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  #61  
Old Tue 17 July 2012, 17:27
smreish
Just call me: Sean - #5, 28, 58 and others
 
Orlando, Florida
United States of America
I will say that I have owned Multicam units with linear slide z axis and my MechMates.
Each require their own little secrets to set up square and true.
By far, because the mass is less on the MM, it is the easier of the two types.

The slides required a lot of m4 m6 hex head cap screws to play with. The MM....6 jam nuts, bur really only 4, because you use the top and bottom to set it all up, then match the middle.

Last time I squared up #28 during it's annual checkup, it took 2 framing squares and socket wrench to reset the plumb in about 15 minutes.
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  #62  
Old Tue 17 July 2012, 17:38
Zouave
Just call me: Eric #115
 
Sacramento, CA
United States of America
Brad brings up a really good point. Replacing a geared motor vs replacing a belt drive motor are two very different costs. I think, as far as accuracy goes, you'll get roughly equal results with either one, potentially better with the belt drive.
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  #63  
Old Tue 17 July 2012, 18:06
darren salyer
Just call me: Darren #101
 
Wentzville mo
United States of America
The z axis, while it took me a full day to complete, was no harder than any other part of the machine.
I doubt that using linear rails/motion bearings will result in a noticeable increase in machine accuracy.
Having completed a machine, I can say, every time I thought I had a better idea, I ended up back on the proven path for one reason or another.
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  #64  
Old Wed 18 July 2012, 03:52
KenC
Just call me: Ken
 
Klang
Malaysia
Ball Screw + Square linear guide is actually easier than it look; as long as you have a reasonable knee mill at your disposal. I have to get base plate milled.
The difficult part is the cost. It cost me around 600~700US$ to get one built. Still going strong.
The plus side is that mechanical reduction is naturally built in (no worries over weak gas spring & loosing steps when carving texture with big diameter (2") ball nose bits). The down side is you can't move Z-axis by hand when power is down.
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  #65  
Old Wed 18 July 2012, 20:02
litemover
Just call me: Chris
 
Auckland
New Zealand
All really interesting points. I mean, I really know very little about any of this, but for some reason, linear motion bearings keeps popping up in various conversations I've read, which caused me to question that. But you are right, I should jut try to get the first one finished as it is currently, then maybe alter it later, as it would require a new design altogether.

The gearbox vs belt drive is a tough decision. On one hand, if you go with a gearbox, it seems much easier to complete the machine, plus very accurate from what Ive seen on other people's builds, on the other, the serviceability seems less with a gearbox. The belt reduction seems like it would be higher torque, but maybe accuracy depends on the drive construction?

How frequently do motors go out? Has anyone here had to replace motors on their machine much?

Chris
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  #66  
Old Wed 18 July 2012, 20:09
riesvantwisk
Just call me: Ries #46
 
Quito
Ecuador
Send a message via MSN to riesvantwisk Send a message via Skype™ to riesvantwisk
Chris,

I dont use my machine to foten (unfortunatly) but i had a motionking (9801) motor going out.it felt stuck... I opened it and cleaned it out, put it back together and voila, it worked perfect again. I dont read much they go out, sometimes do. I have a spare in the shop just in case, also because i am in a country where import is very differcult.
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  #67  
Old Thu 19 July 2012, 22:23
litemover
Just call me: Chris
 
Auckland
New Zealand
Thanks Ries,

I understand that about import. It's tight in NZ also.

Chris
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  #68  
Old Mon 06 August 2012, 07:05
litemover
Just call me: Chris
 
Auckland
New Zealand
Hi guys,

I'm back in NZ, and looking to get some laser cut pieces done, and have a vendor. Should I just trace the plans or is there a set of DXF files for me to take to the cutter to get an estimate? They do one off cutting and folding for great rates.

Thanks!
Chris
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  #69  
Old Mon 06 August 2012, 18:01
litemover
Just call me: Chris
 
Auckland
New Zealand
Going shopping for an enclosure today, and Din rail, wire/cable. Read the posts about the wiring and electronics, very informative stuff. Still not sure about the power supply, but will read that tonight and see what they have at the electronics outfits here in Auckland. Started gutting my old G5 for it's case to install my new Hackintosh, which will be a dual boot PC/Mac OS based off of an Asus Rampage IV Gene board, which is micro-ATX going to the BOB.

Stuffed my shoulder, and received 6 stitches in my head after falling on the rocks out at the beach a few days ago, so waiting for that to heal before I start with the table steel. Hopefully, my arm can move by then and lift some of it (it sounds fairly heavy from what all of you say)

Ciao
Chris
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  #70  
Old Tue 07 August 2012, 14:20
MetalHead
Just call me: Mike
 
Columbiana AL
United States of America
So what was the beer to fall height ratio?

Just kidding - Hope your better soon !!!
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  #71  
Old Tue 07 August 2012, 22:27
litemover
Just call me: Chris
 
Auckland
New Zealand
Hey Mike,

No beer, just stepped onto the rocks and had my camera in one hand, backpack on, rocks were wet, so legs just went right out from underneath. Smacked my head on the rocks in an effort to save my lens. Shattered my filters, but lens was ok, so it was worth the 6 stitches Was just a trip standing up and seeing everyone freak out about the blood gushing from my skull.

