Re: [CAD_CAM_EDM_DRO] Anyone Familiar with an MHP S-24 CNC

Dennis Cartier wrote:

>Jon Elson wrote:
>
>
>
>>Yup, thse are servos for sure. I didn't see any encoders/resolvers/scales
>>anywhere in the pictures.
>>
>>
>>
>>
>
>It must have some form of feedback ... but I am sure it is not scales. I
>asked the seller beforehand to make sure it had ballscrews and servos.
>He confirmed that it didn't use scales, but was unsure as to what it did
>use. I guess at the worst I will have to come up with a way to add
>encoders into the control loop. Perhaps driven off the ballscrews?
>

That should be fine. I have heard of some systems where encoders were
attached to the far end of the screws from the motor.

>
>
>
>>No, that's why VFD's are so great! They do the phase conversion, too.
>>If you intend to run the motor at full power for extended times, you
>>might want
>>to use a slightly higher rated VFD so the rectifier/cap bank won't be
>>overstressed
>>from the single phase power, but they run just fine with single phase input.
>>Surplus VFDs are constantly on eBay, and if you can wait a month or two,
>>a good deal will certainly come along. Actually, 480 V VFDs in modest sizes
>>often go much cheaper than 240 V units, as everyone wanting to use them
>>in their garage want the 240 V VFD's.
>>
>>
>>
>
>I guess the million dollar question is what do 240 to 480 transformers
>go for? That would still be required with a 480V VFD right?
>
>

That's easy. Go to any scrapyard, and look for "step-down"
transformers. These
are used all over industrial plants to convert 480 to 240, and 240 to
120 for
small loads like CNC controls, work lights, accessory outlets, etc.
They are usually
small gray boxes about the size of a toaster oven or a bit larger. They
usually have
a label saying "step down transformer" or "dry type transformer", and a
connection
diagram outside or under an access plate. The ones you are looking for
will probably
be in the 75 - 100 Lb range. They can be conneced backwards perfectly
well to step
UP the voltage. You should be able to get them by the pound, probably
under $100
for the size you want. Depending on where you find it, you might be
able to get it
for WAY under $100. I sometimes find them in the trash at work, still
attached to
some big hunk of gear they are pitching.

Jon