New Machine Build- don't know servo ratings required for diy mill

[jasminder]

hello folks,
I am building a metal mill for cutting pure steel. Weight will be around 300kg.
work area is 12x12x12.
it is having 15mm lm guides, 1 inch dia of ball screws and something to drive them. I have little experience with steppers as i have two of them on my lathe but know nothing about servos. I want to use servos on the mill because there is no place for missing steps. How many watts will be enough for a mini mill. I will not be using very big tools on it. Just 3hp spindle, 2000rpm and not more than 3inch dia of tools (facing tools sometime)
If i have to go for steppers, i have an eye on the 22 n.m. (3000 oz/in) steppers from ebay. But i don't want loose steps and scrapped parts so i guess servo route is better.

please put some light here.
with thanks,
jasminder singh

[Karl_T]

Just a data point for you. I have a similar size mill with 1/4 hp. servos and 2:1 reduction to the ball screws. plenty of torque. i did use steppers on this mill for a while and had trouble with missed steps.

Karl

[hub]

Go for 400W servos for starters with some reduction since you are cutting steel (not high speed requirements).

[jasminder]

Originally Posted by Karl_T Just a data point for you. I have a similar size mill with 1/4 hp. servos and 2:1 reduction to the ball screws. plenty of torque. i did use steppers on this mill for a while and had trouble with missed steps. Karl

Hmm,
What do you think about this?
SAMSUNG 200W SERVO PACK,DRIVER MOTOR 3-AXIS CNC,ROUTER | eBay
i don't know about price range of new 200watt servo in india. Recently talked to a guy in a expo who was charging 1000$ each set (servo+drive) delta 600watt system.
BTW what should i look for in a servo system in case i am planning to buy 3 new sets. I guess encoders should have more than 1000 cpr (0.0005 inch resolution is fine for me) and with a 5mm lead ballscrew, such encoders will get me the desired resolution.
I want to know what else i need to look in servo drives?
like in steppers, there are bipolar that are better than unipolar. Some have thermal and short circuit protection. Some have high speed choppers that keep the steppers cool. What cookies are in servos that i should look for when buying new motors and drives. BTW how good that ebay deal is?

jasminder singh

[mactec54]

jasminder

200w is to small for that kind of work the smallest you could go would be 400w, Dmm have the best package for the money

You can see one working here, on my build http://youtu.be/iTBr_rJXZSw

Motion Control Products - DMM Technology

[Karl_T]

Originally Posted by jasminder Hmm, What do you think about this?...

That looks to be a nicely matched system if you're going with Mach.

Its pretty small. My guess, if you're willing to gear it down about 5:1 you'd get enough torque but at a loss of top speed. For anything you build, I'd allow for trying different pulley sizes to optimize torque vs. speed.

Karl

[jasminder]

Originally Posted by Karl_T That looks to be a nicely matched system if you're going with Mach. Its pretty small. My guess, if you're willing to gear it down about 5:1 you'd get enough torque but at a loss of top speed. For anything you build, I'd allow for trying different pulley sizes to optimize torque vs. speed. Karl

yes, i am going to use Mach. I think that rapids are a very important factor as i am going to use it for production runs. It can eat 30 seconds to 1 minute more while running a bit long cycles and i may end up having hours wasted in a day that i would like to spend in maintaining the machine instead.

i will try dmm tech or contact a local supplier of delta drives and motors for good price. With a local purchase i can get good service and repair (i am very good with frying things. lol..) i am planning for a direct drive but let's see what happens. BTW do you think 16mm hiwin rails are enough for such a 12x12x12 mill?

jasminder singh

[jasminder]

Originally Posted by mactec54 jasminder 200w is to small for that kind of work the smallest you could go would be 400w, Dmm have the best package for the money You can see one working here, on my build Router Build For A Friend First Axes Moving.mp4 - YouTube Motion Control Products - DMM Technology

very nice built mactec.
Very neat and clean machine you have built. I guess you are having a big lead on your ball screws cuz they don't seem to have a 5mm lead. But that is good for routers where you can sacrifice in tolerances and need rapids.

best wishes for your build.
jasminder singh

[mactec54]

jasminder

The Ballscrew I used have 16mm pitch, there is no sacrifice in tolerances, as the Dmm encoders are 14Bit (16,384) count Per revolution of the Ballscrew

[mike_Kilroy]

Originally Posted by mactec54 .... The Ballscrew I used have 16mm pitch, there is no sacrifice in tolerances, as the Dmm encoders are 14Bit (16,384) count Per revolution of the Ballscrew Dmm have the best package for the money

Mach, I think you should not be selling ur DMM so hard by saying it is the best package for the money - if u include a qualifier like "in my opinion" then fine. but to say what you said is wrong to mislead people who may not know it is not necessarily true.

Second Mach, of course 16mm pitch screw sacrifices tolerances compared to a smaller pitch like say 4mm! Your encoder will produce 4x less resolution than on the finer pitch screw!

Mach, a lot of folks come here for genuine help: for you to give such bad info is a disservice to this forum..

[Al_The_Man]

And, Although it does not immediately resemble it, a ballscrew resembles a class 1 lever, the fulcrum is the centre of rotation and the diameter is the effort, increase the dia lowers the effort, the load side is the screw pitch, decrease pitch shortens the load side and lowers effort.
Al.

[mactec54]

mike_Kilroy
(Quote) of course 16mm pitch screw sacrifices tolerances compared to a smaller pitch like say 4mm!

Do you even no what tolerance is

No there is no lost tolerances, Just uses more encoder resolution, & there is plenty of that at 14 bit 16,384 count Per revolution, Positioning is still better than .0001 with there system & the 16mm pitch ballscrew, What more could you want??

Nothing misleading about say Dmm have the best package for the money, You show me another one that can come close to there Performance, Reliability, Ease of Setup, Service & Cost