PDA

View Full Version : Timing Belts



Ricardoco
29-07-2012, 08:04 PM
Ive looked around the forum but still cannot see an answer so here goes, Is there somewhere I can get a T5 x 10mm x 1645mm Continuos belt from.

Rick

mocha
29-07-2012, 08:06 PM
have you had a look at beltingonline.com, they might?

Ricardoco
29-07-2012, 08:39 PM
have you had a look at beltingonline.com, they might?
They do do one you join, but this is to syncronise two trapezoidal lead screws to save slaving steppers and it states they are for low load only, so i'm a little unsure of them..

Rick

Ricardoco
29-07-2012, 11:43 PM
Ok Ive got the task of connecting two Leadscrews that are 760mm apart center to center so they can be driven by 1 stepper. Does anyone know a simple way??? possibly using a Timing belt please state belt & and pulley sizes and source if timing belt is the way to go...

Jonathan
30-07-2012, 12:13 AM
Timing belt please state belt & and pulley sizes and source if timing belt is the way to go...

Timing belt is the only type of belt to use here since it is critical that they remain synchronised. Various ways:

1) Short belt from motor to one leadscrew, long belt linking them with idler to tension it.
2) Long belt linking screws, wrap this belt round the motor pulley with idlers - so 3 pulleys on the one belt.
3) Two belts of a similar length going to motor placed in the middle, will make a 'V shape' so you can move motor to tension.

If you go for 1) then this 1595mm belt (http://www.bearingstation.co.uk/products/Belts/Timing_Belts/5M/PHG1595-5M-15) with 15T pulleys is 760mm center distance (or 1690mm with 34T pulleys is better as more teeth engaged on the pulleys), but that might be a bit risky when it comes to tensioning as if the center distance is slightly more, or the belt is slightly too short (possible due to the manufacturing tolerances) then the belt will not fit or may be damaged. It's safer to get a bigger belt then use an idler to tension it, problem is the next belt length up us 1690mm and the nearest with that over 760mm is 765mm which is too long.
If you go for 2 or 3 there's plenty of options.

Do you consider it critical to avoid slaving the steppers?

Ricardoco
30-07-2012, 12:48 AM
Timing belt is the only type of belt to use here since it is critical that they remain synchronised. Various ways:

1) Short belt from motor to one leadscrew, long belt linking them with idler to tension it.
2) Long belt linking screws, wrap this belt round the motor pulley with idlers - so 3 pulleys on the one belt.
3) Two belts of a similar length going to motor placed in the middle, will make a 'V shape' so you can move motor to tension.

If you go for 1) then this 1595mm belt (http://www.bearingstation.co.uk/products/Belts/Timing_Belts/5M/PHG1595-5M-15) with 15T pulleys is 760mm center distance (or 1690mm with 34T pulleys is better as more teeth engaged on the pulleys), but that might be a bit risky when it comes to tensioning as if the center distance is slightly more, or the belt is slightly too short (possible due to the manufacturing tolerances) then the belt will not fit or may be damaged. It's safer to get a bigger belt then use an idler to tension it, problem is the next belt length up us 1690mm and the nearest with that over 760mm is 765mm which is too long.
If you go for 2 or 3 there's plenty of options.

Do you consider it critical to avoid slaving the steppers?

Evening Jonathan, thanks for the reply, I can drive 1 screw directly with stepper and pulley from one screw to other with pulley, i dont have a choice about the slaving. so option 1, and i will drive 1 screw directly with stepper.. Magic Thanks.

I do have lateral screw adjustment from 755mm to 765mm center to center so fingers crossed manufacturing tolerences should not be a problem..

Rick

JAZZCNC
30-07-2012, 12:58 AM
You can have belts made to any length you want, that what I did with mine. I use a local bearing company so try your nearest decent bearing place.

Regards the belt design and heres one way using 2 idlers on plate that with adjustment for motor. All same size pulleys for 1:1 on my machine I go 2:1 with 5mm pitch screws using 24T on screws 48T on motor but you can use any size pulleys that suits. 15mm wide belts for me.

Edit: My machine doesn't use this system it use's short belt from motor to screw then long belt between screws. This is because my screws are 1300mm centres so suits it better.

