss on the motor is biased in one direction or the other? Try rotating the motor to other positions and see if you get more space? (I don't think the manufacturing tolerances would allow this to make a significant difference, but maybe there's just enough to help at one position?)
Shapeoko 3XL #0006 w/ Carbide Compact Router w/0.125″ and ¼″ Carbide 3D precision collets

jayftee
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Re: Z Axis belt - too much slack

Post by jayftee » Thu May 07, 2015 12:17 am

DannyBoyNYC wrote:Thanks Will - I did not notice the other post. Nice to know I'm not alone. I'll try the recommendations and get back with my findings.

This looks to be a very robust machine and I'm looking forward to running a hello world test sometime this week!
So, how the slack fixing doing? Curious as to see what causes it.

Please report your findings.

Thank you

Jeff
Proud creator of Ike:Core, a 1 cubic foot work area FDM 3D printer based on CoreXY
Shapeoko 3 #00947, Aluminum Bed, Prototype Z Carriage, Porter Cable 450, Min/Max limit switches, Z-Probe, PreciseBits 1/4 & 1/8 Collets, Super-PID v2, IC Dust Shoe

DannyBoyNYC
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Joined: Sat Mar 07, 2015 5:16 pm
Location: Brooklyn

Re: Z Axis belt - too much slack

Post by DannyBoyNYC » Thu May 07, 2015 12:54 pm

WillAdams wrote:One other thing (grasping at straws) --- perhaps the boss on the motor is biased in one direction or the other? Try rotating the motor to other positions and see if you get more space? (I don't think the manufacturing tolerances would allow this to make a significant difference, but maybe there's just enough to help at one position?)
I hadn't though of that and will add it to my list of things to try. Work is kicking my butt at the moment so I'll have to wait until the weekend before I get a chance to try it out.

semmons23
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Re: Z Axis belt - too much slack

Post by semmons23 » Thu May 07, 2015 6:09 pm

I would double check that the belt didn't come out from between the two posts that control the tension. My belt was fine but I had to take it apart and when I put it back together I had a lot of play because it came off one of the posts.
Shapeoko 3 - #0073

DannyBoyNYC
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Re: Z Axis belt - too much slack

Post by DannyBoyNYC » Fri May 08, 2015 7:04 pm

semmons23 wrote:I would double check that the belt didn't come out from between the two posts that control the tension. My belt was fine but I had to take it apart and when I put it back together I had a lot of play because it came off one of the posts.
Nope, that wasn't it.

I tried to get the belt a bit tighter by rotating the motor to what looked like it might be a better position as per the suggestion above and a loosened and re-tightened all the belt pulleys. That might have helped a bit but not enough - the belt slips when testing with the z-axis jog controls in the Carbide Motion app.

jayftee
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Re: Z Axis belt - too much slack

Post by jayftee » Sat May 09, 2015 7:34 pm

I know its not a decent fix, but do you happen to have a GT2 36 teeth pulley?

If you replace the Z pulley with a 36 teeth pulley, it will remove some slack because that pulley is bigger.

However, you will have to dig into the firmware and replace some stepping values because the radius of the pulley would have changed.

But at least that will remove some if not all the slack.

Jeff
Proud creator of Ike:Core, a 1 cubic foot work area FDM 3D printer based on CoreXY
Shapeoko 3 #00947, Aluminum Bed, Prototype Z Carriage, Porter Cable 450, Min/Max limit switches, Z-Probe, PreciseBits 1/4 & 1/8 Collets, Super-PID v2, IC Dust Shoe

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