[gearsoup]

Hello all,

I am in the design stage of my machine. It is a 4'x4' all machined aluminum construction.

I want it to go reasonably fast. 400IPM rapids would be on the low end of what I hope for.

I had considered the 408 oz-in. kit from DMM, but I am starting to suspect in a direct drive setup, it may be slightly underpowered.

Where is a good place to source servos, drives, and appropriate parts that are larger than the DMM servos, but don't come with an insane price tag?

[mike_Kilroy]

I believe Kollmorgen.com AKM motors & AKD matching drives are a practical next step up in both performance and size to DMM.

[mactec54]

gearsoup

Most that are using the Dmm servo's are get 1000IPM +, with the rack & pinion machines,
are you using Ballscrew or rack in pinion, They will do the 400IPM easy for your machine,
which motor size were you looking at

[gearsoup]

mike Kilroy:

All due respect; While the Killmorgen line of servos may be a formidable one, the idea of paying around 1k per motor plus driver costs is well outside of my progects budget.

mactec54:

My machine is designed to be all Thomson shaft supported, ball screw design. I was trying to avoid goin R&P, simply because I have never used it before and a learning curve can be costly.

Currently, I am looking at 25mm ball screws, with either a 10mm or 25mm pitch.
Gantry is weighing in at a little over 200 pounds, the Y axis is coming in at 85, the Z at 40 (according to Solidworks)
I've been looking at ways of dropping weight off the machine and I have a few ways I think I can shed 30 pounds or so without having a negative impact on rigidity...

Currently, I am looking at the larger/slower servos from DMM. I think they are 408 oz/in. constant torque motors, 1015 peak.

[mactec54]

gearsoup

Ac servo's or servo's in general,the larger ones are rated in watts, oz are not normally used because this does not relate to the performace of a servo

If you are using a 25/25 screw you will have to gear it down or you will need a very large servo to drive it 1/1(around 2000Watts with the weight of your gantry) with the 1000watt Dmm servo at 2/1 you would still get around 675 IPM at 3/1 you would get the target you were looking for at 450 IPM, A 1000watt servo would drive your machine at 1/1 no trouble but it is stopping the gantry once it is moving at speed is the hard part, The 25/10 screw you could run at 1/1 with the 1000watt Dmm servo you would get around 540IPM with the 25/10 screw

Also your machine is wide for a single screw 48" you may get racking

[lgalla]

Mactec54.
If I am understanding it correctly the 25/25 will need a gear box or reduction.
The 25/10 will do 540ipm direct drive?Will the torque be double?
Thanks
Larry

[gearsoup]

gearsoup

Ac servo's or servo's in general,the larger ones are rated in watts, oz are not normally used because this does not relate to the performace of a servo

If you are using a 25/25 screw you will have to gear it down or you will need a very large servo to drive it 1/1(around 2000Watts with the weight of your gantry) with the 1000watt Dmm servo at 2/1 you would still get around 675 IPM at 3/1 you would get the target you were looking for at 450 IPM, A 1000watt servo would drive your machine at 1/1 no trouble but it is stopping the gantry once it is moving at speed is the hard part, The 25/10 screw you could run at 1/1 with the 1000watt Dmm servo you would get around 540IPM with the 25/10 screw

Also your machine is wide for a single screw 48" you may get racking

Oh, I am running dual ball screws btw.

The 1000watt DMM servos only output 1000 rpm, correct? In theory, would this not give me a top speed of 397 IPM?
I've pretty much ruled out the 2525 screws. I'm finding the 2510 more readily available and more cost effective. Not really liking the added costs of reduction systems, much rather prefer direct drive.

[gearsoup]

Mactec54.
If I am understanding it correctly the 25/25 will need a gear box or reduction.
The 25/10 will do 540ipm direct drive?Will the torque be double?
Thanks
Larry

I'm just a machinist by trade, so some engineering math is poor for me. However, logically, I would assume that a direct drive 2525 screw would have less than half the torque avaialable as a 2510 screw. However, a 2:1 reduction would almost make it equal to a 2510.
In theory a 2520 screw would have exactly half the torque as a 2510, as it is 2x the lead of the 2510.

[mactec54]

gearsoup

The 1000Watt motor is 1350 RPM the new higher voltage Drive (65Vdc from 48Vdc) have put the power up on that motor

That's a big difference if you are using 2 ballscrews, you could run them at 1/1 on the 25/25 screw, you are then sharing the load of your gantry,The load then become's about half the work for each motor, say the gantry is 300lbs each motor will then be loaded with only 150lbs, each motor can handle just over 300lbs

The 25/25 screw & the 25/10 is 2.5/1 difference

[mactec54]

lgalla

You are getting a 2.5/1 reduction between the 25/25 & the 25/10, The torque from the motor is not changing, just the reduction between the (2) screw's is the only difference

There is more torque for the 2.5/1 reduction than that of the 1/1, But the motor torque does not change only the torque on the screw has changed by 2.5 times from the 1/1 ratio

[gearsoup]

mactec,

I really would rather go with the DMM kit, simply because everything is right there, it's all plug and play basically. Not to mention, speaking with the owner of DMM is a pleasant experience. He shoed me the math, and I agree and understand. The 900 watt motors will be sufficient. However....

He told me that the new drive has not yet been released for sale. I sent him an e-mail to inquire about a potential timeline, but that was only this afternoon. Have not heard back yet.

Now I need to find a good source for 25mm pitch screws. Any suggestions? Oh, and I don't want to break the bank either, lol

[mactec54]

gearsoup

Yes the new drives have not been released, & are being manufactured, you can never no how long they will take to get going

Ballscrews just be careful what you get, I beleave that George is getting some, but I don't know what the quality is like

I have the 400watt running on one axes on my build here
YouTube - Router Build For A Friend First Axes Moving.mp4

[skullworks]

Note that while pulley and belts cost a pretty penny, the cost of high torque rated shaft couplers to connect the motor to the screw and provide for micro alignment issues can cost as much as the pulleys.

Another issue is if you use 1 centered 1000W servo to drive 2 screws via belts you completely bypass all the homing and alignment issues caused when you use dual screws and dual motors without hardware syncing.


I would like to use DMM also but I need Incremental encoder outputs with Index to work with EMC2. Someday EMC2 will be able to use ABS encoders, but not today.