Machining Teflon, need some help on this VooDoo material!
Machining Teflon, need some help on this VooDoo material!
(OP)
I am trying to machine a taper on some virgin teflon.
I'm using a CG5 insert from Circle Tool, with a .007" nose radius. Talking with Circle's engineering group, this is the correct type of insert.
I'm making a 6* taper, with 1 pass with flood coolant. 1400 RPMs @ .0015 IPR
I'm getting a great finish on the part, but when I assemble the part into the mating part, it will not seal. Some parts seal, others don't.
I've spent the past week changing feeds and speeds, adjusting the angle slightly and nothing is giving me the correct result.
I'm starting to wonder if temperature is coming into play, causing the Teflon to warp to different sizes? Perhaps after machining, it is changing after sitting out?
I'm making a light pass, a max of .060" cut at the start of the taper, coolant should be at room temperature.
Any advice?
I'm using a CG5 insert from Circle Tool, with a .007" nose radius. Talking with Circle's engineering group, this is the correct type of insert.
I'm making a 6* taper, with 1 pass with flood coolant. 1400 RPMs @ .0015 IPR
I'm getting a great finish on the part, but when I assemble the part into the mating part, it will not seal. Some parts seal, others don't.
I've spent the past week changing feeds and speeds, adjusting the angle slightly and nothing is giving me the correct result.
I'm starting to wonder if temperature is coming into play, causing the Teflon to warp to different sizes? Perhaps after machining, it is changing after sitting out?
I'm making a light pass, a max of .060" cut at the start of the taper, coolant should be at room temperature.
Any advice?





RE: Machining Teflon, need some help on this VooDoo material!
RE: Machining Teflon, need some help on this VooDoo material!
Basically everything is a ball valve, where the teflon is the rotating part to open/close water flow. I am getting leaks at the top and bottom of the taper. I've been able to elminate a leak at the bottom by bumping the OD larger a couple of ten thousanths, but left the top alone.
My frustration is coming from that I am using a new machine, where my old machine was worn out and very slow. Now that I have my new fancy CNC, I can't get it....D'OH!
RE: Machining Teflon, need some help on this VooDoo material!
RE: Machining Teflon, need some help on this VooDoo material!
What I can't figure out, is that if I run a group, some leak, some dont. The machine is fine, so my guess is the material is distorting from heat on the process right before it.
But with flood coolant on, I would think the part would be okay. Unless the coolant is chilling the part, then later when the part warms up, we are getting a larger part than intended? I can't seem to find anything that relates temperature vs thermal expansion of teflon.
RE: Machining Teflon, need some help on this VooDoo material!
for example:cone=30deg,bore=30.2deg
RE: Machining Teflon, need some help on this VooDoo material!
I thought it might be thermal expansion, but I don't think it is now. I think I'm relieving the stresses, and it's changing shape...but almost like it's shrinking? I would think by relieving the internal stresses, it would expand some.
RE: Machining Teflon, need some help on this VooDoo material!
A HS parting tool with high back rake and plenty of relief might make a difference.
Something else to try is making a partial cut where the parting op will be; then do the taper turning, then complete the part-off op.
Teflon is probably the worst material for squirming.
RE: Machining Teflon, need some help on this VooDoo material!
Sharp HSS tool bit will cut rather than rub the material off.
RE: Machining Teflon, need some help on this VooDoo material!
Use High Spot Blue and see if the tapers match at both ends.
Ed Danzer
www.danzcoinc.com
www.dehyds.com
RE: Machining Teflon, need some help on this VooDoo material!
RE: Machining Teflon, need some help on this VooDoo material!
The only way to use teflon is in compressive stress loading, with a spring or other device to maintain the stress at a relatively constant level, and some means of containing/restraining the teflon so that its inevitable cold flow will not interfere with the part's operation.