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I have built a cnc "lathe" to engrave cylinders, and I am seeking advice on the type of bits to use to engrave lithophanes on PVC pipe. I have tried 30° V bits, but results are dismal due to the PVC melting. I am presently using a Dremel, but will install a trim router (Bosch or Ridgid) soon.
I use my own gcode conversion program and usually engrave with a step over of 0.005 to 0.010 inches.
Thanks for any advice.
John
If it's melting, slow down the rpm.
You might want to try small ballnose cutters.
I know member Greolt has done the same thing, you might want to ask him.
Thanks Gerry.
I am not sure melting is the cause, but my present bit is leaving lots of "fuzzies" on the final image that degrade the work. Perhaps the bit is not cutting properly. I am running the Dremel at it slowest speed. I will see if I can find a way to slow it down even more, or go ahead and change to a trim router with an external speed controller.
Regards,
John Champlain
If it is melting try a stream of air to cool it.
Warning, PVC releases highly cancerous and toxic fumes when heated and melted. Poly Vinyl Chloride is dangerous to melt or mill. Plumbers only make small single cuts along a length, a few thousand in a lifetime will not add-up to the carving gasses you will be releasing in one multi-layered milling of a 2' section of tube.
Just make sure you use adequate ventilation, if you MUST use PVC. Also be sure to coat the finished product with some PVC safe clear-coat or paint. The pipes are coated with a anti-seepage layer, approved for use with water. The heat releases the chloride when milling.
I suggest that you use ABS plastic or acrylic tube, if possible. Even HDPE or PE tubes.
try a lube-- dish detergent watered down 50-50 works well for plexiglass
JD_Mortal
I'm always amazed at what people can come up with about PVC
citrusguy you can machine this material all day every day of your life & it will not hurt your health in anyway
The only time it can cause you a breathing & health problem, is if you burn it, like on fire, it then will give off Hydrogen Chloride gas & Dioxn
Most of the other plastics that JD_Mortal has listed can be just as Toxic as the PVC if Burnt by fire as well, it just depends, on what additives, fire retardents are used in there formulation
The formulation of PVC is CH2=CHCL= is a double bond thermoplastic material
You don't have to coat it with anything after it is machined as well
There was a guy in Australia, that was doing the same as what you are, & got the fuzzy stuff as well, he just brushed it with a stiff brush to take the fuzzy bits off
But I'm sure if you cut it at the right spindle speed & cutter it will cut clean, without the fuzz
Thank you all,
I appreciate your input. For now, I have set aside rotary work in order to have time to make Christmas gifts for family and friends. As I work on this project later, I will post my findings.
Happy Holidays to All,
John Champlain
I have also been trying to find the perfect combination ( step over, feed, tool) to make a good litho out of pvc pipe. I first used a 30deg bit and ran into the fuzzy problem, so bad that even taking a brush to it was not practical for me. My last attempt was using a 3/64 3flut ball EM with .005 stepover. The result was not fuzzies but a lower quality image.
I'm looking to either engrave or print a design on a piece of furniture grade PVC pipe (1/2" PVC) but wasn't sure how to go about this. Does it matter if the furniture grade PVC is colored or not?
might sound dumb, but back in '94 I made a backlit panel used r/c car polycarbonate black paint on lexan, reverse milled thru the paint so all the symbols looked backlit...tried the newhermes style vee cutter, didnt cut clean, just messing around tried a #0 center drill for all the engraving, worked beautifully. my mill only runs about 2000 rpm.
did some wood portraits for a couple friends later that year, again, centerdrill cut cleaner than anything else I tried... no idea why, the geometry sure dont look right, but they do 'mill' pretty clean.
when cutting plastics, its always seemed to me slower is better- if not thick enough chipload, it wants to leave that flopping edge along every cut... colder is better too- a vortex tube chiller blowing/freezing the plastic makes for a clean edge too.
I just built up a little 3" chuck horizontal rotary axis for the bridgeport out in the garage, hoping to do some round engraving stuff too. made a steel cam out of drillrod a couple weeks ago, rigidity with only 1/4 cutter was pretty poor, but it ought to be way overkill for plastic work :) still havent made up a tailstock for it yet...