[raychar1234]

Hello guys,

As many motors and controllers are out there on market, I am really confused to how to select a proper one for my
spindle motor. By the way, I also want to have the control of the rotation position.

As have a spare Nema 34 stepper hybrid servo motor(4Nm) and a general-use controller. Don't know if it can be used as
spindle motor for my cnc machine for aluminum milling work. It is going to be connected to the bearing spindle housing of the
machine thru' a timing belt. By the way, what are the main differences between it and the regular servo spindle ac/dc motor.


Thanks in advance

[footpetaljones]

Hello guys,

As many motors and controllers are out there on market, I am really confused to how to select a proper one for my
spindle motor. By the way, I also want to have the control of the rotation position.

As have a spare Nema 34 stepper hybrid servo motor(4Nm) and a general-use controller. Don't know if it can be used as
spindle motor for my cnc machine for aluminum milling work. It is going to be connected to the bearing spindle housing of the
machine thru' a timing belt. By the way, what are the main differences between it and the regular servo spindle ac/dc motor.


Thanks in advance

Steppers can't be used as a spindle motor, unless your expectations are low. The faster you go the less torque they will have, with a pretty step drop off around 300 rpm. Servos will have a flat torque curve up to their rated speed.

Do you want to be able to command orientation to any position, or only to one position? If you only need one position you can use a shot pin to orient and you can use a three phase induction motor. Shot pins have been used widely by Fadal and Haas. Otherwise you need a servo.

[Azalin]

I am also looking for a spindle motor for my BF20L mill. Induction motors are the best for the job I believe. But they are too big and heavy. Servos are expensive. Treadmill motors I don't know.

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[corry]

So, this wasn't why I was here, but I'll see what others think on this as well. How about something like a 2KW Baldor "higher inertia" servo motor? There was a post on hackaday recently about the stmbl servo controller, like $120 for a servo controllerup to 2KW? Was considering trying anyhow, but the problem is resolution/speed. With 2500PPM in quadrature encoders, that's 10K ppr, which is certainly good, but gearing it down would be better! However, the motor is 4000RPM, and I like that max, so either I'm looking for something like an auto gearbox, or perish the thought, a manual speed change. Maybe that's not so bad, as when positioning accurately, you won't need/want speed. Still not sure if using an actual servo motor is a good idea though!

[mcardoso]

I've tried my hand at several spindle setups for a G0704 type machine. I also work in industry specializing in VFD and servo products. Here are a few thoughts on the things I have tried.

1) Brushed DC motor (stock or treadmill motor): These are actually quite a bit better than people give them credit for. They're fairly quiet and power dense, however they are prone to brush wear at higher speeds, and they seem to burn out more often than other motors. The control electronics are readily available and fairly cheap, however these controls seem to lack the durability that industrial electronics require. An encoder can be added to the motor to be used with a closed loop servo drive. The servo response on a higher power DC motor will be fairly poor due to the high inertia.

2) Induction motor + VFD: Induction motors are the work horses of our modern world. They are plentiful and robust, however they are significantly larger and heavier than other motor options for a given power output. They are typically fixed speed, and require a Variable Frequency Drive (VFD) to adjust the speed. They can be made closed loop with an encoder and a position/velocity control drive, however this significantly increases cost. These motors will practically last forever, unless a bearing fails.

3) AC PM servo motor: I have tried 2 servo setups, and I am currently using one of them. AC PM servos are pretty awesome, and the end all be all of motion control. As far as servo use for spindles, they are perfect for small machining centers up to high performance smaller spindles such as the Brother Speedio. As power output increases, the larger spindles will start to use a high performance induction motor spindle with an encoder. I have been very happy with the setup so far. My first setup was a 750W DMM technology servo with a DYN3 servo drive. It was working well, however I outgrew the power output as I got more skilled in machining. Today I am using an Allen Bradley Ultra 3000 servo drive with a MPL 1.8kW servo motor. This is probably about the largest motor this machine can handle for rigidity. For small machines <5 HP, a low inertia motor is fine, if you are picking a larger spindle, a medium inertia motor trades off acceleration for velocity stability in varying loads (like machining). Edit: Main downside to servos are the price (think around $1000 new for a 1kW lower end servo, and ~$600 for a good industrial setup used). Be wary of servo cables. They are often not included in listings for used systems, or are cut short. They can be well over $100 per cable if you need to replace them

[rcheli]

I'm in the process of converting to a DMM Technology DYN4 1.8K AC Servo for my spindle motor on a Sieg X3 mill. I'm about a week or two away from making the swap. Another member here is using the same servo. See this link

New Machine Build Shoptask 2000 modified - Page 2


John

[raychar1234]

Hello,

Can I use the following motor for the spindle of my small milling/router machine use. (as wanting to have the rotation position control too).
Thinking that it is axis motion drive purpose motor.

2.4NM 750W NEMA34 AC Servo Motor 220V 3000R/Min Drive CNC Machine Kit +3M Cables

[mcardoso]

Raychar,

Yeah that would work fine. Couple of thoughts:

1) 3000 rpm isn't very fast, especially for a mini mill which would need smaller cutters (5000 would be better). You can gear it up, but there are drawbacks to that. It has quite a bit of torque which could drive larger cutters.
2)The big difference in high end servos and low cost ones like these are the documentation. Servos aren't usually plug and play, so configuration and tuning is necessary. Make sure there is a good manual for this.
3) From the picture, those cables aren't shielded. The output is a high frequency square wave voltage source that can spike to >300V. You might run into problems with electrical noise. Higher end servos use expensive shielded cables.
4) Finally, the 2500 ppr encoder isn't super high resolution (10,000 counts per rev). For a spindle this is fine, but for an axis drive motor it might be too low. My servo that I am running produces 8.3 million counts per rev... but it is also a $2k or more system bought new.

For $320 or so that isn't a bad motor, but you may want to consider my thoughts above.

[raychar1234]

So gearing them up is unavoidable. With using tooth timing belt will produce noise, people will use fine v-grooves type belt instead. However,
after thousands steps run, slipping between belt and pulley occurs. Servo positioning function of the motor becomes failure. For
diy guys, can they relocating the encoder out from the motor to the spindle shaft end? Is there any people succeed in doing so?

[skrubol]

Servo drivers need the encoder on the motor, so if you wanted an encoder on the spindle it would need to be in addition to on the motor. The drift of the spindle relative to the motor should be quite slow, would having just an index pulse on the spindle be good enough to 'home' to?

[mick41zxr]

On current build (BF20L clone conversion) I am running a 80 frame (1.1kW) 2 phase WEG W21 Motor with SEW inverter.
Using PolyV belt. Getting approx 5000rpm at spindle, limited by some sort of wierd resonance in low tension side of the belt at moment, an idler/tension pulley is on the cards.
Motor is a little on the large side but fits. Will upgrade to a W22 on next build as tech sheets show it can do 7200rpm.
Check the torque required at rpm. GWizard is a great help there.
Regards,
Michael
Attachment 399690

[rcheli]

I finished installing a DYN4 1.8K servo motor on my spindle. I rigid tapped my first hole last night. This motor is really nice. I have it drive the spindle through a belt drive geared 1:1.8. The motor runs 3000 rpm at 240 volts and at 1:1.8 that gives be 5400 rpm at the spindle. A lot quieter than the old gear train.

John

[Azalin]

Great. What's the frame size of the servo?

I am thinking of a 1.8kw for my BF20L. However the drawbar cylinder leaves a small place for the motor and that is about 120mm.

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[rcheli]

It is 130mm.

http://www.dmm-tech.com/Files/ACSMTR-G1-1002A17A.pdf

John