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  #1  
Old Thu 02 September 2010, 05:53
Quadro
Just call me: Anthony #77
 
South Australia
Australia
Stickers on and cutting #77 - South Australia

Hello Everyone,
Building has started! After building 2 home brew cnc routers and disappointed with the performance, I thought it was about time to build a man's machine.
The size will be 3000mm x 1830mm x 250mm.
I have received the steel and have started cutting away.
The steel was bought from a company that sold it in lengths only(9-6m), this worked out to be 45% cheaper plus the steel left over for other projects(?). They also were able to cut the lengths to size so I was able to get it home.
Ordered the V rollers and bearings from Rick Hoback from SuperiorBearing, Australian suppliers wanted 400% more than Rick, maybe there is gold in the Aussie ones.
I have also ordered the laser profile parts from rnixon.
I found some 640oz steppers on ebay, the vendor also has the G540 Gecko which should be able to run the motors in 'half coil' configuration, I think?(if someone could please agree or disagree with my calculations to put my mind at ease.)
He also has a 48V 12.5A Switching Power Supply.
Anyway, thats where I'm up to, hope to post updates with photos(when i work out how, can't be any harder than EMC2)soon.

Last edited by Gerald D; Mon 07 February 2011 at 23:06..
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  #2  
Old Thu 02 September 2010, 07:15
bradm
Just call me: Brad #10
 
Somerville(MA)
United States of America
Welcome Anthony!

Use the "Unipolar" numbers as equivalent to "half coil" - in both cases you only energize a half coil at a time. The 2.2mH will work (Gecko sez 2.5 to 3.0mH for max output). The torque will need to be derated to the 3.5A the G540 can supply;
if 6.3A = 640 Oz/In and 4.5a = 455 Oz/In, then (as an inaccurate linear guesstimate) you'll have around 350 Oz/In at 3.5A. Do a belt drive to multiple that torque, and it should work. Motors will be loafing, so they should be nice and cool.
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  #3  
Old Thu 02 September 2010, 07:32
MetalHead
Just call me: Mike
 
Columbiana AL
United States of America
Glad to see you have started your build !!!
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  #4  
Old Thu 02 September 2010, 08:18
domino11
Just call me: Heath
 
Cornwall, Ontario
Canada
Welcome Anthony!
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  #5  
Old Thu 02 September 2010, 16:49
Quadro
Just call me: Anthony #77
 
South Australia
Australia
Thanks Brad, Mmmm.... I see where I went wrong. I was thinking 'half the coils half the current' which after rereading other posts it is where others have been 'tripped up'. I was avoiding using a belt drive for now and since my last 2 home brews were under powered (secondhand steppers - missed steps) I don't want just good enough, I will do more research. Thanks again Brad.
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  #6  
Old Thu 02 September 2010, 18:33
bradm
Just call me: Brad #10
 
Somerville(MA)
United States of America
Anthony, I wouldn't necessarily describe it as going wrong. Most MMs use mechanical ratios (via the gearbox in the OM7.2s, or belt drives) to get their torque. The G540 supplies enough electrical power to produce enough mechanical power as long as the motor isn't grossly outmatched. So, as long as you do the belts, you were in the zone. If you choose not to have a mechanical ratio, then you will probably want more power from the motors, and you will need to go the more expensive individual driver and Bob route. Depending on shipping costs, it appears that the UIRobot drives may be the most cost effective.

Me, I'd just plan on using the belt drives - you may end up wanting them anyway.
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  #7  
Old Sun 12 September 2010, 18:37
Quadro
Just call me: Anthony #77
 
South Australia
Australia
Brass Bushes M1 20 220

I should have asked if anyone could see any problems with making the bushes out of brass before I made them.
So I'll ask the question, could bush M1 20 220 be made out of brass?
Attached Images
File Type: jpg R0010694.JPG (59.7 KB, 1302 views)
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  #8  
Old Sun 12 September 2010, 18:49
smreish
Just call me: Sean - #5, 28, 58 and others
 
Orlando, Florida
United States of America
...with the exception you won't be able to weld them to the spider.
The welding is not required, you can easily tap the spider plate and put the bushing in as a spacer/bushing and it will work just as well.

First machine, I did just that and it's still working just fine.

