[bunalmis]

I need the 90000 rpm but my motor turn only 30000 rpm.

Can i use belt-pulley system for this purpose?

[yoopertool]

I am by no means an expert, but my guess would be no. To run at 90000rpm your pulleys are going to have to be nearly perfectly balanced and belts probably wont hold up in those conditions. I may be wrong, but I have never seen a spindle run anywhere close to that range with belts. As I said, I am no expert, and this is just my $.02. Good Luck!

[NC Cams]

Just because you "need" 90K, that doesn't mean that is is wise or viable to run at 90K RPM.

Before you go balancing pulleys and crafting up belts and pulleys to spin at 90K, you'd better go thru the ENTIRE spindle that you plan to run at 90K and see if the bearings are even rated for 90K.

Then, just because they might at the ragged edge of viability of their design window at or approaching 90K, that doesn't mean that the ones you have will be suitable to run at 90K.

High speed bearings usually have special internal provisions to make them high speed capable. THings like special cages, special tolerances, special lubes and so on and so forth are quite the norm for such high speed use. Such spindles are also usually assembled with much closer tolerances. Simply put, what might live for decates at 10k can fail almost immediately at 90K.

What you want to do is NOT technically as simple as running overdrive pulleys and flicking a switch!!!!!!!!!!!!!!

[Oldmanandhistoy]

Just because you "need" 90K, that doesn't mean that is is wise or viable to run at 90K RPM.

Before you go balancing pulleys and crafting up belts and pulleys to spin at 90K, you'd better go thru the ENTIRE spindle that you plan to run at 90K and see if the bearings are even rated for 90K.

Then, just because they might at the ragged edge of viability of their design window at or approaching 90K, that doesn't mean that the ones you have will be suitable to run at 90K.

High speed bearings usually have special internal provisions to make them high speed capable. THings like special cages, special tolerances, special lubes and so on and so forth are quite the norm for such high speed use. Such spindles are also usually assembled with much closer tolerances. Simply put, what might live for decates at 10k can fail almost immediately at 90K.

What you want to do is NOT technically as simple as running overdrive pulleys and flicking a switch!!!!!!!!!!!!!!

You can’t beat a reality check! I commend your generosity and fortitude it is a FACT that the Zone would be a far poorer place without members like you.

Thank you,
John

[Geof]

Never mind bearings I would be concerned about pulleys fragmenting at 90,000 rpm. That is very fast and the centrifugal stresses increase as the square of the angular velocity so they are nine times higher than at 30,000 rpm.

[lgalla]

PDS COLOMBO has 80,000rpm spindles,compressed air cooled or liquid.Too much denero or ADV lira.
I agree with Geof plus much heat generated besides the possibility of the pulleys exploding or fragmentation.
Bunalmis,what is the application?perhaps there is a better solution.
Larry

[bunalmis]

I design PCB engraving machine.

90K Rpm need for high quality cutting. Tool diameter 0.2 mm.

[drk]

Most PCB drilling spindles would not be running of a belt simply because even if you could keep the runout withing .0001", which is the pre-requisite for drilling holes that small, the very vibration from the belt would kill it.

To run that kind of a tool, u have to run ur spindle of a high freq. element.


Dev

[Sump Cleaner]

Can you use a air powered jig grinding moter?

I have used them up to 120,000 rpm on a Moore jig grinder. They should have enough snuff to drive an engraving tool.

Just a thought.....

JK

[bunalmis]

High frequency motor too expensive. 2000-3000 Euro.

Pneumatic hand tools turn around 50K...120K rpm. But this tools need to compressor. Compressor and hand tools make big noise.

Therefore i am planning the belt-pulley systems. Ceramics ball bearings work at this speeds. Also I can do good balanced pulleys.

But belt confused.

[jhudler]

Your looking for round braided or woven belts, like the ones on dental drills.
If your going to use belts, calculate what you torque and inertia requirements are, then size for the pulley's.

Your limiting factor or design consideration for the belts is FPM (Feet per minute).

An idea just popped in my head; what about sacrificing torque for inertia by adding mass to the spindle. Might take some time to come up to speed and PCB having such a short work cycle (time to drill one hole) that it might help lowering the FPM to a less expensive belt (larger drive pulley). Have to watch the spindle speed to make sure it didn't drop bellow limits, then pause until the spindle returns to speed.
Wrap that mass in Kevlar blanket! High speed spindles can be deadly, the life you save could be your own!

[2muchstuff]

Your looking for round braided or woven belts, like the ones on dental drills.

The only belts used today in the dental industry would be on a lab engine. They are like the old belt driven handpieces but are table top units. Lab engines only turn about 5000 RPM at the hand piece.

Todays dental drills (handpieces) will turn up to 400,000 RPM depending on the brand with no load. As soon as you load it down the RPM drops significantly. They are high speed, low torque air driven turbines that use about 2.2 CFM of air. On the other hand, some dentists are using electric handpieces that have either brushed or brushless motors in them and a 1:5 gear head that increases the speed.

[NC Cams]

Do NOT think for a moment that simply bolting in ceramic balled bearings will make your spindle 90K capable!!!

When I was in the ball bearing industry, we had a sales guy offer some generic instrument bearings for "interchange" in a high speed Dumore grinder. When the engineering dept head got wind of the "simply substitution" he went BALLISTIC!!!!

Reason: you have to really do some special stuff to make a high speed spindle live/work.

Balance is one part. Shaft alignment is EXTREMELY critical. Housing and shaft tolerances were generally HALF of the normal tolerances. Cages were special as were the lubes and ball and raceway tolerances. If/when you talk about "rocket ship" bearings, they are NOTHING compared to ultra high speed spindle bearings!!!!

Ceramic balls address the centrifugal force problems but they have NO affect on the tolerances, fits and finishes of the other stuff that MUST be addressed as well in the related//connected spindle components.

Simply put, and again, YOU CAN"T SIMPLY CHANGE PULLEYS AND INSTALL CERAMIC BALLED BEARINGS AND EXPECT A 90K SPINDLE TO WORK/LIVE.

Fore warned is fore armed.

[Andre' B]

A direct drive AC electric spindle is the way to go.
Next best is and air turbine.
These guys make some nice ones.
http://www.airturbinetools.com/mm.html


But if you must make something I would avoid belts and do a friction drive setup something like this. The two motors is just to get a balanced forces reducing the side load on the high speed bearings. The second wheel could be just belt driven from the one motor.


Edit:
One place I worked at got an ID grinder with a 120,000 RPM AC spindle. They went thru 3 sets of bearings before the operator learned that you really do need to make sure the air oil mist is flowing thru the bearings all the time and you can't do a cold start to full speed bypassing the warm up schedule.