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  #31  
Old Mon 09 October 2006, 00:29
Mike Richards
Just call me:
 
Gerald,
I think the high torque is the secret to the lack of 'chatter' with my 3:1 gearbox. Remember when there was a discussion about the effects of having a motor in 'power-down-mode'? (After staying idle for a very short time, most stepper drivers reduce the holding current to the motor to 20% - 30% of their normal holding torque.) I speculated then, that I thought that the reduced holding torque would let an active axis 'push around' an inactive axis. I don't have any proof, but my 'chatter' problem is gone.

As per Ted Hall's recommendation, I changed the steps per revolution on my Alpha motors from 1,000 to 500, meaning, that in reality, my 3:1 gearbox was only 1.5:1. I don't think that a 1.5:1 ratio was enough to cure the chatter problem.

(I've had no trouble logging in at the SB forum)
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  #32  
Old Mon 09 October 2006, 00:55
Gerald_D
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Mike, if the extra torque helps you overcome a "power-down" issue, then that *may* be something unique to Alpha control. Guys with non-Alpha's and torque well under 1000 oz*in are also now getting good quality.
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  #33  
Old Mon 09 October 2006, 03:33
ralph hampton
Just call me:
 
Hi guys.
I get a pretty good finish, but only work at slow speeds. But I am always after a better finish. To this end, I am currently working on beefing up the shopbot structure before investing in more silicon. My theory is that chatter is a result of vibration and harmonics - the noise (vibration) from movement in my system is very dependant on fine tuning the speed - jog at 72mm/second is WAY quieter than 70 or 75. I have analysed the situation by feeling extended parts (top of Z axis - very bad) while heavy cutting (45mm deep in utile at present) and will strengthen as a result.
My point is that if vibration > chatter, then maybe a 1.5 x resolution could take a setup away from a vibration state, and maybe shopbot were just unlucky (especially Mike_r) with their alpha (on many but not all machines) in that respect.

r/
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  #34  
Old Mon 09 October 2006, 04:28
ralph hampton
Just call me:
 
Mike_r: If it was a "powerdown" issue, then surely the chatter would only have appeared when running solely X move or solely Y - which was not the case. The smoothing effect of a belt drive (or to an extent any gear chain) might be more effective than we think, wrt vibrations (remember the beach boys....)

Gerald_d: If it was solely a resolution issue, then why did Mike_r not experiance 2X bad chatter when moving from 1000 step/rev to 500.

It's TEATIME............

R/
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  #35  
Old Mon 09 October 2006, 07:23
Mike Richards
Just call me:
 
Ralph,
Harmonics play a big role in stepper design. The old PH299 motors that I tried are useless with Geckos in a CNC application because of harmonics. The PK299 and the alpha's AS911 motors don't have much of a problem - at least by listening to them. You may have discovered the real culprit that causes chatter. Who knows? Something was causing it.

One of the things about 'chatter' that always bothered me is that the amplitude or height of a chatter mark was several 'steps' high. On an Alpha, each step on a factory configured machine is about 0.0025 inches. Chatter marks can easily be 0.030 to 0.060 inches high - meaning that something is really bouncing around. Harmonics could be part of it. Flex in the machine could be amplifying it. Little green gremlins could be shaking the machine.

Another factor that might be a big part of the problem is that I have a 120-60 size machine. Everything is just a little larger. It could be that one or more axes is a critical length when it comes to vibration. Believe me, before I installed the belt-driven gearboxes, I considered all of this and more.
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  #36  
Old Mon 09 October 2006, 07:51
ralph hampton
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Little green men get my vote...
Krikey, you are talking about chatter that is 10+ steps high! Surely that cannot be a resolution, or pushing steps ("powerdown") issue.
I'm lucky - I have a benchtop (fixed gantry) and can pile on the steel with impunity.
R/
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  #37  
Old Mon 09 October 2006, 17:43
Dick van Randen
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Mike R

I didn't see mention of velocity settings in your posts? It looks like you can change the damping of the controller in the AS controller by using the velocity filter. I have been wanting to play around with it, but have not had time to do the tests associated. Wondered if you had tried or know any more about it.

I always thought it strange that the same setting ( A , they go from 0 to F hex )is used for all three XYZ motors.

