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vini the kiwi
02-01-2010, 04:00 PM
Hi all hope you all had a good crimbo

now I want to get into investment casting. but it seems i need a vacuum device is this really necessary ? could I just pour the silver into the loss wax mould, looking at building my own, don,t like the idea of a centrifuge, hot metal whizzing about.

any clues

thanks for reading

Mystic
02-01-2010, 07:51 PM
Hi Vinnie and yes I had a good Christmas as I hope you did. I am sorry, but I am unable to give you any advise as it's out of my expertese, just hang on for a wee while and some of the others will surely be able to help you. Hope you have a great new year.:)

Emerald
02-01-2010, 08:11 PM
Hi Vinnie if you are only looking to cast 1 item at a time and just one offs then the delft clay is perfect but you couldent pour molten metal into a lost wax mould cos they are rubber! is that not worse than it whizzing around withheld in its own sancturary?:xmas;_):

EndevaJewellery
04-01-2010, 02:54 PM
Isn't investment and lost wax casting the same thing?

Lost wax moulds are made out of the white plaster material (or investment) and that's what you burn/lose the wax out of in an oven/kiln?

ps_bond
04-01-2010, 03:24 PM
You may wish to have a look at steam casting as an alternative if you're using investment. Much less expensive than a vacuum setup, but still capable of reasonable results.

Steam Casting 1 (http://users.frii.com/dnorris/steamcast1.html)

Gerry Kaspers
04-01-2010, 04:13 PM
If you don't use a vacuum pump you end up with air bubbles in the mould and therefore pitting or cavities on your silver cast.

Tim McCreight book "fundamentals of metalsmithing has a really clear explanation of process and images which is worth a read.

Are you desperate to do this yourself? We have just tried wax casting in my college course and then sent the pieces off to be lost wax cast- it cost around £18 for two rings and a silver fish - metal costs included.

vini the kiwi
06-01-2010, 10:47 AM
thank you all for your reply,s

being an engineer I wish to make my own machine ,out of an old pressure cooker and a vacuum pump,

just waiting for the right pump to come up ,

I talked with a guy who supplies investment powder, you rig up a locking type cooker to vacuum pump with a graphite seal . with a hole in the top that can be plugged the same size as a perforated casting flask. plug it with the flask inside with the wet investment plaster put the vacuum on, and suck out the air bubbles , burn out wax and heat mould with your crucible ( MAKING SURE ITS DRY ENOUGH ) remove the plug place hot mould in the hole with another graphite gasket turn on vacuum and pour molten metal. then run from shed with hair on fire LOL #-o PPE essensual

will let you know how it go,s

vini the kiwi
06-01-2010, 10:59 AM
You may wish to have a look at steam casting as an alternative if you're using investment. Much less expensive than a vacuum setup, but still capable of reasonable results.

Steam Casting 1 (http://users.frii.com/dnorris/steamcast1.html)

thanks ps bond

intresting concept

ps_bond
06-01-2010, 04:07 PM
It's just providing the force to get the metal into the mould is all. Delft clay uses gravity (and that's part of the reason for the huge sprues), vacuum casting uses air pressure, steam casting uses the pressure generated by the steam.

A vacuum does make debubbling the investment easier though... An old fridge compressor can do the job there - or a single-stage eductor (if you've got a compressor to drive it).

EndevaJewellery
08-01-2010, 07:23 AM
We have just tried wax casting in my college course and then sent the pieces off to be lost wax cast- it cost around £18 for two rings and a silver fish - metal costs included.

Interesting, do you know the name of the company your college used?

Lisa Quinn
08-01-2010, 10:35 AM
Interesting, do you know the name of the company your college used?

I would be interested in this info too if you have it available !!

Emerald
08-01-2010, 10:42 AM
there are lots of metal casters in the jewellery quarter x

Matp85
09-01-2010, 11:01 PM
ok aint been on the forum for a loooong time but since i use investment powder nearly every day with a vacuum pump and cast every week i can assure you a vacuum pump IS needed.

As someone stated it does take take most excess air out the mixture and reduces the size/content of the air, which forms in bubbles from the surface of the wax to ensure a more smoother finish. This allows a better finished peice with no airholes.

centrifuge (don't knock it, it was how it used to be done) was the old style casting my boss used to use that and although it could be a nightmare it was still achievable and some platinum caster use this method to this day.

We have delft clay but is only good for heavy peices and chunky items. For smaller more defined peices a good casting machine is needed or use a company. I use a mc15 casting machine which is both negative and postive pressured for a good cast.

let me know if you need any help or advice as its over christmas and my busy time is over will be more active and hope to get to know everyone better!

Dennis
15-01-2010, 09:21 PM
Here is my contribution: The investment is a dedicated product that will not crack on heating and expands when heated to compensate for the shrinkage of the molten metal as it cools. It is normally contained in a steel ring with a liner and the object to be burnt out is at the centre.When casting, the investment is brought up to a temperature similar to that of the molten metal.
Improvisation is not recommended because of the danger of exploding investment and molten metal.
Dennis.