This is an example of a production project proposal involving the reproduction of two historically important buttons. This shows how the project is described in terms that allow the client to see what is involved in manufacturing. It is a sample of a description that allows the client a sense of the scope of the job.
Two uniform buttons, with diameters of 2cm and 3.5cm with text and intricate surface detail must be reproduced. 250 units are required. The top surfaces must be crisp and polished. The color must be a bright yellow, therefore they will be cast in a smoothly textured, yellow brass casting alloy. Plating was discussed by the client.
(manufacture of molds and models for production of buttons)
- Making a geltrate (alginate type) mold of the original buttons or models.
- Producing a viable wax from the 2-3 geltrate molds made, usually within 10 attempts.
- Repair and preparation of 3-5 waxes for each button for casting. The back must be constructed and attached to the wax models.
- Spruing up the buttons on a rubber base, after which a tubular steel flask is placed around it and then a refractory investment is poured in and vacuumed to remove air bubbles.
- The flask is burned out in a kiln for about 6-8 hours. The temperature eventually reaches 1100oF or higher.
- Metal is cleaned and placed into a crucible on a centrifugal casting machine. The flask is tied into position on the centrifuge and the metal is melted in the crucible.
- The machine is released slinging the metal into the cavity left in the mold as the wax burned out.
- The buttons are removed, cut off the central sprue and cleaned up with abrasive and polishing tools . A metal sprue is made and attached to the buttons that have been chosen as good enough to be used for rubber mold models.
- A rubber mold is made by layering the metal model with cut sheets of unvulcanized rubber in a frame and heating it under great pressure for an hour to 345oF.
- The mold is carefully cut open in such a way as to follow the contours of the model and release an injected wax easily. Registration keys are cut at the same time into the model using a new scalpel blade.
- The mold is tested for clean injections and adjusted as necessary by further cutting of shaped burning. These steps are repeated for the second button. The molds and the metal models with sprues become the property of the client.
Cost for tooling up for reproduction of two buttons:_________
Logo and Text
(making and applying client’s trademark and ‘reproduced by Client’ on the back of the models)
If possible the Client could supply the positive film for a miniature photoetching of the graphic and text. This should be reduced in size to fit in a circle of no more than 5mm across. This will serve to photoetch a copper sheet to a depth that will survive the finishing procedures. If needed the client can be put in contact with several reliable graphic designers who can supply the completed line film.
One can also approach this problem by producing the artwork, having a printer etch a magnesium plate to the required detail and scale and then rubber molding the magnesium plate to obtain a wax logo to add to the original model. The steps in adding the logo and text include:
- Production of graphic and film for photo-etching.
- Deposition of photoresist on copper plate.
- Exposure to intense light with the positive graphic film over it.
- Developing with developer to remove the areas protected from the light by the graphic.
- Heating to set the photoresist.
- Protection of back and sides of the plate with resist.
- Etching to required depth.
- Cutting out of model disc around etched graphic.
- Brazing the disc to the back of the metal button model prior to making the rubber mold so that the etched graphic is part of the finished buttons.
Price for Production and incorporation of graphic onto buttons:_________
Comparative Price for Magnesium Plate and Wax Approach
Production of Buttons: Manufacturing
- Waxes are injected under appropriate pressure into the molds and cooled for 10-20 seconds before removal from the mold. Approximately 25% are usually unusable for one reason or another.
- The waxes are inspected and any surface repair necessary is made by scraping.
- The waxes are sprued; attached by melting; onto a ‘tree’, a large central sprue for multiple castings. There will be approximately 20 buttons per flask for a total of some 14-16 flasks. There can be up to a ten percent loss rate on the cast pieces, therefore more are cast to make up for this.
- The investing and casting procedure as described above then occurs to the flasks which are done in batches or about 4, due to kiln size.
- The buttons are cut off the tree and filed, sanded, and any repairs are effected.
- They are cleaned of investment residue and any oxidation of the surface that resulted from casting. This may include an initial sulfuric acid treatment followed by neutralization, brass brushing, treatment in a solution of SparexÂ® and Hydrogen peroxide for a minute and then brass brushed and rinsed again.
- The surfaces are treated with liver of sulfur (potassium sulfide) to ‘age’ them and then brass brushed again.
- The buttons are then polished, cleaned, inspected. There are several stages to the polishing process involving various abrasives and procedures. Tripoli is used to finish the surface and rouge (powdered hematite with a grease) polishes the surface bright around the sides and slightly on the details.
- The pieces are waxed by hand and bagged.
The cost for labor and materials and supplies used in production is: __________
Gold plating in Calgary can be from 3-12 dollars at the wholesale/trade level. In the United States plating might run 2-4 dollars per unit, even without duty and taxes on re-import. Plating is a painstaking and long procedure involving cyanides and plating 2-3 different metals on each button in successive beakers.
Plating is however only a thin covering on the metal and a button in use would be likely to have it’s plating worn off fairly soon on the raised areas of the surface. The use of a wax polish and occasional re-polishing and on-going care is recommended. The use of lacquers and sealers other than wax can lead to patchy discoloration with time because they chip off.
Total Value of work for project: _________