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  #38  
Old Mon 09 October 2006, 18:32
Mike Richards
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Dick,
I've totally left the Alpha driver alone, except to change the number of pulses per revolution (which was suggested by Ted Hall at Shopbot). Shopbot has some enhancements in their software that change settings automatically depending on whether you're jogging or moving normally. I really don't want to mess with things when I'm not totally informed about what Shopbot's software does behind the scenes. However, you've pointed out something that might easily enhance the Alpha.
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  #39  
Old Mon 09 October 2006, 18:41
Dirk Hazeleger
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I'm wondering what the difference is between Geralds cut quality and the AlphaPRT. I think that from the Pic he's using direct drive on all axis except the Z. I would expect the cuts to be similar since he's using Geckos and should be at the same resolution of the Alpha.
Gerald what kind of jog speed are you getting out of your setup?
My thinking is putting a compatible torque direct drive stepper motor as that of the Alpha Step motors is going to give you the same cut, adding gear reduction just makes it better.

Also if Mike's right about the torque, use a larger motor with more torque to cut the expense of the reducer.
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  #40  
Old Mon 09 October 2006, 18:59
Dirk Hazeleger
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My thinking in my last post was the advantage of the Alpha is most prevelant in sheet processing with straight cuts, so the increased resolution of gearing wouldn't be as nesessary but increased torque with larger motors is much less expensive than a reducer to reduce chatter.
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  #41  
Old Mon 09 October 2006, 21:37
Gerald_D
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Dirk, the cut quality appears to be on a par with the Alpha, if not slightly better. (Geckos are stepping at 2000 pulses/rev while the Alpha is 1000/rev?). This is going on photos and anecdotal evidence alone.

Max jog speed is a figure I avoid stating because I simply don't know how everyone measures it. It is like asking me what the top speed of my car is. Yes, we did take the MechMate up to the point where it loses steps, but this looked like a nasty speed and so we backed off a lot from there. I picked some force value that I wanted to achieve at jog speed (dragging dust shoes/hoses and cable umbilicals) and checked that with the fish scale. If I went to read off the max speed from the Mach3 setup now, you guys are probably going to find it laughably low. (This max speed is also related to the driver current setting, no?)
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  #42  
Old Fri 06 July 2007, 15:11
crogers854
Just call me: Craig
 
Farmington, Mo.
United States of America
Gerald;
That is truly an awesome looking machine..What size stepper motors does it use and where do I get them? also does anyone have any info on where to get the v rollers and the matching rails??? Is there a parts list that I missed...any help would be greatly appreciated...
thanks
Craig
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  #43  
Old Fri 06 July 2007, 16:17
IN-WondeR
Just call me: Kim
 
Randers
Denmark
Crogers, or craig...

Look through the forum, all your answers is there....
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  #44  
Old Thu 09 August 2007, 13:35
gimapere
Just call me: Giovanni
 
Pitangui - MG
Brazil
Send a message via MSN to gimapere
Jus a file for cutting process

Is there any place here in this forum that we can find the parts for cutting in just one file ? I mean, instead of placing all the pieces to send to cut supplier, we could find one fiel that contains all the parts togheter.

Thanks
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  #45  
Old Thu 09 August 2007, 15:06
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
For all the laser cut parts in 1 file try this.
http://www.mechmate.com/forums/attac...2&d=1181671900
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  #46  
Old Thu 09 August 2007, 15:07
Marc Shlaes
Just call me: Marc
 
Cleveland, OH
United States of America
Send a message via Skype™ to Marc Shlaes
Gerald, I built that and can post it. Let me take parts that I created - the brackets for my bolt-together components - back out of the zip file and re-zip and post. It contains a set of instructions for the contractor, a table of contents and the pdf pages of bending instructions in one nice neat package.
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  #47  
Old Sun 12 August 2007, 09:12
gimapere
Just call me: Giovanni
 
Pitangui - MG
Brazil
Send a message via MSN to gimapere
Exploded view

Thanks J.R. Hatcher for laser cut parts link.
Is there any Exploded View of MechMate here in this forum or anyone have seen it anywhere ?
I am asking this to make easier the assembly process. It will be a good idea.