Sean
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  #9  
Old Thu 13 January 2011, 16:28
Quadro
Just call me: Anthony #77
 
South Australia
Australia
Progress has been a bit slow lately, due to work.
I have welded the Y-car and the gantry as seen in the following pictures.
Cutting the rails is not as easy as I thought it would be.
KenC gave me a few tips which have been very useful.
Whether it is good luck or good management I didn't cut the rails to length,
this allowed me shift away from the gouge that I had put in the rail (see photo) which would have required welding and grinding or a new piece of steel.
Attached Images
File Type: jpg R0011211.JPG (51.6 KB, 1191 views)
File Type: jpg R0011208.JPG (49.7 KB, 1187 views)
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  #10  
Old Fri 14 January 2011, 23:58
KenC
Just call me: Ken
 
Klang
Malaysia
I recon you can epoxy glue the brass to the steel spider, or solder... Nothing is impossible....
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  #11  
Old Fri 21 January 2011, 22:07
clarson66
Just call me: Chris & Leon #100
 
Adelaide
Australia
Welcome and good luck with the build. We to are in Adelaide SA and hope that when my new shed is built we can get back on track with our Mechmate.

Chris
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  #12  
Old Thu 27 January 2011, 04:43
Quadro
Just call me: Anthony #77
 
South Australia
Australia
I found grinding the rails is alot easier when i used one of those sandpaper/grinding disc. It can be ground in less than 1/4 of the time and less cost, 1.5 discs for 3.6m worth of grinding. The normal grinding discs kept on glazing up even the grinding is done near the edge of the disc.
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File Type: jpg R0011377.JPG (49.8 KB, 980 views)
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  #13  
Old Thu 27 January 2011, 08:14
smreish
Just call me: Sean - #5, 28, 58 and others
 
Orlando, Florida
United States of America
That is a great note that I don't think get's shared enough. Start with a 36 or 50 grit and finish with a 80 or 120 grit to polish.

For the new readers, make certain that you have a VERY stiff backer to the sanding disk unit. Some of the backing plates on the disks can be to flexible and not give repeated grinding results. I personally put the sanding disk ON TOP of an actual grinding disk as a FIRM back.

Thanks for sharing.
Sean
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  #14  
Old Thu 27 January 2011, 18:59
Quadro
Just call me: Anthony #77
 
South Australia
Australia
I set the skate so that it was grinding in the middle of the disc with the rubber backing where it is a lot stiffer, as can be seen in the photo with the grey mark. It is not the opitmum spot for grinding (cutting tip speed, what ever it is called it grinding terms?).
I think using a grinding disc instead of the rubber backing is a very good idea and would be far better.
I timed my self and it took 1/2 an hour to grind 3.6m and 1/2 an hour to cut with 1mm blade. It has gone from a painfull process to a painless process.
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  #15  
Old Fri 28 January 2011, 04:08
Robert M
Just call me: Robert
 
Lac-Brome, Qc
Canada
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Allow me to add to your caution SEAN.

Cheep grinders ( like the one I used back then) have some “flex” due to cheep bearing or bushing to chaft tolerance making the “stiff” disc still “wobble” out of axis.
I remember to remedy this had to take VERY very light passes in order to achieve a respectable flatness ….and goes without saying I had to replace that “cheep” darn oem bearing after only one rail ( see this)!

Buy good tools once rather than a "cheep" making it hard on you !

Robert
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  #16  
Old Fri 28 January 2011, 04:47
KenC
Just call me: Ken
 
Klang
Malaysia
be it cheeeep or expensive tools... we still has to be gentle with them
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  #17  
Old Fri 28 January 2011, 15:02
Quadro
Just call me: Anthony #77
 
South Australia
Australia
Base table all made, will post pictures later. dxf shows the design, I don't know how to draw in 3d so it is only 2d. The table is off set so that a indexer/lathe can be fitted on the end at a later date.
Attached Files
File Type: dxf mechmate base.dxf (262.0 KB, 54 views)
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  #18  
Old Sat 29 January 2011, 04:41
Surfcnc
Just call me: Ross #74
 
Queensland
Australia
Anthony

I'm with Sean, the rubber backing pad will give a second class result in comparison to using a grinding disk as a backer.
I have really tried to get this method out there for all to see after reading it on the forum myself.
I asked Redboards to run some comparison tests before he did his rails and he is a convert of the technique.
As Sean says, run up the grits and by the time you get to 120 Grit, it polishes the rails.