Last edited by litemover; Tue 07 August 2012 at 22:28.. Reason: spelling
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  #72  
Old Wed 08 August 2012, 00:54
litemover
Just call me: Chris
 
Auckland
New Zealand
Am I correct in assuming that if I go with the PK296 A2a SG7.2, wiring Full Coil, that my PS voltage would need to be 78.38vDC at 500va? Mh = 6 at bipolar series? Is there a way to build a switch to toggle half or full coil for different uses? Would that even be nessesary?
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  #73  
Old Wed 08 August 2012, 07:33
Richards
Just call me: Mike
 
South Jordan, UT
United States of America
Wire the motors half-coil and use a PS with 35VDC to 45VDC. The gearbox on the PK296A2A-SG7.2 limits the usable torque, so wiring the motor half-coil still gives you all the torque that the gearbox can handle. The bonus is that your top speed is much higher when you wire the motor half-coil.

The only time that I would wire one of those motors full-coil is if I knew that I would never need more than 100 RPM.

To put it another way, if you use 1.25" pitch diameter spur gears with your rack, a 7.2 geared motor running at 100 RPM would move the axis about 55" per minute. That same motor wired half-coil can go 10X faster, or about 550" per minute. Actual speeds depend on ramping, the load (jogging or cutting), and the pulse generator (Mach 3).
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  #74  
Old Wed 08 August 2012, 07:35
domino11
Just call me: Heath
 
Cornwall, Ontario
Canada
Chris,
Mike Richards has posted quite a few comments on why, with that motor, wiring half coil is better. Lower voltage requirements, and mostly that in that configuration, you will produce more torque than the gearbox is rated for. Unless you have a power supply already at that voltage, I would suggest half coil wiring for that motor.

Mike you beat me to it.
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  #75  
Old Wed 08 August 2012, 19:16
litemover
Just call me: Chris
 
Auckland
New Zealand
Half coil huh? Others here have said full coil is better, but ok I'll do it half coil then. Would be much cheaper on the PS, that's for sure.

Thanks,
Chris
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  #76  
Old Wed 08 August 2012, 23:22
litemover
Just call me: Chris
 
Auckland
New Zealand
So in Nz we have 230v 50hz, the only toroidals I can find in stock are
50v+50v 500va
50v 50v 300va
40v 40v 300va
Then 18v 18v 300va
Then it goes down to 160va, I can't find a 25v 25v 300va. Any thoughts? Also, should I wire them series being in a 50hz country?
Thanks,
Chris
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  #77  
Old Thu 09 August 2012, 01:39
KenC
Just call me: Ken
 
Klang
Malaysia
I'm living in a 230V 50Hz country too, that isn't an issue at all when using tranny built for 60Hz.
Check this out
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  #78  
Old Thu 09 August 2012, 02:06
litemover
Just call me: Chris
 
Auckland
New Zealand
Awesome Ken, thanks for that link. RS components is huge, and they are in Auckland. I will go there to get the toroidal. I just thought that it needed to be wired in Series for a 50hz country is all. I'll keep on researching it tonight and get out there tomorrow.

Cheers,
Chris
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  #79  
Old Thu 09 August 2012, 08:19
domino11
Just call me: Heath
 
Cornwall, Ontario
Canada
Chris,
Series or parallel has no bearing on the line frequency.

You wire your primary for the line voltage you have, It might be two windings in series or one winding or two windings in parallel, depending on how they built the transformer.

The secondary is wired to give you the voltage and current you need. For the transformer Ken suggested, if you wanted 35VDC you would wire the two secondary windings in parallel to give you 25VAC(35VDC after rectifying and filtering) and you will get double the current of one winding. If you wanted a 50VAC secondary then you would wire the secondaries in series to give you a 50VAC secondary at a current rating of one winding. (You will want the parallel setup for the a2asg7.2)
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  #80  
Old Thu 09 August 2012, 19:33
litemover
Just call me: Chris
 
Auckland
New Zealand
Thanks Heath,

It all makes sense to me now. All the gist of the motor power threads to me is 32x sqroot of inductance (1.5)= the voltage, but with the PK296A2A-SG7.2 it can be pushed to 4.5 amps just fine without overheating because they are rated lower for some reason? Only need 67% total amperage. The transformer should be 1.4x less before rectifier, as it pushes it 1.4x higher voltage.

Here is the part that is confusing, do Parallel windings on the secondary gives me half the voltage, half amperage, and series gives me twice the voltage, twice the amperage right? I can only wire in series if they are the same correct?

Thanks for the help everyone. It's a great educational process learning how to make your own PS and everything else on this machine. I really love it. Should I regulate the power to smooth the ripples, do I need a breaking resistor on the cap, and last question, is it more preferable to use multiple capacitors to 1 giant one and I bought a rectifier rated at 400v 35a, spade type, is that ok?

