<p>Factually, the correct process is to heat up the mold hot enough to evaporate the positive. </p>

<p>In <a href="https://en.wikipedia.org/wiki/Investment_casting" rel="nofollow noreferrer">investment casting</a> the process to remove the wax or plastic positive is called the <code>"Dewax"</code> and <code>"Burnout preheating"</code>.</p>

<p>The answer to your question depends on the material you use to generate a negative mold of the positive product. E.g. many silicate based materials require up to about 1100&nbsp;&deg;C to fully burnout all residue before pouring in the liquid metal.</p>

CC BY-SA 4.0
2019-04-01T11:39:54.463Z
Wax for molding is usually melting low enough to melt out in a pan, unlike resins
Trish
CC BY-SA 4.0
2019-04-01T11:51:46.040Z
@Trish That is why they need to burn out, oxidize. This requires very high temperatures. This is very commonly done nowadays as it is way cheaper and lead times are way shorter. [This](https://ultimaker.com/en/knowledge/15-prototyping-investment-casting-sample-parts-to-reduce-costs) is a nice article.
0scar
CC BY-SA 4.0
2019-04-01T06:32:46.957Z
2019-04-01T06:32:46.957Z
0scar
<h2>Traditional lost molds.</h2>
<p>The reason many jewelers use wax for making the molds for lost mold casting is, that it has (compared to plastic molding materials) a very low melting and boiling point, allowing to create molds with much lower temperature equipment.</p>
<p>A variant of green sand casting is done with materials that very quickly decompose in contact with the molten metal or that burn out after setting fire to them. Very common in this context is foamed styrene. Styrene melts and burns easily so it is easy to use in this way.</p>
<p>PLA has been used in some experiments as a positive and then molten out in a baking oven. It and other printing filaments are usually thermoplastics, so melting them out is similar to wax.</p>
<h2>Resin is not soft wax or a thermoplastic.</h2>
<p>No, in fact, most resins are a duroplastic, meaning that they don't melt.</p>
<p>If you print a positive from resin and then make a mold from that for lost mold casting, you go the traditional way. But most resins don't melt out the way wax does, and on contact with molten metal don'T evaporate the way wax residue does. You got to properly <em>burn</em> out the remains of the cured resin at a higher temperature and for a longer time than the wax as the melting point is much higher - use a proper burning oven. A proper burning oven in this relation reaches something like an email oven (1100 °C) or a clay burning oven (up to 1800 °C)</p>
<p>Putting the molds with the opening down into one of these ovens at high temperature should help a lot. Make sure to put a spacer and a tray below to allow better airflow and get the resin out.</p>
<h2>Chemical Club.</h2>
<p>Besides heat to destroy the resin, most resins could be solved by very highly aggressive chemicals. Which chemical works highly depends on what the resin actually is - if it is <a href="https://www.microtonano.com/TIN-Removing-Cured-Epoxy.php" rel="nofollow noreferrer">epoxy resin</a> it would be the highly toxic CH<sub>2</sub>Cl<sub>2</sub> while <a href="https://www.epoxy.com/Epoxy_Chemical_Resistant_Chart.aspx" rel="nofollow noreferrer">polyester resin</a> is soluble in isopropanol and sulphuric acid.</p>
<h2>Cold alternative?</h2>
<p>If your product is to be made of a two-component resin or a ceramic that can be shaped cold and that sustains form, then you might also look at silicone molding. This is not an alternative for most metal castings. Among the very few exceptions is pewter, as PunishedPropsAcademy and Evan&amp;Katelyn <a href="https://www.youtube.com/watch?v=umtYcUdOv3U" rel="nofollow noreferrer">showed in their video</a> and there are high temp silicones around that could be used repeatedly for pewter.</p>

CC BY-SA 4.0
2019-04-01T01:31:35.273Z
2019-04-01T17:59:42.320Z
2020-06-18T08:29:41.667Z
Trish
<p>I have a 3D printer and I have printed some models with castable resin. When I burn one of these models in the oven and then do the metal casting, the surface of the metal piece is not smooth.</p>

<p>I did a test with a pan. I put a model of wax and a model of castable resin to heat in a pan, and the wax model melts, but the resin model don't.</p>

<p>The resin I have is the following:</p>

<p><a href="https://i.sstatic.net/o07nG.jpg" rel="noreferrer"><img src="https://i.sstatic.net/o07nG.jpg" alt="enter image description here"></a></p>

<p>What is the correct process to make a correct resin casting?</p>

<p>Thanks for your help.</p>

CC BY-SA 4.0
2019-03-31T02:01:43.567Z
Use silicone mold.
Fernando Baltazar
CC BY-SA 4.0
2019-04-01T12:17:13.123Z
What temperature you burn your mold out at?
Trish
CC BY-SA 4.0
2019-04-01T12:17:40.883Z
@FernandoBaltazar silicone molds are not useable for most metals.
Trish
<3d-models><uv-printer><resin>
What is the correct process to make a correct resin casting for jewelry?
Adrián Juárez
# What is the correct process to make a correct resin casting for jewelry?

