Thread: Machinable Wax Experiments

Originally Posted by Graziano

Hi Ray, that setup is pretty good, I can see the advantages of making your patterns that way, especially for accurate thin walled patterns like tubes and elbows. There's no way you'd easily hand make complex patterns for items like gears without a lot of machining. Is the machinable wax stable over time?, I vaguely remember seeing photos of the stuff shrinking after a few years.

Bob: Without trying to sidetrack this thread (a bad habit of mine)....."Man Junior?", for a second I thought that was a Saxton Hale reference (fictional CEO of MANN corporation). What's the title of the machine rebuilding book you're referring to?.

Mark,

Edward Connelly's 1955 book, Machine Tool Reconditioning. Machine Tool Reconditioning for Machine Tools by Machine Tool Publications

Bob.

Here's the finished test part..







You can see a bit broke away on the center, maybe for one-off patterns I can see it being useful, but I think the real advantage is to be had for checking cnc programs,
and then the actual patterns can be machined out of something a bit more durable. Some kind of plastic perhaps?

The big plus with machinable wax, of course, is you keep the swarf and melt it down for another go...

Regards
Ray

Nice work Josh/Ray. Does/can the cnc move three axes(spellnig?) at once or does it do all the X and Y on one level then step the Z down?

Stuart

Hi Stuart,

Yes it does all three axes at the same time, where it needs to. Interesting to watch, but it does these weird helical lead in tool paths at different places in the program... The finish on the teeth could be better, I think the step-over could be smaller, but, I guess, that's the whole purpose of doing a trial run from machinable wax so the program can be refined.

Regards
Ray

Hi Ray,
Sorry I was typing when you posted your last.
Would you be game to melt the wax out of the mould and then pour? I know its done but I've not seen it done with sand.
Would save a lot of time making the mould if you didnt have to split it to get the pattern out. You also wouldnt have to worry about draw on the pattern etc.
I wonder if the broken piece may have been a little piece of unmelted bag?

Does the cnc keep track of the run time for that part?

Stuart

Hi Stuart,

I must have a go at lost wax casting one day, the procedure would be, make the part out of machinable wax, then use that to make a silicon mould, then make wax parts, could be a different wax if required. Then coat with plaster gunk and build up a thick layer, cure the plaster stuff, melt the wax out and bake the plaster, finally pour the bronze or aluminium, and smash the part out of the mould..

Not sure what the plaster gunk is, or what sort of wax would be suitable, there must be some on-line suppliers, I'm sure it would be easy enough to find.

It's supposed to be good for complex parts with re-entrant shapes and lots of detail.

Regards
Ray

You will find it all here Ray. KerrLab - Jewelry - Home

From memory ( 3 decades ago ) the investment plaster crumbles off in water after the casting process.

BT

That plaster investment casting I have seen needs(?) a vacum chamber to remove the air from the plaster when it is poured around the pattern.

I'd been hoping you could just melt most the wax out of a sand mound(and maybe burn the rest out?) then pour as normal.

I really must get to work on my furance.

Stuart

I think Stewart is on the right track and the chips are as a result of imperfections in the wax mix. The fellows over in Perth gave up on plastic bags and went the path of Pet 2 milk bottle tops - the plastic bottle type. If you look inside the lid there should be a recycle symbol with the number 4. They mix better in the pot and also provide the the colour without additional dye and blue tops being the best in my opinion. Asking family, friends, work mates or a local kindy group will provide ample supplies. Recycling is good and lots want to do it but there aren't convenient opportunities.

BT I'm not sure if you are a having a semi-seniors moment thinking about a CNC machine.
Happy to discuss the pros and cons of a Chinese machine like Ray has - they are good value but there are a few traps if you base your decision on price only.

If anyone is interested in a CNC demo or introduction to CNC I can arrange something for the Perth members. Numbers would have to be limited to six or so at a time as viewing space is limited.

Originally Posted by Stustoys

That plaster investment casting I have seen needs(?) a vacum chamber to remove the air from the plaster when it is poured around the pattern.

I'd been hoping you could just melt most the wax out of a sand mound(and maybe burn the rest out?) then pour as normal.

I really must get to work on my furance.

Stuart

Here is a YouTube vid. Not your typical home shop set up unless you are Ray Gardiner but it does show how it's done. And the casting is bashed out. There is a profusion of clips on YouTube on the subject of lost wax casting.

[ame=http://www.youtube.com/watch?v=1rgfT-PlXqU&feature=related]How does Investment casting work? by www.ops-uk.com - YouTube[/ame]

I hadn't even thought about the expansion of the wax being an issue

Thanks

Stuart

Originally Posted by RayG

or what sort of wax would be suitable, there must be some on-line suppliers, I'm sure it would be easy enough to find.

Regards
Ray

Hi Ray, I believe investment casting wax is actually a low melt point polystyrene. I have a large tin of the stuff originally used for blocking up plastic lenses before CNC milling the surfaces. My stuff melts at about 60 degrees C.

Cheers,
Mark

Originally Posted by Graziano

Hi Ray, I believe investment casting wax is actually a low melt point polystyrene. I have a large tin of the stuff originally used for blocking up plastic lenses before CNC milling the surfaces. My stuff melts at about 60 degrees C.

Cheers,
Mark

HI,
As far as i know you can use nearly any traditional wax.....Lost wax has been done for thousands of years, normally with a clay/straw/dung? (my memory may be hazy on that last one) mix that is fired and the wax is lost in the firing process. Actually they believe that King Arthur pulling the sword from the stone is actually a story based on the casting of bronze swords, and "pulling" the sword from the "stone" (clay)
Making a latex mold of a machined part or hand carving is pretty standard in making sword furniture.

Ewan

My understanding of the process is that the mould is made around the wax, once dry the wax is melted (low temperature) and poured out, then the mould is fired.
Styrene foam is used for investment casting but is basically burnt out by the hot metal (stinks too).
The vacuum is just to get air bubbles out. If you can live with the odd defect, then a vacuum is not essential. I've seen air bubbles removed from mixes just by holding the container the mix is in on a vibrating surface (like a linisher motor). That's usually enough to shake the bubbles out.

Michael