[Bob La Londe]

Ok, as near as I can tell the bearings in the Taig spindle (or similar ones I can buy elsewhere) are rated for upto 17K with grease or 24K with oil mist. I ran the stock spindle at 10K for atleast a thousand hours and its still basically ok, so that doesn't surprise me too much. I wanted more speed though for faster production with small cutters in aluminum. I have a couple thousand more hours running various routers as spindles instead. They definitely can remove material a lot faster, but the nose bearings overheat and burn up when doing long jobs that use a measureable portion of their horsepower.

The stock spindle has a couple problems. Low horsepower and lower top speed than I would like. I can't drive a modest cutter hard enough to take advantage of its size for a decent material removal rate, and I can't spin a smaller cutter fast enough for a decent material removal rate. AND its heavy. That assembly with that fairly nice 1/3 HP brushless motor weighs in at a whopping weighs in at 15 pounds 12 ounces. The weight is great for taking up backlash in Z, but its hell on rapid speed which kills overall production rate when doing complex 3D machining.

The routers have their problems too. A Bosch colt has the horsepower for anything I would ever do with a Taig and the speed, but the heat from heavy cutting will overheat the nose spindle and melt the plastic nosebearing holder. Its light though. Even with the custom aluminum mounting bracket I made for it the total assembley is less than 4 pounds. Rapid speed is great, but backlash is an issue because there isn't as much weight to hold it against the threadss I have to keep the Z dialed in before everyjob. A Porter Cable router is better, but I have still cooked nose bearings. If I only rarely cut aluminum, and mostly cut wood and plastic either would be fine.

I propose a compromise. Use a small router as a drive motor for the stock spindle. Use maybe a 2:1 pulley reduction to drop top speed down to about 15-16K (depending on router choice) and increase torque so horsepower is never an issue. It would be lighter so rapid speeds would still be good have a proven spindle bearing setup. It would not transfer any heat to the motor bearings from cutting, and it would be modestly faster. According to FS Wizard calulations 5000 rpm makes a substantial difference in feed rate and material removal rate. The spindle bearings appear to be mounted directly in the aluminum block which helps with heat dissapation.

I suppose a chinese spindle (or Ugra spindle at much more money) seems like a good alternative, but it adds both spindle and VFD costs to the equation. Most VFDs in this size like 220 3ph, although 1:3ph and 110:220 VFDs are available for 1HP and under applications. I'ld like to keep it a simple 120V machine. The VFD stuff doesn't bother me though. I do have two VFDs inside the cabinet in my big mill working fine. One drives the 5HP spindle motor, and the other runs the motor cooling fan at low spindle speeds.

So who is running a Taig spindle over speed, and how long have you been doing it? What type of cutting?

Its all just thinking out loud right now...

[Bob La Londe]

I decided to give it a try. I already had the router so why not. Worst case is I have to try something else. Only thing I might have to buy is a timing belt.

[bhurts]

I have used a full size 2.25 horse power router as a motor to run a sherline spindle. I used 3/8s wide mxl timing pulleys. A 15 tooth on the router and a 30 tooth on the spindle. That let the spindle max out at 12,500 rpm. The router has a slowest speed of 10,000 rpm so I could run from 5000-12,500. Keep extra belts on hand and make sure you have as little runout on the pulleys as possible. The belts lasted 6-8 months of daily use with no problems other than adjusting the belt tension from time to time.

Ben

[Bob La Londe]

I have used a full size 2.25 horse power router as a motor to run a sherline spindle. I used 3/8s wide mxl timing pulleys. A 15 tooth on the router and a 30 tooth on the spindle. That let the spindle max out at 12,500 rpm. The router has a slowest speed of 10,000 rpm so I could run from 5000-12,500. Keep extra belts on hand and make sure you have as little runout on the pulleys as possible. The belts lasted 6-8 months of daily use with no problems other than adjusting the belt tension from time to time.

Ben

Have you considered seeing if the kevlar fiber reinforced belts are available in your size? It might reduce the adjustments, and increase the overall life.

[Bob La Londe]

Now to put a several hour job on it, and see what gets hot.

[awerby]

Just for the sake of experimentation, I souped up a Taig mill with a 1 hp Perske spindle and VFD. It runs at 18,000 RPM and will spin a half-inch cutter all day long. It works great on wood, but the thing cost almost as much as the mill itself, so whether it's really worth doing depends on your needs. The problem with using hand routers for this sort of thing is that their bearings aren't intended for continuous cutting , but I've heard of some people who've replaced the standard bearings in hand routers with much better ones, and got a lot more life out of them.

Andrew Werby
www.computersculpture.com

[Bob La Londe]

How much does that Perski spindle weigh? Weight is one of the advantages of the brush motors over the brushless induction motors.

I was hoping using the router as just a drive motor would eliminate cutter heat damaging the router bearings, and also maintain fairly constant load on the motor bearings as opposed to cutting directly. I've used them directly as spindles and they will flat remove some material, but they die fairly quickly. I've upraded the bearings on a few of them but it really wasn't that big of a benefit.

In the picture about I have 2:1 speed reduction which puts me below my target max RPM. 20Xl:40XL pulleys gives me 13.5K apx. I just ordered a 32XL pulley for the spindle which should put me right on target or just over at about 16.8K apx. I'll turn it down just a hair to hit 15K, and the speed compensation built into the router should keep it pretty close from there.

