Machinable wax

[Davidh]

Do you have a recipie for machinable wax?

Care to share what you use, its melting point and any neat applications.



I want to make a cast resin nameplate with a detailed logo, raised lettering and logo. So I think using a 60 degree V cutter in wax, pour the resin and then melt out the wax should yield some good detail.



TIA David

[HayTay]

Originally Posted by Davidh Do you have a recipie for machinable wax? Care to share what you use, its melting point and any neat applications.

Check out Overman's Charity Wax - Carving & Modeling Wax Recipes and other cool stuff. You should find some good info to get you started. Here's a direct link to most of the wax recipes and info in PDF.

Don't skip a tour of Gary's site, though, he probably has other cool stuff you may be interested in such as a Wax Injector, Gingery's Lathe, CNC Foam Mill, Gas Fired Crucible Furnace, Gingery's Electric Furnace, & instructions for Making Green Slime. Check it out!

[cbass]

Great link....

Great site!

Thanks,

Carlo

[Davidh]

....many thanks Hay

[therealhood]

i was looking for a way to make machinable wax a while ago...

I am a machine design engineering project manager and so tend to instead of easing into a project jump right in and let er fly. my first part i made was a tiny model of parts from work. these parts are typically 48x48x36 inch castings and have lots of small details. so my first gcode was a circle. the second was a complex multi surface 3D item.

ended up doing this... would like to get some feed back from you guys with what seems like much more time to devote to this than i do and more experience machining in general. I am a newbie and would be interested in knowing what you guys think.

First I got myself a big hunk of parafin wax from an art supply store. $10 bought me a 20lb block

then bought an additive to make wax hard for pillar candles. Stearic Acid (sterine) some places just call it "hardener" $3 gave me about a half cup of the stuff.

I purchased a hot plate from walmart for $12

Had the idea of filling some sort of foam ended up buying foam blocks for keeping cut flowers fresh at walmart 4"x4"x8" box of two blocks cost me like $6

dug around in and came up with an old deep frying pan and a stew pot. free!

went outside (seemed wise) put on the frying pan Tossed in some chunks of wax (harder to cut with a hand saw then you might think). (guess i could have weighed it but im not that kind of guy) i measured it and got an idea of how much was i had cut.

put some water in the bottom frying pan and turned on the hot plate.

the instructions for the steric acid (its made from cow bones) said 2-3 tbs per lb... i experimented and added this... then a second batch twice this .. third batch 4x ... the wax got stiffer and stiffer with each batch and i never reached a point at which the wax became chrystaline as i had been warned would happen on candle forums.

the wax i got was of a nice quality stiff and hard but quite what i is with machineable wax and the mould i used (bread pan) shrunk down in the middle almost half the size of it was when molten. strange thing i noticed and will follow up on next time is i used a piece of aluminium foil to cover the pans... on one pan the foil touched the surface of the molten wax. the wax in this area did not contract as much as it did in the other area of the same mould something thermal happening i would suspect.

On a lark i filled on of the bread pans with a block of the flower foam and held it down with a couple of drill rods on top... filled it with molten wax (the 4x stuff) and was surprised to see the wax sink immediatly into the block as if i was pouring water. when it cooled the block seemed normal and i have cut into it to check for voids which i thought would be all over the place and they were but only a millimeter or so in diameter every 5-10mm from each other. i am guessing this has to do with air in the block.

the block machines nice doesnt smell and holds very fine lines. I didnt have much time to play with this because it exposed something in the ways of my el'cheapo CNC so i have to take it apart and fiddle with the dovetail ways seems there is a rough spot on it and my "square" is really more of a parallelagram.

my next try is to heat the wax in the bread pan and lower the block into this fluid in a first attempt to remove the small voids. not having a vacuum pump ill give this a shot next.

let me know if any of you give this a try and your results.

i also plan on melting in polyethelene straws in the wax mixture to make it more dense.

see this is why i do things outside... my girlfriend would kill me

oh one thing i dont know is if this stuff can be remelted... it looks like fuzzy green dust and since it was so cheap it got sucked into my shopvac and now is someplace in a dump in jersey

[cbass]

therealhood,

Nice reporting.

One thing that machineable wax companies have told me is that the re-melting and cooling of large pieces of wax can make or break your final result. They suggest casting the hot liquid wax into a mold made of aluminum (not sure why this in particular; thermal characteristics?). Then covering the whole mold with a plywood box (open at the bottom) to keep the mass from cooling too quickly. This will help prevent cracks and/or large voids from occuring in the middle of the block.

Keeps us updated!

