LOST WAX CASTING

This topic has 19 replies, 13 voices, and was last updated 14 October 2016 at 17:35 by Brian Oldford.

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12 October 2016 at 22:54 #260749
CHARLES lipscombe
Participant
@charleslipscombe16059
I use lost wax casting to manufacture various motorcycle parts and most of my molds are made from Aluminium/Epoxy which appears to be aluminium powder mixed with Araldite. On completion of the mold the mold maker coats the working surfaces (cavity) with a kind of varnish. Does anyone know what this varnish is?

Reason for enquiry – sometimes the castings are not quite what I need and I need to mill out the cavity, thus destroying the "varnish" Also the milling process can expose porosity in the mold which needs correcting with one of the "plastic metal" compounds.

Chas
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12 October 2016 at 22:54 #24798
CHARLES lipscombe
Participant
@charleslipscombe16059
13 October 2016 at 07:44 #260778
Chris Evans 6
Participant
@chrisevans6
We used to make low volume or prototype moulds fro "Kirksite" I never got involved with lost wax but do remember some form of coating being applied. I am sure someone with knowledge will be along soon.
13 October 2016 at 10:09 #260794
KWIL
Participant
@kwil
I have only seen lost wax molds made from a flexible "rubber" cast around the master pattern of the required final part.

Wax submasters cast from the flexible mold and hence joined to a ingate and all coated in ceramic prior to final burn out and casting.

What is the OPs process?
13 October 2016 at 10:18 #260796
MW
Participant
@mw27036
Hi Charles,

Is the aluminium powder white in colour and very fine? i'm just wondering if it's aluminium oxide? I've only ever done silicon mould rubber castings with Polyurethane 2 part plastics.

Michael W

Edited By Michael Walters on 13/10/2016 10:20:25
13 October 2016 at 11:25 #260809
steamdave
Participant
@steamdave
Would the mould maker tell you what coating he is using?

Dave
The Emerald Isle
13 October 2016 at 11:39 #260812
Senior Yates
Participant
@senioryates
Hi Chas,

I spent 20 years as a production manager in one of the UK best aerospace foundries. The tools we mainly used were all aluminium with brass cores, there was the odd resin type we always used silicone spray on each shot to release the wax pattern. The company you should speak to is Blaysons.

Hope this helps

Senior
13 October 2016 at 11:44 #260814
Circlip
Participant
@circlip
So re paint the area with an Epoxy resin.

Regards Ian.
13 October 2016 at 13:29 #260830
John P
Participant
@johnp77052
I have used washing up liquid (Fairy) diluted with water to coat
metal moulds ,allow to dry before injecting the wax.
Photo in album Furnace and casting.
John
13 October 2016 at 15:32 #260855
Bob Stevenson
Participant
@bobstevenson13909
Forgive my ignorance, but how is this "lost wax casting" if there is a mo(u)ld that is permanent and split open etc?
13 October 2016 at 19:24 #260902
John P
Participant
@johnp77052
Hi Bob

In order to produce a finished casting a suitable wax
pattern needs to be produced ,this is usually done with
metal mould in similar way to plastic injection moulding.
In the photo i posted in the album in the top left corner
is the mould to make the semi-circular waxes seen
in the centre the pale green parts ,from here the waxes
are sprued to a pouring cap, bottom left and also in another
photo.The assembly is fitted in a suitable flask and filled with
mixed investment (similar to plaster of paris) .When set the
flask is fired in a burn out kiln ,the wax melts out and and is
"lost" leaving a cavity to cast the metal in.As other posters
have mentioned these moulds can be also made of rubber.
Art objects may use patterns made by hand built up from pieces.
More modern methods are available now for those who have
3D printers ,the castings seen here were done sometime around
1990 .

John
13 October 2016 at 19:47 #260906
MW
Participant
@mw27036
It's quite interesting, John, but i'm afraid i can't see the picture? is it just me (for the time being ofc) ?

Ps: i can see some in your folder but it isn't appearing on the post, atleast not for my monitor.

