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.
First thing to read up on is what protocol the EMC and Mach software talks over the parallel port to these CNC machines. As for driving the motors, should be pretty straight forware direction and speed. The PID algorithms for taking encoder feedback is the tricky part, much like the PID programming on Arducopter. But I suspect if we go with good encoders, they'll be less prone to noise signals, which is the case with the copters.
The UHU servo board has a few options that will alter a build, ergo the parts required.
Good news: I should be done sourcing all the available DigiKey part numbers/prices today (June10) . This will give an approximate $$ figure for parts of a single board.
Bad news (not too bad): As implied above, there are some parts not available from DigiKey.
The surprises: Trimmer pots are not cheap (there is one on the board).
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.
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.
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've been out of town and working ridiculous hours since Monday so no new progress on the parts list. In the mean time the grandkids are now over for a few days so that will slow down my progress. 4 year olds don't know how to do Digikey searches... yet.
I did more reading on the controller Uli makes (Rev. 3). His price is very resonable. He also has a 'trade' aspect. He will trade beer, hotsauce, or other surprises.
There are many suprise holders here on DIY and maybe we could approach him with a 'bulk' order?
Family first, fun later. ;-)
I'll ping my guy at SOC Robotics, and update him with the interest level to see if he wants to make the populated boards for us.
so, is this 2 or 3 axis for the table, and 3 or 4 for the machining arm?
not a six-axis arm, right?
these are rotational axes (aka degrees of freedom), right? (or at least some of them are, 2-3 must be translation axis?)
Ok, my internet was down all morning and afternoon. Monroe, don't forget that one of the desired features is to be able to mount a "hot end" on it so that 3D printing with plastic extruders can be done.
Here are a few videos of a makerbot in action:
Here's a linke to the extruder head itself:
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.