[HuFlungDung]

This thread reads like my experience with machinable wax. Its a royal PITA

A cam program with a good simulation beats the pants off of machining wax any day, IMO. With all the fuss that is required to make a wax billet, it in itself becomes too valuable to screw up.

I wonder if wax will cold flow under pressure? Maybe a press could squeeze wax chips together enough to make a machinable puck without the fuss of melting, etc? Anyone tried it?

If a wax model was the desired product, that is a different matter, so no offense intended to those who are using wax.

[charper]

I am interested in wax molds in order to cast platics into like those from www.smooth-on.com. So mold making is my thing. Also looking to do some lost wax casting with ceramics in the kiln. So, unless I am missing something, I need the wax. My models I sacrafice in pnk styrofoam which I have aplenty

[cbass]

Hu,

Good idea about pressing, except you will end up with air pockets. Ok for proofing a program, but not for taking an impression.

I'm in a similar boat to Charper. I will be melting the wax away after I cast around it (hopefully avoiding the need for multiple-part molds .

I don't think it needs to be a PITA. We just need to get a system down. Think of the money saved, even with all the time involved...

Carlo

[HuFlungDung]

Maybe pressing the wax chips in a heated aluminum mold would work better, to get a better bonding effect. I'm thinking more about a way to reduce the insanely long cooling off period whose only benefit is to reduce shrinkage.

Heat the mold, put the wax in, press on, and then cool it off (with a water jacket around the mold), or something like that. When cold, release the press. I'm talking about a simple hydraulic jack type of press.

[Geof]

...I'm in a similar boat to Charper. I will be melting the wax away after I cast around it (hopefully avoiding the need for multiple-part molds ....

Before you get yourself deeply involved it may be worthwhile figuring out how much thermal expansion you get with the wax before it melts; the shrinkage you see on cooling is partly reflected as expansion on heating. It would be annoying to say the least if you wax pattern shattered your ceramic coating when you heated it enough to get the wax out.

[cbass]

I hadn't even thought that far ahead

I gues that opens a whole new ball of wax (pardon the pun).

The aproach may very well be to work backwards. Find a wax that doesn't expand too much (ie. a wax made for the lost wax process), then see if it machines.

Carlo

[MrWild]

If shrinkage and resulatant crater is the only problem when cooled quickly, you could easily get around this problem and still cool the wax fast. The problem is caused by the center retaining heat and remaining n a liquid state as the edges cool. Because the depth starts high due to the expansion of the wax, the edges cool in the high level. As the wax cools and shrinks, less wax is available to keep the level up. What if you cooled the center?

A peltier(sp?) cooler the center of the pan rests on will cool/chill the center quickly. It may actually form a mound if cooled too quickly. With some experimentation I believe strongly that the crater problem can be addressed without long cooling periods needed at all.

[Geof]

..The aproach may very well be to work backwards. Find a wax that doesn't expand too much (ie. a wax made for the lost wax process), then see if it machines. Carlo

Just use regular lost wax wax but set your machines up in a deep freeze and wear warm clothing.

[cbass]

Just use regular lost wax wax but set your machines up in a deep freeze and wear warm clothing.

Not a bad idea LOL.

Actually, cooling the wax before machining may help if it proves too sticky/gummy at room temperatures.

[Geof]

I am interested in wax molds in order to cast platics into.....

How experimental do you want to be? I have often thought that sawdust reinforced wax might be a good material for making molds for plastic; one advantage would be you already have the mold release agent as part of the mold. I figured take ordinary candle wax that is quite low melting and stir in as much fine sawdust as possible then just let it set. My feeling is that there would be less shrinkage than pure wax and the strength should be much greater. The type of surface finish possible when machined would probably depend on how fine the sawdust was.

[HayTay]

How experimental do you want to be? I have often thought that sawdust reinforced wax might be a good material for making molds for plastic; one advantage would be you already have the mold release agent as part of the mold.

Great idea, Geof, I think MDF dust would make an excellent filler. The correct wood/wax ratio would have to be ascertained when using the material for lost wax casting so that it would all get melted/burned out before casting. Though, for goofing around, testing, and prototyping I'd bet a fairly high wood/wax mix could be used. You'd need just enough wax to keep everything together during the machining process.

