Dear Open3DP readers and members of the Maker Community,

This is a question that was send to us recently from a local high school and we are reaching out to you (the reader community) for a better answer.

cncwax

 

{ Image from CNCZone.com}

Question:

“I have been working with #### at ### HS with Model making and we have been thinking how great it would be to have a material we could cut with a cnc and then be able to recycle it, forming it back into a block that could be cut into another model. Schools have zero budget for materials and so the hope is to be able to recycle much like they now recycle with machinists wax. For fast cutting on  small cnc the machinists wax is so dense you have to go to slow.. The density of 2lb per cubic foot extruded styrene foam or 10lb polyurethane is nice but not recyclable.

You have so many amazing materials. Can you imagine a combination of materials that could first create the block and then be able to grind or reduce back into components that could then become another block?    Thanks…###”

Our response:

“###, I would experiment by making your own cutting wax.   I would add a filler to standard paraffin to reduce the density (making cutting possible).  Also, you should likely add *Stearic acid to your wax as it will raise the melting temperature slightly and make it harder (and less gummy).  Basically any material could work but something that doesn’t melt in the temperature range of paraffin (thus allowing you to remelt the wax to reform your machining blocks).   Adding fillers will allow you to adjust the density and material properties of your wax.     You might try something as simple as wood flour (finely powdered wood dust or dry clay body).   Please keep me posted. “

Related Link:

http://www.myheap.com/chapter-1-materials/overman-charity-waxes.html

If you have a better suggestion, please respond via comments.   Thank you for your time.

24 Comments on Community Help Please — DIY Machining Wax (from a high school)

  1. Zack says:

    A possible option is to try to make a wax foam. This would reduce the density of the block and should increase your cutting speeds, and increase the amount of blocks you could have. However, because you are introducing bubbles into your media this will probably reduce the strength of of your blocks, and your surface texture should be interesting. Note when you are working with molten wax it will be hot and could burn you so use the proper precautions for safety. A couple of ways that you could try to introduce the bubbles could be by whipping the molten wax with a paint mixer and then cooling it rapidly to trap the bubbles. Problems with this method is that you will probably not achieve a uniform foam. Another potential way to do this would be to use a food industry style whipped cream dispenser to produce the foam into a cold mold to form the block. This should create a more uniform foam however, the whipped cream dispenser may not work properly with a heated liquid or even with molten wax. Pressure is also a concern when using the whipped cream dispenser because they are pressurized with CO2 cartridges and introducing a hot liquid to a pressurized gas using the Ideal Gas law because the volume cannot expand inside the container the pressure must increase with the increase in temperature. Proper precautions should be taken around pressurized objects.
    Hope this is useful, …. Zack

  2. Zack says:

    A possible option is to try to make a wax foam. This would reduce the density of the block and should increase your cutting speeds, and increase the amount of blocks you could have. However, because you are introducing bubbles into your media this will probably reduce the strength of of your blocks, and your surface texture should be interesting. Note when you are working with molten wax it will be hot and could burn you so use the proper precautions for safety. A couple of ways that you could try to introduce the bubbles could be by whipping the molten wax with a paint mixer and then cooling it rapidly to trap the bubbles. Problems with this method is that you will probably not achieve a uniform foam. Another potential way to do this would be to use a food industry style whipped cream dispenser to produce the foam into a cold mold to form the block. This should create a more uniform foam however, the whipped cream dispenser may not work properly with a heated liquid or even with molten wax. Pressure is also a concern when using the whipped cream dispenser because they are pressurized with CO2 cartridges and introducing a hot liquid to a pressurized gas using the Ideal Gas law because the volume cannot expand inside the container the pressure must increase with the increase in temperature. Proper precautions should be taken around pressurized objects.
    Hope this is useful, …. Zack

  3. Stephan Buchholz says:

    I had read an article on the about making machinist wax. Can’t remember where but this link is similar to what I’d seen

    http://daleshort.cc/doku.php?id=pages:machwax

  4. Stephan Buchholz says:

    I had read an article on the about making machinist wax. Can’t remember where but this link is similar to what I’d seen

    http://daleshort.cc/doku.php?id=pages:machwax

  5. Stephan Buchholz says:

    Also try here

    http://repraplogphase.blogspot.....e-wax.html

    I’m pretty sure this was what I’d read

  6. Stephan Buchholz says:

    Also try here

    http://repraplogphase.blogspot.....e-wax.html

    I’m pretty sure this was what I’d read

  7. Leo Dearden says:

    If you want to make foamed wax you could try foaming with a sudden pressure drop. To get a good even foam you need to dissolve something evenly in your liquid wax at one pressure and then drop the pressure suddenly.

