[psiron]

Hi,

Im trying to figure out what servo motors I need for a new build I am currently planning. The machine is 3000mm x 1500mm and not sure which motors would be required to start/stop the gantry weight.

I am trying to use a servo setup from DMM Technology if possible (DMM Technology Corp.).

The Y axis including the Z axis weighs around 75kg and I would like to rapid as quickly as possible due to the size of the bed. The machine will use a rack and pinion (25mm o/d) and the X axis is geared 3:1 so every revolution the gantry will travel 25mm.

I have scoured the net and cnczone but I just cant work out what motor wattage/nm would be best and hope someone could spend a little time helping me out if possible.

Im quite happy to provide any other information if needed and would be very grateful for any help.

Thanks very much,

JJ

[Al_The_Man]

Just off the top, I would say a higher ratio would have been ideal if you want high accel/decel rates.
This allows much more efficient use of a servo, especially as the torque remains high up to a high rpm.
Did you run some numbers through one of the free sizing programs such as Kollmorgen etc ?
Al.

[psiron]

Hi,

I have downloaded the kollmorgen sizing software but to be honest I just dont get it. It seems beyond my capabilities and have no confidence that what I end up seeing is even correct!

The 3:1 reduction is seemingly typical from what I see from some of the commercial machines, I do think that the low RPM of 1000RPM for the largest DMM Tech motor seems a little low which could cause me a problem obtaining a reasonable rapid rate. At this stage though I would take a lower RPM due to their cost and the fact that its an AC servo setup for a pretty good cost.

I will keep searching for a solution and contact DMM for some help in determining the correct motor anyways.

Thanks for your swift reply :-)

[Al_The_Man]

Yes at a 1000rpm they seem rather low for AC servo's?
The minimum rpm of the ones I use are at least 3000rpm and go up to 6000rpm.
I don't see what the limiting factor is with DMM Tech servo's?
Typically DC brushed are around 2500?
But typically with a R&P the ideal is to use high gearing together with high rpm motor.
Al.

[psiron]

Yeah the problem higher gearing with the low speed servo is sacrificing speed. I could reduce further if the 3000rpm servos would be sufficient to drive the gantry.

[mike_Kilroy]

[QUOTE=psiron;1064144]I have downloaded the kollmorgen sizing software but to be honest I just dont get it. It seems beyond my capabilities and have no confidence that what I end up seeing is even correct!/QUOTE]

maybe u should try this again? it really is not that hard once u play with it a while.... if u try, you can EXPORT your work file (under file tab at top) and attach it to a post here. if u do that, and include a brief description of what u r trying to do, some of us (I will at least) will IMPORT it into our Motioneering(tm) program and check it for you....

[psiron]

Cheers, I'll give it another blast and see if I can get something on the right track.

[mactec54]

psiron

The 1050RPM motor With the 48V drives would give you 1033 IPM with the 25mm pinion
This motor will also be able to move up to 150KG

The same motor with the 60V drive runs at 1350 RPM would give you 1328 IPM with the 25mm pinion

The new drive 120/240v which will be released some time in March can run the same motor up to 6,000 RPM

With your Machine having R & P this is the right size motor for what you want to do, you have not said how fast you want to rapid at

[lgalla]

Psiron you could go with the 400Watt at 3/1 and the speed would be the same as the 900Watt.You would have a little more torque with the 400Watt,but have the cost and time of building the reduction.Using the 900Watt direct is much simpler,but I can not say if it is enough torque for you.There is another thread that may have some answers for you...
DMM tec servos
Larry

[psiron]

I'm Looking for the best trade off for both speed and torque. Primarily its more important that I can ensure the motors can handle the gantry weight, secondly i am looking to achieve a reasonable resolution at the same time without sacrificing too much speed. Due to the varied cuts and drilling of the large sheets I produce I am looking for rapid movements as fast as possible but around 1500ipm if possible. I have been looking at the camaster machines and see their resolution on the cobra machine is .0005 which is similar to what I should get with a 1" pinion and 3:1 reduction, this is by my thinking anyway.

The key to this is using a 3000rpm servo which can drive my gantry weight without overheating. I'm not looking for blistering speed unnecessarily but as my work involves lots of movement positioning speed is important, as is good resolution and quality finishes.

The 6000rpm drives sound awesome, I'd like to consider these but really need to be ordering something really soon to get this all underway.

Thanks for everyone's time and help, it's really appreciated.

[mactec54]

psiron

With a gantry weight of 75Kg this would be only half of what ( 1 ) motor can move, you will be using ( 2 ) motors for the gantry so each motor would be only having to move 37.5 KG, Each

Just remember if you are using Step/Dir to drive your machine The motor will only go as fast as the Pulses put out by your computer or the addition of a smooth stepper type board, most servo's can not get to Max RPM from the step rate coming straight from the computer

Here is a PDF of the new drive, this is scheduled for release in March I'm sure you could still order it ahead of it's release