The Shop > Electronics & IC Programing
Cheap Cnc Controls.
Dawai:
THE video of what I have stuck together so far.. a large format Wax 3d printer for my aluminum casting shop.
Anthony.. I have a communication problem, Sometimes I type-or talk and nobody has a clue. The best educational thing you can find on cnc's how "home made" ones work is the "mach3" manual, download the pdf and read.
I can do you a drawing on "how this one works", almost the same as how my 1976 bridgeport cnc works, the parallel cable pins pulse the drives, one pin for each function, ie: pins 2 is the x step, pin 3 is the x directional pin, 3 is y step, 4 is y direction, 5 is z step, 6 is z direction. THE inputs, pins 10, 11, 12, 13 are normally used for home limits and a estop.
THE tb6560 board has limit input places, supplies 5 volts for them, has opto-isolated inputs on the parallel cable. Only has 3 amps of output, so you are limited to about 280 oz motors thou.. for larger motors than a table top mill you will need gecko drives or similar ones.. some gecko drive require a "negative" pulse, not a positive one.. that is where things get complicated.. you are required a break-out board to invert the signal pulse.. THE gecko 203's I am using here are one of the most expensive drives they sell.. the 201's like I have in the bridgeport cnc are cheaper.
I recently redid the controls on the Bridgeport, my old bulldog Butch pulled the cables out the side and tore them in two.. I think he was after a mouse?? He was quite a character to have around the shop, he'd steal every screwdriver he could get his teeth on, I have not found them in the 8 years he has been deceased.
Dawai:
So.. new stuff.. A RASberry Pi, small micro-computer running a Arm processor. Does run in debian Linux, Java, Python, QTmaker software. Loaded Grbl controller by Zapmaker, he has instructions on how to do this, it came from github software repository.
THE Pi can be loaded with a usb memory stick, dump to the arduino running grbl line by line of gcode, freeing up the computer to continue to monitor the wax burnout and smelter preheat, stl file cleanup, meshlab, slic3r and of course run the Bridgeport cnc .
Not as complicated as it all sounds, really.. That big bridgeport would probably run fine on a grbl Arduino, it has a cross slide that weighs about 350lbs and is slow as hell with the geckos just throwing 7 amps at the 1200oz steppers. BUT then all the great wizards Art put in there would not be at my disposal. (polar holes, hole arrays, text engraving, etc)
I am fixing to wire that mega to a parallel cable.. choosing to use jumper wires going to a terminal strip, or wire wrap, heat shrink and solder to the tiny wires in the cable. THOSE db25 cable wires are so small when you tighten a screw, it cuts them in two and they fall out.
Dawai:
Comparing the Grbl code ran arduino-stepper to a 10 year old computer running Mach3 is like trying to fly side by side with a 1900s biplane versus a SR71 blackbird. (old skunkworks but still a badass plane)
Question is , do you need all the speed? A cnc really messes things up "fast" and makes good metal into scrap.
vtsteam:
--- Quote from: ieezitin on August 17, 2014, 09:04:06 AM ---Hi.
I am more than interested in making my mill a cnc but I have never made electrical boards or connected computer parts together, but I am more than capable of reading schematics, any chance someone could make a detailed thread on building such equipment to make the brains of this system.
Many thanks.
Anthony.
--- End quote ---
Your question deserves an answer, Anthony. Let me think about how to do a thread on it. In the meantime let me just give you some basics of what I have and use (but not everything in the world possible re CNC by a long shot!).
I use steppers, not servos. If I had a financial choice for adapting a heavy mill table, I'd probably have servos. Servos move smoothly, steppers move in steps. Presently a stepper system is cheaper and easier (I believe -- not being totally up on latest developments) to put together yourself,
Steppers can be controlled in 2 ways, the first is by having the controller output the proper number of steps to get a tool to move to a particular position. This is the commonest method for stepper drivers
The second is by having a feedback system where sensors (scales) continuously monitor the position of the tool and the controller uses that information to output steps and rates to the stepper motor. It is the same method a DRO -- operates on essentially it is a digital read, with the positional data being fed to the stepper controller rather than a readout. Naturally there is often an integrated physical DRO with this type. This is the only type of control method used with servos.
My CNC systems are stepper systems with counted steps. I use older computers as well, and tend to use free software throughout.
One system uses an integrated combination stepper controller board (HobbyCNC) which can output directly to stepper motors all the drive signals they need at the power they need.
Another system I have uses separate individual components to do the same thing. That means that each stepper motor has its own driver component, and there is also a breakout board -- which is what the computer cable and various driver boards and power supply all attach to.
Both systems are set up for older computers and connect to them with a parallel printer cord. Newer computers do not have a parallel port, so must use other methods of connection.
That's about it, in general for what you need, if you want a similar system:
1.) a computer to read G-code and run the CNC program
2.) standard printer (or other input) cable to connect the computer to the driver(s)
3.) either an all-in-one multi axis driver board with built in connector and a power supply -or-
4.) separate drivers for each axis, and a breakout board to connect them all together with a power supply and a cable socket.
5.) stepper motors adequate for the speed and torque required for the job (a somewhat deep subject of discussion)
6.) mechanical drive method (ie ways, bearings, screws or racks) that will optimize the characteristics of your mill AND the stepper motor specs and type.
That's a start, anyway.
ieezitin:
VT..
That was to me a very useful, simplified explanation of the total mechanical / electrical needs of a cnc. Most of which I understood, i have used and owned stepper machinery in the past so I really relate to it. but at the time of ownership of the equipment I got a bit lost in the G code thing, but! i know software today interfaces all that.
i know parts are more than available( stepper motors and screws etc) are cheap on the market.
Thank you for your time in the explanation, a detailed thread on a build on the brains of it would be more than welcome by allot of people, its a tease to me that for a small investment i can achieve a fully automated machine.
thanks again.
Anthony.
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