    One advantage of this is that as your volatile blowing agent boils it will cool the wax substantially, so you may be able to get that to solidify the wax.

    Try using something non-polar that you can dissolve in molten wax at 2atm, but that boils below the melting point of wax at 1am. http://www.trimen.pl/witek/cal.....zenie.html may be helpful for working this out. IIRC, one machinists wax formulation melted at 116C, so toluine which boils at 140C at 2atm and 110C at 1 atm would be a good candidate.

    You can use a pressure cooker from a yard sale or similar. Put some wax, a few ball bearings (as stirrers) and a _little_ of your chosen blowing agent in the cooker. Heat it in an oil bath containing a thermometer to avoid over heating. Do the whole experiment in a fume cupboard or outside, and have a fire extingusher handy. When the wax is melted, take it out of the bath and turn off the heat. Swirl it around gently for a while to mix it thoroughly. When it starts to go a bit sludgy, take the weight of the pressure cooker and wait for it to cool, standing well back. If the temperature and type and quantity of blowing agent, and the wax formulation are all correct, you’ll have wax foam. If not, then you need to adjust.

    This is broadly how some PE foams are made, except CO2 at high pressure and room temperature is used instead of a medium weight hydrocarbon at moderate pressure and elevated temperature.

    I haven’t tried any of this, so I don’t know if it will work. You do it entirely at your own risk 🙂 and it’s up to you to take suitable precautions. There is a small risk that it will explode, though I don’t expect it to. YMMV.

  8. Leo Dearden says:

    If you want to make foamed wax you could try foaming with a sudden pressure drop. To get a good even foam you need to dissolve something evenly in your liquid wax at one pressure and then drop the pressure suddenly.

    One advantage of this is that as your volatile blowing agent boils it will cool the wax substantially, so you may be able to get that to solidify the wax.

    Try using something non-polar that you can dissolve in molten wax at 2atm, but that boils below the melting point of wax at 1am. http://www.trimen.pl/witek/cal.....zenie.html may be helpful for working this out. IIRC, one machinists wax formulation melted at 116C, so toluine which boils at 140C at 2atm and 110C at 1 atm would be a good candidate.

    You can use a pressure cooker from a yard sale or similar. Put some wax, a few ball bearings (as stirrers) and a _little_ of your chosen blowing agent in the cooker. Heat it in an oil bath containing a thermometer to avoid over heating. Do the whole experiment in a fume cupboard or outside, and have a fire extingusher handy. When the wax is melted, take it out of the bath and turn off the heat. Swirl it around gently for a while to mix it thoroughly. When it starts to go a bit sludgy, take the weight of the pressure cooker and wait for it to cool, standing well back. If the temperature and type and quantity of blowing agent, and the wax formulation are all correct, you’ll have wax foam. If not, then you need to adjust.

    This is broadly how some PE foams are made, except CO2 at high pressure and room temperature is used instead of a medium weight hydrocarbon at moderate pressure and elevated temperature.

    I haven’t tried any of this, so I don’t know if it will work. You do it entirely at your own risk 🙂 and it’s up to you to take suitable precautions. There is a small risk that it will explode, though I don’t expect it to. YMMV.

  9. Collin says:

    Slow to comment, but I came across similar recipes to those posted above:

    http://www.machinistblog.com/f.....eable-wax/
    http://www.machinistblog.com/m.....nable-wax/

  10. Collin says:

    Slow to comment, but I came across similar recipes to those posted above:

    http://www.machinistblog.com/f.....eable-wax/
    http://www.machinistblog.com/m.....nable-wax/

  11. Austin Schneider says:

    Can’t “Plaster of Paris” be reconstituted? It may not be that strong, but once formed, you could pulverize it back into a powder and formed back into blocks for reuse. I’m not sure if there is a limit on how many times you can rehydrate that type of material, but it’s cheap and it seems you could do this process at least several times per batch of powder.

    {Austin, sorry Plaster of Paris changes chemical composition when it sets. Thus, simply crushing it for reuse is not likely to work. However, if set plaster or gypsum is heated above 200°C, then calcium sulfate anhydrite is formed, which will also re-form as gypsum if mixed with water.

