Spindle motor replacement

[Jim Dawson]

You might look at the DMM Technology 880-DST-A6HK1 servo motor and a DYN4 drive. I think that would give you similar performance to your existing motor. It's an 80mm frame motor so I think is a bit larger than your motor. You will have to look at the drawings to see if it will fit.

http://www.dmm-tech.com/ac_servomotor_main_a1.html

[A_Camera]

I am trying to figure out the best way to get my mill up and running again, i am considering all of the ways of doing so then i will do what ever is best. Right know i think the best way is to just figure out what replacement brushed dc motor would work for the rpm and mounting.


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The best and cheapest way would be to replace the brushes and clean the contacts. That's what I'd do if I was happy with it otherwise. Everything else is more expensive and more complicated. Have you looked at Kress? Also a brushed motor, and you probably won't be able to control it the same way you control your motor but many people are using it happily and Í think it would be a simple installation with some minor mods. On the other hand, if you intend to keep the low rpm then I think your choices are limited.

[KyleWarren]

I would like to try to keep my rpm low and use the r8 collets, I would be willing to spend more to get a quality product that lasts rather than replace the brushes and contacts. For the servos what is the difference between low and medium inertia, would the medium inertia servos be better?


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[KyleWarren]

Would the DYN2 AC Servo Drive and the 86M-DHT-A6MK1 work for a spindle?


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[Jim Dawson]

I would like to try to keep my rpm low and use the r8 collets, I would be willing to spend more to get a quality product that lasts rather than replace the brushes and contacts. For the servos what is the difference between low and medium inertia, would the medium inertia servos be better?

From the DMM website: DHT and DST series servo motors are available in both medium inertia for high rigidity, high load applications and low inertia for faster response and higher speeds.

The Medium Inertia motors have more torque for a given power, but they won't accelerate quite as fast, and in general may sacrifice max speed. The max speed limitation does not seem to be the case in the DMM product line.

Would the DYN2 AC Servo Drive and the 86M-DHT-A6MK1 work for a spindle?

According to the specifications, DYN2 drive can be paired with the 86M-DHT-A6MK1, but it would limit your max speed to 3000 RPM. The real downside is that you would have to purchase a power supply for the drive, the DYN2 is limited to 75VDC max input.

[KyleWarren]

i did just remember one think that might be a problem the belt and pulley system that is on there has a 2:1 reduction, that is one reason i thought the hobby brushless motor because i found one that goes 6000 rpm so the spindle would be at 3000 rpm. with the reduction the servo motors wouldn't work because there max speed would be around 1500 rpm and i don't think that is enough for milling.

[Jim Dawson]

i did just remember one think that might be a problem the belt and pulley system that is on there has a 2:1 reduction, that is one reason i thought the hobby brushless motor because i found one that goes 6000 rpm so the spindle would be at 3000 rpm. with the reduction the servo motors wouldn't work because there max speed would be around 1500 rpm and i don't think that is enough for milling.

That is an important point. But RPM is not the only parameter to look at, the torque curve is important also. Yes you need the RPM for milling, but take a look at the motor torque curve if the specs are published. In a perfect world, the torque would be flat from 0 to max RPM, but in general, the torque will be flat to some RPM then will drop off. The good news is that milling at high RPM on a small machine requires less torque because you are using smaller cutters.

[KyleWarren]

the motor i was looking at was 1400 watts brushless and there wasn't any torque information

[Jim Dawson]

the motor i was looking at was 1400 watts brushless and there wasn't any torque information

If that motor maxes out at 6000 RPM, then it may have enough torque. The other questions that come to mind are: Is that motor rated for continuous operation and does it require any cooling? Not trying to rain on your parade here, I'm just throwing out some of the concerns that I would look at if I were specing a motor for any application.

Maybe a link to the motor you have in mind would be helpful.

[KyleWarren]

https://hobbyking.com/en_us/turnigy-...v-60-glow.html that is the motor i was thinking about useing

[Jim Dawson]

I have no idea how well that would work but it would be an interesting experiment. It would take a massive low voltage power supply to make it work. Maybe a large battery charger?

[Al_The_Man]

Having used RC motors in the normal application (RC) I would Never consider them for CNC use, keep in mind they are typically ran in short duration due to battery charge, and rely on some method for cooling, prop etc.
BTW the 300Kv refers to the rpm/v or revs per volt.
Al.

[KyleWarren]

i have no idea what power supply i could use to power a motor like that

[Al_The_Man]

i have no idea what power supply i could use to power a motor like that

Just below in the ad, a Turnigy 70A SBEC, requires a PWM signal to operate.
https://hobbyking.com/en_us/turnigy-...ontroller.html
Al.

[KyleWarren]

i know what motor controller to use, i don't know a power supply that would be able to power that motor.

[Al_The_Man]

Probably have to build it, a simple linear P.S. using a Toroidal TXFR that you can wind on a simple secondary with a few turns. and a bridge rectifier.
Are you still considering it?
Al.

[KyleWarren]

If i can figure out a power supply and a cooling solution, a brushless motor is probably what i would go with. I have a 24v 15 amp transformer but I don’t think that is enough to drive the motor.


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[Al_The_Man]

Probably a 1Kva min Toroidal.
I thought you want low rpm control?
Al.

[KyleWarren]

Low rpm control would be nice to have but I don’t see myself using it often, I normally had my spindle at max or almost max rpm.


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[Al_The_Man]

Then you may as well go with a Kress or similar with a simple triac controller.
I always got a kick out of the numbers quoted around RC motors etc.
Like a 2Kw for a motor you can fit in your hand!
Al.