[Lozzy]

Been here once in a while, always getting some help from guys here.

Recently, I got a brand new desk-top mill, Optimum BF-16.
It doesn't have rich information in network, probably not quite polular than its bigger bro, BF-20 (or Grizzly 0704), anyway, as soon as I saw the real one,
I decided to buy it and to convert it for light CNC milling job.
I dissembled it to measure x-y table/underneath available space for ball screw, and already ordered 12mm diameter/4mm lead ball screws for this baby.
I also got a very good deal of 3 sets of used 200w servo motor+driver from Yaskawa, SGDA series and successfully tested it via parallel port mach3 board using pulse/dir and this fascinated me. Very quiet, smooth and fast.

However, this 200w power seems to be beyond my necessity for this micro mill and I am thinking of reserving these sets for my future modification for current CNC router I am operating which is 600mmx1200mm dimension, moving gantry, steel frame, a lot heavier than this mill.
Then, I will need another sets for this mill.

I am currently looking at 100w versions, but I do not know if 50w can simply meet my demand.
Main use of CNC mill is for light(really light) milling. It will never cut 45C steel with 1mm DOC.
Slow feeding, light cut, mostly 6061 aluminium or brass, and then sometimes normal steels.

So here comes my question:

Will 50w be enough for the job or do I have to consider at least 100w motor sets?
Considering mill's size and type of duty, I guess 50w may do the job if I use reduction pullies and ball screws with 4mm lead.
I wish someone can suggest some helpful advice.

* I don't consider stepper motors at this moment. I have been using steppers for years until now but I now have access to various used gears from dissembled factory automation. They are not expensive and they work good. And the size of motors really grabbed my eyes. I am new to servo motors and this is a new world to me. All are yaskawa/mitsubishi/samsung/omron things, though recent products are a bit more expensive than old ones. I believe I will stick to servo systems for a while until.... hmmm.. I don't know

[hub]

You have to estimate, or calculate the force required to get the required torque & check the servo's data sheet to see if it has enough torque.

Maybe a place to start:
http://www.orientalmotor.com/support/selectionTips.pdf
Application Entry Form

[mactec54]

Lozzy

The 200w servos should be just fine for your mill, you might find 200w is to small for the Z axes, they won't be any good for a router the size you are planning to build

[Lozzy]

hub/

thanks for the link, I will look into it!

mactec54/

hmmm? I can freely lift and swing my x-table with one hand, it is below 10kg I guess.
Considering total weight and other parts' weight, I suppose Z-axis weighs below 20Kg although I didn't measure it yet.
As stated, it is for very light duty and thus I don't need high-speed rapid or feed.
One thing that I mind using these 200w motors with the mill is that motors' footprint is too big for the mill.
Frame size is like 80mm. Recent products have smaller footprint with same wattage thanks to stronger magnet but mines are older ones.
Machine's total weight is under 70kg. Do you really think 200w is still below required torque even when using reduction belts?
For example, motors at my hand is specced as 0.637Nm(or 90.1 Oz-in) and 3000rpm as rated. With 2:1 reduction, torque will be 180Oz.
100W has half of the power(with much smaller footprints which I like best) and with 4:1 reduction it will have same torque.
I am not a machinist by trade and inertia things are not quite familiar to me.
Any short answer to my quriosity? Like definitely NO or possibly YES ???

Thanks for all the help from the forum!

edit: You can think of Sieg X2. This BF-16 is very much alike X2 in its size and capacity. It has 14mm x 2mm TM screws for X & Y slide.

[mactec54]

Lozzy

Yes the 100w would do the X & Y axes with a reduction of 2:1 would do with a screw with 2mm pitch, but you will need more power for the Z axes more like 5:1 with the 100w, the 200w for the Z axes would need at least 2:1

[Lozzy]

/mactec54,

thank you very much for your valuable advice.
I will look up 100w motors for x/y and 200w for z axis.
One of the motors in my hand will suit for Z-axis and two more sets of 100w will do the job.

And...

you really don't think of 50w for the job, right? too weak to do anything?
ballscrews already ordered for x/y have 4mm lead.
2mm-lead ball screws are all very high precision and are crazy expensive.... they are usually grounded.. and hard to find any used gear in this range.
I am heading for rolled/c7 grade ballscrews.
btw, thanks again!