(Asked by: username_0 on 2019-03-30)

I have a 3D printer and I have printed some models with castable resin. When I burn one of these models in the oven and then do the metal casting, the surface of the metal piece is not smooth.

I did a test with a pan. I put a model of wax and a model of castable resin to heat in a pan, and the wax model melts, but the resin model don't.

The resin I have is the following:

[![enter image description here](https://i.sstatic.net/o07nG.jpg)](https://i.sstatic.net/o07nG.jpg)

What is the correct process to make a correct resin casting?

Thanks for your help.

**Tags:** 3d-models, uv-printer, resin

> **Comments:**
> **username_1**: Use silicone mold.  
> **username_2**: What temperature you burn your mold out at?  
> **username_2**: @username_1 silicone molds are not useable for most metals.  

---

## 2 answers

### Answer by username_3 on 2019-04-01. Score: 2

Factually, the correct process is to heat up the mold hot enough to evaporate the positive.

In [investment casting](https://en.wikipedia.org/wiki/Investment_casting) the process to remove the wax or plastic positive is called the `"Dewax"` and `"Burnout preheating"`.

The answer to your question depends on the material you use to generate a negative mold of the positive product. E.g. many silicate based materials require up to about 1100 °C to fully burnout all residue before pouring in the liquid metal.

> **Comments:**
> **username_2**: Wax for molding is usually melting low enough to melt out in a pan, unlike resins  
> **username_3**: @username_2 That is why they need to burn out, oxidize. This requires very high temperatures. This is very commonly done nowadays as it is way cheaper and lead times are way shorter. [This](https://ultimaker.com/en/knowledge/15-prototyping-investment-casting-sample-parts-to-reduce-costs) is a nice article.  

---

### Answer by username_2 on 2019-04-01. Score: 1

## Traditional lost molds.

The reason many jewelers use wax for making the molds for lost mold casting is, that it has (compared to plastic molding materials) a very low melting and boiling point, allowing to create molds with much lower temperature equipment.

A variant of green sand casting is done with materials that very quickly decompose in contact with the molten metal or that burn out after setting fire to them. Very common in this context is foamed styrene. Styrene melts and burns easily so it is easy to use in this way.

PLA has been used in some experiments as a positive and then molten out in a baking oven. It and other printing filaments are usually thermoplastics, so melting them out is similar to wax.

## Resin is not soft wax or a thermoplastic.

No, in fact, most resins are a duroplastic, meaning that they don't melt.

If you print a positive from resin and then make a mold from that for lost mold casting, you go the traditional way. But most resins don't melt out the way wax does, and on contact with molten metal don'T evaporate the way wax residue does. You got to properly *burn* out the remains of the cured resin at a higher temperature and for a longer time than the wax as the melting point is much higher - use a proper burning oven. A proper burning oven in this relation reaches something like an email oven (1100 °C) or a clay burning oven (up to 1800 °C)

Putting the molds with the opening down into one of these ovens at high temperature should help a lot. Make sure to put a spacer and a tray below to allow better airflow and get the resin out.

## Chemical Club.

Besides heat to destroy the resin, most resins could be solved by very highly aggressive chemicals. Which chemical works highly depends on what the resin actually is - if it is [epoxy resin](https://www.microtonano.com/TIN-Removing-Cured-Epoxy.php) it would be the highly toxic CH2Cl2 while [polyester resin](https://www.epoxy.com/Epoxy_Chemical_Resistant_Chart.aspx) is soluble in isopropanol and sulphuric acid.

## Cold alternative?

If your product is to be made of a two-component resin or a ceramic that can be shaped cold and that sustains form, then you might also look at silicone molding. This is not an alternative for most metal castings. Among the very few exceptions is pewter, as PunishedPropsAcademy and Evan&Katelyn [showed in their video](https://www.youtube.com/watch?v=umtYcUdOv3U) and there are high temp silicones around that could be used repeatedly for pewter.


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