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  #1  
Old Sat 16 November 2013, 21:02
miguel juan
Just call me: mike
 
Montreal, Quebec
Canada
Looking for Power - Montreal, Canada

Greetings to all,

I no longer remember how it is I stumbled across this forum some two years ago but suffice it to say that it is the best thing that ever happened. Around that time, I had recently visited a respectable CNC manufacturer and was giving serious thought to buying one of their entry level machines. As I gave my project further thought, I came to realize that their machine may not in fact be best suited for what I had in mind. While their brochure promised impressive speed, that quality was not necessarily important for my interest in 2.5D work.

Quite simply, the Mechmate can be built as per the plans or modified to suit one's needs. My intention is to build as per the plans and learn all that needs to be learned in the process. Hopefully, as I work on my project, one day I too will have the chance to contribute to the forum.

As of today, the Laser Cut Parts have been acquired (thanks to Heath in Cornwall), all metal necessary to complete the Gantry has been purchased and one of the Y rails has been cut.

Winter is fast approaching so the plan is to cut and grind the rails as quickly as possible so that I can later complete all the necessary drilling indoors. I was hoping to weld the Y car soon but that will invariably have to wait until Spring. In my case, quality before speed. The winter season will be perfect to order all the electrical components and complete that critical portion of the build.

The attached picture shows me sanding one of the Y rails that has already been cut. In my excitement, I did not sand the underside first. I won't make that same mistake twice.

Mike
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File Type: jpg Preparing Y Rail.jpg (50.1 KB, 725 views)
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  #2  
Old Sun 17 November 2013, 06:27
MetalHead
Just call me: Mike
 
Columbiana AL
United States of America
Glad to see your getting started !!!
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  #3  
Old Sun 17 November 2013, 07:15
zumergido
Just call me: Fernando
 
BS AS
Argentina
100% safety first. you forget to put your shirt inside your pants. if the grinder catchs it, you going to have a bad time.
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  #4  
Old Mon 18 November 2013, 19:41
miguel juan
Just call me: mike
 
Montreal, Quebec
Canada
I am in the process of cutting the second Y rail and progress is extremely slow. I am using a Black and Decker 4.5" angle grinder which is rated 5.5 amps. I did manage to purchase the PFERD discs highly recommended here on the forum. The first 7.5 foot (90 inch) length of HRS 2.5" X 2.0" angle iron must have taken me some 4 hours to cut. With the second rail, I have invested a good 2 hours so far I am sure. I am about 60 percent done, which means that I will be at it again tomorrow evening.

When cutting, the blade generates a hearty dose of sparks but I suspect it is not really removing much material in the process. Oddly enough, the first rail did not consume much of disc. As can be seen in the attachment below, the used disk was only worn down to a diameter of 4 1/8".

I have been on the PFERD website (For Stainless Steel (INOX) - Universal Line PSF For Stainless Steel (INOX)) to see if the disc I was sold is indeed the most appropriate for the metal I am trying to cut. Should I rather be using a disc for steel and cast iron?

Mike
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File Type: jpg P1040485.JPG (156.9 KB, 686 views)
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  #5  
Old Mon 18 November 2013, 22:15
parrulho
Just call me: Paulo #108
 
willemstad
Netherlands Antilles
Hi,

Inox - Stainless is the one but your is 1.6mm thick. you should look for a thin disc, 1mm or less, I don't remember exactly.

paulo
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  #6  
Old Tue 19 November 2013, 03:59
KenC
Just call me: Ken
 
Klang
Malaysia
1.6mm works fine too. It really doesn't matter how thin, as long as it can get the work done. The advantage of thicker disc is that the disc is less likely to break if things went wrong.
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  #7  
Old Wed 20 November 2013, 03:04
Robert M
Just call me: Robert
 
Lac-Brome, Qc
Canada
Send a message via Yahoo to Robert M Send a message via Skype™ to Robert M
Hey Mke !!!
Glad to see ya finally starting this dream of yours after all our exchanges !
1.6mm is what I used as many of us around here did, it is fine to use this !
Tu peux compter sur moi si autres infos te serais utile
Bonne route
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  #8  
Old Thu 21 November 2013, 18:56
miguel juan
Just call me: mike
 
