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
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.
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.
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? ;-)
The heated platform link is here:
http://store.makerbot.com/makerbot-cupcake-heated-build-platform-v2...
Here's the relevant description:
They also have a small conveyor belt platform, but I can't seem to find the link to it right now.
Monroe, yes the ESCs use back EMF to adjust the pole timings. But since we're using DC servo motors, it's simpler, and we're driving at a higher level. So it's more closer to how the AC sends pwm signalling to the ESCs to turn the motors at a certain speed. So instead of reading the gyros, and acceleromters etc., we're reading the encoders to tell us exactly where our motors are, and how fast to drive them to get to the destination point.
The ArduCNC library is in my head. ;-) My imagination is vivid.
I am going to go out on a limb here... if we as group center on *one* control electronics scheme AND it involves DIY soldering of a control pcb (through hole only), I would be happy to assemble the boards for those who are not experienced at the work.
The UHU servo board could be done this way. Then again...we would also have to make a bulk order of parts to load on the pcb.
This ASSUMES we have a total kit ready to solder and then test. Testing would require some basic jig/apparatus that could control at least one motor. I would also volunteer to make the proposed jig.
The UHU board requires heatsinking for the FETs. There are many choices here also.
There is much to getting a machine like this running and worrying about 10 different people soldering 10 different ways is a recipie for frustration.
Two items I have not seen mentioned are cabling and packaging(of the electronics). The better the system is packaged, the more reliable it will be.
Another consideration should be limit switches. Depending on software/encoder references only is asking for trouble.
In short, I offer my 35+ years of electronics experience (including one selfbuilt CNC,and countless kits of all kinds) to the cause.
I did some shopping today! :)
Went to BusyBee locally instead of paying shipping fees.
Let me know if they are good enough, price was good. But dial is only imperial, not metric... is this an issue?
Caliper
Product Description
Digital Caliper
Range: 0-6"/0-150mm
Resolution: .0005"/.01mm
Easy conversion from inch to metric and vise versa
http://www.busybeetools.com/products/DIGITAL-CALIPER-METRIC%7B47%7D...
Dial
Product Description
Dial Indicator 2" Dia. Face - 1" Travel
These dial gauges fit all standard magneticc bases|
Satin chrome-plated case
Easy-to-read faces .001" reading
Precision ground hard chrome-plated stem and contact point
http://www.busybeetools.com/products/DIAL-INDICATOR-TYPE-A1-921-1IN...
http://www.busybeetools.com/products/HOLDER-MAG-BASE-FINE-ADJ..html
http://www.busybeetools.com/products/STEEL-RULE-24IN.-STAINLESS.html
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