How to become a Mould Polisher and enjoy it!
The first and absolutely essential requirement is interest. Your first interest in the job may be because it pays a little better than assembly or maybe you prefer a little quieter environment. The polishing operation itself must hold your interest or you won't enjoy it. You must develop pride in what you do, not just in the final finish but in each step along the way. You must have confidence that each step that you do is in direct progression to where you want to go.
When you start on a large core or cavity it can be a little disheartening. When you first start digging away at those pits it can seem that the mirror finish is a million hours away. Don't even think about the finish. It's in there and it will come up automatically as you just methodically work one step at a time. It may be that there are 60 square inches on one side of the cavity. Don't think about that either. Just take about a 2 inch square of that surface and rub all the pits out of it. Anybody can handle a 2 inch square, right? Absolutely, and when you have all the pits out of that 2 inch square that is a success, right? You need those successes. Don't give the whole side of the cavity "a lick and a promise" and then have to go back over the whole thing again. There is nothing that can bring on that feeling of futility quicker than that. Just decide what stone to use, and if it is a burned finish it will no doubt be the EDM series. If the surface is extremely good you may start with the 53xx series. Whichever you decide to use, have confidence, absolutely know that you are doing the right thing. This makes the work much easier.
As you progress along the side of the cavity a little at a time you will become pretty much absorbed in it. Pay no attention to what other people are doing.
You will develop a way of living inside your own head. The time will pass quickly and you will surprise yourself and other people with how much you get done. Choose a kind of music that does not irritate you and keep it low.
Knowing when to move on is important also. Keep a close watch on the surface so you don't do a lot of needless rubbing. Don't use too wide a stone when you are roughing on a hardened block of steel. You need a little extra pressure for those pits and you get more pressure per square inch from a 1/4” wide stone than from a 1/2” or 3/4” stone. Softer steels require a little lighter treatment but you will learn that very quickly. With your final stone, even on hard steels, you will want to be a little gentler.
These are all things that make the job more interesting. Know before you even start on a block of stainless steel that your biggest problem will be a tendency to over-polish (a tendency that you share with almost everyone who has ever tried to polish).
Sometimes it is required that shops cut prototype moulds in aluminium before building a permanent one in steel. If you have to polish aluminium remember that it cannot stand rough treatment. Gesswein makes a super-soft stone such as the #7002. This might put on the finish that you need. If you need a higher polish than this stone gives, try Green Diamond with a brush, then felt, then hand rub.
Accept all these things as a challenge and it will definitely be an aid in keeping boredom from creeping in. Keep in mind, also, that not every job you work on has to be a showpiece. It is not practical, economically speaking, to attempt that. An adequate finish in the least possible time is what we are after. Several different things determine what is an adequate finish, things like type of material to be run, colour, and product application.
They certainly release a lot easier without a high shine and reducing this shine may cure a lot of sticking problems. Nylon, for instance, is a material that sticks pretty badly to a highly polished surface.
Mould polishing is a many faceted, highly skilled operation. Learn the basics first, then be inventive. Be constantly on the look-out for a better way. Remember that education would be in pretty bad shape if the student didn't ever out-do the teacher.