Graphite manufacturing 2

[brianlaser]

I was given a task of developing a manufacturing system to produce blocks out of a graphite material that our company produces. The graphite is natural graphite. The plate size of the graphite that we produce is 26” x 26” x 1” thick. We need to produce block to a 1+-.03” x 1+-.03” x 2+-.001” dimension. The 1” x 1” sides need a 63 finish and need to be parallel to each other within .002”. The 1” x 2” sides only need a 250 finish. Two of these 1” x 2” sides do not need to be saw cut because the initial finish of the 26” x 26” x 1” plate is sufficient. We may produce 2-3 million of these per year. Also, we would like a manufacturing system that is flexible to allow us to produce different rectangular shapes in the future. If anyone has any advice on how to manufacture these economically, please reply.

Currently, we manufacture these using a band saw and a surface grinder. A significant amount of deburring time is necessary because the material flakes. We have experimented with water jet cutting, however, we cannot get the tolerance that we need.

 

[bklauba]

Have you ever talked to any of the makers of motor brushes? They would be very familiar with the material, and means of getting it the size and finish you desire.

BK

 

[unclesyd]

You might want to checkout this approach we used this type saw for cutting Graphite anodes. We built our own machine and I'm pretty sure these people will recommend a machine manufacturer.

http://www.ukam.com/dicing_service.htm

 

[BillPSU]

What is the requirement for corners? Handling will probably be your biggest enemy on the corners. A nice .015"-.060" x 45 degree bevel on the corners would be advantageous. Mitering equipment could be used to produce the corner condition.

Question to be answered: Does band sawing, milling, cold sawing cause unacceptable flaking of corner?

Stack saw plates into 1" x 2.01" x 26" blocks. Surface grind 2" side to length and finish. You could try duplex milling or grinding the 2" dimension. Cutoff using cold saw or band saw to 1" finish length.

 

[brianlaser]

Bill, we do not have a corner requirement. Currently, we band saw the material. This will cause flaking. The flaking is removed during surface grinding. The material is not a hard graphite. It machines similar to wood.

 

[brianlaser]

Bill, can you recommend companies that sell stack sawing and duplex milling machines?

 

[BillPSU]

For the saw I was thinking about either HEM or Marvel. They both make large capacity saws which could cut these parts. You would have to build a special feed table mechanism to clamp the parts and to reposition the stack after each cut.

Duplex mills are a very old technology and you may have to have one built. There is old used equipment on the market but may not hold your length tolerance and finish. There are many tooling shops who could build you a machine. You could try using a vertical mill with some precision vises such as a Kurt vises to prove out the concept of milling these parts.

 

[unclesyd]

Personally having worked on graphite and carbon components I don't see the use of a milling machine if precision is desired. Milling will always require a secondary operation.
I don't have the numbers but we we able to slice and dice both graphite and carbon, good edges and surface finish, without any secondary operations.

 

[BillPSU]

unclesyd

How do you get +/-.001 length tolerance by your approach and how are you slicing and dicing?

 

[unclesyd]

We used diamond blades, though we originally we used thin tool steel slitting saws. The original blades were quite small and thick but eventually larger thin blades came along.
We used them originally on a Cincinnati Milling machine.
We built a machine that incorporated some features of the milling milling but had better options for holding the part, speed control, and air cooling package. The machine also had a built-in vacuum table that could either hold a part or catch dust.
We also had a Swisher Grinder that we modified to work on Carbon and Graphite with diamond tools.

 

[brianlaser]

Unclesyd,

Do you have a contact name and number for UKAM? I called the number on the website, the person that I talked with did not provide much information.

 

[unclesyd]

UKAM was just on company that I found in my notes. There are several others that make similar equipment. I'll look around to see if can find another. I'll try to contact a colleague who worked directly with the Carbon and see if he remembers a name.

That is the hardest part these days getting by the front desk to find someone who knows the business.