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Wax Injector


Since we started making jewellery, we have always attempted to make our own equipment.  This is for a number of reasons:

 Firstly, the equipment we make is tailored exactly to our needs - we do not make tens of thousands of items and most of our jewellery is small.  Most commercial equipment is far too large for our needs and in any case we do not have the space.

Secondly, we can adjust our own equipment to meet a specific, maybe one-off need, since we know how it was made and how to take it apart, make adjustments and re-assemble.  Often commercial equipment is made to prevent user access - in our opinion, quite rightly.

Thirdly, we can make equipment which is not available commercially and is designed for a specific purpose - which no one else could possibly want.

And last, discounting the inevitable scrap produced by creating equipment which needs to be 'tweaked' before it will work as required, commercial equipment is too expensive. It is often too large and uses too much power.  We would rather spend our money on raw materials rather than equipment which we may only use spasmodically.

We are embarking on Investment Casting to produce jewellery and will be making all our own equipment.  The most complex of which will be the wax injector.  A wax injector 'sqirts' liquid wax into a cavity created in a rubber mould for later insertion into a casting flask.  We might intend making silver earrings from acorns, for example.  The acorns will be surrounded with silicone rubber in a frame and once cured the rubber will be parted and the acorns removed.  Every time we wish to make an acorn earring, we will squirt wax through a channel in the rubber so that it fills the acorn shaped cavity.  The wax must be molten and forced under pressure into the mould.  This is the function of a wax injector.

There are many commercial injectors available.  But we want a small one.  We do no want to melt 1.5kg (the smallest we could find) of wax every time we make a pair of acorn earrings.  Most commercial injectors are about 4' high and weigh upwards of 15kg and cost a minimum of £300.

Ours will be small, low power, fully adjustable and hopefully cheaper than £300 (but based on past experience this may be wishful thinking).

The initial plans are shown below and I will be updating this page as we progress (hopefully)!







Schematics of wax injector.

Well, I have made some progress and all seems to be working well - just a nozzle, oil bath and various other equipment to make and we'll be ready to cast some metal!


wax injector assembly

The nozzle proved to be far, far too long. Once set up, the biggest problem was getting the injection nozzle up to a temperature such that the wax would not solidify.  In the end, most of the tubing was removed and replaced with the nozzle shown below:


This is now working well, with a wax  temperature of 80C and a nozzle temperature of 72C. The heater is a Kanthal coil running at 130W with a 30V AC transformer controlled by an aquarium heater controller.  It amazes me how slow wax is melts inside the pressure vessel.  I tried using vegetable oil as a heating medium but this gets too hot locally and the whole room soon had an odour reminiscent of a fish and chip shop.  Water evaporates from the heating bath so needs a regular top up.  The pressure is achieved through a bicycle foot pump - well it was to begin with.  Now we use an Argon cylinder which we use primarily for our plasma arc welder - is so much easier to adjust the pressure to between 5 and 10 psi.  If anyone would like detailed plans, please let me know.



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