Setting this discussion up to gather up and brainstorm ideas.
LIST OF EQUIPMENT AND MATERIALS UNDER CONSIDERATION:
Motors/Controllers:
- cadcamcadcam.com (servo motors and controller)
- 3-axis Stepper Motor System based on DQ542MA, on Ebay
- 6-axis Stepper Motor System based on DQ542MA, on Ebay
- DC1 Servo Motor Controller, from Makerbot
- Spindle Motor Controller (Super PID)
- Cheap source of motor encoders
- Brushless DC Motor Controller from Jameco
- NANOTEC, yet another closed loop control, but this one has all components.
- NANOTEC NEMA size equivalents
- PD2 is Nema 17
PD4 is Nema 23
PD6 is Nema 34
- SuperTech Complete 3-axis Servo System
- A 3-axis Servo Kit Make in Canada
- Nice Low Cost Servo Board(UHU)
- http://www.xylotex.com/ (stepper system)
- Spindle motor candidate from SCIPLUS
Materials to be Used:
- Steel Bed?
- Aluminium Bed?
- Wooden Bed?
Some design considerations:
- What weight for the whole machine?
- What size the bed?
- Fixed sized gantry with customizable length?
- 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 $1000 to spend, the wooden bed isn't my biggest challenge. (It's gantry twist and probably runout for PCB Boards).
6. 3D printers want speed more than brute rigidity - most blogs on the subject of hybrids concede this point - which said - there are many parts which can be made slowly - but some parts call for a flying buttress - which does depend on a certain rate of speed.
Replies
Why use stepper motors? They are inherently an open loop system, where you prescribe a certain amount of rotation to the stepper motor while you hope the gantry follows your model of rotations -> linear translation.
Austria Microsystems has great encoders for a cheap price (Note that I do not work for them ,however I did receive some samples) http://www.ams.com/eng/Products/Magnetic-Encoders/Linear-Encoders, 500 nanometer resolution for 6$. The big disadvantage is they come in a very small package which you need to solder, and it requires two interrupt channels on a micro controller. The normal Arduino Uno only has 2.
With this you could use encoders as your input, DC drive with spindle and PD control as a controller.
Well, I sent out a few requests to Alibaba suppliers, and the Ebay shop selling those controllers I listed above. The Ebay shop says no closed loop systems currently. I've asked if they can develop something on request. We'll see whether I get any positive results.
No, I hope to do a lot more than PCB's, but I would like to do PCB's easily. A lot of the reviews on hobby CNC's when I started looking last year referred to them being a problem in terms of having a sturdy enough base to hold the copper down evenly for etching.
Well, I'm going to start looking at sites like Alibaba to expand my search for the servo motors and controllers. Ebay is tapped out. I don't think we will find anything that's affordable.
I'd like to help in this if I can but I'm a bit out of my depth.
What thoughts should go into the design if one wanted to make PCB's ?
After getting stung in the Lumenlab Micro debacle last year for a grand, I have almost given up on having a capable CNC. If I had a dollar for every time I've thought 'if I only received that machine I could do x' I'd be able to buy two of these :)
I'm very happy to see this group !
for this, what microcontroller are we using? arduino? or is there something better control-wise for A CNC?
What about this?
http://www.vhipe.com/product-private/SuperPID.htm
Super-PID is a closed loop speed controller that allows low-cost 1/4" and 1/2" routers
to be used as speed-regulated spindles.
Enough?
Here are the main points of my CNC build (see the use in my Arducopter blog on this site)
I would be happy to build an replacement for this machine and think this group has enough resources to hammer one together. There are legions of options and choices now.
I would like to be able to do a max length cut of 48 inches. That's about the limit for most garage shops or 'spare rooms'.
Also, I find 24x48 will be a little too big. How about a nice 24x24? Or design it in some way that the platform can be expanded. Probably we need the gantry width to be predefined, say 24", and allow for the length to be expandable.
interesting blog about building one cnc http://www.liming.org/cnc/index.html
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