Montreal, Quebec
Canada
Paulo,

Confident I had been given the right disk, I never took the time to examine the fine print on the label. Thanks for your sharp eyes. Since the second Y rail was already half done, I kept on using the same disk. When I tackle the X rails, I will certainly use the 1 mm disc. My 5.5 A grinder is not really intended for this kind of work, which is why I am not pressing hard and it is invariably taking a long time. Changing the disc mid way ran the risk of disturbing the current height adjustment. I opted to be prudent and carry on as is, in the hopes that the final height is the same across the entire length of the rail.
Mike

Last edited by miguel juan; Thu 21 November 2013 at 19:09..
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  #9  
Old Thu 21 November 2013, 19:07
miguel juan
Just call me: mike
 
Montreal, Quebec
Canada
Quote:
Originally Posted by KenC View Post
1.6mm works fine too. It really doesn't matter how thin, as long as it can get the work done. The advantage of thicker disc is that the disc is less likely to break if things went wrong.
Ken,

Funny thing you bring up the "if things went wrong'' scenario for that is precisely what happened. The nuts on two of the columns became loose and the disc began to wobble. Had I been using a 1mm disc, it might have broke.
Since one disc is plenty to cut the length of a 7.5 foot rail, I suspect it is best to avoid changing a disc during the course of an operation in an effort to maintain the same settings. I found that when came to replace the spent disc with a new one prior to starting the second Y rail, I still had to spend considerable time adjusting the nuts to get the correct height. When comes time to tackle the X rails, I am considering adding a mm and then grinding down afterwards to make sure both are exactly the same height.
Mike
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  #10  
Old Thu 21 November 2013, 19:33
miguel juan
Just call me: mike
 
Montreal, Quebec
Canada
Quote:
Originally Posted by Robert M View Post
Hey Mke !!!
Glad to see ya finally starting this dream of yours after all our exchanges !
1.6mm is what I used as many of us around here did, it is fine to use this !
Tu peux compter sur moi si autres infos te serais utile
Bonne route
Thanks Robert, you have been a great help so far. The folks at Oxygene Rive Sud are friendly and helpful. I feel like a kid in a candy store when there, in this case it is my wallet that is suffering and not my teeth.

En ce qui concerne de l'aide supplementaire, les photos que tu as utilise pour documenter ta construction sont fort utiles. D'ailleurs la prochaine etape etant l'electronique, j'ai pu remarquer que tu es le seul qui a pris le soin de placer tous les elements (accompagner de l'emballage) sur une table de travail. Comme dit le vieux dicton, une photo vaut mille mots.
Michel
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  #11  
Old Thu 21 November 2013, 19:38
parrulho
Just call me: Paulo #108
 
willemstad
Netherlands Antilles
I must agree with Ken and Robert, safety first. I was only thinking on time save... sorry.

Paulo
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  #12  
Old Thu 31 July 2014, 21:07
miguel juan
Just call me: mike
 
Montreal, Quebec
Canada
Y Car and Gantry are ready to weld

Y Car and Gantry are now finally ready for welding. I had initially used threaded rod in both instances but found that even supplementing the former with an array of welding magnets on the Y car was no gaurantee that everything would remain square. In the end, I purchased some 1 inch aluminum tubing and cut spacers on the metal lathe. All parallel running tubing is identical to .001 of an inch. I have also cut some polyethylene spacers to center the rod at each extremety of the aluminum tubing.

I had purchased a Dewalt chop saw (almost $200) to cut my metal tubing but found it to be good for nothing. The 14" blades shakes so badly, everything vibrates uncontrollably. To make matters worse, the support at the rear is poorly made and has some play in it. In short, I would not recommend this product. In the end, I found a large welding company in the industrial park which was kind enough to cut them to spec. Both are indentical.


Rail grinding has proven to be my achilles heel. I eagerly read the forum posting before doing anything for as they say "measure twice, cut once''. Only after cutting the rails down to 1.25" (where does that number come from you say, don't ask me?), did I come across a note in the plans suggesting to use a belt sander to level the bottom side. Fortunately, initially cutting to high allowed me to clean the bottom and cut to the desired height. However, I am not happy with the rails and have decided to go with aluminum.

The aluminum route has not been an easy one. Fistly, I have been unable to locate 2.5'' x 2.5'' x 1/4'' (no inside radius) material. I have phoned far and wide and it would seem that nobody stocks it. In the end, I had to purchase 4'' x 4'' x 1/4" tubing. I have cut two sides and from that I now have two rail lenghts of 72". I am in the process of ordering the v cap rails from Rick at Superior Bearing. That should be here sometime next week.

