Getting rid of waves when rolling metal

[elfixx]

Perhaps someone with experience in jewelry making or coin/bullion minting could help me out here. I was wondering is there any kind of tricks or something to get rid of waves created when rolling metal? Having wavy stirps will shure affect the final look of any bullion made from them.


Thank you

 

[Harold_V]

Perhaps someone with experience in jewelry making or coin/bullion minting could help me out here. I was wondering is there any kind of tricks or something to get rid of waves created when rolling metal? Having wavy stirps will shure affect the final look of any bullion made from them.

Thank you

It's unlikely you can eliminate the waves but they aren't an issue so long as you keep a constant thickness, so your planchets weigh the proper amount. When you strike the planchet, not to worry---any waviness that may be present will have long since been eliminated. Probably even before, when the planchet was punched from the stock.

You haven't made it clear how you intend to use the material, but if you intend to blank and not strike afterwards, you can flatten such items easily by pressing between two smooth steel plates. Something as simple as a three ton arbor press would likely provide enough force----or if you have a punch press at your disposal, that would work, too.

Harold

 

[nickvc]

Sounds to me like your trying to break the metal down too quickly. Try reducing the metal less each pass through the rolls and it should stay flatter, it will obviously take longer but as I think your rolling fine metals that time is saved by the lack of the need for annealing.

 

[Oz]

While I have no hands on experience with rolling precious metals I have done a good bit of forge work. I think that you should pay more attention to the annealing.

Better advice could be had if we knew more details on the material being rolled, and the specific details of your current procedures.

 

[elfixx]

The material rolled is gold and silver, I recentrly purchased a 75 ton press for my blanking and embossing operation, both the blanking and stamping die are being manufatured at the moment I should receive them soon. If those waves don't affect the quality of the final product that's great.

 

[goldsilverpro]

I agree with Nick. Make more passes. Also, with the minting operation we had in LA (which I didn't really get that involved with), I'm thinking the metal was always annealed after each several passes and after the final pass. We had a conveyorized annealing furnace about 15 - 20 feet long. As the metal is put through the rolls, it work hardens. Whether this could contribute to the waviness, I don't know. Annealing makes the metal less hard and prevents cracking, etc., when rolled, as I understand it.

 

[nickvc]

Are the metals fine gold and fine silver? If not then annealing is a must after passing through the rolls 3 or 4 times to avoid work hardening. Fine gold can be reduced to almost nothing very easily as is proven with gold leaf but it will wrinkle if you try to reduce it to quickly. If you want perfect stampings then your sheet needs to have a good surface to start or the imperfections I think will transfer to your blanks.

 

[goldsilverpro]

Are the metals fine gold and fine silver? If not then annealing is a must after passing through the rolls 3 or 4 times to avoid work hardening. Fine gold can be reduced to almost nothing very easily as is proven with gold leaf but it will wrinkle if you try to reduce it to quickly. If you want perfect stampings then your sheet needs to have a good surface to start or the imperfections I think will transfer to your blanks.

We were minting 999 silver coins. Annealing was needed every few passes to eliminate the work hardening.