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  #1  
Old Thu 28 January 2010, 21:26
TURBObuck
Just call me: Robert
 
Garner (NC)
United States of America
Education Underway - Garner NC USA

Hi, I am educating myself on the various aspects of building my own CNC router with hopes to start building within the month. I look forward to picking you brains for ideas and methodologies for building and designing and CNC. I want a 4 axis machine with encoder stepper motors with Gecodrive controlers. I am leaning toward using rack and pinion instead of acme lead screw. My immediate problem is wether to build in my garage or rent wharehouse space as a shop.
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  #2  
Old Thu 28 January 2010, 21:54
domino11
Just call me: Heath
 
Cornwall, Ontario
Canada
Welcome Robert.
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  #3  
Old Thu 28 January 2010, 22:17
riesvantwisk
Just call me: Ries #46
 
Quito
Ecuador
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Robert,

welcome to the forum and MM club. The mm is rack and pionion based, but no worries, if build according to the plans you will be a very happy person.

Riesling
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  #4  
Old Thu 28 January 2010, 22:19
KenC
Just call me: Ken
 
Klang
Malaysia
Welcome, you will achieve what ever your goal as long as if you start working on it.
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  #5  
Old Thu 28 January 2010, 22:35
lumberjack_jeff
Just call me: Jeff #31
 
Montesano, WA
United States of America
Welcome!

I'd be interested to know what you see as the benefits of encoders with your steppers. Most of us (if not all) run our machines open loop.
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  #6  
Old Fri 29 January 2010, 06:08
sailfl
Just call me: Nils #12
 
Winter Park, FL
United States of America
Great question Jeff
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  #7  
Old Fri 29 January 2010, 07:02
J.R. Hatcher
Just call me: J.R. #4
 
Wilmington, North Carolina
United States of America
Send a message via Skype™ to J.R. Hatcher
I always wanted the assurance of accuracy myself. Then I started running my MechMate and quickly realized, it's not necessary. JMHO
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  #8  
Old Fri 29 January 2010, 13:41
TURBObuck
Just call me: Robert
 
Garner (NC)
United States of America
It is my understanding, that you have to have encoders for the feedback if you want to digitize an existing carving.
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  #9  
Old Fri 29 January 2010, 13:47
domino11
Just call me: Heath
 
Cornwall, Ontario
Canada
Many people use digitizing probes with steppers. Digitizing is not demanding on the steppers and you are moving slowly so missed steps should never be a problem. I do not believe the feedback will give you anything extra in that situation.
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  #10  
Old Fri 29 January 2010, 18:46
TURBObuck
Just call me: Robert
 
Garner (NC)
United States of America
I guess there is a lot more for me to learn. So endcoder are not required, I guess that is good since it will lower the cost of the build.
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  #11  
Old Sat 30 January 2010, 17:55
bankodave
Just call me: Dave
 
Raleigh, NC
United States of America
Hey Robert,

If you have the room in your garage I would build it there. If you are anything like me you will want to work on it as much as you can and having it close makes that possible. Also you will not have the added expense of a shop space.

I live in Raleigh and have my 4x8 CNC in my garage. Let me know if you need any help with it.

Dave
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  #12  
Old Sun 31 January 2010, 21:08
TURBObuck
Just call me: Robert
 
Garner (NC)
United States of America
Thanks for the advise and the offer of help. Most of the time I am excited about building my machine and the more I learn the more I realize there is so much more to know. I would love to see you CNC and pick you brain on the key area of the build.
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  #13  
Old Mon 01 February 2010, 20:30
bankodave
Just call me: Dave
 
Raleigh, NC
United States of America
There is a lot to know and it is very addicting. Prior to joining this forum I was having all sorts of problems with my older Shopbot. Since joining I have rebuilt and rewired the control box, redressed the guide rails, rebuilt the X and Y axis motor mounts, changed to the proper spur gears for my motors and installed a Z zero plate. The machine now cuts with some accuracy.

You are in the right place to make a great CNC machine.

Dave
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  #14  
Old Mon 01 February 2010, 22:11
TURBObuck
Just call me: Robert
 
Garner (NC)
United States of America
Here goes. I am looking for a lot of advise on the parts for the simulator.

