Brainstorming Specifications.

Setting this discussion up to gather up and brainstorm ideas.

LIST OF EQUIPMENT AND MATERIALS UNDER CONSIDERATION:

Motors/Controllers:

  1. cadcamcadcam.com (servo motors and controller)
  2. 3-axis Stepper Motor System based on DQ542MA, on Ebay
  3. 6-axis Stepper Motor System based on DQ542MA, on Ebay
  4. DC1 Servo Motor Controller, from Makerbot
  5. Spindle Motor Controller (Super PID)
  6. Cheap source of motor encoders
  7. Brushless DC Motor Controller from Jameco
  8. NANOTEC, yet another closed loop control, but this one has all comp...
  • NANOTEC NEMA size equivalents
  • PD2 is Nema 17
    PD4 is Nema 23
    PD6 is Nema 34
  1. SuperTech Complete 3-axis Servo System
  2. A 3-axis Servo Kit Make in Canada
  3. Nice Low Cost Servo Board(UHU)
  4. http://www.xylotex.com/ (stepper system)
  5. Spindle motor candidate from SCIPLUS

Materials to be Used:

  1. Steel Bed?
  2. Aluminium Bed?
  3. Wooden Bed?

Some design considerations:

  1. What weight for the whole machine?
  2. What size the bed?  
  3. Fixed sized gantry with customizable length?
  4. Dremel adapter for light work?

Everyone feel free to inject any comments.  This is your chance to provide input on what features go into the DIYDrones CNC Machine!

Current Bed Size:

Currently we're thinking the bed size will be 18x24 inches.

Insights from bGatti:

Some observations I can offer from experience:

1. Inexpensive skate bearing are not well sealed, and will likely stick if exposed to wood dust.

2. The most vibration on my machine is twist across the gantry - so make the gantry height ~twice the height of the lower extremity (from the table).

3. Parallel ports are increasingly harder to find - especially on laptops.

4. It doesn't take a lot of power to move a cnc machine - you will probably want to turn down the power to avoid breaking bits / bending the spindle shaft anyway - so don't specify a motor system which is stronger than your specified spindle. Anything which can be cut quickly on a strong machine, can be cut slowly on a lesser machine. $1000 is a lesser machine.

5. I have a wooden bed; I'd love an aluminum bed, but with $1000 to spend, the wooden bed isn't my biggest challenge. (It's gantry twist and probably runout for PCB Boards).

6. 3D printers want speed more than brute rigidity - most blogs on the subject of hybrids concede this point - which said - there are many parts which can be made slowly - but some parts call for a flying buttress - which does depend on a certain rate of speed.

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Replies to This Discussion

Permalink Reply by Ellison Chan on May 29, 2012 at 8:01am

That's very useful.  I add this to the top of the discussion so we have it for reference.

Permalink Reply by Fabien Bruning on May 29, 2012 at 2:27pm

Couldn't you make a "bridge" , so that instead of moving the gantry you'd have only a moving bridge up top? That's how most commercial machines I know work, for example this one: http://www.gakusainet.com/jimtof_product/jimtof2010_photo/jimtof029...

The picture makes it a bit more clear, instead of placing the y axis on a gantry and moving the entire support you'd make the sides of the gantry very stiff while moving up top. 

Permalink Reply by Todd Hill on May 29, 2012 at 9:04am

@Monroe,  been looking at this to start off with.  Its cheap (around $500 total), requires a bit of DIY, and lets me use my Dremel 4000.  I like the wood table (16X24"), as it seems that it will allow room for error if cuts run to deep while learning.  I only plan on cutting 2.5mm carbon panel in the short run.  Was thinking of using Mach3, as suggested. 

Permalink Reply by Todd Hill on May 29, 2012 at 9:27am

More for learning and prototyping.  The material that I have been using machines very well, better than most other carbon panel material I have used, and it is very affordable for prototyping.  When the group comes up with a better alternative at the projected price point I am sure I will jump on it.  But for the mean time I want something to help build basic working knowledge at a low initial price point.  Thanks!   

Permalink Reply by Ellison Chan on May 29, 2012 at 9:57am

I contacted the Nanotec guys to see what the NEMA equivalence is for their motors.  Also there may be a possibility of larger quantity discounts.

Permalink Reply by Ellison Chan on May 29, 2012 at 6:55pm

Ok just thought I'd share an e-mail I got from my buddy Steve @SOC Robotics.  His company also has CNC controllers in production, but they use steppers.  I'll post more about those when I get more info.

Hi Ellison,

Steppers are the work horse of the CNC industry.  They are simple, usually reliable and can be driven with low cost drivers.

The issue with servo's is that they only close the motor rotation loop - not the carriage position - which must still rely on the use of zero backlash lead screws for precise movement and they are expensive.

Our new magnetic position sensor technology doesn't rely on zero backlash leadscrews or servo's so low cost acme screws can be used - in fact DC motors can be used in place of steppers delivering extremely high speeds. The quickest stepper motor is capable of 4000 full 1.8degree steps/sec or 1500rpm.  DC motors can turn at 20,000rpm.  The magnetic technology is also capable of just under 1m/sec linear motion detection while still maintaining a 2 micron position measurement (or 0.000078").

I'll send you the links when they become ready.

Steve



Permalink Reply by Fabien Bruning on May 29, 2012 at 11:30pm

That's the same tech I mentioned, and he's completely right. Not to cut your buddy out, but I already ordered from the manufacturer directly and they ship quickly.

One disadvantage: they're pure SMD components and they don't sell breakouts, which is somewhat of a problem for most of us I think.

Permalink Reply by Carl La France on May 29, 2012 at 7:11pm

Hey guys I scooped a copy of "Design Engineering" from the doctors office today when I was in for a check up I scanned the page with the list of advertisers on it and the magazine deals with every thing you guys are talking about the advertisers might have some of the parts you need position sensors with pressure equalization stepper motors and drives,air cylinders ,linear solutions.automation products baldor power transmissions .High accuracy pressure transducers  load cells etc . How big a machine are you guys building?  2 foot work table? 6 foot work table? 12 foot work table ?20 foot work table Have a good day1 Guys!

Permalink Reply by Ellison Chan on May 29, 2012 at 9:52pm

Carl, the table is currently proposed as 18"x24".

Permalink Reply by Ellison Chan on May 30, 2012 at 9:39am

Ok, just got a response back from NANOTEC on the motor size equivalents:

PD2 is Nema 17
PD4 is Nema 23
PD6 is Nema 34

Sounds like we want to go with at least the PD4.  

Also looking more closely at the PD2 specs, Ruwan has a point it looks like the PD2 is not closed loop.  However as I mentioned in my previous post, we should maybe consider a solution where we're using stepper motors for the x, y axis, in combination with linear decoders.

Permalink Reply by Kevin Bouchard on May 30, 2012 at 6:06pm

After showing him my drawings, my dad (mechanical designer) tells me we could find interesting parts here regarding linear motion:

http://us.misumi-ec.com/

Worth a look at the very least.

Permalink Reply by Kevin Bouchard on May 30, 2012 at 6:52pm

heh yeah that's what I thought :( He told me it was quite affordable, but he buys stuff from there with other people's money so affordable is relative :p

I'm all for going DIY all the way!

About the bar, want me to add it to the drawings? Or "you wish" because there's a reason that would be impractical?

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