Chris
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  #81  
Old Thu 09 August 2012, 19:59
litemover
Just call me: Chris
 
Auckland
New Zealand
One more question guys, can I use a resistor to lower the voltage if for instance I could only get a 40v transformer?
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  #82  
Old Fri 10 August 2012, 00:48
danilom
Just call me: Danilo #64
 
Novi Sad
Serbia
You need no regulation of power supply, no breaking resistor is needed,
As for the capacitors its really what you can find, usually capacitors bank consists of 2 or 4 pieces to gain 20.000uF .

And no, you can't lower this kind of power with a resistor, for that you would need a really big resistor, or a heater element

I must say that I unsubscribed from this thread, my opinion is that these elementary questions have been answered many times before in other threads long time ago. All you should have done to learn the basics of what is what, was to read 5-10 threads.
Look at the pictures, they would say it all. If you don't know what part to get, get the same as everyone else.
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  #83  
Old Fri 10 August 2012, 01:42
litemover
Just call me: Chris
 
Auckland
New Zealand
I do read the entire sticky section and the top few threads before asking. The fact of the matter is that this site is comprised of many varying opinions of what to do, and how to do it in order to build the same machine. Particularly with motors and electronics. Not everyone agrees, and it's confusing to me. I am sorry to have offended you for needing to understand but unfortunately, I need to understand what I am doing and verifying this prior to just going out and buying the parts that there is conflicting information on.

The confusing part of the electronics is how one can run more voltage through to the motors than what the spreadsheet prescribes (39v max) so it of course becomes a question. Also, the spreadsheet says I'll need 25.000 uf not 20.000uf capacitance. Can I use 2x 10.000 and 1x 5000 without problems?

Very grateful for all the help, I am so very sorry that I am so useless at this.

Chris
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  #84  
Old Fri 10 August 2012, 02:49
KenC
Just call me: Ken
 
Klang
Malaysia
Chris,
RS do stock 25,000uf cap , both stud mount & PCB mount.
Yes, you can parallel a whole bank of any number of caps to build up to your desired capacitor value. just make sure the voltage rating is correct.
BTW, all the numbers are reference values, you won't sink New Zealand with 10~20% off.
Honestly, you need a degree in rocket science to understand every single detail of the PSU theory. Sometimes, you gotta just accept & do it.
I agree with Danilo, is nobody use components in question, than you don't need them. If you want to oversize things, oversize as you wish & tell us if that set fire on anything later.
Again, every single question you posted were answered many times over, just keep reading.
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  #85  
Old Fri 10 August 2012, 08:04
domino11
Just call me: Heath
 
Cornwall, Ontario
Canada
Chris,
For your questions,

No regulation needed. It would actually add complexity and more points to fail. (Regulators are also more work. )

Breaking Resistor (I am assuming you are referring to a bleed resistor to drain the bank on shutoff) is not needed but can be used. Just leave it off and check the voltage on the bank with a multimeter before servicing.

One large capacitor or two smaller capacitors is fine. I would err on the side of more capacitance. If for example you wanted 20,000uf and you could only get 15,000uf caps, I would go for two 15s.

400V 35A rectifier is perfect. You just need to select a rated voltage higher than what you are running and a current rating at higher than you need. Good choice.

Now for the secondary series parallel question,
If you have a transformer with two secondary windings that are the same (same voltage , same current, which is usually the case) if you
1. Wire parallel you get 1xV and 2xA
2. Wire Series you get 2xV and 1xA
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  #86  
Old Fri 10 August 2012, 17:42
litemover
Just call me: Chris
 
Auckland
New Zealand
Thanks for clearing all that up. Especially about the Xformer amperage, capacitance, and bleed resistor as I'm a bit wary of huge charged caps. So since these are rated at 25mf I ought to get 30mf, that's good to know.

I have an equiss meter, and it was only $20, so I'm checking to make sure it will handle all that ok. . Much appreciated Heath.
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  #87  
Old Fri 10 August 2012, 21:23
domino11
Just call me: Heath
 
Cornwall, Ontario
Canada
Chris,
What capacitance are you shooting for? My 30,000uF was just a number to show a point. I was just trying to show that if you are shooting for x uF and using two caps gives you a little extra going the extra is better than not having enough.

Most multimeters sold today will more than meet most peoples needs. You can find them on sale at big box stores all the time under $20. At least up here in Canada.
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  #88  
Old Fri 10 August 2012, 21:27
litemover
Just call me: Chris
 
Auckland
New Zealand
The spreadsheet says to go with 25000uF. But since I am going to be driving them with slightly more voltage, 40v, I think it is a bit higher.
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  #89  
Old Fri 10 August 2012, 22:29
KenC
Just call me: Ken
 
Klang
Malaysia
Again, the numbers are not cast in stone, & you will not go to jail of kill anyone/thing if you don't use exact figure...
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  #90  
Old Sat 11 August 2012, 10:19
domino11
Just call me: Heath
 
Cornwall, Ontario
Canada
Chris get a cap or two that give you something in the order of 25,000 to 40,000 uF. That is where I would be aiming. Also make sure the voltage rating of the caps is well over what you are using. Also take into account for line surges and spikes.
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