Machining Soft Plastic

[MozamPete]

I am trying to make some sample/souvenirs from an offcut of large power cable we are installing at work. Think coasters made out of thin slices. It cuts OK on the bandsaw (and I may end up leaving it at that) but I was going to try and get a better finish by either facing it off in the lathe of running a large endmill over it in the mill.

Cable is 400kV, 630mm² stranded aluminium conductor with XLPE (cross linked polyethylene) insulation.

Have had a try facing it on the lathe but I'm not getting a good finish. The XLPE (large white coloured area) doesn't come off as strands but stays as a thin disc no mater how thin a cut I take, and the stranded aluminium in the center 'smears' so that the individual strand are not nicely defined.


The tool was a bit old so will try again once it is freshly sharpened, but would be interested in any other suggestion from people with experience machining soft type plastics.

 

[JimDawson]

Really sharp HSS tool with a lot of back and side rake, no nose radius. Like a razor. Adjust feed and speed to get the finish you want.

Or try sanding it on a disk sander if you have one.

 

[chips&more]

If you have a 6 X 48 belt sander or similar, maybe try that…Dave.

 

[Bill Gruby]

Freeze it then cut it. And use a very sharp tool as Jim said. Don't cut fast or you will thaw it too much before the cut is done. Light cuts only. Old school technique.

"Billy G"

 

[cascao]

If anything else work, hand sand it

 

[TommyD]

Wot rpm's you facing the plastic at? I have found slow speeds work better, too fast and the friction kinda melts the plastic,making a mess.

The center aluminium is probably loose in the plastic sheath, moving around ad you try to cut it.

Maybe try a mix of the above, soak it in water and then freeze it, water between the aluminium MAY keep it in place. Face it.
Freeze it and hit it on the belt sander.
Accept it with as little work as possible.

Personally, I have had better luck machining plastic using hss and a generously radiused tip. Aluminium too.

 

[MozamPete]

Soaking in water is not an option and one (two actually) of the layers that make the cable is a water barrier tape designed to swell up if it gets wet - but I will give all the other options a try over the weekend and see what works best (have a piece in the freezer already) .

 

[John Hasler]

Use WD40 on the aluminum if the plastics will take it.

 

[rallycat]

I like the freeze idea for the PE. If you can pot the aluminum strands in epoxy or acrylic that will keep them from smearing. If you have a vacuum chamber you can get a good bubble-free fill between the strands, then freeze, then machine, and wet sand if needed.

 

[TommyD]

I was going to mention vacuum inpregnation for the alum. but figgered it was a bit over the edga. I used vacuum impregnation at the university Geology Dept. I worked at for sand core investigations or porous stone that was fragile. It definitely give stability to the strands for machining.