DMM Tec Servos

[ihavenofish]

ihavenofish

A different way to look at it, but not correct

48V x 8amp=384W this is the minimum it could ever be at 48V

The motor runs close to 10amps when running which makes that 480W so the kit as you get it is 48V 480W with a max of 20amp 960W output

The 60V option 60 x 8=480W at 10a running 600w with a max of 20amp 1200W output

wow, no. power draw isnt a helpful piece of information, well, unless you need to run it on batteries

power output is 300w at 1000rpm, which is what the kit on the site lists. at 60v youd need to provide another torque curve (although its most likely still flat to 1300rpm-ish.

peak torque/power isnt useful to mention either unless its qualified with a duty cycle. i have parker motors that claim 300 oz in peak, but its a rating of 6 seconds with a cool down to 60C (half load for several minutes in ambient air) rendering it mostly useless on a mill axis.

anyhow, this is not the point of my comments. my comments were that the "big" motor is overkill unless you have a big spindle, and the "little" 1.27nm motors are quite adequate with the 2525 screw with the smaller spindles that most people run on these machines. and if you want to run a 10hp spindle on the demon, you may have a little more to worry about than the servo motor rating

[mactec54]

ihavenofish
Quote
power output is 300w at 1000rpm
wow, no. power draw isnt a helpful piece of information, well, unless you need to run it on batteries

It is very clear what the power draw is, Batteries or not

Very basic skills will tell you that the motor could never have a 300Watt rating, that you keep on saying the motor is

The power draw is around 10Amps (Plus) when it is running normal, This depends on what it is driving

The power draw at 1080 rpm 10amps= 480watts & is closer to 500watts because most I have tested have run at 10.4amps to 10.9amps when running normal, with machine drag these numbers will change to the machine condition or what the motor is driving

At idle holding power is 2.9nm at 8amps= 380watt Being supplied with 48V

The max power for this motor is 20amps=960watts 7.2nm Being supplied with 48V

[ihavenofish]

power = torque x speed / 9.5488
2.9nm x 1000rpm / 9.5488 = 303.7w


this isnt an argument, its fact. your dont rate a motor on power draw, you rate it on output at the shaft. thats the only useful number.

so, with the 48v kit, you have a 300w motor.

its a nice cheap powerful servo, why try to mislead?

[mactec54]

ihavenofish

its a nice cheap powerful servo, why try to mislead?

No body is missleading anybody,

Volts X Amps = Watts so what ever the Amps are when the motor is running that will be what the Watts are of the motor

[azam1959]

ihavenofish and mactec54,

I do remember your discussion on XZero site few months ago and reading posts here with lot of interest (thanks). I did my engineering in 70s and forgot most of the technical stuff which I do not use on day to day basis.

I am getting four 900W motors, controllers are upgraded for 75v so is the power supply (there will be three power supply in the control box). I made the deal with the vendor and I will pay them in Jan when I have funds.

I am OK with over power, who knows if XZero is as good as folks are saying, I may upgrade my 3hp spindle and inverter/vfd in future but for now .... if over power means damaging the machine, I will have to reconsider my decision and talk to vendor again.

Please help me make the right decision. Will these motors damage any of the screws in x,y or z direction?

ihavenofish

its a nice cheap powerful servo, why try to mislead?

No body is missleading anybody,

Volts X Amps = Watts so what ever the Amps are when the motor is running that will be what the Watts are of the motor

[ihavenofish]

I am OK with over power, who knows if XZero is as good as folks are saying, I may upgrade my 3hp spindle and inverter/vfd in future but for now .... if over power means damaging the machine, I will have to reconsider my decision and talk to vendor again.

Please help me make the right decision. Will these motors damage any of the screws in x,y or z direction?

they should be fine on the X, if a little ovekill. the 2525 screw can handle 19000N force, the support bearing handles 9000N, the servo puts out at peak only 2000n. the frame can take the force just fine. so the motor is overkill, but wont damage anything.


on the y, with a 2010 screw, you can deal with 15000N, the support bearing only 4500N, and the motor can push 5000n peak. 5000n is 1000lbs, which gets into teritory that could cause harm to the machine as well as the bearing. so its not only overkill, but potentially bad.

on the Z you have a 1605 screw. this screw can handle about 10000N, the support bearing 4500N, and the motor at peak will push with 10000N. this is a recipe for disaster.

NOW... keep in mind this force wont come into play in cutting or acceleration, its just not needed. it WILL come into play if you crash the machine.

so, id recomenend the big 2.9nm one on the X, and 2 of the 1.27nm ones on the y and Z.

[mactec54]

ihavenofish

Before you start giving people information you need to first buy a system & run it to see what it will do or won't do

The information that you have been putting in these posts is not CORRECT

I just called DMM & spoke with Hui the Owner Designer & Builder of there servo system

The motor that you keep saying is 300watts is Rated when on 48V at just over 500Watts just as I have been saying

So Please get your information correct before posting, So others users are not confused
as to what is correct

Build a machine your self & then tell everyone your experience with there system, you have no credibilty at this point untill you have use there system in all the situations you are talking about

[hub]

I have tested a 400W DMM servo & drive. Not much problems. Works pretty fine. I wish it had auto tuning etc etc.. But for the price, it performs well.

Reading all this... I don't see what RPM has to do with it. My DMM drive is rated max 60V DC I think. Using 48V @ max 400W is 8.3A. RPM does not change that.

[Al_The_Man]

Reading all this... I don't see what RPM has to do with it.

Read answer from Ihavenofish.

power = torque x speed / 9.5488
2.9nm x 1000rpm / 9.5488 = 303.7w

Al.

[hub]

Read answer from Ihavenofish.



Al.

Thanks
But currently that doesn't make sense. Unless you want to have constant torque independent of RPM. ?

[ihavenofish]

Thanks
But currently that doesn't make sense. Unless you want to have constant torque independent of RPM. ?

torque in most AC servos is constant or near constant to the rated rpm (in this case 1080 on 48v). at 100rpm is 30w. at 2000rpm it would be 600w. at 500rpm it would be 150w.

marketing cant change the laws of physics.

recomendations for this specific machine (which i have assembled and run several of) are based on experiece and math. the big -300- watt motor it too much for the y and z, and overkill on the x.

you can claim whatever you like about the motors and manipulate the numbers to sound sexy, you cant change reality.

this was never meant to be a pissing match. the motors are nice. they ARE 300w at 1000rpm, and they ARE overkill for the 2525 screw on machine being asked about.

people on this forum have a great tendency to use motors far more than the machine can handle. the idea that more is better is perpetuated by alot of manufacturers by listing useless numbers like peak torque or power. BETTER is better, MORE will often just break your machine.

[mactec54]

ihavenofish
you can claim whatever you like about the motors and manipulate the numbers to sound sexy, you cant change reality.


Your caluations are not in question

This only tells you how many Watts are Needed at 2.9nm x 1000rpm=303.7W This would be With No Load just sitting on the bench for this motor & not connected to anything

It does not tell you the motor rated watts, with this caluation, This is the part that you don't have correct