how to get started with stepper motors and hall effect sensors

[graniteman74]

I am trying to build a machine for cutting out sinks here at my granite shop.  I am pretty handy with the mechanical side of things but this is my first project to get involved using arduino.   I don't know where to start so i figured I would reach out and see if one of you out there could help me get this ball rolling.  I have built a machine that will rotate 360 degrees and follow a template of the sink cutout. What I need to do next is figure out the best way to incrementally drop the router bit down a specific amount after each rotation of the cutting .   I am thinking of using a stepper motor that would rotate a number of turns ever time a hall effect sensor would sense a rotation around the template.   If anyone has any suggestions i would appreciate your expertise... 

[michinyon]

You are really looking at a 3 axis CNC setup,  there are probably better places to ask.  Yes, you can use
the arduino to control the stepper motors.  For less than $100 you can buy a CNC controller which will
save you a lot of development time,  communicate better with your computer,  and probably has the
protection issues better thought through.

[graniteman74]

Thanks for the response.  I am trying to keep the machine as simple as possible so any of my guys can setup and operate it.  In my machine I used a gear motor to move the spindle around the template,  all the operator needs to do is set it in the center of the cutout and turn the power on.  It will spin around the template until he turns the power off. With each rotation I need to drop the spindle down about a 1/8".  I was thinking that a arduino powering a stepper motor or a gear motor that is triggered by a hall effect sensor or a momentary switch each time the spindle goes around would work well but I am completely clueless on where to start with the setup and coding.  I could really use some advice on how to get this accomplished. 

[kf2qd]

Programming a CNC is really quite easy, and you can effectively have many more templates because they are not stored on a shelf, but in a computers memory. It would be very easy to generate the CNC code based on some simple parameters - length, width, corner radius and thickness. It would also give you the possibility to cut other shapes (possibility of profits from the scrap). GRBL is a CNC driver for the 328 that is the chip used in the arduino.

What you are talking would be fairly easy to implement. A limit switch would do as well as a hall effect switch - and might be easier to test and troubleshoot.

Every time the switch is hit the arduino would move a stepper motor a fixed number of steps. When the cut cycle is complete you would want another switch that when pressed would return the router to a full up position. and maybe a second push button that would let you jog the bit down to the surface at the start of the cut cycle.

[wildbill]

CNC does sound like the way to go - take a look at the reprap project or Grumpy_mike's CNC milling machine for inspiration. Since you've already got your mechanics somewhat done though, your stepper motor/limit switch setup sounds quite plausible. You'll obviously need some hardware to permit the arduino to switch mains power e.g. relay, SSR, powerswitch tail depending on your comfort with mains voltage. The code for it should be simple enough to copy from examples on the site and there will be plenty of help available here when it doesn't work. If your interest is in getting it going rather than becoming a C/C++ programmer, you might ask to have this moved to the Gigs and collaborations forum to get some paid help once you have the mechanics and wiring figured out.

[graniteman74]

Thanks for your input. For the last year I have been looking into building a cnc and have nearly pulled the trigger on getting it started.  I plan on making that my next obsession after I get this machine completed.  I like the idea of getting some help with the coding.   After all we can't know everything,  it's nice to know I can reach out and get some help from time to time.