How Tight is Right?

[Eaglezsoar]

I have finally got the uprights installed and the belts installed. The top idlers are at the bottom of their slots and I pulled the
belts as tight as I could by hand and tightened up the belt clamps. At this point comes the confusion on how tight the belts
should be. Using the top idler slots as a guide, when the belts are tight enough is the top idler against the top of the slots,
halfway up or what? I have read nothing definitive on how tight they should be but I have read all the horror stories of belts
that are too tight being chewed up. The average price for a set of these belts is approximately $75 and I don't want to be
replacing them every two weeks. This IMO is one of the worst aspects of building any 3D printer, they all say to tighten the
belts but nowhere is "tighten" defined. All opinions are welcomed on how to determine the proper tightness.

Carl

[Polygonhell]

I have finally got the uprights installed and the belts installed. The top idlers are at the bottom of their slots and I pulled the
belts as tight as I could by hand and tightened up the belt clamps. At this point comes the confusion on how tight the belts
should be. Using the top idler slots as a guide, when the belts are tight enough is the top idler against the top of the slots,
halfway up or what? I have read nothing definitive on how tight they should be but I have read all the horror stories of belts
that are too tight being chewed up. The average price for a set of these belts is approximately $75 and I don't want to be
replacing them every two weeks. This IMO is one of the worst aspects of building any 3D printer, they all say to tighten the
belts but nowhere is "tighten" defined. All opinions are welcomed on how to determine the proper tightness.

Carl

Short version is I don't know, FWIW too loose is just as likely and possibly more likely to result in eaten belts.
I do know if you move the cheapskates up and down and adjust the belt tightness in between at some point you can feel a significant increase in the amount of force requires to move them. I think this is because of the side loading you are placing on the stepper shaft bearings, so I try to avoid too much tension.
Mine are about at 1/2 way up the slot currently, but I'm not sure that's useful since it depends how tight you got them with the belt clamps.
FWIW I can't find a spec on the belt that states a range for working tension.

[cambo3d]

its kind of a guess, but here's what i do to make sure its almost the same for all three.

1. make sure the top pulley is at the lowest point in the slot.
2. when you clamp down the belt to the cheap skate, pull it snug. do this for all three.
3. when you go to adjust, use a phillips head screwdriver and gently raise the top pulley while, using your other hand to check the stiffness of the belt near the pulley at the bottom.
4. how tight will be your judgement here but i left a slight amount of "springiness" in the tension of the belt, i test this by how much i can push on the belt at the lower pulley. If you push on the belt and it moves more than 1/8", I would say its too loose. (just my guess)

5. then just try to match up the rest.

[Eaglezsoar]

Thanks for your replies, both of you have been helpful for me determining how tight to make the belts.

Carl

[mhackney]

Carl, I posted on this topic a while ago here: http://forum.seemecnc.com/viewtopic.php ... belt#p5537

It is my experience that most people tighten these belts way too tight. I've also noticed that with the CNC crowd too. Something about wanting a nice tight belt I think! Anyway, take a look at the link and the reference I posted. You do not want them too tight. I have 100s of hours on mine, no backlash from belts and no discernible wear.

[Eaglezsoar]

Carl, I posted on this topic a while ago here: http://forum.seemecnc.com/viewtopic.php ... belt#p5537

It is my experience that most people tighten these belts way too tight. I've also noticed that with the CNC crowd too. Something about wanting a nice tight belt I think! Anyway, take a look at the link and the reference I posted. You do not want them too tight. I have 100s of hours on mine, no backlash from belts and no discernible wear.

Thank you for reminding me about your writeup. As I add up everyone's ideas I am finally getting a handle on how tight they should be. Autos use a belt tensioner device perhaps one day the printers will have a spring tensioning device
to maintain the correct tension without us having to worry about it. Thanks again Michael.

Carl

[mhackney]

The challenge with measuring tension on the Rostock is that the belt is in the groove in the towers and there is very little room to push them. You would have to loop something around the belt and PULL it out to measure tension.

[cambo3d]

I adjusted mine between the bottom pulley and the stepper gear.

In my opinion, adjusting from the center isn't accurate because the rostock has those other two pulleys at the bottom. If it was just the stepper and the top pulley then yes center adjustment would seem right. just my thoughts.

[JohnStack]

Perhaps it can be measured.

What if a specific size of allen head wrench was used to roll into the top bearing while allowing for the absolute minimum amount of play?

[Eaglezsoar]

Now that I have the belts adjusted to what I think is right, the cheapskates are definitely much stiffer to move now.
I think that is normal. When the belts are loose the cheapskates are also very easy too slide now not so easy. It is
difficult to know how stiff they should move. I think I will continue on until I get everything wired up and see how they
move under control of the steppers. Thanks to everyone for you guidance in how to adjust this printer.

Carl

[JakeCShake]

Remember not to move the cheapskates around TOO much by hand....the steppers could create a charge to the board. Just an FYI.....

[Eaglezsoar]

Remember not to move the cheapskates around TOO much by hand....the steppers could create a charge to the board. Just an FYI.....

I'll remember that, while I'm doing the belts the board is not connected. Good tip though and I'll be careful when everything is connected. Just a quick question, do your
cheapskates seem stiff to move after tensioning the belts?

[Polygonhell]

Remember not to move the cheapskates around TOO much by hand....the steppers could create a charge to the board. Just an FYI.....

I'll remember that, while I'm doing the belts the board is not connected. Good tip though and I'll be careful when everything is connected. Just a quick question, do your
cheapskates seem stiff to move after tensioning the belts?

There is a point when tensioning that if you get beyond it the cheapskates will feel very stiff, IMO this is too tight, you're placing too much side load on the stepper bearings.