|
Custom Medal Production Process
Medals can be struck in base metals such as copper, bronze or nickel, or precious metals such as silver and gold. Sizes can vary from 10 mm up to 100 mm. Whilst shapes are usually circular there is no limitation to the final shape that a medal can be produced.
Medals, medallions, coins, tokens and plaques all have the same general process in production and take from 3 weeks to as long as 12 weeks to produce. The usual delivery times for medals are from 4 to 6 weeks.
Design – weeks 1 to 2.
The artist prepares designs in consultation with the client. The designs are initially as concept drawings and finalised with the assistance of the computer. Upon customer approval the design then proceeds to the sculptor to sculpt the plaster model. Decisions such as finished size, metal and type of surface finish need to be established at this stage although some flexibility does exist.
Sculpting of the plaster model – weeks 2 to 4.
The sculptor works from the design first in plasticine or clay on a sheet of glass to build up the image of the design. This is called bas-relief sculpture.  A plaster is then cast from the plasticine and then using special hand tools the sculptor further works the plaster model until complete. The sculpting process takes around 1 to 3 weeks depending upon the complexity of the design. One plaster model is required for each side of a medal.
Reducing machine master tooling – weeks 3 to 5.
From the plaster model a silicone rubber mold is cast then an epoxy resin model is cast from the rubber mold. This epoxy resin model is a copy of the plaster model only in a more durable medium required for the next stage using the reducing machine.
The reducing machine is a unique tracing and engraving machine used specifically by the minting industry. The epoxy resin model is traced by the reducing machine over a period of several days cutting the design into special tool steel, first with a roughing cut and then a finer finishing cut to capture the detail that the sculptor has skillfully sculpted into the model. The copied design cut into steel is known as the reduction punch or hob.
The reduction punch is checked by a hand engraver to ensure that there are no imperfections from the tracing and cutting process. This task is performed under a microscope and requires great skill in using specialist hand tools. Once the engraver is satisfied with the finish the reduction punch is heat-treated so that the steel is appropriately hardened for the next process known as hobbing.
Production die tooling – weeks 4 to 6.
The hardened reduction punch is then placed into a hydraulic press for the hobbing process.
The reduction punch is pressed into  another piece of tool steel at incredible pressures of up to 800 tonnes to create a production die that has a negative impression of the design. This may take several attempts to achieve the full size and detail of the medal or coin design with an annealing (softening) of the steel between each pressing as the production die work hardens when the pressure is applied.
This negative is called the die. The die is used to strike the medals after it has been machined in a lathe and heat treated (hardened), otherwise known as the production die.
Pressing of Medals – weeks 4 – 6.
 Two production dies are prepared for fitting into a hydraulic press, one for the obverse and the other for the reverse of the medal. Medal blanks are prepared. The blanks are placed between the dies in the press and contained by a collar. Then squeezed at pressures of around 300 to 600 tonnes to form the detail of the medal design. Depending upon the height of the relief in the design the medal may have to be struck several times with intermediate anneals (heating to soften) to achieve the full detail of relief.
Finishing of Medals – weeks 4 – 6.
The medals are then finished accordingly. Some may have a patina applied to give an antique or a frosted satin finish maintaining the original metal colour. Some may be electroplated with gold or silver or a proof like finish that is a polished appearance straight from the dies during the pressing process.
Occasionally medals may have fittings applied to hang from ribbons to be worn around the recipient’s neck or pinned to their lapel.
The medals are then packed into their presentation boxes. Presentation boxes come in a variety of styles from soft-bodied leather style cases to custom made wooden boxes.
|