Lastly, I have included a photo of the skate plate which shows my use of aluminum spacers. It is a little more work, but in the end, I know that everying thing is sitting perfectly horizontal. The base is UHMW Polyethylene.
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  #13  
Old Tue 01 December 2015, 19:09
miguel juan
Just call me: mike
 
Montreal, Quebec
Canada
I am in the process of tackling the wiring to the various boards which will comprise the control box (PMDX 126, PMDX 137, PMDX 134) and would need some clarification regarding connecting the Toroidal Coil to the Power Prep Module (PMDX-137).

I am fairly certain I have wired everything correctly, that is to say, the primaries and secondaries are both wired in parallel. In reading an article ( http://sound.westhost.com/xfmr2.htm#s82) it is recommended to use a fuse when testing the system. Needless to say that this is my first attempt and before actually applying current I would like to know if there is an easy way to determine if everything has been done correctly. Unfortunately, the PMDX -137 user manual does not address this important test step.

There is also a warning which appears in the document, "The AC input must be transformer-isolated from the mains input. Auto-transformers and variable (variac) transformers DO NOT provide suitable isolation." Is there something else I must do? I have applied power to the Breakout Board and it is working fine. I am eager to connect the motor and see it do its thing.

Regarding the last picture below:
As for the parallel wiring of the primary. Current is delivered to the blue and violet wires and ground is connected to grey and brown. As for the parallel wiring of the secondaries, black and orange are connected together and red and yellow are connected together.
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File Type: jpg P1050029.JPG (142.7 KB, 370 views)
File Type: jpg P1050030.JPG (143.9 KB, 369 views)
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  #14  
Old Wed 02 December 2015, 04:48
MetalHead
Just call me: Mike
 
Columbiana AL
United States of America
Your PMDX-126 can be directly wired from your 115/220 inputs. This is the simplest way to power the PMDX-126.

The PMDX-134 will take the DC outputs from the PMDX-137. You should have sized your Transformer to give you the correct DC out on the PMDX-137 for your motors.

I used PMDX-133, but they wire the same as PMDX-134 (3 vs 4 Gecko 203v)

Also your transformer can be wired a few ways, but I show how I think you have yours setup.

I did a simple sketch, and look at this thread.

http://www.mechmate.com/forums/showthread.php?t=3561
Attached Images
File Type: jpg PMDX Power Setup S.jpg (35.1 KB, 360 views)
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  #15  
Old Thu 03 December 2015, 14:42
miguel juan
Just call me: mike
 
Montreal, Quebec
Canada
Connecting the Toroidal Coil

Thanks for the clarification Mike. I should have noticed that on the right hand side of the wiring schematic on the coil itself, the 0V and 115 V values are marked accordingly. By symmetry, the left hand side would be as you indicated in your reply above. Had you not clarified that for me, I would have had the current entering at the top left and the ground connected to the lower left. You have saved me a lot of grief.

The second photo is the recommended setup from PMDX. As can be seen, I have connected the EStop button as indicated. What has me puzzled is the rotary switch (Ferraz Shawmut FSLBS25 rotary load break switch) I am using. Wired the way you see it, current flows through when the switch is open. That is to say, 2 flows to the otherside (1), while 6 flows through to 5. Maybe I should have current entering into 1 to invariably flow through out to 2 and simarly have the ground connected at 5 to flow through to 6. I am assuming the mechanism is bidirectional so there is no difference. What has me confused is the middle connection. When I do a continuity test, nothing happens, no matter if the switch is on or off. With only two wires, I can make do the way it is wired. Surely that empty slot (3/4) must serve a purpose?
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  #16  
Old Sun 06 December 2015, 04:20
lonestaral
Just call me: Al #114
 
Isarn
Thailand
Send a message via Skype™ to lonestaral
Looking for power.
Try this.
https://www.youtube.com/watch?v=nm6DO_7px1I
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  #17  
Old Mon 07 December 2015, 12:09
servant74
Just call me: Jack
 
Nashville (Tennessee)
United States of America
Yo... Dude!
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  #18  
Old Mon 07 December 2015, 12:23
Robert M
Just call me: Robert
 
Lac-Brome, Qc
Canada
Send a message via Yahoo to Robert M Send a message via Skype™ to Robert M
....
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  #19  
Old Thu 10 December 2015, 15:25
miguel juan
Just call me: mike
 
Montreal, Quebec
Canada
Connecting PK296a2a-SG7.2 Unipolar

As many have done before, I am attempting to connect the recommended Vexta stepper Unipolar. I have read the thread (http://www.mechmate.com/forums/showt...ng+motor+gecko) describing how to go about selecting the 4 wires which will be used. Looking at the 203V Gecko, I suppose the A, A-, B, B-, markings are intended for Bipolar wiring. In Unipolar mode, I will be using only half the coil of winding A and half the coil of winding B. If I do the same as Richards (post 39 of the aforementioned thread), I would have Black/Yellow from coil A and Red/White from coil B. This should be hooked up as follows to the Gecko 203v.

