Its a project in the making ! A small scale CNC router. i want to be able to rout PCBs with it, but time will tell if it will be good enough to rout PCBs. the mediator between the PC and the motor controllers will be an arduino.
here are some pics for now ! Sorry for not writing a lot of info ! a picture is worth a thousand words :P
Regular CNC engraver
Actuators / output devices: geared stepper motors
Control method: autonoumous
CPU: Atmega168 with arduino bootloader and any computer system
The printer head can be accurate enough if you use the arduino to intercept the step instructions from the PC and cache them, then as the steps are asked for that direction also reference the optical encoder on the print head to verify its movement. Correct for variations with every step. I personally have wanted to build one for a while and this was one of my biggest design fetures, optical encoder strips on all Axis to confirm the step has been taken and that it was only one. this way you can monitor the EXACT location of the head without worrying about step slip (also correct for it when it happens).
Using the optical encoders and the Arduino it is also possible to send the head home repeatedly during the engraving to re-calibrate alignment.
Again the biggest part of this system is using a device to cache the instructions coming out of the controlling PC and be able to add steps in between and controll the “Play” speed dynamically.
I actually trashed the encoding stripe! Besides, it will be a mess to set this up ! And as far as i know, steppers don’t miss a step if you use the correct driver and driving code
Steppers dont miss steps they try to accomplish everyone however,
an object at rest tends to remain at rest unlesss acted upon by an outside force, and an object in motion tends to remain in motion unless acted upon by an outside force.
basically if the matrial provides to much resistance and the rubber band streches or the head cant move because the stepper isnt powerfull enough it can miss a step that way.
Immediately change design from moving gantry to moving table. I such a small cnc mill it’s not very efficient way to accomplish good accuracy (less play). You can try to stop left side of gantry with one hand, and then try to move the second side with the other hand - how much have it moved? I am also not very convinced about those steppers, they look a bit small, but time will show BTW, what is the part you are using to connect motor with this milling “tip” (don’t know the english name for it)? I am looking forward to see more progress, especially because i am planning making small cnc mill maybe for a year
Im building one of it myself, and compleated all the code, so now im on the electrical part of my cnc, later i will have to do the design of it, but that wont be a problem.
problem is getting some cheap drivers. Anyone knows some store? or doing it myself will be the best solution? (will have to learn how to, but i know the principle)
Im also curious if someone knows some cheap linear encoders, since i found just some expensive :S
i took the whole motor and coupling from a cordless hand rotary tool. i prefer the gantry, i still have to do some design changes before it becomes perfect its not done yet.
building such machines by your self will give you great experience. but the resolution and speed always the question.
many times i was thinking in making similar machines by myself. however i m not thinking of that any more because china make every thing cheap look at these sites :
What did you use as slides for the gantry? Unless they are linear bushes I would be really concerned about flexing. Something like these clamped in the gantry sides. Otherwise looking forward to more updates.