Good luck with your build.

Ross
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  #19  
Old Sat 29 January 2011, 19:31
Quadro
Just call me: Anthony #77
 
South Australia
Australia
Ross
I don't disagree with you or Sean.
If I was to to it again I would do as you have explained. When I had read Sean's post I had alredy completed the grinding.
The local Hardware Store only had 36 and 60 grit, so did the main cutting with the 36 and finished with 60. The surface still had machine marks so I draw filed with a 12" finishing file.
If some can tell me a good reason(s) why I must have 'polished' rails (apart from me being able to see myself combing my hair) I will do it, I think it is acceptable.
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File Type: jpg R0011398.JPG (64.3 KB, 882 views)
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  #20  
Old Sat 29 January 2011, 19:41
Surfcnc
Just call me: Ross #74
 
Queensland
Australia
Hi Anthony

The accuracy of the rails are the only consideration, everything else is really only cosmetic. Small scratches will not interfere with the operation of the machine.
The section of rail you have shown looks to be the goods - well done.

Regards
Ross
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  #21  
Old Sun 30 January 2011, 01:02
KenC
Just call me: Ken
 
Klang
Malaysia
Not just for combing your hair, Polishing the rail is also a great way to kill time.
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  #22  
Old Sun 30 January 2011, 05:43
smreish
Just call me: Sean - #5, 28, 58 and others
 
Orlando, Florida
United States of America
Anthony,
No reason to polish the rails. I guess to be accurate, I shouldn't have used the word "polish" and should have said - final finish pass. I treated the milling procees like any other metal removing process by using a "rough cut and removal", then a "fine finish pass"

Good luck to all the future builders! It gets easier every time.

Sean
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  #23  
Old Sat 05 February 2011, 12:47
Quadro
Just call me: Anthony #77
 
South Australia
Australia
Finishing Build in South Australia

Started final assembly yesturday. Found that the cable chain bracket on the main beams were to high and didn't allow enough room for the drive gear(see picture). I lowered it 20mm, re-drilled and re-tapped, no biggy, trap for new players.
Started wiring up today, maybe cutting tomorrow(?!).
Attached Images
File Type: jpg R0011417.JPG (56.2 KB, 801 views)
File Type: jpg R0011418.JPG (51.0 KB, 793 views)
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  #24  
Old Sat 05 February 2011, 12:50
smreish
Just call me: Sean - #5, 28, 58 and others
 
Orlando, Florida
United States of America
...been there....moved that! It all depends on the Diameter of the cable chain you order.
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  #25  
Old Sat 05 February 2011, 13:24
Quadro
Just call me: Anthony #77
 
South Australia
Australia
Yes Sean, that was the determing factor of the original position of the bracket.
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  #26  
Old Sat 05 February 2011, 16:44
MetalHead
Just call me: Mike
 
Columbiana AL
United States of America
I would just make the portion shorter that bolts to the side of the machine. The weight of the chain should not be a problem.
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  #27  
Old Sat 05 February 2011, 17:05
Quadro
Just call me: Anthony #77
 
South Australia
Australia
Metalhead,
the picture maybe not clear but the bottom of the gear is bellow the thread for the bracket bolts. Yes, cutting the brackets could be an idea if it was only 5mm.
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  #28  
Old Sat 05 February 2011, 21:20
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Those bracket legs were lengthened, see the revision note on the drawing 1060215PB. The request came from http://www.mechmate.com/forums/showt...1&postcount=29
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  #29  
Old Sun 06 February 2011, 00:37
Quadro
Just call me: Anthony #77
 
South Australia
Australia
Gerald,
I mean no disrespect to the design. I used smaller cable chain than I should have which ment I raised the brackets to keep the top of the chain parallel to the bottom when it is doubled over. Due to the different makes/models and sizes that is used, to help others I thought I would point it out so they didn't make the same mistake.

This is the first forum that I have engaged in and find it difficult to write all of what I'm thinking or what not to write with out offending.
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  #30  
Old Sun 06 February 2011, 05:50
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
This is the first forum that I have engaged in and find it difficult to write all of what I'm thinking or what not to write with out offending.

Been there….got shot down……rethought my « thinking »…matured for forum exchange….today less aggravated & aggravating

Think pink, think positive, think to help….if any other….shot the f up and keep it to your self
That’s my “moto”
Amiclament, Robert
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