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Thermoformed 3d chocolate molds: theory (1/3)

This article is the first of a series of 3, introducing the creation of custom chocolate molds, in short cycle, at home with a small 3d printer and a small thermoforming  (or vacuum forming) machine. The method shown can be the basis for any beginner or chocolate maker, if he or she contemplates building a small customer offer, with fast, reliable but not very accurate results. In short, an appetizer!

Here is an overview of the article series:

  1. Thermoformed chocolate molds: theory (1/3). We explain the molding techniques on the market and argue for a choice of simple machines.
  2. Thermoformed chocolate molds: practice (2/3). Overview of the design and manufacturing work from our logo, with TinkerCAD and 2 small machines.
  3. Thermoformed chocolate molds: review (3/3). A qualitative review of the economic potential of setting up an in-house molding unit, if you are a food artisan.

For your information, La Pâtisserie Numérique already offers a very complete training on creating 3d silicone pastry molds.

A – Theory : Chocolate molding and 3d printing

To make chocolate molds, we have to choose a molding technology and make the object to be molded (the matrix) if needed.

Overview of molding technologies:

Usually custom chocolate molds are made with the following materials and food technologies – ordered by increasing hardness:

  • gelatin (animal or vegetable), bioplastics and food gels;
  • platinum or peroxide silicone;
  • thermoforming (materials: EVA, PS, PC, PET, PETG, PLA, PVC);
  • injected polycarbonate (PC) or die-cast plexiglass (PMMA);
  • aluminium.

Most of the time, a matrix is created. This is the opposite form of the mold, which is also called positive or negative depending on its orientation or molding order. Each material mentioned above must be suitable for food contact.

How are molding dies created?

To create molds, we generally start with the matrix, a solid object:

  • a fruit or a plastic or metal object;
  • a modeling or a manual sculpture in clay, plaster;
  • a block of resin, aluminum or wood, machined by a numerical milling machine (CNC) or engraved-cut by laser;
  • a 3d print.

Some of those objects, even if clean, are not suitable for food contact, it is then necessary to cover them with a varnish or food safe insulation before molding. This is especially important for long duration or close contact molding technologies (gelatin, silicone, injection).

If your matrix is very clean, not powdery and dry, in a clean environment, thermoforming it and washing the mold can result in a product suitable for food contact.

Why 3d printing and thermoforming?

Most installed chocolate molders create their molding matrices by CNC machining (basically: a drill that navigates to remove material from a block of material). Then they choose to create each new mold by thermoforming, casting or injecting plastic or even an elastomer (silicone..).
Copyright: KolbTechnology CC BY-SA 4.0, via Wikimedia Commons

The machining technique, although very reliable, is nevertheless long to master for a neophyte. In particular, it requires thinking about the part “in negative” (removal of material), mostly in low relief only, with a change of tool (milling cutters) to remove the material in several passes of increasing precision.

In contrast, 3d printing with filament for example, is done by adding material – easier to imagine, and you don’t have to change the tool unless you change the filament colors in the meantime (rather useless for molding matrices).

Timelapse d’une imprimante à filament RepRapPro – License CC-BY-SA

Currently, the 3d printing technologies available to the general public are filament-based (mostly) or resin-based (more difficult to handle).

Resin vs filament : 2 types of 3d printing for chocolate molding

3D resin printing:
3D resin printing Formlabs Form 2 SLA. Photo Flickr par Creative Tools – CC BY 2.0
Copyright : Paolo Cignoni, CC BY-SA 4.0, via Wikimedia Commons
#3DBenchy made on a formlabs Form 2 SLA 3D printer v3
Imprimé 3d en résine transparente par imprimante 3D SLA (Formlabs Form 2) – de 3dBenchy / Flickr / CC-BY-2.0
#3DBenchy made on a formlabs Form 2 SLA 3D printer v5
Imprimé 3d en résine transparente par imprimante 3D SLA (Formlabs Form 2) – de 3dBenchy / Flickr / CC-BY-2.0

3D resin printing (SLA, DLP, MSLA…) is more and more used professionally together with thermoforming. It consists in polymerizing 3d ink (resin) in a small bath, by projecting a laser beam or images layer by layer. The resin is sensitive to certain types of light (typically the 450 nanometer wavelength in the ultraviolet) and a plate moves vertically. The results are a little less smooth than machining if you are picky, but still almost shimmery!

3D Printing Filament:
3D filament printing Makerbot Ultimaker 2 – par Guy Sie – Wikipedia – BY-SA 2.0

Copyright : KholoudabdolqaderVector: Jona, CC BY-SA 4.0, via Wikimedia Commons
Exemple de rendu strillé naturel de surfaces d’imprimés 3d par filament – CC BY-SA 4.0 par 0scar (StackExchange)

The 3d filament printing (acronyms: FDM or FFF) is used by rare chocolate mold makers. Rare because it gives results with surfaces that are difficult to smooth, in steps. The final striation is found in the end on the molded chocolates, unless there is an important smoothing pass, manual most of the time, with or without chemical treatment (with questionable food safety).

3D FDM printing for chocolate molds: the not so wrong choice

Most craftsmen completely new to digital design will tend to buy or use a 3d filament printer to start with (instead of a resin printer), because this type is the most widespread in amateur circles at the moment. This choice, cheaper, can be suitable to create molds of chocolate subjects (10-30cm high) with a fairly easy handling without dirt and non-negligible health risks (vs. leftover unpolymerizede resin from SLA/DLP printing). Though, the result will be a bit too coarse for smaller and finer chocolate products (from bars to napolitains).

Well! Why not try to optimize the deal with such slightly disappointing machines as filament printers, if they are already purchased?

Let’s make the not so wrong choice too!

Overview of thermoforming

Vacuum former
Thermoformeuse Formech DT 2 de bureau, avec une matrice positive sur sa grille, prêt à thermoformer – Crédits Christchurch City Libraries (Flickr) / Donna Robertson – licence CC BY-NC-ND 2.0

Thermoforming consists in heating a plastic plate which softens, followed by a suction (vacuum-forming) or blowing (compression-forming) of this plate against a shape – the matrix or the positive. The image below shows a thermoforming computer simulation onto a slightly pyramidal block.

Crédits : Colagor, Public domain, via Wikimedia Commons

Thermoforming machines for professionals (e.g. from Formech or Decorelief, Vaquform DT2, Mayku Multiplier) are sometimes expensive, for large canvas sizes with industrial vacuum/pressure pumps.

Vacuum Forming & Molding Machine
Mini-thermoformeuse dentaire Jentai – une des moins onéreuses du marché

If you are looking for something smaller and cheaper, the dental world has been offering small thermoformers for a long time. Otherwise, Mayku sells its Formbox, which can be plugged to an external household vacuum cleaner. The latter is used by more and more food artisans, for example pastry chef Quentin Z below:

You may have seen or read about homemade thermoformers made from toaster heater and vacuum cleaner pumps! A school teacher in Croatia lets her teenage students assemble them in large volumes… It’s up to you to try out this kind of DIY. In terms of heat temperature and vacuum or pressure level, your mileage will vary 🙂

Theoretical conclusion: let’s get practical!

If you have read this far, you now know a little more about 2 forms of 3d printing (resin, filament) and a particular molding technique: thermoforming.

Our idea here is to not wait too long in terms of equipment to acquire to do some initial testing! You have the potential to make chocolate molds like a… semi-professional, very soon if not now!

That’s what the next article in this series is all about… How to make your own custom molds with… a free 3d web application for kids, a filament printer and a dentist thermoformer?

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