Carlo

[FieroNate]

If you are casting wax, and need it in sheets, might I suggest using glass plates as your upper and lowersurfaces and surround them with some high heat material like wood or aluminum. The shrinkage is just the natural shrinkage of the wax, the center shrinks because it stays wamrest and thus softest longest.

When you cast anything you will see similar problems. Metals this is particularly a problem. To avoid this with metals often times they will determine where shrinkage will occur and place a tube with an insulator on it, so as the part cools there is a resivour of liquid material to be sucked into the contraction space.

For wax you'd probably need three holes in it, a pour hole, a vent hole and a resivour hole. With glas this would give you an excelent and uniform panel.

I'm still playing around trying to find the right mixture for making my own machining wax, but this is what I plan to do when I'm done.

[FieroNate]

More to add to the knowledge base:

I have been experimeting more with HDPE and LDPE here is what I've found
I can heat a mixture of LDPE and HDPE in wax up to almost 580 F (severe caution is advised). When I do this its a small amount of wax (about 1/4 lbs) that I used for experimenting, I also keep the lid to the container near by (more on that below).

I have noticed that in mixing and trying to disolve the HDPE and LDPE in various batches that the paraffin steams quite a bit for a while then stops. It has come to my attention (and is confirmed after discussion with a polymer chemist friend of mine), that the parraffin is being refined as it "steams" what is actually happening is the low grade small molecule paraffins are vaporizing and turning into something that looks like steam. For any given paraffin there comes a point when I've boiled off all the low grade material. The result is quite interesting, a parafin that more closely resembles what I think migt be a smaller crystaline structure.

To further investigate this I decided to repeat the experiment with better controls, mainly pure paraffin. This time I used much less paraffin and attempted to boil it. Interestingly enough around 550 F the pure paraffin steamed like crazy, not long after that it suddenly burst into flames (this is where the lid comes in). I quickly placed the lid on the container and removed it from the heat source, it smoked like crazy and actually changed colors slightly (could have been some of the die that was left in the pan from previous experiments). SO... I have to repeat this experiment with an electric range, since my first experiments used only an electric range and later ones a propane camping stove. My theory is that the vapors of paraffin (which are flamable) found the open flame and caused the chain reaction. Use of a non combustion heat source will verify this. In any case it proves to me that refining the paraffin is a good step toward making a more usable wax. If I make larger batches I plan to basically make a still like would b used for alcohol, except I'm going to seal the mixing vat and purge it with argon welding gas to make sure no combustion is possible. I suspect the steam will be condensable into a low grade paraffin wax (no idea what i'll do with it).

Another idea I have is to mix in some soap to see if I can somehow lengthen the molecules of paraffin. A third idea is to mix in some activated charcoal to the mix,see if I can increase the length of the paraffin molecules (see the wikipedia entry on Paraffin).

I have also found through wikipedia that there are several types of waxes, including ultra low density Polyethylene, ultra low density polypropylene etc... I am trying to find a source of these, but I suspect that they will cost a lot, hence defeating the purpose of home made wax.

The interesting thing about LDPE is that it changes the way the wax molecules form, and that is the key to waxes. So I'm looking at a variety of household items to mix into the wax. Additionally I will look into bee's wax and see if it to vaporizes, I think using a strong base or acid can make or break the chains (have to confirm with a friend of mine). In any case its soon time to start better mix control, so I need to get a small scale of some sort. I also plan to try the rins on soda cans and water bottles (the PE plastic that holds them together seems proming). I'm thinking mix them with some paraffine and beeswax and see what I get.

One last thing add die last to your mixes since it can chemically break down at high temperatures.

of note the latest batches of refined PE and paraffin wax had some cooling issues. I allowed them to room cool but got the stuck in their mold, so I put them in the freezer which shrunk them and released them, but upon warming up to room temperature cracked them. It appears what happened is a difference in crystaline structure caused a thermal crack in them. So I'm trying to trace the problem down and find out why. In the mean time I've found real machinist wax at http://www.machinablewax.com/ the price seems to be pretty good, under 100 lbs the price is about $4.00/lbs which isn't bad. I can't imagine making anything for less then about $2.50/lbs, and for the hassle I'm not sure if its worth it.

Does anyone have an experience using machining wax for lost wax casting patterns? I'vr seen there are various grades of waxes and was curious what the differences were.

[FieroNate]

Just thought I'd update, I have made more headway with wax forumulas, quite interesting actually. I repeated the above experiment with a a few variations on the prefered formula. I have found that 7.75 parts wax to 1 part polyethylene painter's drop cloth works well (the clear kind of plastic). I have also found that the oil based color dies used in candle making should not be added until AFTER the plastic is added. Adding it first causes the plastic to not dissolve properly.

