My Homemade CNC

[CVMichael]

Yea, the programming for that is tricky... (I did not do that yet). Probably a recursive function.

Your idea works only if the object you are scanning is metal.

I'm on my way home (I'll leave work in a few minutes). When I get home I will post some pics (partial pics because I dismantled half of it) of the touch probe I made. If you are interested to see ?

[wossname]

I'm always interested, and we'll always be separated by many hours of global rotation.
My project isn't getting finished in a hurry, so don't worry about it No rush.

[arunb]

the screw drive system is slow, you should replace it with a timing belt and a stepper motor drive system.

The timing belt drive will make the system extremely fast, but you need to use a track and a linear bearing for this. The system would be similar to a printer.

For the Y axis you can have another timing belt drive system. So basically you gave one linear motion system mounted on another to get the X and Y motions.

Mechanically its a bit complex making a belt system, the electronic for the system would also get complex as special drivers are required to run the stepper motor, but then you can find many resources on the internet for stepper motor controls.

thanks
a

[CVMichael]

Hi wossname,

As I said before, I dismantled the probe I made, I only have part of it left (the electronics of it).

I used Google Sketch to design the hardware part (today was the first time to try using Google Sketch, it took me a few hours to make that).

The idea is: A laser points down into a mirror that reflects back the laser into the middle of 4 photodiodes. The mirror is on a spring, and in the center of the spring and mirror there is a thin rod (I used a 1/32 drill bit glued to the back of the mirror).

When the rod touches anything (in any direction), the mirror moves, therefore moving the laser pointer towards one (or 2) of the photodiodes. There is a paper on top of the photodiodes to blur the laser pointer.

The photodiodes are connected to the analog of the microcontroller PIC16F88, and also the microcontroller turns on/off the laser.

When the laser is off, it takes the ambient light from the 4 photodiodes, when the laser is on, it can calculate the exact position of the pointer by the intensity of the light on each photodiode.

The thing was soo sensitive that the lightest touch would make a big difference on the angle of the laser.

The touch probe was connected to the microcontroller of the CNC, and it was updating the "touch" about 20 times per second (so the laser was pulsating when it was reading the "touch"). Sadly, I did not get to the part to program the CNC microcontroller to move the motors and do the scan.

[CVMichael]

OK, since I had the camera in my hand, I took 2 more pics.

One is the current state of my CNC. I removed the top so you can see what's under.

So, the updates (since I made the video on YouTube) are:
I changed the stepper drivers to these: http://www.motiontek.ca/StepperDriver.html, two D42 for X & Y axis, and one D56 for Z axis (the one that moves the whole gantry.

On the right/down you can see a round wheel, that is the manual jog. I am using a small stepper motor (in reverse), when I spin the wheel it generates a signal that is amplified, and goes to the microcontroller (PIC16F88) to detect how many steps were moved and what direction.

Above that you can see a keypad, with 2 displays. One displays the X,Y,Z coordinates in Inch, and the other coordinates in steps (6400 steps/inch). The keypad is used to tell the micro what axis to move (X or Y or Z) when I do the manual jog, and what speed (multiplier). So I could use a 1 to 1, meaning one rotation of the jog it means one rotation of the cnc stepper motor, or I could multiply up to 8, so one rotation of jog means 8 rotations of cnc motor (which also equals to half an inch).

In the other picture you can see what I am working on in the last few days... Yes... that is a ultrasonic range finder. It sends a pulse at 40KHz, waits for the reply, and calculates distance by the time it took for the echo to come back. I am still working on this, as you can see the logic port has many connection on it , meaning I have problems with it... but I will figure it out soon.

[Nightwalker83]

@ Michael,

Did you ever finish the vb.net app (whatever language it was) to control the CNC?

[CVMichael]

Unfortunately no...

Last year, in October (I think), my C drive just died. I lost a lot of stuff I had on it, including the code for my CNC. I did not have a backup of the .NET code, but I did have an old backup of the C code for the microcontroller. Unfortunately I did not backup everything I had on it...

This is the reason why I did not do anything new for my CNC since then... I will have to re-build the software, and it's not easy.

Since I have to start from scratch, I will do another re-design. I will have it work like a regular (standard) CNC, so that I can use free (or cheap) software that already does this. Then I will modify the electronics side (flip a switch) for when I want to do manual stuff (like the manual jog) or other things I want to add, that the standard software does not have.