Instructables

Cheap, super-sensitive digitizing probe for cnc... harkman's probe

Picture of cheap, super-sensitive digitizing probe for cnc... harkman's probe
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it's so simple, and sensitive... i named it after myself... harkman's probe

if you want to scan, or digitize a model in a cnc program, it requires a digitizer probe.. unfortunately they are expensive, or, hard to
make yourself..
lots of examples use ball bearings, 3 contacts, for sideway forces, a spring...
here is one solution i didn't find... an easy one..,
while looking for a cheap solution (DIY) i couldn't help thinking about a very sensitive device, the needle of a turntable..
or something equivalent..
the solution...

a nail soldered on a piezo buzzer,

with a microprocessor as a converter,
with adjusable threshold..
While it can be done cheaper, i think this is the easiest way...

it takes about 10 minutes to make one... and is very sensitive, adjusable, easy to use, or to custom, to your own needs
what you need

1 small piezo buzzer
1 film can
1 nail,
foam (mousepad or something softer) for mechanical vibration-insulation)
small wire
an arduino, or other micro processor
(or use electronics, like an op-amp etc)


If using an arduino, download the knock program from arduino..
and read up on piezo as a sensor
the led should light up, when just scratching the nail....
then connect the ground, and an output port (saay 13) to your input (parallel port) as an digitizer..

the rest is up to you... digitizer is connected to the limit switch of the z axis but there are to many programs and cnc machines to tell what step is next to take...

here it is in it's first test

and one to test it in digitizer probe style (apparently)


comming up... the results of a scan...with my cnc machine
Azuria28 days ago
Would you share The code?
grostire8 months ago

This seems to be a good idea. I guess the hardess part would be to perfectly align the nail in the center when you mount it on the CNC. It would be interresting to see it in action !

alfcreatevi10 months ago

Excellent idea, thank you so much for sharing

mpreto1 year ago
Great design! I am excited to see next steps, and I will try to make one!
bogaskilop2 years ago
Hello did you make any progres with connecting it to real cnc machine ?

I'm not skilled with electronics can you tell me what is "op-amp "

I want give a try to make such digitise probe .

lemonie3 years ago

This is only going to pick-up your edges, as the piezo generates on movement.
How would you distinguish between up/down edges?
Across a perfectly flat surface there's no signal.

L
harkman (author)  lemonie3 years ago

when scanning/probing with a cnc machine the probe normaly goes down, until the probe touches anything, then it goes up...then a step sideways, then down again, until it touch .....etc...to make a point cloud... the differences in height wil result in a curved surface, where a perfectly flat surface wil generate lots of the same heights...


btw...
On a perfectly flat surface it doesn't need to pick up, as it is perfectly flat..
lemonie harkman3 years ago

OK I understand it, you weren't doing the up-down in the video, but then you ain't a machine.
Thanks

L