What Pulley/belt system I should use?

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31 Oct 2021 14:53 #224769 by PhilipME
Hello

What Pulley/belt system I should use to transmit the power from my ac servo motor to the bt-30 milling spindle

the servo motor power is 1.5 kw and rated for 3000 rpm

I have been searching for quite a while. Most of the belts/pulleys I came across, they seem to be suitable for the xyz motion, not for a spindle. It looks like the GT2-5m or the HTD but for some reason I do not see wide belts. Not sure if 10 mm wide timing belt/ pulley can transmitt the 1.5 kw at the 3000 rpm.

I will appresciate the slightest hint


Thanks

Philip

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31 Oct 2021 15:04 #224770 by tommylight
Go to a car mechanics shop or shop online for toothed belt, the only car that has a short one that i can recall is VW/Audi 2.5L V6 diesel engine, the one for the high pressure pump. Pulleys are easy to find just mind the pitch and tooth shape.
Car parts are very cheap compared to machine parts so i always look for those first.
BTW, the same engine has also the longest wide toothed belt i could find at 1580mm, i think. I used it on a plasma machine for over 10 years, it was used when i got it! :)
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31 Oct 2021 15:50 #224776 by spumco
I tend to use B&B Manufacturing for timing belts & pulleys.

Good web site, online ordering, and they have a nice belt length calculator.  Prices are pretty good considering you are getting components with known dimensions/characteristics and actual quality control.

HTD5m belts have a bit too much backlash for really precise positioning applications, but are perfectly suitable (designed for, actually) for a spindle motor application.

FWIW, I have a 3kw 8kRPM spindle motor, 1:1 pully ratio, and am using a 25mm wide HTD5m belt arrangement.  At your power level, a 15mm wide belt will be more than adequate, and the pulleys will weigh less (important for spindle accel/decel).

Rant: I bet the GT2 belts you've been looking at are for 3D printers.  You will be spinning the motor at 3kRPM, and the spindle will probably be faster - you don't want cheapo, unbalanced garbage disassembling itself at speed.  When you are standing in front of your benchtop mill and the spindle is humming along at 6kRPM, what's the closest thing to the belt & pulleys... your face.

Stop looking at 3D printer parts on Amazon and ebay, and start looking at industrial drive component mfgrs and distributors:


B&B Manufacturing
Brecoflex
TB Woods
Continental
Gates
Rainbow Precision
Stock Drive Products (SDP-SI)
Plenty of others in the same league


End rant.

Downside to timing belts is that they are noisy compared to a poly-v (multi-rib) belt.  Downside to poly-v belts is that they can slip a little (not good for a synchronized spindle without a direct spindle encoder) and require a more belt tension which may not be great for your bearings long-term.

If you can attach an encoder directly to the spindle then poly-v belt slip is a non-issue for rigid tapping or spindle synchronization.  If you don't plan to rigid tap, I'd suggest looking for an 8-rib J-series poly-v belt arrangement before using an HDT or other toothed timing belt.

Your ears will thank you.

Backing up a bit, the hardest part will be attaching a pully to your spindle.  The motor pulley is easy - there are QD and taper lock bushingings available to mount just about any pully to any shaft.  But your spindle probably requires something a bit non-standard.  Before anything else - belt type, profile, width - figure out what and how to attach a pulley to your spindle.

So first questions:
  • What is the spindle drive end size and how is the pulley attached/retained?
  • Is the pulley used to load or retain the top bearing (or spindle shaft itself)?
  • How large of a pulley is possible? (interference with other items on head like motor, PDB mount, etc.)
    • This is important because if you have a large spindle shaft and want to use a QD (or similar) bushing, the shaft size dictates the bushing 'series', which in turn disctates the smalles pulley available in that series.
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31 Oct 2021 16:56 - 31 Oct 2021 17:22 #224780 by PhilipME
Very clear for my pathforward
 True that most of the search results came out to be related to 3d printers simply because I did not know where to look.
Many thanks

spumco
this is the spindle I purchased (Now after you mentioned it, I do not even see a keyway for the pulley haha)

www.aliexpress.com/item/4000837824999.ht...1.0.0.34b04c4dEoclzJ

I have no clue how to attatch the pulley to the bt-30. I have not done this before, but I know I will make it work.