Back about 10 years ago while I was working at a custom injection molding operation they were testing HDPE/PP coupled with a wood filler. The molded parts looked and felt really nifty. The smell, though, would make you nauseous, even weeks after being molded. These parts were for a company that made office furniture. I couldn't imagine being trapped in an office with the wood filled plastic parts for any length of time. I guess they couldn't either as the project fizzled out before the parts ever made it to market.

[HayTay]

Has anyone thought of, or tried.... drum roll, please... CRAYONS?

I was browsing through the local 'Mighty Dollar' store while my wife was picking out some birthday cards and came across a whole display rack loaded down with packs of 64 crayons for, you guessed it, $1.00 US. The pack, I'm guessing, weighed maybe a half pound. Not bad for a dollar.

Upon further inspection, the crayons seemed to be fairly hard. Anyone who has used crayons know that they run the whole gamut from soft (turn pliable with just the heat from your hand) to extremely hard (after some effort they break with an audible 'SNAP').

Melting all of the crayons together would, no doubt, produce an "ugly" colored block, but would it be suitable for machining? Any thoughts???

If crayons turned out to be a viable solution, someone that worked for a school (hint, hint, nudge, nudge, CHARPER) could probably start a 'Crayon Recycling Program' in the lower grades and obtain the wax for almost free. The only problem is getting volunteers to "peel" all of the crayons before they're melted. Heating or soaking the crayons in water would probably expedite the wrapper removal process. Heating would have the added benefit of kick starting the melting process before the crayons are mixed with any hardeners or fillers.

I've seen crayons available in bulk packs with as many as 3000 pieces, yielding crayons at around 3.5 cents a piece. The 'Mighty Dollar' is still less expensive at approx. 1.6 cents per crayon, though. Suppliers to educational institutions may also offer other incentives, packaging, or discounts for large purchases that aren't available to the public.

Other types of crayons are also available. Several that come to mind are marking crayons and lumber crayons. Additionally, my father used to work in a steel mill and he used marking sticks that melted at specific temperatures to write on the steel. I don't know if they are classified as crayons, or how much they cost, but some of them were so hard (high melt temp.) that when broken they crumbled into chips. These wouldn't be good for machining but the lower temp. ones might be. Just a few of my thoughts, for now.

[ViperTX]

so crayons are made of paraffin.....machineable wax appears to be a synthetic wax.....paraffin can be burned out in lost wax castings....not sure about the synthetic wax....

[HayTay]

As a bonus, crayons are also non-toxic.

DixonUSA Prang Wax Crayons MSDS

Binney & Smith Crayola Crayons MSDS

Speaking of crayons, here's a funny story from my childhood. When I was a kid, my sister and I had to make sure that we put away our crayons ASAP when we were finished using them. We also had to keep our crayon stashes in a couple of old metal lunch boxes complete with latch. We colored a lot and the lunchboxes were usually full of a wide variety of crayon colors and sizes. Our dog Smokey, half Husky & half German Shepherd in case anyone is interested, was the reason we couldn't leave the crayons laying about. Smokey just loved to eat them, color or brand didn't seem to make any difference. Losing a bunch of used, stubby, warped crayons to Smokey wasn't too bad, but the unopened box of 64 Crayola Crayons with sharpener and 'NEW' colors, left under the Christmas Tree, was another story.

One of the interesting side effects of Smokey's crayon eating was that she used to crap in Technicolor. No kidding, there were all kinds of colorful 'lawn sculptures' in our yard after a crayon eating frenzy! Nothing like a little extra color for the Holidays (Christmas, New Years, Easter, St. Patrick's Day, Fourth of July, etc., etc.)

There was one plus, however, it made it easy to locate the colorful piles for disposal or avoid the 'land mines' when playing in the yard.

[charper]

you guys scare me
I LOVE IT!!!!
crayons... It would make a great experiment to try the crayons with varying levels of PE film to get a great consistency..but only after the machineable wax success because I

still haven't made the machinable wax...I need to buy a small stove, my oven isn't getting hot enough and it made me so frustrated, I just quit trying. I have been such a slacker these last 6 weeks.

