[Jim Dawson]

Just to put this in perspective, first concider that 400 Nm is about the torque output of a mid-sized auto engine, and that number seems pretty reasonable for a direct drive tube bender. That would be a huge servo motor.

But not very practical in this application. First you don't need to turn the tube bender at 2500 RPM, more like maybe 2 RPM. A much smaller servo motor and a massive gear reduction would be practical. Maybe a gear reduction of about 1000:1. The gearbox is going to be more expensive than the servo motor. The motor torque is multiplied by the gear ratio. I would be looking for a planetary gearbox in the 500 to 1000 : 1 range, then choose a servo motor to match.

[garthos]

Just to put this in perspective, first concider that 400 Nm is about the torque output of a mid-sized auto engine, and that number seems pretty reasonable for a direct drive tube bender. That would be a huge servo motor.

But not very practical in this application. First you don't need to turn the tube bender at 2500 RPM, more like maybe 2 RPM. A much smaller servo motor and a massive gear reduction would be practical. Maybe a gear reduction of about 1000:1. The gearbox is going to be more expensive than the servo motor. The motor torque is multiplied by the gear ratio. I would be looking for a planetary gearbox in the 500 to 1000 : 1 range, then choose a servo motor to match.

I don't think it require a gear box as the speed of a servo can be controlled, and you are right it's going to be more around 2-3rpm.
I want it to remain quite compact and using a gear box is not going to be compact.
If you look at the CNC Tube Bending machine on the market, many seems to be direct drive with a big servo with a size of around 15cm X 15cm X 30 cm.

[Jim Dawson]

I don't think it require a gear box as the speed of a servo can be controlled, and you are right it's going to be more around 2-3rpm.
I want it to remain quite compact and using a gear box is not going to be compact.
If you look at the CNC Tube Bending machine on the market, many seems to be direct drive with a big servo with a size of around 15cm X 15cm X 30 cm.

To get a servo motor with that much torque for direct drive you are going to need one in the 75KW range. There are some lower power, low speed, very high torque servo motors available, but it would be less expensive just to buy a CNC tube bender.

I looked at a number of electric servo tube benders on the net, and all of them had a gear box on the bending mandrel drive. I agree that the servos are about 30 cm long, but about 15 cm of that length is gearbox.

[garthos]

I was looking a CNC like that:
https://www.youtube.com/watch?v=Ux1GB1gpXDw

I'm not 100% sure but this kind of CNC seems to use Servomotor, and I'm not sure it's really relevant to speak of kilowatt, the important point is the torque.

from what I see there is 3 possibilities for the bend:

- a electric induction motor (like an industrial 2 hp motor from Mitsubishi for example), a gearbox, and then control the rotation angle with a sensor
- a hydraulic actuator , with also an angle sensor
- a servomotor

I looked many model of CNC bender and the one that uses hydraulic actuator always have visible hydraulic pipe.
the smaller bender (Not CNC) but electric, seems to use the first option but many CNC seems to be using servomotor for the bend as well.

So before to eliminate the Servomotor option, I would like to see some reference of servomotor that have a sufficient torque (eg: 400Nm) and see how much space it take and how much it costs.

The reason I would prefer using a servomotor is also for high accuracy.

By the way, it doesnt matter if the servo have an integrated gearbox, as long as it comes with the servomotor and it's accurate that's fine, any reference of such servo to share?

[garthos]

In addition, I found this article that tend to confirm my thought:
https://www.thefabricator.com/tubepi...ectric-machine

the bend can be ensure by a servomotor, the question is more then what reference is suitable, any of you have experience with the Yaskawa or any other brands that have very high torque?
My domain is IT and electronics, no issue for me to do the programming part but I have no clue how to calculate the required torque, any suitable servomotor reference will allow me to make some progress

if I look the machine proposed here, they claim that there is no hydraulics component and that it consumes less than 5kW:
https://www.blmgroup.com/en/tube-bending
so the 75KW servomotor mentioned earlier seems to be way oversized.

I also found this Servo with geared mounted on it that seems suitable:
https://precision.nabtesco.com/en/products/detail/AF-N
Is anyone know those servos?

[Jim Dawson]

so the 75KW servomotor mentioned earlier seems to be way oversized.

I also found this Servo with geared mounted on it that seems suitable:
https://precision.nabtesco.com/en/products/detail/AF-N
Is anyone know those servos?

You were the one that insisted that a gearbox was not acceptable and must be direct drive. A 50 KW servo would almost do what you want. Of course a 75 or 50 KW servo is ridiculous. You can find one of these if the $50,000 range.

The servo in the link above would work. But my guess is those are expensive.

[Jim Dawson]

So before to eliminate the Servomotor option, I would like to see some reference of servomotor that have a sufficient torque (eg: 400Nm) and see how much space it take and how much it costs.

The reason I would prefer using a servomotor is also for high accuracy.

By the way, it doesnt matter if the servo have an integrated gearbox, as long as it comes with the servomotor and it's accurate that's fine, any reference of such servo to share?

A servo motor drive is a good option, but it needs a gearbox.

One option of a slow speed, high torque servo is the Mitsubishi TM-RFM series, for the torque required you would want the TM-RFM240J10 motor https://www.yumpu.com/en/document/re...-j3-b-rj080w/5

These are only about $35,000. https://www.powermotionstore.com/products/TM-RFM240J10 And that does not include the drive for it. The drive for the motor is pretty reasonable at only $3400 https://www.powermotionstore.com/products/MR-J4-500A-RJ So for about $39,000 you could have exactly what you are looking for. There are other brands available, but all are around the same price.

Now for a more standard servo motor, the Mitsubishi HA-LP50K1M4 is rated at 318 Nm and a peak torque of 792 Nm. A bargain at only $54,195 not including the drive. https://shop.gibsonengineering.com/products/HA-LP50K1M4 Of course this is only a 50 KW motor so does not quite have the rated torque required. But I got tired of looking at motor specs. But it would probably direct drive your machine, if you have about 400 amps of 400V, 3 phase power available.

I'll look up a motor gearbox combination tomorrow, it's past my bedtime now. But about a 1 KW servo motor and a 500:1 gearbox would be about the right combination for your needs, and not expensive. You normally buy the gearbox and motor as separate pieces, but the motor just attaches to the gearbox, looks like all one unit when assembled.

[garthos]

I'll look up a motor gearbox combination tomorrow, it's past my bedtime now. But about a 1 KW servo motor and a 500:1 gearbox would be about the right combination for your needs, and not expensive. You normally buy the gearbox and motor as separate pieces, but the motor just attaches to the gearbox, looks like all one unit when assembled.

Totally missed that point, I didn't read properly
Seems to be a more reasonable solution

Do you have any references to recommend?