NEED HELP spindle motor selection

[cyclotron]

Hi all,

I've been trying to find a small dc motor to runt he spindle on
my gantry type machine. ( here is my thread http://www.cnczone.com/forums/showth...t=39189&page=3 ) I am using a Taig spindle and I originally intended to use their .25 HP ac motor. I quickly realized that this thing was way too big and heavy to be pushing around on the gantry, so I started looking for alternatives. I found this
>>> http://www.mechanicalphilosopher.com/kshaw11.jpg <<<

note the small motor being used, it is a swiss maxon dc motor. here is what the owner says about it :

" The DC motor is rated at approx. 0.15 HP but has lots of torque -- like 100 oz-inches (continuous, 500 oz-inch max) at the step pulley shaft running at around 1550 RPM i.e. I can run the motor up to 8000 RPM continuous with no problem at all, and I use this to advantage by using a base reduction gear of 1:4.5 So I cut some small 6061 T6 aluminum parts up to 3/4" diameter and ripped off metal at a high rate, just like the GE clunker"

I took this as a sort of proof of concept for finding a small but powerful motor.

Anyway according online power-RPM-torque calculators, my Taig motor outputs 73.64oz-in (.52 Nm) of torque at its standard output of 3450 RPM

I have found a maxon motor for sale (surplus) that claims to have a max continuous torque of 280 oz-in and a no load RPM of 5280. On the surfac, it would appear that the maxon motor outputs more torque at a higher RPM than the Taig motor. Somehow this seems too good to be true. Am I missing something? Are there other factors that I should be looking into?
Also, can anyone think of any alternatives to this problem of finding a smaller motor? I intend on milling plastic and doing some light aluminum facing and drilling. Any insight would be very appreciated.

[guhl]

Hi.As I know, there're direct connection between power and overall dimensions of the motor. And AC motor has a benefit in this. You can reduce dimensions by using the high frequency AC motor (e.g.400Hz). Really, there're DC motors with rare-earth magnets; they're smaller than electric field DC motors.

[wcarrothers1]

Don't have time to examin what you are trying to fit.. How ever I might recomend looking at a sewing machine motor. Might sound funny. But they are AC, Variable speed is built in (but have to modify the peddle) and are pretty easy to get. And I'm pretty sure they are powerfull enough. And they are small.

I'm about to modify my wolf gang eng spindle to run from one of my wife's old surger sewing machine motor rather then the little motor he sells with the setups.

Just an idea. Probably could get a cheep sewing machine from wall mart and mutilate it for the motor for very little motor.

b.

[Eurisko]

I picked up a nice little sewing machine motor for 10 bucks at a local sewing machine sales/repair shop.

Seems to work well with my Harbor Freight router speed control.

Won't know for sure until my machine is finished, but it looks promising...

[guhl]

Originally Posted by wcarrothers1 Don't have time to examin what you are trying to fit.. How ever I might recomend looking at a sewing machine motor. Might sound funny. But they are AC, Variable speed is built in (but have to modify the peddle) and are pretty easy to get. And I'm pretty sure they are powerfull enough. And they are small. I'm about to modify my wolf gang eng spindle to run from one of my wife's old surger sewing machine motor rather then the little motor he sells with the setups. Just an idea. Probably could get a cheep sewing machine from wall mart and mutilate it for the motor for very little motor. b.

RPM controling system of sewing motor realizes the V/F control without speed feedback. All lathes, mills etc. AC drives realize vectorial type of controlling. Other words, in case of V/F control without speed feedback, if load-on happend, the velocity of your spindle being reduced. If V/F control with speed feedback is realized, when the load-on happens, spindle loses the RPM for duration of several seconds.

[wcarrothers1]

guhl... I have a VFD drive on my router mill. So I'm firmilure with them now (posts you might have missed about me fitting my VFD control from automation direct along with a ekstrom carlson spindle motor) so I understand whatyou are trying to say. How ever I thought the orignal question was for a possiable replacement. Seeing I wanted a more powerfull motor for my other spindle (don't use the VFD for the real small stuff) I was in the process of mutilating my wife's dead sewing machine and the motor in it looked perfect for it..

I'm still waiting for the pulley I ordered yesterday to finish the job and try it..



b./