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LOST WAX CASTING

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CHARLES lipscombe12/10/2016 22:54:03
118 forum posts
8 photos

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

Chris Evans 613/10/2016 07:44:28
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1661 forum posts

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.

KWIL13/10/2016 10:09:16
3239 forum posts
63 photos

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?

MW13/10/2016 10:18:51
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2051 forum posts
51 photos

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

steamdave13/10/2016 11:25:02
438 forum posts
33 photos

Would the mould maker tell you what coating he is using?

Dave
The Emerald Isle

Senior Yates13/10/2016 11:39:48
34 forum posts
1 photos

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

Circlip13/10/2016 11:44:31
1104 forum posts

So re paint the area with an Epoxy resin.

Regards Ian.

John Pace13/10/2016 13:29:38
181 forum posts
171 photos

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

Bob Stevenson13/10/2016 15:32:17
397 forum posts
6 photos

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

John Pace13/10/2016 19:24:35
181 forum posts
171 photos


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

MW13/10/2016 19:47:23
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2051 forum posts
51 photos

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

John Pace13/10/2016 20:04:47
181 forum posts
171 photos

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

MalcB13/10/2016 20:29:04
257 forum posts
31 photos

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

CHARLES lipscombe13/10/2016 23:05:29
118 forum posts
8 photos

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

Michael Gilligan13/10/2016 23:22:00
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15723 forum posts
687 photos
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.

CHARLES lipscombe13/10/2016 23:31:34
118 forum posts
8 photos

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

AndyP14/10/2016 01:13:36
188 forum posts
30 photos
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

Bob Stevenson14/10/2016 07:35:01
397 forum posts
6 photos

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.........

Brian Oldford14/10/2016 17:35:42
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653 forum posts
15 photos

"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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