Motor size

[Philmollatt]

What size stepper motors would drive a series I bridgeport x, y, axis and knee, or motor/pulley size variants. Ive had a look around the net and it seems servos would be better but just cant afford them,
Also has anyone here done a bridgeport conversion?
Thanks

[graffian]

I got a stepper motor off an old matchmaker mill, it was in my local scrapyard. The motors were
10A size 42 motors, the one I took powered the x-axis direct drive. I would guess your needs are
pretty similar; you might well find modern 34 motors are as powerful as old 42's?

[Gary]

I have supplied a number of people converting mills of this size, and allways went for the SY85STH156 with either the PM980 or PM2278.
Most converted the quill, not the knee though.

[Philmollatt]

Thanks for the replies
Ive looked at the motors and drivers on the zapp site they look like they will do the job, i will still be doing the knee rather than the quill, but with reduction set up with pulleys. Ill have to save up a bit though 3 motors and 3 controllers will be pushing my budget a bit (along with brackets, plugs, sockets, wiring, enclosure box, etc). This hobby can get expensive very quick.
Also can i drive the PM2278 from a 220v three phase supply from an inverter

[Gary]

The 220V is the max voltage and single phase is 230 but can peak up to 280V.
I suggest using an isolating transforma giving a max voltage of 110V.


Thanks for the replies
Ive looked at the motors and drivers on the zapp site they look like they will do the job, i will still be doing the knee rather than the quill, but with reduction set up with pulleys. Ill have to save up a bit though 3 motors and 3 controllers will be pushing my budget a bit (along with brackets, plugs, sockets, wiring, enclosure box, etc). This hobby can get expensive very quick.
Also can i drive the PM2278 from a 220v three phase supply from an inverter

[Robin Hewitt]

The 220V is the max voltage and single phase is 230 but can peak up to 280V.
I suggest using an isolating transforma giving a max voltage of 110V.


It says 175VAC in your advert.

My knowlege of transformers is slight, but I do seem to remember they are wonderfully isolating, so it should be possible to wire several transformers in series so long as the windings can handle the extra current. (unless you can find a supplier for 175VAC kit).

Also, Amps :nope: 7.8 Amps at 175VAC is 1.3kW. Obviously you don't need transformers rated for that, the motor would melt. So how many VA do you actually need from the transformer to drive this beasty?

[Gary]

The PM2278, does not have a transformer inside and just rectifies the AC into DC, and pumps this into the driver.
So if you had 220V AC, this would be about 310V DC onto the driver and would burn most motors.
We say the 110V as a maximum because most motors are not designed to take such a high voltage.
Also the 7.8A is the phase current to the motor, and is not the current that the driver pulls from the transformer.
As a rule of thumb, if a driver is set to 7.8A, the actually pulled current will be about half.
You can use the 110V transformers that are used fro 110V power tools.
They are not that expensive.




It says 175VAC in your advert.

My knowlege of transformers is slight, but I do seem to remember they are wonderfully isolating, so it should be possible to wire several transformers in series so long as the windings can handle the extra current. (unless you can find a supplier for 175VAC kit).

Also, Amps :nope: 7.8 Amps at 175VAC is 1.3kW. Obviously you don't need transformers rated for that, the motor would melt. So how many VA do you actually need from the transformer to drive this beasty?

[tribbles]

You can use the 110V transformers that are used fro 110V power tools.
They are not that expensive.

That's what I used - a 3kW one from Screwfix Direct - it was about £68 from memory.

It officially isn't rated for 100% use, but I ran it for about 3 hours and it didn't get hot at all (37 deg.)

http://www.tribbeck.com/steel/stlcutter2/DSC00174s.JPG (http://www.tribbeck.com/steel/stlcutter2/DSC00174m.JPG)

In fact, it says that you should run it for only 5 minutes every 20 minutes.

ETA: It runs all 3 of my motors (although now I've got a 4th to go in, I'll see how much hotter it gets).

[m.marino]

Being that I grew up with 110 just remember that crap will grab and hold you if you get caught by it. Be very careful with 110; as I personally know of more than one person who has had near death experience at it's kind touch. One of the nice things about 230 is that it does tend to throw you more than grab hold and burn through you.

Michael