Ricardoco
30-07-2012, 01:17 AM
I will PM you about those as i cant use them on this project, but i can on another that im having some bits made for on pay day Ive just got to send the drawings off..

Rick

JoeHarris
30-07-2012, 02:20 PM
Edit: My machine doesn't use this system it use's short belt from motor to screw then long belt between screws. This is because my screws are 1300mm centres so suits it better.

Images of Jazz's set up - link below (posted when I was asking a similar question!)

http://www.mycncuk.com/forums/showthread.php/4513-3-Axis-CNC-router

Jonathan
30-07-2012, 06:46 PM
using 24T on screws 48T on motor but you can use any size pulleys that suits.

Within reason - using too small pulleys can stress the belt too much or risk leaving not enough belt teeth engaged with the pulley. I avoid using less than 15T pulleys for this reason.i

boldford
30-07-2012, 06:55 PM
Evening Jonathan, thanks for the reply, I can drive 1 screw directly with stepper and pulley from one screw to other with pulley, i dont have a choice about the slaving. so option 1, and i will drive 1 screw directly with stepper.. Magic Thanks.

I do have lateral screw adjustment from 755mm to 765mm center to center so fingers crossed manufacturing tolerences should not be a problem..

RickAm I missing something but, isn't it possible to locate the motor between the two lead screws and fit two pulleys to the motor to drive two belts?

Jonathan
30-07-2012, 07:06 PM
Am I missing something but, isn't it possible to locate the motor between the two lead screws and fit two pulleys to the motor to drive two belts?

That's tricky with a Nema 23/24 motor since the shaft is not long enough to accomodate two pulleys for 15mm wide belts. You could bolt two pulleys together, so one would overhang on the shaft, but that might be a bit much force for the motor bearings. Adding an extra bearing would sort that, but if you don't have access to a lathe or milling machine that gets tricky.

Ricardoco
30-07-2012, 07:51 PM
Am I missing something but, isn't it possible to locate the motor between the two lead screws and fit two pulleys to the motor to drive two belts? You are quite correct you could do that in a simillar way as stated in another post and have a V arrangement to cover tensioning, however i havnt mentioned it before but i have such a limited working space that there is only just enough room below the bed for the belt .. But thanks anyhow...hope that makes things a little clearer..

Rick

boldford
30-07-2012, 08:00 PM
That's tricky with a Nema 23/24 motor since the shaft is not long enough to accomodate two pulleys for 15mm wide belts. You could bolt two pulleys together, so one would overhang on the shaft, but that might be a bit much force for the motor bearings. Adding an extra bearing would sort that, but if you don't have access to a lathe or milling machine that gets tricky.Bore 'em out then fix 'em on a common sleeve. The tension on the two belts would tend to cancel out if the thrusts are arranged to be reasonably opposite. The belts don't necessarily need to be the same length so the motor need not be centrally between the leadscrews.

Just my two-penny-worth.

Jonathan
30-07-2012, 08:27 PM
The tension on the two belts would tend to cancel out if the thrusts are arranged to be reasonably opposite.

Yes of course, but one of the pulleys is much further from the front motor bearing so there will still be a larger moment load on the shaft. Still, I'm probably being being overly cautious.

JAZZCNC
30-07-2012, 11:41 PM
Within reason - using too small pulleys can stress the belt too much or risk leaving not enough belt teeth engaged with the pulley. I avoid using less than 15T pulleys for this reason.i

If you look I said any belt that "suits" and obviously too small giving wrong tooth engagement wouldn't suit would it.?


Am I missing something but, isn't it possible to locate the motor between the two lead screws and fit two pulleys to the motor to drive two belts?

Yes it is and that's how I did it first time but found it hard to get even tension on each belt.! It also means having the screws offset or one machined longer or like in my case where I hadn't allowed for this when machined due to originally going to use slaved motors screw extensions needed making.

The way I have it now isn't pretty but it works very very good and super reliable and easy to swap ratios.!

Jonathan
30-07-2012, 11:54 PM
If you look I said any belt that "suits" and obviously too small giving wrong tooth engagement wouldn't suit would it.?

True, hence I clarified for anyone who does not know that a small pulley not be suitable.