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  #1  
Old Tue 19 August 2014, 12:18
leostaines
Just call me: Leo
 
Miami, Fl
United States of America
Heavy duty Mechmate build!

Hey guys,

So I'm planning to build a Mechmate and would like to know some information.

The mechmate Will be controlled by the Centroid m39, the reason is because this controller can control ATC and up to 8 axis, and is a more industrial than Mach3. On the table itself, I would really like to switch the v rails to a bearing type linear rail. Also the rack and pinion would also be switched to a ballscrew system. Delta AC servos would drive the machine and I was looking at a 11 hp atc hsd. For the future I am considering adding a second z axis for a pan and tilt "2axis" spindle. Has anyone had any experience with any these? My budget is probably at the 20k-25k mark. And I know used machines go for around 30k but looking to get a 5x10 customizable table.
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  #2  
Old Tue 19 August 2014, 16:00
bradm
Just call me: Brad #10
 
Somerville(MA)
United States of America
Leo, before we wade into the pros and cons of bolting all those upgrades on to the MechMate, maybe you could tell us a bit more about what you're planning to cut, and thus we'll understand what goal those changes address. That way, you'll get the benefit of collective experience thinking systemically about issues you may not yet have considered.
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  #3  
Old Tue 19 August 2014, 16:36
leostaines
Just call me: Leo
 
Miami, Fl
United States of America
Hey Brad,

I'm planning on cutting Baltic birch, acrylic, and some aluminum. The work that my customers want has to be extremely precise and fast. The machine will be immediately used for small production but will more than likely increase within the first 3 months. The pieces that I'm cutting require around 6 tool changes which doing it manually for us wouldn't be in any way beneficial. Servos are something I would definitely want, and an atc cable of being a work horse cutting 1" plywood is something we need. The control system is definitely going to be centroid (or one very similar... Fanuc?) because it allows easy programming of the atc, and also allows me to use 8 axis. So far it is one of the most reliable controllers I have found that has 5 axis and an atc. Other breakboards haven't really caught my attention.
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  #4  
Old Tue 19 August 2014, 17:01
danilom
Just call me: Danilo #64
 
Novi Sad
Serbia
I don't think 11hp atc spindle will fit the mechmate Z axis... and it weights around 30 or more kg. My recommendation is to look for a custom built frame and if its allowed I can suggest someone.
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  #5  
Old Tue 19 August 2014, 17:03
leostaines
Just call me: Leo
 
Miami, Fl
United States of America
Send me the information please!
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  #6  
Old Tue 19 August 2014, 20:10
ger21
Just call me: Ger
 
Detroit, MI
United States of America
You do realize that the spindle is going to eat up 50% of your budget?
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  #7  
Old Wed 20 August 2014, 00:30
leostaines
Just call me: Leo
 
Miami, Fl
United States of America
$7,500
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  #8  
Old Wed 20 August 2014, 01:55
danilom
Just call me: Danilo #64
 
Novi Sad
Serbia
what about rack and atc holders how much is that on top of 7500

11hp vfd etc...
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  #9  
Old Wed 20 August 2014, 04:48
KenC
Just call me: Ken
 
Klang
Malaysia
How extreme is your "extremely precise"? in comparison to hand saw MM is ultra precision, but low precision when compare to wire-cut.
Ball-screws are not suitable for length over 800mm, & expensive.
"Bearing type" rail, which type? & also expensive.
The tool holder for 8 station will be super expensive.
Servo motors + encoder will be ultra expensive. ( still cheaper then the tool changing spindle)
I guess you are asking too much for your 25K... even if the table materials & labour are free...

With the kind of budget you have, u should be looking at stepper motors. Servo is not for improving precision, its there to push up the price tag.
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  #10  
Old Wed 20 August 2014, 06:21
ger21
Just call me: Ger
 
Detroit, MI
United States of America
Yes, toolholders with collets can run $150-$250 each. You also need addtional solenoids, relays and possibly other devices to get the spindle working.
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  #11  
Old Wed 20 August 2014, 06:24
ger21
Just call me: Ger
 
Detroit, MI
United States of America
Quote:
Originally Posted by KenC View Post
Ball-screws are not suitable for length over 800mm, & expensive.
I've been using machines with ballscrews on 3000mm and 3500mm axis for years. They use spinning nuts, and probably cost about $5000 each. But they work fine, and are available.
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  #12  
Old Wed 20 August 2014, 08:55
leostaines
Just call me: Leo
 