Black = A
Yellow= A-
Red=B
White=B-

In Unipolar mode, Yellow is technically not A- but rather the center tap. Also, White is not technically B- but rather the center tap.When connecting the four wires to the Gecko 203V. The end points connect to the first letter (A or B) without the bar and the center tap is connected to the letter (A or B) with the -. Is my reasoning correct?
If I am not mistaken, the motor can be wired Unipolar in many different ways,

Black/Yellow - Red/White
Black/Yellow - Blue/White

Green/Yellow - Red/White
Green/Yellow - Blue/White

As for the toroidal coil. I connected a light bulb (as RobertM did in his post) and was able to get it to light up. Once again, I thank Mike for pointing out my mistake on initially connecting the ground incorrectly. All that remains to do now is connect the PMDX power module.
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  #20  
Old Fri 11 December 2015, 07:42
bradm
Just call me: Brad #10
 
Somerville(MA)
United States of America
You are correct, the motor can be wired for many combinations of Bipolar Half-coil connections. I say "Bipolar Half-coil" and not Unipolar because they aren't quite the same. Unipolar uses all six wires, but only energizes one half of the coil at a time.

Let's label the the six wires as either "Left", "Center", or "Right" on each of Coil A and Coil B. So we have AL, AC, AR, and BL, BC, and BR. And let's assume we're using a battery with a '-' and a '+' terminal.

For Unipolar operation, We permanently wire AC and BC to '-'. We then have a switch that can connect either AL or AR, but not both to '+', and a switch that can connect either BL or BR to '+', but not both. Each time we toggle a switch, it reverses the flow in a coil, and the motor takes a step. The order in which we flip the switches controls the direction of the motor.

Why does the flow reverse? Looking at one coil, it's AL ---> AC <--- AR so when AL is energized, it's left to right (center), and when AR is energized, it's right to left (center).

Unipolar has simpler control electronics, because it's only four switches, all acting on a single pole; within the control electronics, the flow never reverses. However, in modern electronics, it's no longer very difficult to have reversing flow, thus true unipolar isn't seen much outside of simple hobby circuits.

Bipolar half-coil achieves the same effect by swapping the flow. So if you wired using AL and AC, and BL and BC, the control electronics would ensure that you had AL(+) ---> AC (-), or AL(-) <--- AC(+) and the same for the Bs. Each toggle again moves from current flowing in one direction in half of the coil, to current flowing the other. You could use AR and AC instead of AL and AC - the effect is just to reverse the flow. Or you could just swap wires between AL and AC and you'd also reverse the flow. This is why we correct motors that run "backwards" by swapping the wires on one coil.

That's why you use the "Unipolar" numbers for "Bipolar Half coil". The Gecko drivers are always Bipolar, they can't do unipolar. The A and A- markings are really just to tell you that those two belong together on the same coil; in operation, the polarity toggles for each motor step. You could just as easily label them A1 and A2.

To complete the terms explanation, if you were to wire using AL with AR and BL with BR, you would be wiring "Bipolar series" - you're now using the entire coil, which is twice as long as half (duh), and thus has twice as much resistance thus providing more power at the expense of heating. No need to do that in this case.

Finally, if you had an 8 wire motor, then instead of AL --- AC --- AR you would have AL1 --- AL2 AR1 --- AR2 which if you combine AL2 and AR1 together, you have the AC of a 6 wire motor. Same thing on B. In this case, you also have the choice of wiring AL1 and AR1 together, and AL2 and AR2 together. Then, when you energize AL1,2 ----> AR1,2 or toggled AL1,2 <---- AR1,2 you are again using the entire coil, but as two half coils wired in parallel. This is "Bipolar parallel", which has half as much resistance.