If it doesn't work a high speed 3 phase spindle will be my next thing to try, and ultimately would probably be the better choice. It just costs more.

[awerby]

That Perske spindle isn't light, but it's the smallest one they make. I don't think it weighs much more, if any, than the stock spindle/motor configuration, and being on center instead of offset to the side makes it less likely to bind up. I've also got some fairly powerful servos on that machine instead of the usual steppers, so it hasn't had any problems lifting the spindle so far.

Using the router motor indirectly as you're proposing might cause it to last longer, but I doubt it will make that much difference. I don't think the heat from cutting is really the culprit in bearing failure; they're just not built to run for very long. Did you put the really-expensive ceramic bearings (with the approved high-speed grease) in those routers, or just better bearings than the ones they came with?

Andrew Werby
www.computersculpture.com

[Bob La Londe]

For anybody who has followed this... nose bearing on the Taig spindle has a rubber seal which generates heat from friction. Most of the sources for that size bearing I have found with a rubber seal list it at 12000 rpm. Still faster than Taigs recommended 10K limit. A metal shield bearing in its places would allow the spindle to turn much faster, but the risk would be particles in the bearing from cutting over time. The real solution might be to use open bearings with external labyrinth seals and an oil mist pressurized spindle to lubricate and keep particles from working in. Hmmm... time to do some thinking... and time to go work a spindle hard to see what it will really do.

[somenewguy]

I am doing mostly plastic work on my new-to-me taig, which is really way too slow most of the time. Since upgradeing the axis is expensive, I am going to try and just whip up a quick mount for a dremel to replace the whole motor head when doing microdrilling, which is a common use for me. I will probably use a Proxxon brand tool as in a side by side hand comparison (no real measuruing tools were involved) the proxxon seemedto have less spindle runout then the dremel brand, both were brand new out of the box, the boss man had accidently ordered them both at the same time when he thought he was just window shopping... Must be nnice to have money lol.

as for axis speed to keep up with the spindle, I might see if I can re-wire an old linear supply (read:busted battery charger) as an el-cheapo 45v source for the steppers, as I am running on the stock 24v and gecko combination. However I have no idea what kind of sideload the dremmel can really take anyways, and since I don't have spindle speed feedback I am probably safer just using it for drilling only and sticking to the real spindle for any milling.

[awerby]

What control are you running on your machine? How fast can it reliably cut? I can see using a Proxxon IB/E as an auxilliary spindle, if you want to do engraving or ultra-fine milling with tiny tools. You could make a mount for it that interfaces with the dovetail that holds the standard spindle, so it would be a slide-off, slide-on replacement. It spins at 20k rpm, (but I'm not sure how long it will do that). However, they aren't very expensive, so you can consider them a consumable item and replace them as they die. I'm sure one of them would last longer than a Dremel, anyway. But for general-purpose milling, the Taig spindle is actually really good, and it just keeps going...

Andrew Werby
www.computersculpture.com

[somenewguy]

true, but it is very very common that when I calculate ideal speeds and feeds, I land in the 20k-60k range, so think I will try it. The hardest thing will be getting the mount plumb, as I don't want to align it usign the Z axis, that way as you said, it canb e a slid on/off operation, no re-leveling the column.

oh and I was thinking of slapping a monster stepper motor onto the Z axis to get my feed speeds up higher, as currently I am limietd to 30 IPM in warm weatehr, 20-22 in the cold as my shop i unheated. I see people getting 60-100 and I think I can do the same for about 100 bucks in upgrade. I am runing a G540 so I just need to up my voltage, although the Z could probably use a 300 ozin motor.

[Bob La Londe]

Make a mount that slides on the dovetail block of the Z that's already there. Once you get your high speed spindle aligned once it should be "pretty close" every time you mount it after that. As long as you don't hit it with a hammer or drop it anyway. There is a guy on Ebay who makes mounts for the 65mm and 80mm 3 phase spindles that way.

[somenewguy]

I don't konw that I ahve the ability to machine a dove tail like that, but I will give it a shot. might need to make it out of 3 pieces and bolt together or some such foolishness. if it actually turns out repetable I'll pin it. I think I will make it more of a V block layout than a full circle, so I can have universal mount for different dremmels as they burn or as I want to try new things.

hmm I wonder if I could make the VFD act as speed control.. a digital pot should be easy enough unless it actually runs power thru the thumb wheel....

[Bob La Londe]

Huh? A VFD is usually used for running a 3 phase motor at different frequencies to control its speed. Many have the ability to accept voltage level external control. 0-10V or 0-5V. A dremel or other electric grinder is typically a single phase universal brush motor. They can be speed controlled by pulse width modulation (if soft start and other speed control circuits are removed and thrwon away). There are pulse width speed controllers out there that will also accept 05 or 0-10 input for speed control. Your PC and breakout board may already be capable of this or you can add a voltage level output to it.

I am summarizing a lot here and skipping over a lot.

... sometimes a VFD is just used to run a 3 phase motor on single phase.

I do both on my big mill. It was a 5HP 3phase spindle motor I run on one VFD at 3hz to 120hz for 96-3600 rpm operation. It also has a 1/2 HP fan motor inside the case of the spindle motor that cools the big motor. I run that on another smaller VFD at a fixed 60hz.


~~~
A v-block might work, but there will be practical limits of course.

[clmenz]

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