Miami, Fl
United States of America
Hey guys, thanks so much for all of your answers and advice. I appreciate it so much and you guys have been such a great help. Although I am in the planning phase it's very true on details that your guys are giving me! Thanks guys so now my question is, building he mechmate with DC servos, and rack and pinion what can I expect in terms of precision?
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  #13  
Old Wed 20 August 2014, 09:10
danilom
Just call me: Danilo #64
 
Novi Sad
Serbia
You can achieve precision and repeatability it has nothing to do with machine plans or Mach3 or Centroid, for me 0.5mm is acceptable for work in wood and other non ferous materials, ofcourse this is always more precise but around 0.2-0.3mm on my mechmate.
Searching for precision and fast feedrates or DOC from a sub 2ton machine in 5x10 dimension is too much. For a precision measured in hundreds of mm even machining centers can't achieve this without right programming, endmills, cleanup passes, temperature compensation, combining climb cut and conventional etc.
Using precision gear rack and building all components very carefully, it has no matter what motors you use if they are capable of the task they are put to, if going to servos advice is to use modern AC servo motors, maintenance free and now cheap enough (Leadshine or Xinje around 450 usd set for 750w motors and drives). You will need to build belt reductions for them or use some off the shelf which can get pricey when looking for low backlash.
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  #14  
Old Wed 20 August 2014, 10:32
bradm
Just call me: Brad #10
 
Somerville(MA)
United States of America
As Danilo points out, the precision and repeatability are influenced by many factors beyond the drive system. Ultimately, your feed rates and precision are going to be defined by the tool as it goes through the material. Can you keep the tool perpendicular at a consistent speed, feed, and temperature without snapping it, while the material stays firmly in place? All of the characteristics of the machine need to work together to hit this mark, and it's a balance.

Have you thought through your tools / number of passes? see http://www.onsrud.com/xdoc/FeedSpeeds That should give a sense of what feed and speed targets you have, which can then take you back to sizing motors and spindles.

From there, we can talk about whether anybody has gotten close to what you're proposing. I don't recall any prior 11 HP spindles on MechMates, and I'm personally a bit skeptical that it will be practical - seems like we're talking 5/8" to 3/4" tooling territory to use that power level, which raises stiffness questions in my mind.
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  #15  
Old Thu 21 August 2014, 12:01
Richards
Just call me: Mike
 
South Jordan, UT
United States of America
Look at the way ball-screws are used on a Thermwood. Vibration is kept to a minimum. I'm sure that Thermwood has a patent, but I'm not sure how patents pertain to home-use, home-built equipment. A lawyer could tell you.

Look at the specs on ball-screws. "Whipping" is a phenomenon influenced by the diameter of the ball-screw and the speed at which it is being driven. As Ger21 pointed out, using spinning nuts instead of spinning the screws will eliminate "whipping".

I've seen several V-rail CNC machines retrofitted with linear rails. In each case, all "shudder" was eliminated. Curves and circles cut precisely without the need for sanding. The cost was substantial, but where quality was required without the need for sanding, the additional cost was acceptable.

Linear rails and ball-screws were particularly helpful when cutting aluminum.
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  #16  
Old Thu 21 August 2014, 16:17
Duds
Just call me: Dale
 
Canberra
Australia
Quote:
but I'm not sure how patents pertain to home-use, home-built equipment. A lawyer could tell you.
All jurisdictions are different. You can't patent or protect ideas, only the expression of an idea. In the context of home builds it doesn't take a lot of imagination to take an idea and express it in your own implementation. Also, from a purely practical and risk perspective copying these kind of ideas is low risk due to difficulties identifying and pursuing protection. Just how does Thermwood discover that you have a one off custom copy of their ball screw. And if it's in your garage how do they get evidence to prove your infringing. Further, if your not selling the machines how do they prove your infringement is causing them damage.

Companies get very noisy about IP but it's mostly bluster except in the most blatant of commercial copying. It's also a necessity to engage in bluster because it's part of the whole protection process. It's pointless buying a big dog if it doesn't bark at everyone who comes near the fence.
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  #17  
Old Thu 21 August 2014, 22:43
KenC
Just call me: Ken
 
Klang
Malaysia
This will turn out to be a scratch design altogether.
Maybe you will find more info in CNCzone or elsewhere.
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