Michael W

Edited By Michael Walters on 13/10/2016 19:48:46
13 October 2016 at 20:04 #260913
John P
Participant
@johnp77052
Hi Michael

I am only able to post photo's to the albums ,when i click on the camera icon i just get half of a top cursor arrow and a blank grey screen ,i don't know why.

Photo's in album Furnace and casting.

John
13 October 2016 at 20:29 #260925
MalcB
Participant
@malcb52554
Have you considered using Rocol mould release?

You may also find something from the Foseco Dycote stable that would help you.

Edited By MalcB on 13/10/2016 20:33:38
13 October 2016 at 23:05 #260953
CHARLES lipscombe
Participant
@charleslipscombe16059
Many thanks to everyone that has replied to this thread. I shall now check out Kirksite, Blaysons and Foseco Dynacote.

There are 3 types of mold used for lost wax:

Silicone Rubber – the cheapest but not all foundries will accept these molds due to problems with flexing while injecting the wax. The quality of the castings tends to be lower than from Al/epoxy molds or Aluminium. Life span of the molds is shorter than the other types which is a factor for repeat production. The only choice if you have re-entrant curves in the job.

Aluminium/Epoxy are good, don't suffer from flexing but are more expensive. Probably the easiest to use for complex shapes because they are made by casting around the original pattern.

Aluminium molds show very little of no wear and are the material of choice if possible, but if you have a complex shape you are faced with machining out the cavity so unless you are pretty good with CNC milling (not me I hasten to add!) this is not an option.

The material used in Aluminium/Epoxy molds is definitely metallic Aluminium, not the oxide but I dont know why

All my castings are produced in stainless steel and I don't have the facilities to do this. Also producing ones own waxes is feasible but can be more trouble than it is worth if the waxes distort or get chipped in transit. In my case the foundry is 600 miles away so stuff gets posted back and forwards to the foundry

John Pace's reply opens up a whole new vista! Does anyone know if it is possible to 3D print in wax and produce the patterns in this way?

Chas
13 October 2016 at 23:22 #260955
Michael Gilligan
Participant
@michaelgilligan61133
Posted by Bob Stevenson on 13/10/2016 15:32:17:

Forgive my ignorance, but how is this "lost wax casting" if there is a mo(u)ld that is permanent and split open etc?

.

Bob … I think the moulds in question are being used to mass-produce the waxes for a subsequent 'lost wax' process.

MichaelG.
13 October 2016 at 23:31 #260958
CHARLES lipscombe
Participant
@charleslipscombe16059
Bob … I think the moulds in question are being used to mass-produce the waxes for a subsequent 'lost wax' process.

MichaelG.

This is exactly what is done

Chas
14 October 2016 at 01:13 #260962
AndyP
Participant
@andyp13730
Posted by CHARLES lipscombe on 13/10/2016 23:05:29:

John Pace's reply opens up a whole new vista! Does anyone know if it is possible to 3D print in wax and produce the patterns in this way?

Chas

This is exactly what Adam at **LINK** is doing – stunning detail! I print pla and burn it out but not with that level of detail.

Andy
14 October 2016 at 07:35 #260969
Bob Stevenson
Participant
@bobstevenson13909
Yes, I get it now….thanks to all for putting me straight!

……….It's certainly possible to 'print' wax masters digitally………This is frequently done in the 'defence industry' and if I recall is used to cast bayonets for the Army's current rifle (SA80 derivatives) 50 at a time in a "christmas tree" construction where the printer forms the wax assembly completely automatically and the spraying of the ceramic is then carried out by a robot……

…………Probably not a shed type process,…..although………
14 October 2016 at 17:35 #261107
Brian Oldford
Participant
@brianoldford70365
"Does anyone know if it is possible to 3D print in wax and produce the patterns in this way?"

Although I have yet to do it personally, I've done a bit of research for a project of my own and "lost wax" patterns can be 3D printed using a bio-plastic material known as PLA. There's a bit more info at http://3dtopo.com/lostPLA/

I hope that is helpful.
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