DIY CNC Router
Make something similar to MakerBot but leaning more toward the 2D / routing / cutting aspect. Something that could concievably be distributed as a "kit" with open-source design, off-the-shelf or lasercuttable/makerbottable parts.
Phase 1 - "Get something working"
We have general sketches, but need to nail down some details, and prototype the CNC.
- How will the motors and drive assembly be linked to the T-Slot frame? Custom parts may have to be made.
- Something like this: http://www.garagefab.cc/user/albanetcsr/photos/size-23-stepper-mount
- It would be optimal if we can design for any custom parts to be constructed of metal plate, because it makes it more feasible that they could be fabricated on a similar CNC machine.
- How will we achieve low-friction movement between axes constructed of T-Slot? Plastic skid plates, wheels, etc?
- plastic, self lubricating skid plates.
- less likely to be clogged by cutting debris
- they are available as COTS (commercial off the shelf) parts
- alternately you can procure blocks of the plastic and machine / carve your own
- there are many low-tech alternatives that could be used. For example, I bet you could cut something out of wood with a hand saw and saturate it with motor oil -- good enough that you could then use the CNC to machine your own plastic plates out of melted down milk bottles or something..
- plastic, self lubricating skid plates.
- What electronics should we use in prototyping? Should we purchase a set of RepRap electronics, or start with something simpler?
- If there is something more simple than the RepRap controller available, we should look into it, but I am not aware of anything. The RepRap people already went through this exercise, with the exact same requirements - low cost, simplicity, etc.
- What software package will drive the prototype?
- What should be toolhead #1? Spring-loaded Sharpie marker?
- Yes. A hexagon should be our first test drawing.
|Frame||COTS (Lubic)||We have cjdavis' Lubic kit. Frame construction can begin. Hopefully we have enough pieces.||T-Slot. Various lengths. Lubic is ~16mm square extruded t-slot aluminum.|
|Motors||COTS (Mendelson's)||Dave bought a set of 3 NEMA23 motors at Mendelson's. They are untested.||Target motor: NEMA23 stepper dimensions|
|RepRap Gen3 Electronics||COTS (MakerBot.com)||Needs to be purchased.||$175 http://store.makerbot.com/generation-3-electronics-mostly-assembled.html http://www.reprap.org/bin/view/Main/PartsSupplies|
|Threaded rods||COTS (hardware store)||Needs to be purchased.||mcmaster: 98861A080 / 330mm Metric Thread Size: M8 (How many? What lengths?)|
|Skate Bearings||COTS (skate shop or http://www.thebigbearingstore.com/ )||Needs to be purchased.||At least 6, maybe 12. ( http://www.thingiverse.com/part:416 http://www.thingiverse.com/part:415 http://www.thingiverse.com/part:459 )|
|Nuts, bolts, washers||COTS (hardware store)||Needs to be purchased.||Sizes: fitted to the threaded rods (M8), fitted to Lubic frame, fitted to NEMA23, fitted to electronics.|
|Belts, Gears||COTS (??)||Needs to be purchased.||Lengths? Teeth?|
|Plastic skid plates||COTS (??)||Needs to be purchased.||Number? Sizes?|
|Sharpie Toolhead||Custom built.||Not yet designed.||Spring loaded Sharpie Marker. Detachable from frame.|
|ATX Power Supply||COTS||Several on hand already at Hive13.|
|Motor Mount Plate||Custom built||Not yet designed.|
|Bearing Mount Plate / "Pillow Block"||Custom built.||Not yet designed.||Something like this: http://www.thebigbearingstore.com/pillowblockbearing.html|
|Captive Nut Mount Plate||Custom built.||Not yet designed.||Something like this: http://www.garagefab.cc/user/albanetcsr/photos/captive-nut-angle|
|Electronics Mounting Plates||Custom built.||Not yet designed.|
|Endstop flags||Custom built.||Not yet designed.|
Phase 2 - Redesign for simplicity, replicability
- Reduce number of unique parts.
- Reduce number of custom made parts.
- Integrate open-source electronics, software packages (RepRap).
- Refine toolhead interchangeability.
- Document and publish design, instructions online.
Phase 3 - ...
- Produce a product that can be purchased either as a kit you can put together over a weekend, or as a fully pre-assembled machine. A shameless copycatting of the Makerbot Cupcake idea is what we are after here.
Design of a CNC
- I think it would be smart to try to design a frame that can be created using the CNC itself, so that it is self-replicating. DaveMenninger 15:32, 3 September 2009 (UTC)
- Just like the RepRap, I think this should be a primary design goal, but I'll consider the first one a success if it can carve balsa wood :) --Cjdavis 21:27, 7 September 2009 (UTC)
- What size cutting area are we looking to have? TP
- I think I would shoot for 8.5x11 as a minimum. Hopefully more like 10x14 or 11x17 would be doable. The bigger, the better, IMO. DaveMenninger 18:35, 6 September 2009 (UTC)
- We should base the design on t-slot aluminum extrusions.