Thanks.
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  #48  
Old Sun 12 August 2007, 11:06
Marc Shlaes
Just call me: Marc
 
Cleveland, OH
United States of America
Send a message via Skype™ to Marc Shlaes
Hi gimapere:

Check out post #1 in this thread:

http://www.mechmate.com/forums/showt...light=sketchup
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  #49  
Old Mon 13 August 2007, 05:30
gimapere
Just call me: Giovanni
 
Pitangui - MG
Brazil
Send a message via MSN to gimapere
MechMate Sketchup

Ok Marc, many thanks for the tip and Link. I can now see this incredible machine in details. It will be very helpfull in future.

Thanks again.

Giovanni
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  #50  
Old Wed 19 September 2007, 21:46
thesaent14
Just call me: Manny
 
Miami
United States of America
Gerald i have to say i am getting a bit up ses lol in building this machine is there a way i can see a small video of the machine cutting if you can please


BTW i was joking about the up ses part lol are we all

thanks


manny

Last edited by thesaent14; Wed 19 September 2007 at 21:51..
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  #51  
Old Wed 19 September 2007, 23:40
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
I was wondering when someone was going ask if this is all just smoke and mirrors

Manny, it does seem that the right thing to do these days is to load videos to YouTube. I don't have any "stock video" at the moment. Let me see if I can set it up . . . . . .
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  #52  
Old Thu 20 September 2007, 10:26
domino11
Just call me: Heath
 
Cornwall, Ontario
Canada
Gerald,
The video idea is GREAT. I have seen lots of videos of peoples cnc machines form the zone but not of the wonderfull big blue. I for another would love to see it cutting some stuff. Maybe CamCraft could show some on their website too? Might be nice for prospective customers to see the beast first hand.
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  #53  
Old Thu 20 September 2007, 10:36
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Cameras and sawdust don't mix so well

CamCraft has promised me an hour next week for some videoing. Then I have to learn that YouTube stuff . . . . . . and how to clean a camera!
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  #54  
Old Thu 20 September 2007, 10:42
Doug_Ford
Just call me: Doug #3
 
Conway (Arkansas)
United States of America
I'd love to see some video too. It will be inspirational.

PS. Gerald, can you put in a cameo appearance like Hitchcock used to do?
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  #55  
Old Thu 20 September 2007, 10:49
domino11
Just call me: Heath
 
Cornwall, Ontario
Canada
Gerald,
Sometimes when I am doing some dirty photos or stuff, take a clear poly bag and cover the camera, one that is soft enough to get at the buttons and then tape it to the lens so only the lens is getting dirty. I have used this a few times, then when finished blow off bag carefully, remove, clean lens and you are done.
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  #56  
Old Thu 27 September 2007, 06:51
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
The original MechMate - Cape Town, South Africa

The big MechMate built from scratch: (Front of dust foot removed)
http://www.youtube.com/watch?v=hGVQQf_iQpI

What was originally the 8x4' Shopbot is now fully converted except for the X-rails, x-racks and x-pinions:
http://www.youtube.com/watch?v=uGQ2J4GgXkg

The workshop where it started - now the home of CAM Craft
http://www.youtube.com/watch?v=dSelxyC5LU0
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  #57  
Old Thu 27 September 2007, 07:21
Greg J
Just call me: Greg #13
 
Hagerman, New Mexico
United States of America
Gerald,

Those are GREAT!!!

Thanks. I can't wait till my MechMate is cutting and being productive
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  #58  
Old Thu 27 September 2007, 08:13
cbboatworks
Just call me: Gene
 
Wilmington NC
United States of America
Hello Gerald

Thank you for posting the video.I will have to say your video has put me in over-dive. I do have a question and I may need to ask elsewere..I would like to know of a supplier here in the US for a spindle? I would like to buy one for my MechMate build. Thanks


Gene
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  #59  
Old Thu 27 September 2007, 08:53
Hugo Carradini
Just call me: Hugo
 
Pto. Ordaz
Venezuela
Well guys, now I can testimony that those videos is not a trick It is real. The Blue Beast in action.
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  #60  
Old Thu 27 September 2007, 08:57
Marc Shlaes
Just call me: Marc
 
Cleveland, OH
United States of America
Send a message via Skype™ to Marc Shlaes
I agree, very inspirational. Thank you for the time and effort.
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