    Ref: http://en.wikipedia.org/wiki/Plaster

    Great Idea! …Open3dp

  12. Austin Schneider says:

    Can’t “Plaster of Paris” be reconstituted? It may not be that strong, but once formed, you could pulverize it back into a powder and formed back into blocks for reuse. I’m not sure if there is a limit on how many times you can rehydrate that type of material, but it’s cheap and it seems you could do this process at least several times per batch of powder.

    {Austin, sorry Plaster of Paris changes chemical composition when it sets. Thus, simply crushing it for reuse is not likely to work. However, if set plaster or gypsum is heated above 200°C, then calcium sulfate anhydrite is formed, which will also re-form as gypsum if mixed with water.

    Ref: http://en.wikipedia.org/wiki/Plaster

    Great Idea! …Open3dp

  13. kc says:

    You can reuse machinable wax scraps. Just find a baking tin the right size to pour it into after melting in a double boiler.

  14. kc says:

    You can reuse machinable wax scraps. Just find a baking tin the right size to pour it into after melting in a double boiler.

  15. I think the key thing here is that the teachers need something that can be re-formed almost effortlessly — teaching high-school kids is enough work already without having to maintain a custom-built wax-foaming apparatus 🙂

    I think the original idea of parafin (cheap) with a filler (to make it cut more easily, and quickly) is the right way to go. My suggestions for fillers are:

    1) Rice crispies. Seriously. They’re cheap, and available, and won’t melt or dissolve in the wax as it’s re-melted in an oven at 200 deg. Just make sure the dimensions of the smallest detail of the part is greater than 3x the dimension of a rice crispy

    2) Puffed millet, smaller puffed grains. These are also cheap, and should be available if you search around. They will have the same benefits as above, but will let you mill smaller objects.

    3) Fine sawdust, preferably fir, pine, or ideally balsa. Similar to above, but even smaller particle size, and super-easy to find.

    4) Polyisocyanurate or Polyeurethane foam particles or dust. If you have access to this stuff (from cutoffs from housing insulation or from modeling foams like Renshape) it’s amazing for it’s high temperature resistance, so melting, or softening shouldn’t be a problem like with polystyrene foams.

    Other than that, try any other particulate material with a high melting point relative to the wax, a low density, and a low strength.

  16. I think the key thing here is that the teachers need something that can be re-formed almost effortlessly — teaching high-school kids is enough work already without having to maintain a custom-built wax-foaming apparatus 🙂

    I think the original idea of parafin (cheap) with a filler (to make it cut more easily, and quickly) is the right way to go. My suggestions for fillers are:

    1) Rice crispies. Seriously. They’re cheap, and available, and won’t melt or dissolve in the wax as it’s re-melted in an oven at 200 deg. Just make sure the dimensions of the smallest detail of the part is greater than 3x the dimension of a rice crispy

    2) Puffed millet, smaller puffed grains. These are also cheap, and should be available if you search around. They will have the same benefits as above, but will let you mill smaller objects.

    3) Fine sawdust, preferably fir, pine, or ideally balsa. Similar to above, but even smaller particle size, and super-easy to find.

    4) Polyisocyanurate or Polyeurethane foam particles or dust. If you have access to this stuff (from cutoffs from housing insulation or from modeling foams like Renshape) it’s amazing for it’s high temperature resistance, so melting, or softening shouldn’t be a problem like with polystyrene foams.

    Other than that, try any other particulate material with a high melting point relative to the wax, a low density, and a low strength.

  17. Dr Atomic says:

    I too lecture (Mech), therefore I know your pain in trying to obtain suitable resources at almost zero cost.. I’m uk btw.

    I believe the question was machinable wax for cnc’s. Foams are no good!. Also the filler needs to be non-abrasive for good tool life and surface finish.

    After a few months R&D. trials, and tests I have formulated a reasonable equivalent to TryCut (commercial MWax). However, there are two routes you may take to get good results (application of use not detailed above – only small scale cnc work).

    Disclaimer: Be smart !! Be safe, this is hot work, which can and will burst into flames without good temp control. Even though this is very safe if precautions are taken care of properly. However, as with everything its at your own risk.

    Methods: (All waxes should be refined through regrinding and re-melting at least once!)

    1. Simple: 70% Paraffin wax (un blended), 30% HDPE (recycle 2 here in uk), or LDPE (recycle 4 in uk) heat wax until it reaches the melting point of the polymer +10ºc. Slowly add polymer in small amounts and allow to coagulate into molten mass, then add more.

