Breaking drive belts - getting the right tension. . . . .

[javeria]

I have lost 2 belts till now just bcos of over tensioning - experts kindly advice me how to come to a conclusion that a belt is just tight enough -

RGDS

IRfan

[J.R. Hatcher]

Irfan, I am no expert but I haven't lost a belt yet. I don't see the need for a tensioning screw (it could encourage over tightening).
To adjust the belt: I loosen the motor screws just until the motor moves freely, I then apply pressure using the motor, with my hand only and re-tighten the screws. Afterwords I check the belt to make sure it is tight but not over tightened. I've only adjusted my belts once, that was when I setup my belt drives, well over a year ago ...... I am running 4 drives ...... I've never jumped a tooth, never broke a belt. I hope this helps

[javeria]

Thanks JR - I think I should take care while tensioning the belts.

[Richards]

Depending on the length of the belt, there should be some deflection. On the XL/150 length, I had about 1/4th inch (6mm) deflection with moderate thumb pressure.

[Andrew_standen]

3 weeks ago I broke a belt. A 037 150 xl Rubber belt with glass reinforcement.
My fault I ran into the safety stop at 8000mm per min hard stop.
So I went on line and ordered some kevlar reinforced belts. 5 belts . Thats a full set of four plus a spare.
They arrived today. ...dang they are 1/4 inch wide not 3/8ths . So I will order again. Thats 5 at 12.50 each plus 5 delivery. Comes to 67.50 gbp thats 110 us dollars! A mistake that hurts.
My question to you guys is. Whilst I wait for new belts can I use the smaller 6.35mm belts.
Is this 6.35 kevlar belt as strong as my rubber and glass 9.35 belts ?
I have looked everywhere on the internet but cant find a comparison.
What belts do you guys use. Rubber with glass, poly with steel or the poly wih kevlar.

[Andrew_standen]

I have been without my machine as I'm currently running with my rubber and glass spare belt.

[sailfl]

Andrew,

You are not returning the smaller belt! So give the smaller belt a try. You have nothing to lose. Center the belts

[Andrew_standen]

Post 6 should read. I have not been without my machine. As I am running a spare rubber belt.

In reply to nils. Yes I will give them a go. Just wanted to know uf anyone had any perfornance figures or stats on the strenght of the differnt belt types.
I cant retrn them ad the handling fee is more than half the cost.

My fat fingers on my mobile phone !!!!!

[smreish]

Depends when they break?
Did you hit a hard stop or did it break on Acceleration?

I had belt failure issues on my Multicam fairly often - but only when I hit the end stop. The challenge with using the kevlar reinforce belts that when the machine hit the end stop caused the drive to over current, then go into protect. The rubber/glass belts I found to last about a year each in really heavy (40+ hrs a week).

[Tom Ayres]

Is hitting the hard stops a frequent thing? How much damage can it cause?

[lonestaral]

Hitting the hard stops should not be a frequent occurrence.

1. Check your soft limits and make sure they are turned on.

2. Double check your work offsets (G54 - G59)

3. Double check your height offset.(G49)

4. When starting a new program, turn on "Single block" for the initilal positioning moves.

5. Stand near the "E stop" button. (Your best friend)

As for damage to to the machine.

Scored motor shafts.
Grub screws to be replaced.
Missing teeth, rack and pinion.
Blown fuses.
Fried board.

Damage to you.
Death.
Disfigurement.
Missing limbs and or digits.
Missing teeth.
Brown underwear, A.K.A. Brown adrenalin.

You have only one issue of life and its bits ans pieces.

Take care.

[Tom Ayres]

Should I have asked? is death optional?

[lonestaral]

On a MechMate death is optional.
When your number is up it is compulsory.
No arguing with the Grim Reaper.

[Tom Ayres]

yep, you know it.

[Andrew_standen]

First and only time I have hit the hard stops.
Dont think the soft limits would have helped as I was jogging on the keyboard .
Only damage visible on the machine was the broken belt. Maybe its best to run rubber belts and have a weak point.

[lonestaral]

Probably best to have a weak point.
Something that is cheap and easy to replace.
Save the more expensive items.

[KenC]

I'm with Al.
Apart from saving expensive parts, it is safer to anyone around the MM too.

[Andrew_standen]

That's sound advice, I will go with the weak point.
Always good to bounce ideas and thoughts off other people.
Thanks Guys.