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.
Hi, I have been reviewing controller board options but am unable to find source /price for UHU controller chip, web sites do not open. Have you located a source? Years back there were two other authorised suppliers of the chip. Is this 2005 design now out of date?
I also found a more recent design under NoMi Locus: DC servo controller, Atmega8/88MCU @16Mhz very near completion but moving very slowly since November 2011. I would be interested in comments regarding suitability or as basis for higher capacity design.
Any other potential builders of this mill in UK?
I have been researching the UHU for this project and Uli, the original developer, was still in business this weekend. UHU Servo has German and English sections. HERE is the English. His marketing method is somewhat direct to him and if his claim of thousands of shipped chips is valid, he will probably not change his method.
In other news, now a fellow has a drop-in replacement for the original UHU chip. If you have a board, or build one, for the original chip, this module is pin-for-pin compatible with some pins not used. HERE is Henrick's sheet on the module. You can back-URL to find his site.
I am collecting parts for three EAS UHU boards, just arrived this past weekend.With the discovery of Henrick's module, though it is 30 Euro per module, we now have at least two choices for the UHU option.
NOTE: UHU Servo has NOT been selected as the official drive system. There is no official drive system at this time. This project is *budget* targeted and as such we are trying to find a solution with that goal.
It may well be that those who want this platform will provide their own drive solution that goes out of budget.
R D, Thanks for above, Henrick's site very interesting, still unable to access UHU.
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.
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.
That would be an excellent option if it worked out.
Discovering that there is another controller chip option for the UHU board was a real joy..even though it is more expensive. Uli (orig chip) does not have a clean sales structure. His online documentation states 'about 5 to 10 Euro' per chip. Henric is stating 30 Euro per chip for the upgrade controller module.
Servo circuitry is not complicated and has not changed much in decades. The controller chip firmware/interface is the heart of the system.
UHU design is dated but will work. The Kerr products have their controller chip available if we want to make a board around that device or just use their board ready to go.
Rolling our own is somewhat like reinventing the wheel and to make this as cheap as possible, a kit is probably the answer. The labor for assembling, testing, validating is where the cost is saved/added.
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.