Question about power supply for the motors

[SteveC68]

I already built a power supply for my hot wire and just tonight I finally pulled the trigger on a hobbycnc 4 axis foam cutter package with 4 of the 84oz-in stepper motors.

What size transformer do I need for the board/motor power supply?

Thanks,
Steve

[NC Cams]

How much PEAK power do you need??? THat determines your transformer requrement.

To economize, you don't need to be able to run ALL the motor at locked rotor simultaneusly. Thus 50% to 60% of the TOTAL THEORETRICAL peak current you migh ever draw should suffice.

Bob Cambpell's site gives some good insight into P'S sizing in case you wish to learn a bit more....

[SteveC68]

I looked at the Bob Campbell Designs web site specifically at his Power Supply pdf and he recommends a DC voltage of 20 times the motors rating. I purchased the small 84oz-in motors from HobbyCNC that have a rating of 6V. 6 x 20 = 120 VDC recommended power. Divide by 1.4 = ~85Volts AC. I don't think that many people are using a 115V Primary, 85V Secondary transformer. I guess I will just wait until the board shows up and look at what they recommend.

[vulcom1]

I have the Hobbycnc pro board and use the 80oz. motors on my foam cutter. I am using a 15 amp supply at 24 volts with no problems. It is overkill with the amps but I believe they reccommend 10 amp. Just had one available so used it.
Be advised the board will only take around 42 volts and a 24 volt supply unregulated gets up there. Also do not run your foam cutter wire from the same source. Use a separate transformer as in my case you will blow some chips. Been there and done that. I use a 5 amp transformer for my bow.
John

[SteveC68]

That's what I needed to know. I built a foam cutting power supply already so that's done. It uses a 25.2 volt 2 amp transformer.

How do you run your tensioned hot wire? Do you have your verticals supported at the top or do you have a bow so the verticals don't see any tension? I'm thinking of using a bow so I don't have to support the top of the verticals. Still looking at different options though. I have a small 24" bow that I am using freehand and my power supply can support 24" or 48" bows. Unfortunately I have to build a new fire place for the house, before I can really work on the Foam cutter so it will likely be a month or two before I can really start work.

[vulcom1]

I use a bow for my wire as I did not like the idea of putting tension on the towers. The bow is on insulated pegs trapped between a couple of fibre washers and the weight of it keeps it there. My bow is 3/4" alum. tube with the ends insulated and 10" x 1/4" music wire for tension. Have had no problems that I know of.
John

[Juancar]

I looked at the Bob Campbell Designs web site specifically at his Power Supply pdf and he recommends a DC voltage of 20 times the motors rating.

Are you sure of this??

[Kelinginc]

KL-100-24 24V/4.5A will working for you, check the link here

http://www.kelinginc.net/SwitchingPowerSupply.html