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
There's been mention of 3/8 and 3/4 inch bed thicknesses. I assume the plan is to have ribbing on the bottom of either thickness of bed? This would add a lot of strength to any bed. I was talking with a guy at work today who has built some CNC machines (including one out of an old microscope -- I would have liked to have seen that one!). In his calculations, even 3/4 inch steel could flex enough because of torque to cause the machine to be off 0.001 or more. Adding ribbing prevented this.
Update to the initial posting: The Jameco link above is for the Kerr 3-phase brushless motor controller.
HERE is the link for the brushed DC controller. The price difference is significant. $240 reduces to $160 per axis.
Hi Everyone. There was reference in one of the other threads to brainstorming 3D printing here, so I wanted to throw out some info that may be helpful:
When 3D printing, one primary difficulty is that model must stick to the bed without peeling up to early (warping). As you can imagine, if your model does not stick well to the bed and peels up early (due to warping) your model won't be any good. Likewise, if your model sticks too well to your bed, it can break when coming off. There are a few solutions to this: (1) the tape can be used, but it can be a hastle to cleanup all the time. (2) construction of a 'raft'. This is a printed raft which your model sits on so that when you pull your model off the bed, it's likely that the raft gets damaged rather than your model. (3) a borosilicate glass bed is an ideal bed. With a glass plate, a raft is generally not needed.
The heated bed is used to help get an ideal temperature for making your model stick properly, both to the bed, and as additive plastic to the rest of the model. Honestly, the best 3D printing environment for this type of printing will be a completely heated case (not just a heated bed). But as this is likely out of the question for this unit... those who want to do 3D printing with this should probably consider:
1) adding a glass plate on top of the bed and trying to print without heat
2) adding a heated plate and using tape
3) adding a heated plate and putting a glass plate on that
There more involved, but this is the basics of it. I hope it helps answer some of the unanswered questions.
Bump... I've been working on an Eagle 6.x version of the UHU schematic. Not that we are totally committed to the UHU servo drive system but with an up-to-date version, we hope to have bids from board houses on fabricating them... IF the UHU is what we center on.
For those of you proficient in Eagle, you know the most difficult tasks often involve finding the correct part in the *vast* libraries available. If the part does not exist in a library, you have to make it yourself. This is not at the same pain level as dental surgery but it does take some time to learn to do it well.
So FWIW, this project is moving at least on two fronts: Machine mechanical drawing development (in another thread), and a UHU update development (centered on this thread) for fabrication bidding purposes.
With a frame/gantry/table a builder could choose the drive system from one of dozens already out there. We are not trying to reinvent the wheel but just get the wheel as cheap as possible within the budget goals of the group.
What I have personally done? Put some minor skin in the game by purchasing 3 each of the EAS board version of the UHU. That is what the Excel spreadsheet at the top of this thread is based on. My personal parts stash is big enough I might get them running except for the UHU controller chip that must be obtained from the original designer.
There was a reference earlier to "parallel ports are not common". I would like to add that serial ports aren't so common anymore either. Fortunately, the CNC machines at our office each have an old serial port and I've been adapting each one to use the network for programming and even wifi. It's made the machines so much easier to use. Our 3D printer is also networked.
An embedded webpage for settings, etc... would be a nice plus.
Also, not that mobile access is needed for a CNC machine, but a networked / wifi CNC machine also opens up the possibility of some nice apps replacing the joystick and other type of controls.
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:
http://reprap.org/wiki/List_of_electronics
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.
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.
$70.60
THIS IS INFORMATIONAL ONLY AND NOT AN OFFER OF A KIT.
BOMUHU_Dkey.xls
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.
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!
If you go to his website, Jeff Kerr and follow the coordinated motion link, you will find FREE control software for a 3 axis system.
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.. :)
Can we have this type of water jet head? ;-)
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