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Thread: CNC mill $6 plotter pen
04-28-2010, 02:53 PM #1
CNC mill $6 plotter pen
measured and made 3D model of a plotter pen for HP plotters. a Koh-I-Noor_6401.01F
Plotter Pen 0.3mm
basically it is a short fiber tipped marker that can be used on a CNC mill to draw on the part the tool path. on hot rolled steel white shellac alcohol based can be used as machinist bluing so black lines show better.
i got a package of 5 for $30. a regular sharpie type marker bends too much. by using a plotter pen that about an 1" long (0.450"dia) held in a drill chuck it is much more rigid. should not be hard to make a spring loaded holder but i have found it works ok for flat parts using nothing more than just the plotter pen.
of course the plotter pen is about 0.3mm wide when new so it is only showing the center of the tool , tool path. by making parallel lines close together is how a plotter makes wider lines.
it would be interesting to try a paint marker to see if a cnc mill can be used to paint a metal sign.
04-28-2010, 04:59 PM #2
With dimensions to accept technical nibs.
More info for those in need.
04-28-2010, 05:11 PM #3
I have seen spring loaded holders for these pens. I don't have one myself, but it makes sense to me that spring loading would allow for a little error in Z without causing a "pen crash".
05-01-2010, 02:22 AM #4
$6 plotter pen and making holders
i made a spring loaded holder for plotter pen. Took me 4 hrs. the delay was not having the right size stock and trying a sponge spring which did not work that well and had to find cut grind a steel spring
1) pen is over .450. I measured 0.456" in spots. pen is plugged by a pressed in cap and this area slightly bigger. the cap got stuck in tight bore and was removed accidentally from plotter pen. looks to me it should not be hard to refill plotter pen with ink.
2) i saw package says pen should have 30 grams force. i only had a spring that gave about 1 lb or 450+ grams. So 0.3mm pen gave a 1+mm line.
3) addition clearance to allow the plastic plotter pen to float i tried 0.005". i made pen holder from 1018 CR steel. i am thinking using teflon or rulon bushings or using acetal / delrin might actually work smoother and allow tighter clearance
4) since pen force recommended is about 1 ounce i am thinking just a brass bushing to act as a weight might be all that is needed if always pointing pen down like on a vertical mill.
5) i will make another plotter pen holder of a different design.
6) got some cup washer belville or solon type rated at 0.011" depression at 3700 lbs. i am thinking of a pressed in $3 Dremel Carbide engraving point in a Steel shape like a plotter pen. maybe same holder might be able to exchange plotter pen with Carbide plotter pen shape for scratch engraving. Spring seems to help both types last longer as if overloaded with too much pressure (Z axis change of even 0.004") damage to point easily occurs.
7) apparently there are many US patents some even mention adjusting plotter pen off center to simulate cutting tool diameter path. before tool path simulation software was available this was probably popular. i think using plotter pen on a CNC mill if nothing else after engraving lines in metal if engraved lines were made black with plotter pen the engraved lines would be 10X easier to see.
8) painting hot rolled steel with white shellac does make black lines 10X easier to see. brush strokes are easy to see so spray painting with flat white quick dry spray paint might look better. i do not see why signs could not be made on a CNC mill.
05-04-2010, 11:22 AM #5
Plotter pen / Floating Sharpie marker CNC mill
Drawing attached as a gif image in a zip file to meet forum size requirements.
Basically drawing show both designs using a brass bushing and it's weight to apply the 1 ounce of force recommended with plotter pen and sharpie marker.
The reason the 2nd design uses a Sharpie permanent ink marker is the ink is water proof. I want to apply lines, arcs, numbers and letters to a metal part but in general I do not want the lines to wash off with cutting fluid. After scratch engraving with carbide or diamond the sharpie marker can make the engraving black so it is easier to see on shiny metal.
It is not easy to have something move smoothly with only 1 ounce of force. it required sanding and polishing the parts.
letters smaller than 1/2" show a dot where sharpie marker pauses. I will have to look for extra fine point ones.