- There are a number of suppliers of them, many of which are compatible with each other.
- If we handle the design correctly, simple steel box tubing could easily be used in place of the extrusions, which is available pretty cheaply anywhere in the world.
- There are even linear motion parts for use with them that could remove a lot of design effort to start with - see ( http://8020.net/Application-106.htm ) from this page ( http://8020.net/Solution-8.asp ). However, I think this is probably too specialized a part to use in a long term design. We should at least have an alternative for people using box tubing for example.
Parts that need to connect to the frame somehow
- skate bearings
- captive nuts
- driver boards
- endstop sensors
- atx power supply??
- We need at least 3 stepper motors.
- Target motor: NEMA 23 stepper.
- Standardized dimensions: http://www.rhonmac-cnc.co.uk/Nema_23_drawing.gif
- NEMA 17 motors from Sparkfun?
Possible Arduino compatible solutions:
- RepRap Gen3
- Will drive all three (3) motors
- Includes connections for Min/Max prox switches (RepRap calls them EndStops)
- Adafruit Motor-shield
- Can only control two (2) stepper motors
- Sparkfun EasyDriver
- Can only control one (1) stepper motor
- Most cost effective ready-made solution identified so far
- Home Grown
- Potentially even more cost effective
- Adds DIY feel to motor driver system
- Brandable kit potential
- Research and Development effort required
- http://www.cs.uiowa.edu/~jones/step/types.html (suggested motors so far are all bipolar type)
- If successful, could be used for other projects, like Eggbot
A sub-project page has been created to explore EasyDriver and Home Grown approaches: Bipolar Step Motor Driver
Something Arduino-based seems like it would be a good idea
Control software will need to know where each axis is located at the beginning of each part run. One way this could be done is to run each axis down against a prox switch to 'find' the min position, and then move to center. Not sure if a max switch is absolutely required or not. Prox switches can also be used to protect machine from CNC programming errors, which if used in this way a max sensor would be good.
- TP: I have four (4) magnetic hall-effect sensors on order that may be usable for this purpose. I suddenly wish I had ordered six (6).
Should be swapable as quickly as possible. The Makerbot is pretty cool in that you can just disconnect a single cable and pull the entire extruder platform out (is that possible, or do you have to unscrew the extruder head first?) Wait, is that true? Can we just mount a tool holder where the extruder goes in the Makerbot?
- Ink pen
- Rotary cutter (Dremel or router motor)
- RepRap extruder
- Laser cutter
- Vinyl / paper cutter
- Paint air gun
- Maybe we can use the RepRap electronics or at least the stepper motor driver boards ( http://www.reprap.org/bin/view/Main/Generation3Electronics ) DaveMenninger 15:24, 3 September 2009 (UTC)
- Agreed. Unless there is another open source, currently supported and sold controller - that we already have a bit of familiarity with - using the motherboard and stepper controllers from the RepRap / Makerbot would make the most sense to me. The firmware will need customization, but I think there will be zero physical electronics redesign required. I'd suggest the full Makerbot Gen3 electronics kit ( http://store.makerbot.com/electronics/assembled-electronics/generation-3-electronics-mostly-assembled.html ) since we need everything but the extruder controller, but that could be used to build a second extruder for Dave's Makerbot. --Cjdavis 19:26, 7 September 2009 (UTC)
- Step Motors:
- The controller interface for the RepRap stepper driver board ( http://www.reprap.org/bin/view/Main/Stepper_Motor_Driver_2_3 ) has the signals Min, Max, Dir, Enable, and Step - with Min/Max just routed straight through to the opto boards. So it sounds like we could probably wire [the funky] motors straight to the motherboard, OR get the RepRap stepper drivers with more standard steppers - with little to no redesign needed. --Cjdavis 19:26, 7 September 2009 (UTC)
- These motors might be appropriate for this project, esp given the target cutting area: http://www.automationdirect.com/adc/Shopping/Catalog/Motion_Control/Stepper_Systems/Motors_-z-_Cables/STP-MTR-17048 ($19 each, minus shipping). Depending on the tool, the Z-axis motor might need to be a little beefier than this. Nice bonus - they come cabled with reasonable connectors. Being basic 4-wire steppers, they should work with any driver system chosen. TP
- I would suggest a trip up to Mendelsons, they literally have 2 Aisles of just assorted stepper motors. They are very assorted, and finding 3 matching ones could be a challenge, but it would save us shipping and we might find a good deal. Paul
- Frame: I have an Aerocool Lubic 4480 computer case kit, which was basically a set of slightly smaller t-slot aluminum extrusions. I think they are 5/8" square if I remember correctly, and there are 12 of the longest pieces, which are ~18" long. There should be plenty of pieces for a full design. We can at least mockup the design with them, but they should be just fine for a fully functional CNC. The design should be directly transferable to use with any standard t-slot extrusion available.