[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]

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]

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]

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]

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]

....
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

[mike_Kilroy]

actually mac, ur 14bit is only .00009" per pulse; most designers go for 10+ pulses or more resolution. someone should tell u that positioning as a servo system will dither +/- 1 count minimum. u describe a poor design that probably will not hold .0001 with perturbations as it will be bouncing .0002 all day long anyway.

as for ur comment that dmm is bestest, forget it; u do them a disservice spouting such nonsense.

[mactec54]

mike_Kilroy
(Quote) actually mac, ur 14bit is only .00009" per pulse; most designers go for 10+ pulses or more resolution. someone should tell u that positioning as a servo system will dither +/- 1 count minimum. u describe a poor design that probably will not hold .0001 with perturbations as it will be bouncing .0002 all day long anyway.

May be thats what happens to your poorly designed systems do, But mine do not

(Quote) bestest, forget it; u do them a disservice spouting such nonsense.

I see you are still blowing smoke, as usual

Thats why a major US optical company is using there system,on all there new equipment they manufacture, I guess they like the way they have perturbations as it will be bouncing all over there lenses

I use 20Bit encoders on some of my builds, But 14Bit/17Bit is what I use most of the time for a nice smooth ride

I did not say it was the best system there is, It is the best AC Servo system for the money

[jasminder]

chill guys, Christmas is coming.

I was just trying to say that a 16mm pitch screws is good enough for a router where you don't need a caliper to measure having a resolution of 0.0005.
I mean it is just not good for machines that need to cut serious steels (mostly high-chromium).
And my experience says that ballscrews have the tendency to back drive the motors driving it(in his case, the servos) The more the lead, the more the torque on his motors he would need while cutting under loads. But because he is having powerful enough servos on his build, and he is cutting wood or alu only. There will be less problems.
I cannot imagine to replace the 16mm lead balscrew with the existing 5mm lead balscrews on my lathe to get more rapids ( i will loose steps on the steppers and may need to decrease the rapids and will have almost the same rapids i had before, if i am not wrong)

As for DMM tech. Yes they are very supportive and prompt . At least in case of giving price quotations that i have tried. But I will try something being distributed locally because as i said earlier, i am always afraid that something will fry up.

One question still stands.--- What should i look for in a servo system if going with Mach3. I know i need step/dir inputs and not those +-10 or +-20.
What else should i look for?

However, those 16mm lead balscrews will be perfect if they have around 3 inch diameter (thanks to Al)
regards,

jasminder singh

[Al_The_Man]

One question still stands.--- What should i look for in a servo system if going with Mach3. I know i need step/dir inputs and not those +-10 or +-20.
What else should i look for?
jasminder singh

Once you have determined the torque required, and the maximum rapids or rpm required of the motor, it is a question of which technology you want to go with, when buying used, the less hassle of mix and matching different drives and motors is to go DC brushed, these can usually be had fairly reasonable off ebay, the main down side to brushed is lower max rpm and brush wear has to be checked periodically.
The next easily mix & matched is DC Brushless with 3 commutation pulses.
Again Ebay is a source.
When going AC sinusoidal, (the motor is practically identical to DCBL), it often pays to go with a matched motor & drive, as often the commutation method is alot more complicated, resolver or other technology.
For DC drives there is Larken, for DCBL there is Granite devices which will take motors such as Fanuc sinusoidal and obtain the commutation off the quadrature differential encoder, for just a couple.
Al.

[jasminder]

Once you have determined the torque required, and the maximum rapids or rpm required of the motor, it is a question of which technology you want to go with, when buying used, the less hassle of mix and matching different drives and motors is to go DC brushed, these can usually be had fairly reasonable off ebay, the main down side to brushed is lower max rpm and brush wear has to be checked periodically.
The next easily mix & matched is DC Brushless with 3 commutation pulses.
Again Ebay is a source.
When going AC sinusoidal, (the motor is practically identical to DCBL), it often pays to go with a matched motor & drive, as often the commutation method is alot more complicated, resolver or other technology.
For DC drives there is Larken, for DCBL there is Granite devices which will take motors such as Fanuc sinusoidal and obtain the commutation off the quadrature differential encoder, for just a couple.
Al.

Dear Al,
i am planning to buy new sets because automation hardware is not very common here in india to be found in surplus stores (it is like diamond if you see it in a such a store if the drive and the motors you got are not matching even) I will go for AC servos with matching drivers but can change my mind if there is a big difference in the DC/AC versions. Keeping the things for long life i will buy brushless only and i don't think that 3phase or 220 single phase versions makes any big sense to me. I will buy any of them. it is a matter of availability also and not only of choice. However, i am always thinking if a 220 servo giving 400watts or 2nm output is same to the 440 servo giving 400 watts or 2nm output in every sense of performance. Isn't it?

regards,
jasminder singh

[Al_The_Man]

The identical values of wattage and torque on different voltage levels remain equal.
A decrease in current is approximately directly proportional to the voltage increase.
3 phase for drives are usually required when using larger high current demand motors.
The drives I use, require 3ph supply for anything over 40amps if used at their optimum value.
Al.