I am trying to locate a viscosometer to measure the viscosity of the plastic/wax mix at temperature. The reason for this is that to much plastic makes a higher viscosity mix with the consistancy of pankake syrup. I fear that for lost wax process this is to thick to properly run out of the mold. SO I will try to get some readings on the viscosity at a given temperature and rate the wax based on that as well.

Here is my general reccomendation for wax mixes, note though that I used unrefined low grade paraffin bought at craft stores. This means I have not evaporated the wax "steam" which is the low grade wax, instead I have kept the melt temperature below 400 F (around 350 is my normal prefered temp). I advise caution at these temperatures as splashed wax will instantly burn the skin and eyes (saftey gear recommended). Additionally above 400 F pure Paraffin is flamable/combustable. As stated in my previous post I have had some burn. I am pretty sure however it was due to the fact that my heat source is an open source rather then hot plate. So I would say its ok to use a hot plate above 400 F but be very careful as I place no garantees on it. A tight sealing lid for the container should be sufficient to put any fire out. I also recommend not doing this in the kitchen but in a well vented open area, as it will avoid filling the area with fumes and any fire hazard can more easily be contained.
Also keep a good powder fire extringuishe around (or a gas type, but avoid a liquid type as liquid and hot wax are not a good combination).

Next I will try some high grade wax soon though. Note that all measurements are by weight not volume (this does matter), Additionally I used painters plastic drop clothes 0.7 mil thick (1 mil would also work). To more readily dissolve them I take the sheet and twist it into a rope and cut 1/8" slices off the rope with a good pair of scissors (Cutco brand works great for this). The result is a thin plastic strips that resemble the fake grass used for easter (which might be a good option for pre cut polyethylene, IF it is in fact made of polyethylene). I will try a blender soon to make it powdered, however I have yet to locate a Blendtec blender (www.willitblend.com they blend almost anything its kinda scary).

For machining I recommend a higher plastic content as it delivers good hardness and a bit of flexibility, without sacraficing edge sharpness: mix 7.5 parts paraffin candle wax with 1 part Polyethylene sheet

For a bit harder wax try 8-8.5 parts wax with 1 part Polyethylene sheet

For a more flexible wax try 6-6.5 parts wax with 1 part Polyethylene sheet

For a durable wax that has less of a waxy feel, try 6.5 parts wax, 1 part polyetheylene sheet and 0.5-1 part low temp hot glue sticks (A.C. Moore Craft store brand melts at 230 degrees F and easily dissolves) the downside of this wax is it doesn't hold an edge quite as well but would be great as a prototyping wax as its reusable and flexible to a degree. However I wouldn't recommend burning this wax as a cande.

For even more flexibility (but less tensile strength) try the following:
7 parts wax, 1.5 part hot glue, 0 parts plastic. It produces a rather unique plastic thats extremely flexible.

Also of note is that none of this batch produced any cracking on cooling as previous low Polyethylene content batches have. I even tried feezing the waxes and then warming them in my hand (How I cracked a different batch) and these seem pretty stable. They do however contract quite a bit in the freezer, which I will be using to see how castings might shrink.

Now for something new: Molds!@!

I have been experimenting with low cost molding techniques to make billet wax. The cheapest I have found is duct tape lined cardboard boxes. I have tried the metal foil duct tape to seal the corners of the box (alternatively 3M trim adhesive spray would work to glue heavy duty aluminum foil to the cardboard and then use the tape to tape up any seams. It surprised me because I expected it to leak through and melt the adhesive, but all I did was press the seams as flat as possible and had no leaks. One thing that is important is that I poured the wax at about 230-260 F rather then the 350 F mix temperature, this keeps my mold boxes from being damaged. For sample pours I use bead storage containers (also found at AC Moore crafts) they look like stackable petri dishes found in my high school bio lab. The main difference is that the bottom of one dish is the lid for the next etc... I have found that these work for pouring paraffin, but I have also found that to high a pour temperature puts a hole in them (I suspect above 240 F is to high).

More to follow.

[FieroNate]

Forgot to mention, I tried Activated Charcoal, its a no go but makes a nice black color wax. The idea was that it will chemically change the low grade wax into high grade but it did not do that. So for now stick with my previous post.

[dr.rehab]

Has anyone tried another molding material other than aluminum?
I'm rather curious as to how well the new silicon baking pans would work as a molding item?

[guru_florida]

Great thread! Keep up the good work!