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  #31  
Old Wed 13 January 2010, 07:00
blakekoehn
Just call me: Blake #47
 
Macon, MS
United States of America
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?
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  #32  
Old Wed 13 January 2010, 07:57
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
See this post for JR's motor choice
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  #33  
Old Wed 13 January 2010, 23:05
Kenrbass
Just call me: Ken
 
Richmond Tx
United States of America
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
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  #34  
Old Fri 15 January 2010, 08:38
blakekoehn
Just call me: Blake #47
 
Macon, MS
United States of America
Does anyone use the PMDX-136 Powersupply?
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  #35  
Old Fri 15 January 2010, 13:28
blakekoehn
Just call me: Blake #47
 
Macon, MS
United States of America
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?
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  #36  
Old Fri 15 January 2010, 15:06
blakekoehn
Just call me: Blake #47
 
Macon, MS
United States of America
Base Table welded

Base table welded and turned over.
Attached Images
File Type: jpg table base.jpg (87.1 KB, 977 views)
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  #37  
Old Fri 15 January 2010, 20:58
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Quote:
Originally Posted by blakekoehn View Post
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? . . . . . Thinking of that is uni-polar the way i should wire it?
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.
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  #38  
Old Fri 15 January 2010, 20:59
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Nice strong all-welded table
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  #39  
Old Sat 16 January 2010, 05:28
MetalHead
Just call me: Mike
 
Columbiana AL
United States of America
So who noticed that Routed computer desk in the background? Did you do that with your old shop bot?
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  #40  
Old Sat 16 January 2010, 08:15
blakekoehn
Just call me: Blake #47
 
Macon, MS
United States of America
Quote:
Originally Posted by MetalHead View Post
So who noticed that Routed computer desk in the background? Did you do that with your old shop bot?
Yes I did.
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  #41  
Old Sat 16 January 2010, 08:22
blakekoehn
Just call me: Blake #47
 
Macon, MS
United States of America
Quote:
Originally Posted by Gerald D View Post
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.
Gerald I got those calculations from the information in this post.

Particularly this:
Quote:
So, where do we go in the range 24 to 80V? Find the inductance of the motor from its specsheet in milliHenry, take the square root of the mH value and multiply that by 32. For example, a motor that is rated 1.5mH needs: 32 x √1.5 = 39 Volt
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?
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  #42  
Old Sat 16 January 2010, 11:45
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
From this question:

Quote:
Originally Posted by blakekoehn View Post
Does anyone use the PMDX-136 Powersupply?
....it looks like you only want a transformer to feed the PMDX-136. Then you confirm that you are only looking at the transformer:

Quote:
Originally Posted by blakekoehn View Post
According to my calculations I need a transformer that outputs close to 39V and 321VA Is this correct?
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.
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  #43  
Old Sat 16 January 2010, 12:18
blakekoehn
Just call me: Blake #47
 
Macon, MS
United States of America
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...
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  #44  
Old Sat 16 January 2010, 12:38
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
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.
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  #45  
Old Sat 16 January 2010, 14:04
domino11
Just call me: Heath
 
Cornwall, Ontario
Canada
Blake check these out.

Capacitor
at digikey

Transformer and Bridge
transformer
bridge
at parts express

just food for thought.
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  #46  
Old Sat 16 January 2010, 21:51
Sergio-k
Just call me: Sergio #61
 
Athens
Greece
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
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  #47  
Old Wed 20 January 2010, 18:04
Drad98_98
Just call me: Dave #52
 
Fort Ripley, MN
United States of America
Looking good Blake, trying to keep up with you.
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  #48  
Old Thu 21 January 2010, 08:23
blakekoehn
Just call me: Blake #47
 
Macon, MS
United States of America
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!
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  #49  
Old Thu 21 January 2010, 08:45
Sherman McCoy
Just call me: "Krasch"
 
Portland,OR
United States of America
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.
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  #50  
Old Fri 22 January 2010, 11:22
MetalHead
Just call me: Mike
 
Columbiana AL
United States of America
It just hit me today. Did you use the skate to grind the rails? Or did you start before you got the parts?
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  #51  
Old Fri 22 January 2010, 11:30
blakekoehn
Just call me: Blake #47
 
Macon, MS
United States of America
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.
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  #52  
Old Sat 23 January 2010, 16:18
blakekoehn
Just call me: Blake #47
 
Macon, MS
United States of America
Progress Pictures

Some proof that we aren't sleeping in Mississippi.
Attached Images
File Type: jpg ycar.jpg (91.8 KB, 774 views)
File Type: jpg gantry.jpg (86.6 KB, 767 views)
File Type: jpg gantry2.jpg (73.0 KB, 772 views)
File Type: jpg rail1.jpg (89.2 KB, 774 views)
File Type: jpg rail2.jpg (83.0 KB, 774 views)
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  #53  
Old Sat 23 January 2010, 17:12
MetalHead
Just call me: Mike
 
Columbiana AL
United States of America
Yeah - Not sleepin at all Nice work.
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  #54  
Old Mon 25 January 2010, 07:21
blakekoehn
Just call me: Blake #47
 
Macon, MS
United States of America
I see my title changed... just like magic!
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  #55  
Old Thu 28 January 2010, 15:43
blakekoehn
Just call me: Blake #47
 
Macon, MS
United States of America
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?
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  #56  
Old Thu 28 January 2010, 16:25
Polder48
Just call me: polder
 
Edam
Netherlands
Hi Blake

Look at the solution from Alan C at this post

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

Regards Polder
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  #57  
Old Thu 28 January 2010, 16:34
blakekoehn
Just call me: Blake #47
 
Macon, MS
United States of America
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.
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  #58  
Old Thu 28 January 2010, 17:20
bradm
Just call me: Brad #10
 
Somerville(MA)
United States of America
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.
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  #59  
Old Thu 28 January 2010, 20:13
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
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?
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  #60  
Old Thu 28 January 2010, 23:10
Sergio-k
Just call me: Sergio #61
 
Athens
Greece
Blake

Did you wire the rectifier like this :

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