[hardwic]

Just wondering how much success has been had with this. I worry that wax flash point is 230F and polyethylene mealting point is 270-275F. People have been talking upto 400F.

How often has this been done and without accident?

[charper]

OK. I am at it again. Pulled out the stuff after months of gathering dust and I still can't get the damn PE to melt down with the Parrafin wax. I am just going to bring the setup home and try it on my kitchen stove because the crock pot just won't get hot enough and I still haven't bought a hot plate from Walmart. But since I am trying to make a soap mold project for a Mother's day end of the year bash. HELP AGAIN! Maybe I am in over my head. Do you suggest heating via electric or gas? What will get me hot enough?

[Metal Head]

This process works for me. This applies to the blue stuff that we use so it may or may not work with other types of machinable wax.

First step is to download the MSDS sheets so that you understand what you are dealing with. Google "machinable wax MSDS" and you'll find several sources.

1. I only recycle the big pieces. The chips and dust are usually contaminated with other stuff that has been in the chip tray like metal, plastic, wood, etc.
2. Put the blocks into a Teflon coated brownie tin.
3. Put the tin in an oven for 30 minutes at 350F degrees.
4. Take the tin with the melted wax out to cool. As others have noted here, a big part of being successful with this is to cool the wax SLOWLY. I usually leave it set for 8+ hours before doing anything with it. How long this takes will also depend on how thick the wax slab is.
5. After the block has cooled, it should shrink away from the sides of the brownie tin by about 1/4" and you should be able to just turn it over and the slab should fall out on the table top.
6. You can use a band saw to cut the slab into smaller blocks. A planer works well if you want to smooth out the top and bottom sides.

About the crayon thing... you may find that the material chips more than you would like, when you try to machine it.

Hope this is helpful.

[cbass]

Hey Metal Head

Thanks for sharing...

Carlo

[FieroNate]

Just was experimenting around with making my own wax. Tried a few things. Using Paraffin wax as a base I tried adding got glue sticks.. this kind of worked dissolvability was an issue. I also found that Sears sells PE drop cloths for painting at about 2 bucks a lbs. It is marked as #4 recyclable which is Polyethelyne. I took the "log" of drop cloth and sliced it with a serated knife. Worked fairly well. I then melted the wax, added the PE and the die color (blue in this case).

One thing I did that most people probbaly did not is I experimented with HDPE and PE and Hot Glue. I also experimented with temperatures. According to the MSDS the flash point of Pariffin is above 450 F in open air and the Flash point of HDPE and PE is also above 450 F (someone check that to confirm, don't take my word for it). In any case I used a Digital Multimeter from Sears with a thermal Couple on it to measure temperature more exactly. I also used a stainless bottomed cooking pan. Worked fairly well took it right up to about 460 F (the self ignition temperature of these materials are way above 450 F so no worries there provided I don't accidentally drop a flame into them). I was able to melt most of the hot glue (I only added one small stick to about 1.5 shot glasses worth of Paraffin beads). I also added about half a shot glass of PE to it to see what happened. Turned out quite well. The wax is slightly flexible when cool it can be broken still but it gives a bit when you flex it and also cuts well (Haven't tried milling it yet).

I also tried half a shot glass of HDPE in a different batch couldn't get it to melt so I removed it. This batch is significantly more brittle then the one with PE and Hot Glue in it. I then mixed up a final batch with only PE in it this too is a bit more brittle then I want but probably better for machining.

Moral of the story dont' be affraid to heat up to 450 F with these but make sure you are very very careful. Wear a face mask and some protectant clothing. Also have a fire extinguisher near by just in case. And I recommend doing it where the fumes won't be a problem.

The hot glue addition is going to be a fun experiment.

Here is the hot glue I used (from Walmart)

http://www.adhesivetech.com/industri.../adhesives.cfm

Even melted it is still a bit more viscous then I'd like. It also raises the solidous temperature of the wax. At 200 F the PE Wax started to congeal. I guess it really depends on your application. I'm still looking into what temperature they cook the wax out of lost wax casting molds.