I bought air cooled spindle for wood work. I will install it and use the machine as wood router first, and take my time studying the milling spindle and the motor.

I am glad you pointed me to the chalanges ahead so I know where to focus.

 Philip
Last edit: 31 Oct 2021 17:22 by PhilipME.

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31 Oct 2021 21:09 #224796 by rodw
This is an Aussie web site that specialises in timing belts. Go to someone similar in your country
www.naismith.com.au/
If you follow their website on timing belts you will find a PDF for HTD belts that shows torque recommendations in a graph.
Looks like HTD-5M goes to 25mm width
HTD-8M goes to 85mm width
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31 Oct 2021 21:13 #224797 by rodw
Also, the diagram on your spindle shows there is a keyway on the input shaft.
The specialist supplier I mentioned will machine the  pulley ID to your specs if required. ie add the keyway if you don't have a broaching tool.
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31 Oct 2021 21:48 #224807 by spumco

 
I have no clue how to attatch the pulley to the bt-30. I have not done this before, but I know I will make it work.

 



As Rod pointed out, you have a keyed input shaft and the diameter and keyway specs are on the spec sheet.

Looks like a 25mm shaft.  It should be very simple to find either an HTD or poly-v pulley and have the supplier put an appropriate keyway in it.  It's retained with a threaded nut on the end of the spindle.

Your other option is to buy a 25mm taper-lock or QD bushing and matching pulley.  If you use a tapered bushing there's no need for a key or the nut as the bushing clamps to the shaft more firmly than any other method.

Here's a JA-series bushing:

www.bbman.com/catalog/product/JAx25mm

And here's a a 10-rib poly-v pulley:

www.bbman.com/catalog/product/10J200JA

That one is about 2" diameter.  Get a matching 3" one and appropriate bushing for the motor, and you've got a very quiet drive drive with no custom parts needed that'll go to 4500rpm.  If you want 6kRPM you can see if a 4" pulley with fit on the servo motor.

The 10-rib pulleys will be heavier than the 6-rib and everything is a bit more expensive, but you need a little less belt tension with the wider belt to stop any signficant slipping.

The same site also has HTD pulleys that fit the same QD bushing system if you're dead set on a toothed belt.
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01 Nov 2021 03:33 #224825 by PhilipME

 
I have no clue how to attatch the pulley to the bt-30. I have not done this before, but I know I will make it work.

 


As Rod pointed out, you have a keyed input shaft and the diameter and keyway specs are on the spec sheet.

Looks like a 25mm shaft.  It should be very simple to find either an HTD or poly-v pulley and have the supplier put an appropriate keyway in it.  It's retained with a threaded nut on the end of the spindle.

Your other option is to buy a 25mm taper-lock or QD bushing and matching pulley.  If you use a tapered bushing there's no need for a key or the nut as the bushing clamps to the shaft more firmly than any other method.

Here's a JA-series bushing:

www.bbman.com/catalog/product/JAx25mm

And here's a a 10-rib poly-v pulley:

www.bbman.com/catalog/product/10J200JA

That one is about 2" diameter.  Get a matching 3" one and appropriate bushing for the motor, and you've got a very quiet drive drive with no custom parts needed that'll go to 4500rpm.  If you want 6kRPM you can see if a 4" pulley with fit on the servo motor.

The 10-rib pulleys will be heavier than the 6-rib and everything is a bit more expensive, but you need a little less belt tension with the wider belt to stop any signficant slipping.

The same site also has HTD pulleys that fit the same QD bushing system if you're dead set on a toothed belt.

I can not thank you enough

 

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01 Nov 2021 03:55 #224831 by PhilipME
I sent inquiry to bbman and supplied them with the motor and spindle data

 

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01 Nov 2021 04:27 #224833 by spumco
Don't forget to check ebay once you figure out what parts you want.  there are tons of QD bushings on there.  Not as many pulleys, but you could save a couple bucks.

 
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