Re: Machining car end?


In a message dated 1/29/2016 10:22:04 P.M. Central Standard Time, STMFC@... writes:
I don't, but I'm not sure that directly answers your question, Since I cut very little directly into the cavity. Maybe Brian Leppert will take a stab at this, as I believe he does more 'hard milling'.

We are mostly an EDM shop (Electro Discharge Machining) so what I'm actually cutting are graphite electrodes that will be used to " ;sink" the cavity through a controlled erosion process. While the process is designed to erode the steel, it also erodes the graphite, albeit much more slowly, so that tends to obscure the tool marks. The process also leaves a consistent matte frosted finish on the steel.

Any surface that needs a higher polish for release purposes is "benched", polished by hand starting with diamond files, on to fine stones, and sometimes continuing with diamond polishing compound.

The same holds true with cavity work that is cut directly, which in our shop is mostly aluminum. This material is sufficiently soft that the diamond files aren't needed, but fine stones make quick work of the tool marks.

Dennis Storzek
Only thing I have to add is we use hand held die grinders to do any touch up at work. Most of out die work is contracted out but we do occasionally do our own die repair at work, as well as we do change some parts of the die which ware down or fail with an accelerated rate. With a new die we run some test shots see how it runs and material flows and look for any marks in a finish surface. Any problems are marked depending on work needed from hand polishing to getting hit with the die grinders.

As the original poster wanted advice as to cutting dies for freight car ends having most or all the work EDM cut is the way to go. The first cost maybe high but you might see if a small local shop has the capability particularly if you have the work done as a low priority or "free time" project between regular orders for shops wishing to keep their machines and staff busy. depending on what your cutting and the tooling there is the matter of tool wear. As the tooling runs it physically wares down and looses its sharpness pushing metal rather than cutting it pushes a bur  of metal out of the way that is more bent over than cut.

At our shop part of my duties is to verify the machine operators gages are in spec and taking the measurements to assure the ware is being compensated for as the part is machined. So another step maybe to have pauses in the program or brake it into steps so you have the opportunity to stop and check the tooling and machine. Its easer to go back a short distance and recut than try to figure out were to go back a few hours or a day to redo a cut.

My final bit of advice is if nothing else go slow with the feed rate running at the max or close to it over the length of the cut is usually not worth the trouble particularly on a new program or one that needs to be  all it does is get you in trouble faster. I've never herd of any project coming in better than planned by over speeding but plenty that have gone bad, not only in quality of the cutting but also damage to the machine it's self.
Mark Rickert

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