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Grooving Plastic

M

Machinistsss

Plastic
Joined
Sep 25, 2019
I'm looking for recommendations on inserts for grooving plastic.

I have some mirror polished razor sharp carbide inserts from seco for turning, I am wondering if anybody uses anything similar for grooving?
I'm always creating interrupted cuts with live tooling for a chip breaker etc, but for the fine finish on grooves I need something sharp.

Aside from a route such as the link, which would make life simple. The grooves are .153" I need to do, I have made thousands of plastic parts, but I'm never as happy with the groove surface finish as I am with the OD finish.
Kit #32 3/4 inch Groover
.125" Cut-off Groover Right Hand

Or is anyone using good carbide ground and polished inserts they can link?

Thanks
 
I would say play with a rake angle that would not pull the material in but would reduce the compacting...Might take very little perhaps only 1* for starters. might take a slight scallop at the blade top sides.
Guess I would have a good lathe hand on a manual lathe and HSS bits experiment with different geometry.
 
What approach are you taking with the actual cutting? for the finish have you tried feeding in and across and then up and out?
I have found a pc of hss sometimes works better than carbide, just some suggestions. Also you never mentioned what type of plastic.
 
I run an endmill in the groove with the C-axis engaged and remove 90% of the material that would birds nest. Then I enter with a radius in on the tailstock side plunging to the floor, feed across, feed out and radius out. The question is what Carbide insert do you use, or are you hand grinding your own.

I machine 90% UHMW the worst of the worst, but this job will be nylon.

I'm sure some companys make an ultra sharp polished insert for grooving, but every company's website is crap tbh for finding inserts. They want you to call a rep.
 
Machinistsss said:
but this job will be nylon.
Click to expand...

Either find one that is polished made for aluminum, or take some HSS and make your own.
Nylon sucks, as does UHMW as I'm sure you're aware of and is virtually impossible to break a chip so I usually just peck feed my cuts to get control of chip management.
 
I sell Walter tools as a distributor. Walter has a sharp chipbreaker for grooving/ cutting off in their CK8 geometry. Also Arno a less known brand has a similar tool maybe even sharper.

Walter's website is a train wreck like most. Here's a link hopefully it works Walter CK8
 
We cut plastic on the VTL, granted our grooves are bigger 1". We also use HSS ground to the profile required. Cheap and works great, oh also what ever the profile always use a neutral rake.
 
Sometimes an really high feedrate will do the trick in UHMW.
I've seen a guy run a regular steel CNMG insert on UHMW on an OD application.
He started out at .1 DOC and .01 ipr.
Of course it made strings then.
So he cranks it up to .15 doc and like .03 ipr.
At that point it was making such a thick chip that it was
practically fracturing instead of rolling over the chipbreaker.
Looked like it was snowing..... :eek:
 
ChipSplitter said:
Sometimes an really high feedrate will do the trick in UHMW.
I've seen a guy run a regular steel CNMG insert on UHMW on an OD application.
He started out at .1 DOC and .01 ipr.
Of course it made strings then.
So he cranks it up to .15 doc and like .03 ipr.
At that point it was making such a thick chip that it was
practically fracturing instead of rolling over the chipbreaker.
Looked like it was snowing..... :eek:
Click to expand...

I usually take .350" DOC when roughing at up to .05 FPR if workholding allows..but the chips are so heavy that if they do wrap up its bad. That is why I always mill a keyway into the cut so the chip can only by as long as the diameter * Pi
 
.125 Blade I would try a long scallop top face. That would be a 3/6 or ¼ radius on the top going the length of the blade. In doing that the end would take on a concave radius so I would counter that with just enough convex radius to return thw\e end back to leaving a flat.
Easy work for your surface grinder hand, just dressing a radius and grinding long way on the blade in an experimental HSS blade, with working you can order a special carbide blade or just put a diamond wheel on the SG and make them in house.
I would experiment with different top back rake angle, it is possible a 2 to 6* back rake igt work better than a neutral top rake.
Yes, would also try the same on the narrow blades.

From here I cant tell if the .125 has any side clearance.
 
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