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Electronics for homemade CNC machine

Hi all!

I plan to build CNC machine. I have already found 3 unipolar stepper motor from old printer.

Type of CNC will be like http://reprap.org/wiki/WolfStrap-English#WolfStrap-Fran.C3.A7ais

For electronic part I have two options:

  1. L298 driver (3psc=12.48$) + Arduino Mega (14$) from aliexpress.com In addition I don’t any information about any other complete solutions for arduino. Could you please advice if you know or have experience in this subject? 
  2. 3 Axis TB6560 3.5A 16 Segments CNC stepper motor driver from (40$) http://www.aliexpress.com/item/3-Axis-Stepper-Driver-Controller-stepping-motor-Driver-Board-TB6560-UC045/327355240.html  

Please help me, and give me some advice which option is better, based on your experience? I liked the first option, because it is based on arduino.

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Thank you all for your time and for sharing experiences! Now my plan is to create a 3D-printer. It was just the kind of information that was needed to me. For electronics I chose Reprap Shield with Driver A4988 and with ready extruder.

I have a great deal of personal experience on this one, and I second what TinHead said, a mill is not a printer and a printer is not a mill. 

Here's my 2 cents (about CNC's in general)....  In my mind, there is no reason to build a "hobby" machine at all. It is nearly impossible to build a machine stiff enough using MDF and (God forbid) drawer glides. In the end, you will have a machine that will indeed move in 3 directions, but won't cut much more than styrofoam. So in the end, you have spent maybe $500 on a machine that you can not use for really anything. 

Instead, I would put that $500 into building (or buying) a proper machine. As a point of reference, my machine is built of 2"x3"x 3/8" steel box tube. There is not a piece of metal on the machine that is less than 1/4" thick. It weighs about 700 lbs. and eats aluminum alive...   That said, I still wish it was twice as heavy and stiff. --As a matter of fact, I built this machine twice, having underbuilt the first version quite a bit. I personally believe that one really can't make a proper machine from anything but metal.

Again, there is really no "middle ground" in my mind. You are building a printer, or you are building a CNC toy or model, or you are building an actual machine you can actually use. Again, only going a few hundred dollars into this thing will not get you much --One really has to be looking at $2000+ to get into something you can acutally use.

 

Please correct me if I am mistaken.

 

  1. Software like Mach3 is using for design

  2. Software like Mach3 can prepare Gcode

  3. Gcode can be for 3d printer or for CNC base on chosen option in Mach3?

  4. Gcode interpreter send commands to Control board

 

 

 

 

 

 

 

 

 

 

 

 

 

I plan to make CNC which I will be able to modify in the future in the 3D printer. So in this case, can I use for example Reprap Shield for CNC also?

 Reprap shield http://www.aliexpress.com/item/RAMPS-1-4-3D-printer-control-panel-printer-Control-Reprap-MendelPrusa-free-shipping-drop-shipping-Red/1223532342.html

... or you will get in trouble.

A CNC machine (even hobby ones) need to be sturdy to put it in one word, to get any precision out of it. 

A 3d printer needs to be fast but not so sturdy.

Now making a machine sturdy enough to do lightweight milling (plastics, wood, aluminum) but fast enough to do printing is going to get real expensive. I have tried it and others too, there is no real win out of it. Also think about having to change the work head everytime you switch from printing to milling ... I would suggest you build either a printer or a CNC, get it working nicely then use it to make parts for the other.

Regarding the software the toolchains for printing vs milling are different:

- printing - 3d design software -> slicer software -> machine control software 

- millig - 3d or 2d design software -> Mach3 or EMC2 

Main problem is that printers usually use a usb connection emulating a serial port and interpret the GCODE sent over on the controller, while CNC machines and software usually use a parallel port connection to the controller and the gcode is interpreted on the PC. 

Of course electronics is two worlds too ...

Enough said have a look at the things I have posted ... lots of info in there.

A CNC mill is built to hold position while it is cutting. This means for it to be accurate it has to be sturdy. By hobby standards, sturdy means it will have a fair bit of mass and not move terribly quickly.

A reprap is built to position itself quickly with very little resistance to its movement. It has to be sturdy and stable like the mill, but, the head should have as little mass as possible.

We have a member that tried to make a printer out of a mill. He actually ended up with a broken mill and no printer. This all boils down to, if you want a mill build a mill and use it as such. If you want a printer, build a printer. If you want a repstrap, say as much and realize what you are getting yourself in to.

Thank you birdmun! What about if I will use CNC only for wood or plastic with thikness max 3mm. Stepper will work slowly. In this case I can use light weight spindle and some time I can change spindle to extruder. How you thing it can be done in this way? In my CNC i plane to use screw.

Thank you for you help! I read this many time. I made own unipolar driver spend approximately 4 days base on this http://robozone.su/cnc-home/24-drajjver-shagovogo-dvigatelja-na-osnove.html If you look to power supply line V+ you will see that power goes straight to unipolar motor and to SLA7024m You also can read this http://arduino.cc/en/Reference/StepperUnipolarCircuit (Sorry for my English)

You said you have unipolar stepper motors.  The L298 is for bipolar steppers.  I don't know about the other option, but you should check it as well.  Sometimes, a unipolar can be used as a bipolar, but not always.  I suggest you do some research before attempting a project of this magnitude.

Unipolar stepper motors have additional 2 wires. And you need just connect this 2 additional wire to supply voltage of L298 driver. I also prepared the driver which is based on SLA7026 (3A). But at the end driver is not work.