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.
not so cool price for sure! ....
I like the snail pace on the marble! but hey it cuts it and pretty clean and nice. this is for when CanadaDrones goes pro grade (as soon as I win the lottery!) hehe
Though not quite finished, the single part purchase pricing (worst case pricing) for the UHU servo board is over $51.00 PARTS ONLY (Digi-Key prices). NOTE: NOT ALL THE PARTS ARE INCLUDED IN THIS ESTIMATE!
The missing parts from the list will easily put the estimate above $65.00.
The bare pcb from embededtronics is $15.00/axis + $5 shipping (no note on combined shipping).
So a good estimate is $90 to $100/axis unassembled NOT tested. NO MOTORS.
Each builder would be assembling their own kit of parts because embededtronics does not supply a kit of parts.
This price would go down depending on how much personal parts stock each builder has. I have many of the needed parts (unsorted except for type) because I salvage nearly all the old circuit boards I obtain.
The build price would also vary if the builder uses different motor supplies. Some of the circuit components are different depending on the motor power supply and current rating.
I hope to wrap up the last few missing parts on the list in the next day or so.. the grandkids have gone home.
Btw, I thought from looking at the wiring schematic that this was a 4 axis board.
Sorry Ellison, not so. Look at each of the dotted boxes in THIS schematic of a system wiring. Each dotted box is a UHU single board.
Also to be added to each axis is the encoder..if someone wants to go that route.
I think the concentration of this project should initially be the mechanics of the unit. Get that built as the bulk of the time will be fit, finish,and function of that part of the system.
Motion control tech is changing constantly and the prices are just all over the place and vary month to month. If we have 25 folk interested, the actual number of machines finished and running will always be less.
Ellison, Here's another consideration, cheaper than the first Jameco listed (that unit handles more than just brushed DC motors).
Jeff Kerr Brushed DC Servo pcb at $160/axis(single unit) ready to run, it is very competitive with a DIY board. 10 machines (3 axis x 10) gets the price to $145/axis! Most importanty, it is supported!
Though he does not support application uses of the software, it is an ideal development start because..
"This application will allow designers of machine control software to evaluate the operation of the PIC-SERVO SC, as well as providing source code which can be modified or included in specific applications. PSCNC can be used with a variety of different machines by modifying parameters in its initialization file. Also provided is an application note for retrofitting a small desktop milling machine with DC motors and PIC-SERVO SC controllers."
I suspect we have a couple programmers in this group that could handle this.. :)
RD, yes I see it. I think to really make this practical, we're going to need to get a company to produce larger quantities for us. So far we have about 18 people interested, so that's 54 boards and motors/encoders, for 3 axis. That seems like a reason sized order to get a decent economy of scale, I think.
I also agree that design of the frame should be the priority. We should design it for standard motors, keeping mind that some people will want to go the servo route, with encoders at each axis, and some will want to just go the stepper route.
Finally found some missing part numbers and have now uploaded the UHU BOM with single unit pricing from DigiKey.
Single unit pricing for the parts only. No micro controller, no motor, no encoder.
THIS IS INFORMATIONAL ONLY AND NOT AN OFFER OF A KIT.
Reading up on CNC machines lead me to read about 3D printing (a lot of things seem to lead me to read about 3D printing...)
It occured to me that maybe we could use a board from the RepRap family of open-source 3D printers to control our motors:
They're basically GCode interpreters after all. Right now I can only see them using steppers, but maybe we can tweak the firmware to use servos as well. Maybe someone with better electronics knowledge than me can investigate if the outputs can be fed to the UHU control boards. That way we could DIY the control board as well, if we took the Generation 7 board for example.
I also stumbled upon this seemingly simple hack for a 3D printer extruder, though I don't expect a CNC machine to do a very good job as a 3D printer... http://hackaday.com/2012/06/05/tearing-apart-a-hot-glue-gun-for-a-3...
We should keep the core project as CNC printer and people who are willing to can then try to gun for the extruder head.
Sounds great, Kevin. Even at single quantities, we seem close to the $60 per board that Monroe, was hoping for.
I've also added this new spreadsheet to the top of the discussion, so we can get too it easier.
I see some savings could be made if even half of the people who committed actually go forward with it. That's good. Thanks R.D.