So, Mike, you've got it right, other than this little terminology quibble. Don't get too hung up on the A and A- labels, or the "center tap"; the A and A- are just an electric source that toggles polarity back and forth, and the winding wires just let you choose your preferred coil length.
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  #21  
Old Sun 13 December 2015, 03:06
Tom Ayres
Just call me: Tom #117
 
Bassett (VA)
United States of America
Brad, that was an excellent summary, I hadn't given steppers any thought since I first made the same choices for my own set-up. Thanks for the refresher!
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  #22  
Old Mon 14 December 2015, 21:12
miguel juan
Just call me: mike
 
Montreal, Quebec
Canada
Stepper Motors for dummies

Thanks Brad for that thorough explanation. Unlike the classroom, the learning process in this endeavour is much more iterative. Something which is frustrating, for you are continuously searching out the forum (or other sources) in the hopes of coming across what it is you need to know to complete the next step. In the classroom, the subject matter is covered incrementally from the first chapter to the last. In my efforts to understand which wires I should be connecting, I discovered that there is much more going on behind the scenes. After reading your reply, I went looking on youtube for instructional videos which might graphically show the subtle differences in wiring options. The following video (https://www.youtube.com/watch?v=Qc8zcst2blU) is one among many which attempts to demystify the subject. It's been a good 25 years since I have resorted to the old left hand rule, but it sure came in handy watching the video.

I have connected the toroidal coil to the PMDX-137 Power Prep Module. Interestingly enough, the text on the PC board seems to correspond to the 8020 version and not the 5020 which is the model I purchased. That is to say, power in is 18 to 56 volts (8020 version) and power out is 24 to 80 volts DC. I will assume that PMDX makes one Board and simply varies the integrated components to meet the desired specifications. Assuming my module (5020) is indeed rated 18 to 36 volts AC IN and 24 to 50 volts DC OUT, I am border line. My 330 VA Transformer is delivering around 33 volts AC which in turn is producing some 47 volts DC Out. I will rerun the numbers again tomorrow, but suffice it to say that I am near the outer limits. It might have been more prudent to purchase the next model up for some 10 dollars more but my reason to opt for the 5020 model was due to the fact that the literature recommends the 5020 for lower voltage applications due to greater filter capacitance. I am not yet operational so I will continue as is and consider ''upgrading'' as the requirements solidify.

The coming days will be dedicated to testing motor functionality via the test mode of the PMDX -126
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  #23  
Old Tue 15 December 2015, 19:22
MetalHead
Just call me: Mike
 
Columbiana AL
United States of America
I would use what you got and adjust only if needed.
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  #24  
Old Wed 06 January 2016, 20:36
miguel juan
Just call me: mike
 
Montreal, Quebec
Canada
Test mode completed (PMDX-126)

The holidays are over and there is no better way to forget about chocolate than to once again take out the electrical components and begin "wiring stuff".

I have finally been able to find the time to sit down and carefully wire the PMDX-134 (motherboard for the 4 G203V Gecko motor drivers). The wiring as seen in the photo is a temporary situation for test purposes only and will be replaced by shielded cables once they are ordered and have arrived. I must say that I was very lucky to get the motor running on the first try since the axis on the gecko motherboard don't match those of the breakout board. That is to say, Axis 1 (J1) on the PMDX -134 corresponds to Axis 4 (J4) on the breakout board.
Axis 2 PMDX-134 = Axis 3 PMDX-126
Axis 3 PMDX-134 = Axis 2 PMDX-126
Axis 4 PMDX-134 = Axis 1 PMDX-126

Since the Gecko motherboard (PMDX-134) is mounted correctly and there is no mention of this anomaly anywhere, I suspect that the lack of correspondence must lie with one end of the ends of the ribbon cable being inverted. I could always test using another cable (which I would invariably have to purchase) or simply leave everything as is. Does it really matter if the left to right sequence on the Gecko motherboard is 4,3,2,1 rather than 1,2,3,4? It is only a matter of making the right adjustments in Mach. Suffice it to say, troubleshooting this particular issue was a lot of fun. I invariably had to reread many sections of the 126 manual carefully and in doing so got a better appreciation of what was being discussed.

As for the test results, I was able to get the motor to turn in both directions in each of the 4 axis. Although the manual says that test mode ramps the steps to 1000, I found that the motor did not turn quickly. Since I have never done this before, I am not sure what effect 1000 pulses per second would have on the PK296A2A-SG7.2 with a 7.2 gearbox. By the looks of it, I would say that the shaft took close to 10 seconds to make one complete turn. I have reread Brads earlier reply above to the effect that the motor is connected Bipolar Half Coil but that we use the Unipolar numbers to make all necessary calculations. The DC volts out are 44.7 and the resistor value is 36,000 in my case. Theoretically everything is fine. Should the motor shaft be turning as it is or should it be spinning much quicker? As Hamlet would say, "that is the question''.
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