    Stir only once and a while (be patient), it takes time for the polymer, to co-polymer with the wax. Hours depending on batch size. Try and avoid air getting trapped, as the viscosity is thick when molten.

    Depending on the molecular weight of the polymer added the properties are roughly as follows. HDPE = Harder, more brittle, LDPE = Softer, some malleability. Small delicate stuff use LDPE, Larger more robust components HDPE.

    2. Technical: Due to its nature, the process of manufacture differs. Stuff needs to be done in order at particular temps. However, I can give you the ingredients, for further info on manufacture contact me. I’m not happy to just leave info to the un-skilled…

    Order is not an indication of dominate quantity:

    Carnauba Wax
    Vybar 103
    Paraffin wax
    HDPE
    EVA
    Oil based dyes.

    Degassing, heated moulds and stripper plates/rings are also used to produce a high quality product. It is hard but not brittle, does not clog tooling, and give excellent surface finish, with good material handling can last for many recasts.

    Never re-melt wet or damp swarf!! the action of boiling off the water is in effect steam distillation and removes al lot of the VO’s from paraffin wax making it more crystalline. This degrades it each time until its is of no use.

    Have fun..

    Regards

    Dr Atomic.

  18. Dr Atomic says:

    I too lecture (Mech), therefore I know your pain in trying to obtain suitable resources at almost zero cost.. I’m uk btw.

    I believe the question was machinable wax for cnc’s. Foams are no good!. Also the filler needs to be non-abrasive for good tool life and surface finish.

    After a few months R&D. trials, and tests I have formulated a reasonable equivalent to TryCut (commercial MWax). However, there are two routes you may take to get good results (application of use not detailed above – only small scale cnc work).

    Disclaimer: Be smart !! Be safe, this is hot work, which can and will burst into flames without good temp control. Even though this is very safe if precautions are taken care of properly. However, as with everything its at your own risk.

    Methods: (All waxes should be refined through regrinding and re-melting at least once!)

    1. Simple: 70% Paraffin wax (un blended), 30% HDPE (recycle 2 here in uk), or LDPE (recycle 4 in uk) heat wax until it reaches the melting point of the polymer +10ºc. Slowly add polymer in small amounts and allow to coagulate into molten mass, then add more.

    Stir only once and a while (be patient), it takes time for the polymer, to co-polymer with the wax. Hours depending on batch size. Try and avoid air getting trapped, as the viscosity is thick when molten.

    Depending on the molecular weight of the polymer added the properties are roughly as follows. HDPE = Harder, more brittle, LDPE = Softer, some malleability. Small delicate stuff use LDPE, Larger more robust components HDPE.

    2. Technical: Due to its nature, the process of manufacture differs. Stuff needs to be done in order at particular temps. However, I can give you the ingredients, for further info on manufacture contact me. I’m not happy to just leave info to the un-skilled…

    Order is not an indication of dominate quantity:

    Carnauba Wax
    Vybar 103
    Paraffin wax
    HDPE
    EVA
    Oil based dyes.

    Degassing, heated moulds and stripper plates/rings are also used to produce a high quality product. It is hard but not brittle, does not clog tooling, and give excellent surface finish, with good material handling can last for many recasts.

    Never re-melt wet or damp swarf!! the action of boiling off the water is in effect steam distillation and removes al lot of the VO’s from paraffin wax making it more crystalline. This degrades it each time until its is of no use.

    Have fun..

    Regards

    Dr Atomic.

  19. Kamber says:

    Ok, so according to the patent (currently/last held by Freeman), machinable wax comprises a blend of paraffin wax, two types of polyethylene wax (assumed to be a combination of paraffin wax and ldpe/lldpe/hdpe polyethylene), hard microcrystalline wax, ethylene vinyl acetate (EVA) with an 18% vinyl acetate content and BASF oil blue II dye. So it looks like you got pretty close. I’m assuming the carnauba and vybar have a similar hardening effect as per the hard microcrystalline wax in the Freeman recipe.

  20. Kamber says:

    Ok, so according to the patent (currently/last held by Freeman), machinable wax comprises a blend of paraffin wax, two types of polyethylene wax (assumed to be a combination of paraffin wax and ldpe/lldpe/hdpe polyethylene), hard microcrystalline wax, ethylene vinyl acetate (EVA) with an 18% vinyl acetate content and BASF oil blue II dye. So it looks like you got pretty close. I’m assuming the carnauba and vybar have a similar hardening effect as per the hard microcrystalline wax in the Freeman recipe.

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