This raises some questions in my mind... I was going to go with the "7.2" geared motor. Now here there seems to be some insinuation that it may not be as fast as some other options.

I sold a slow shopbot, one of my reasons for building a MM is speed. I have watched J.R. surface his table at blinding speed and that is remarkable.

Would the belt driven transmission option be faster? Which motor is used in that combination?

See this post for JR's motor choice

Blake, just an fyi on the old bot. I have those same motors on my prt and prs machines. It will jog at 10 inches a second withought loosing steps with the 4g board. That board has 50 volts to it and uses gecko 202's.

Gerald kind of talked me into welding my frame up on the prt and changing the y carrige hold down. Thanks Gerald, but I still ended up buying a prs. lol

Anyway, those motors would work at faster speeds and do very well. You could put geckos and reuse your power supply if you wanted to.

Good luck

Kenneth

Does anyone use the PMDX-136 Powersupply?

I have been doing some calculations on a transformer. I am using the PK296A2A-SG7.2 Motor from Oriental Motor. I believe I will wire it unipolar. According to my calculations I need a transformer that outputs close to 39V and 321VA Is this correct? Does someone have a link to what they used in this configuration?

To add onto the above post... It would seem to me that the motor I am using would have plenty of torque geared down that far, and that i would want to be able to get the most RPM possible out of it because of the low gears. Thinking of that is uni-polar the way i should wire it?

Base Table welded
 

Base table welded and turned over.

Blake, that is the most common motor used for MM's and it is usually wired "half-coil" You may mean the same thing when you say "unipolar" because the naming has changed a bit over the years - these days we are more inclined to say half-coil.

Your 39V looks like a mistype - how did you get that value?

300VA is more than enough for 4 of those motors used on a router.

Nice strong all-welded table :)

So who noticed that Routed computer desk in the background? Did you do that with your old shop bot?

Yes I did.

Gerald I got those calculations from the information in this post.

Particularly this: I believe if I am reading the the spec sheet correct. The inductance is 1.5, the same as the example. Or what am I doing wrong?

From this question:

....it looks like you only want a transformer to feed the PMDX-136. Then you confirm that you are only looking at the transformer:

However, the PMDX-136 will increase the voltage by a factor of 1.414X (-1.5) see page 6 of http://www.pmdx.com/Doc/PMDX-136_Manual_10.pdf

So, if you want 39V out of the PMDX, then the transformer output must be 29V, and that is why I wondered if you mistyped the 39.

Practical experience tells us that a 30VAC, 300VA transformer works fine for those motors wired half-coil.

If you are buying a ready-made DC supply, then 40VDC, 300VA is fine.

I neglected to clarify. I have pretty much decided not to use the PMDX 136. I will either build a PS or buy one. I would like to buy one but not sure where. Building one does not seem to complicated...

If you are building one, you shop for a 29 or 30 V transformer. Many use a 25 V because that is fairly common.

If you are buying a ready-made power supply then you shop for 40V.

Blake check these out.

Capacitor
at digikey

Transformer and Bridge
transformer
bridge
at parts express

just food for thought. :)

Blake

I have bought the same motors and i have builted my PS.
I intend of wiring them also half coil so i used these specs :

Toroid : 28v 300VA
Rectifier : 25A
3x capacitors 10000 63v
33k resistors on the G203V Geckos.

I get a nice 39v output from my PS.
Hope it helps.

Sergio

Looking good Blake, trying to keep up with you.

You might pass me up... I had quite a bit of work come in here in the sign shop, so MM is not progressing very fast this week. Grinding rails is also proving to be a bit of a challenge, wish I would have went with the BWC rails.

The bad thing is, is that I am without a router right now since I sold my shopbot to fund this MM. I have to get it up and running soon, I use it quite a bit to fabricate my signs.

Your build is looking great also!

Blake-

I pondered the BWC rails too, but they were out of stock (thank God) when I tried to order them, so I went the grinding route. For almost nothing(certainly less than the additiional cost of BWC's), a local industrial knife sharpening shop ground, straightened and put an edge on one side of my angle iron( both sides would have been more). In about an hour, I did the other side, and, "Bob's your uncle", in less than a week I was done.

It just hit me today. Did you use the skate to grind the rails? Or did you start before you got the parts?

I had some bearings from another project so I built my own skate. It aint pretty but it works.

Grinding the angles was easy. It was getting em cut straight where I had the trouble.

Progress Pictures
 

Some proof that we aren't sleeping in Mississippi. :D

Yeah - Not sleepin at all :D Nice work.

I see my title changed... just like magic!:D

How are you passing the parallel connector into the control box? Do you cut it off and solder all the wires back together or is there something easier?

Hi Blake

Look at the solution from Alan C at this post

http://www.mechmate.com/forums/showt...3&postcount=25

Regards Polder

I have this rectifier. I have 33 AC volts going into it and 87 DC volts coming out... What am I doing wrong? I have a 30 volt transformer so I was expecting something like 42 DC Volts.

Blake, it's not unusual for a completely unloaded power supply to give a high reading. Of course, you don't want to risk your expensive electronic devices to prove this. You can use a dummy load (resistor) across the output to get a measurement. A low wattage light bulb (like 15 or 25 watts) can act as a dummy load.

Blake, a rectifier cannot cause a 260% increase in voltage. My first reaction is that your voltmeter is (very) faulty. Can you provide some pictures of your wiring connections and your voltmeter setup?

Blake

Did you wire the rectifier like this :

http://i890.photobucket.com/albums/a...ectifier-1.png