I recently came across this patent application.
Apparently several people are making apex seals using the EDM process. Any
metallic material will work.
One can start with chrome molly 4340 pre hardened steel or any other cast
iron or steel alloy. Even some of the new high temp NASA cast aluminum or
BeAl alloys might be used and MAY work.
Don't breathe the fumes. The problem is the seals can run over 500 degrees F
destroying the lubrication. They must be kept cool by an adequate quantity
of oil. This is the main reason charged cooled rotors don't work in heavy
duty rotary engines. The rotor temp. can run up to 650 F.

http://www.rotaryeng.net/OMC-heat-release.pdf

This is probably what caused the demise of the charged cooled Rotamax
engine.

I can see two problems with home made apex seals and I noticed this with
after market seals I have inspected with a mass spectrometer and a
microscope.

Problem number one: Mazda stock apex seals have a slight crown.
Read http://www.rotaryeng.net/seals.html Hard to do with EDM.
The first thing you will notice is a reduction in compression pressures.
This is because the seal is leaking.

Two: The finish on the seal is not mirror smooth as it is on the stock
seals. Stock seals are heated with laser and chilled in liquid nitrogen. A
less than mirror finish in conjunction with hard steels is death on rotor
housings.
EDM does NOT give a mirror finish.

Acicular cast iron used by Mazda is porous and retains lubrication.
Mazda spent millions on apex seal R&D so my advice is to stick with the
stock seals.

http://steel.keytometals.com/default.aspx?ID=CheckArticle&NM=21


Paul Lamar


Paul,

The RotaMax engine used all Mazda 13B seals, any attempt to use other
materials and or seals made by others failed.

Never had problem one using Mazda factory direct purchased seals and
springs.

Eric Barger RotaMax Inc