Motors PK296A2A-SG7.2
Drivers G203V standard
BOB pmdx-132 or 122 have not decided
SmoothStepper for the USB interface
Power Supply ????
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  #15  
Old Mon 01 February 2010, 22:46
KenC
Just call me: Ken
 
Klang
Malaysia
Your selection is fairly "standard" if I remember correctly, but not the Smooth Stepper, running USB interface (without lost step or jitter) will be too slow for this application. but can always use it if you don't mind jitter or slow travel speed....
(I assume you did your reading here.)
Wiring the PK296A2A-SG7.2 motors & power supply voltage selection
Selecting motors for the MechMate
and a few more others.
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  #16  
Old Mon 01 February 2010, 23:04
riesvantwisk
Just call me: Ries #46
 
Quito
Ecuador
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Ken,

I am not sure if you understand the smooth stepper concept correctly. But the smoothstepper takes of the realtime task of the PC when it comes to pulse train generation for the drivers and stepper motors. The basic idea of the smooth stepper is that the device can generate the pulses for the stepper motors/drive much better then a PC.

Technically I am not sure how the smooth stepper is exactly implemented, because it's unfortunately not as easy as just letting something else generate pulses, but since the real time task is taken over by the device, the motors can be controller over USB with more precision and accuracy.

I believe that the smooth stepper is still a bit in testing phase and not everything works yet as smooth as you want to, and if somebody ask me to use a PC with Mach3/EMC or the smooth stepper I would properly say a PC with Mach3/EMC, it simply allows you to have a bit more options IMHO.

From the smoothstepper (ST) doc (it's been a while since I did scan through it) it's not clear how some curves are implemented, are they send as a lot of short lines to the ST or can the ST handle curves/circles in 3D aswell? I know that some controllers for example do have implementations for 2D circles and semi circles, but in 3D they need to revert back to lot's of single lines. Now, I didn't dig to deep into the ST, but my advice to Robert is to talk to some people, read there experiences and understand the limitations of the ST, because from what I remember is that not everything is implemented in the ST that you can do with Mach3/EMC as of yet, you have a PC already... and a PMDX is a bit cheaper then the ST.

Just my personal 2 cents, I am not a guru in the subject!
Ries
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  #17  
Old Mon 01 February 2010, 23:53
KenC
Just call me: Ken
 
Klang
Malaysia
Ries,
I am not expert in SmoothStepper as well, what I learn from the net is more or less what you said.

I can't remember where but there are report of good results on table top CNC routers/engraver using lead screw, Knee Mills, CNC (metal & wood) lathe but fail to deliver the travel speed required on faster machines due to jitter/loss step. This was confirmed by a few practical report from users. So, emphatically speaking, SmoothStepper is not suitable for fast moving machine such as MM. After knowing this I stop digging any further & moved on.

I too would like to have a reliable USB interface for the MM, but until such product comes out, lets just stick to the old trusty parallel port.

Russel,
IMHO, Learning & building a MM is a big project as it is, even after Gerald has trashed out most of the design issue..., letting too much experiment/development in the way will only slow down the build momentum. Eliminating unknown will make the journey much more pleasant.

Just my opinion from the system design aspect.
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  #18  
Old Tue 02 February 2010, 00:59
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Quote:
Originally Posted by KenC View Post
. . . So, emphatically speaking, SmoothStepper is not suitable for fast moving machine such as MM. . . ..
I emphatically disagree

The Smoothstepper is not clever enough to know what type of machine it is driving. The stepper motor speeds in milling machines are the same as in routers - just the gear ratios are different.

I am not recommending the SS, or saying to avoid it, just trying to be correct.
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  #19  
Old Tue 02 February 2010, 03:01
KenC
Just call me: Ken
 
Klang
Malaysia
Sorry, I meant to say "empirically"

Well, there's always mixed opinion over ST, rave argument over it in other forums. Now, at least for me, Parallel port is my friend

Last edited by KenC; Tue 02 February 2010 at 03:05..
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  #20  
Old Mon 01 March 2010, 07:54
salewis
Just call me: Stan #67
 
Littleton, NC
United States of America
Looks like NC is becoming the center of MM'ers. Don't worry I'll stand at the border and let other MM'ers in...

Got to keep the riff-raff out...

Seriously, welcome....
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  #21  
Old Wed 10 March 2010, 12:52
danmcgee
Just call me: Dan
 
Petersburge (VA)
United States of America
I am also considering building a MECHMATE just a bit smaller, I am in Petersburg Virgina, is any of you here in VA with a built MM or which is closest to me in NC I could come look at.

Dan
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  #22  
Old Wed 10 March 2010, 16:24
salewis
Just call me: Stan #67
 
Littleton, NC
United States of America
I'm right on the VA/NC border just west of Roanoke Rapids, NC. Right around 2 hours south of Petersburg on I-95

Stan
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