Setting this discussion up to gather up and brainstorm ideas.
LIST OF EQUIPMENT AND MATERIALS UNDER CONSIDERATION:
Materials to be Used:
Some design considerations:
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.
That's very useful. I add this to the top of the discussion so we have it for reference.
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.
@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.
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!
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.
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.
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.
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.
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!
Carl, the table is currently proposed as 18"x24".
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.
After showing him my drawings, my dad (mechanical designer) tells me we could find interesting parts here regarding linear motion:
Worth a look at the very least.
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?