Making Silicone Molds without Air Bubbles

One of the most common methods for chocolatiers to make their own molds is to use food grade, liquid silicone rubber.  The problem is that liquid silicone rubber is very expensive and can take a long time to set.  If your silicone inadvertently gets air in it while mixing or pouring, you may very well go through the whole process only to find that your mold did not turn out right because of one unsightly placed air bubble.

There are several things that can be done.  The simplest form is not over-mixing and brushing a small layer of the silicone on the model before pouring the whole mold.  This way you get into the detail and have less air bubbles on the surface where it matters most.  The next best thing you can do is use a vacuum degasser.  To use a vacuum degasser, the mixed liquid silicone is put in a chamber before it is poured.  This process will break up most of the air bubbles before casting.  This is very effective, but not all the way as air can be brought back during the pouring.

The best way to ensure a bubble free mold is to use a pressure casting method.  A pressure pot is a metal chamber that uses a compressor to cure the mold under pressure.  The liquid silicone is poured over the model then placed in the chamber.  The pressure, max 60 psi, eliminates the bubbles during the cure process.  You can buy pressure pots at Smoot On, or I have seen them used for the paint industry which can be bought at many places, even Amazon (link will take you right to the pressure pots).

Word of caution:  do not attempt to make your own pressure pot as they can explode.

To read more about mold making see our in depth instructions on The Chocolate Mold Factory's Main Site under "Personalized Molds".  There are tutorials about designing molds and how to make them.  Though the site is geared towards chocolate molds, these instructions are the same as would be for any other type of non food grade mold.

Can you Make Chocolate Molds with a 3d Printer?

I have spent a lot of time researching 3d printers for a solution to make chocolate molds.  A 3d printer would be ideal as you do not have to know how to use CAM software or generate toolpaths as you do with CNC machine.  Just design in 3d modeling software and print.

To date, I am yet to find an acceptable 3d printing solution that is affordable.  There are certain machines that are capable of very high quality fine printing, but they cost over $150,000.  The lower priced machines are good for making larger models with larger text.

First, most 3d printers use only certain types of materials that are not food grade.  It may be the type of plastics that are used or the adhesive functions used to build the layers that are not certified for contact with food.  So, while it may be fine for your individual use or display purposes, this would not be acceptable for use in food or molds you are selling.

Second, 3d printers are best suited for larger items and cannot get the best detail for text in a small format.  I once tested this on a Dimension 3d printer which makes parts by basically melting a thin plastic rod (looks like the weed whacker spool) and then depositing it.  I wanted to make a standard size bonbon with small text on it.  While it was fine to make to the base of the chocolate, the text did not come out.  It was just a blob of illegible melted plastic.  I did see the ZCorp 3d printer produce small text.  But the ZCorp machine uses non-food grade materials and has a very rough surface.  That process is of depositing a thin layer of a plaster or starch type substance, then adhering between layers.

Third, the surface finish on a 3d printed part is still quit rough no matter which you are looking at, unless you get into these very expensive printers.  Even with sanding, it's not going to have a good enough surface to produce a smooth chocolate.  Chocolate will pick up very fine detail in a mold.  It will not have the proper luster.

That being said, I know they are making huge advancements in the 3d printing world daily and I continue to seek for a solution. 

New Vacuum Forming Machines

Now you can buy vacuum forming machines through Amazon.com. There are two sizes available: 12" x 12" and 12" x 18". Below are pictures/links to the machines.

The item description for the machine is: Our Table Top Vacuum Former is perfect for small businesses and hobbyists who want to create parts in plastic up to 1/8" thick. Produce intricate shapes with results that rival expensive commercial machines in their incredible accuracy and detail: prototypes, custom packaging, RC car bodies, model rocket nose cones, molds for plaster or concrete, chocolate and candy, candles, and soap making. Our 12"x12" Vacuum former includes a perforated aluminum vacuum platen (the top surface that delivers the vacuum under the hot plastic) that is computer designed and precision CNC machined to maximize air flow and eliminate unnecessary volume - both critical to rapid air evacuation and professional vacuum forming results. Detailed, step-by-step instructions along with sources for vacuum formable plastics are included. Compatible with all types of thermoform plastic: ABS, Acrylic (Plexiglas), Butyrate, PET-G, Polycarbonate (Lexan), Polyethylene, PVC, Styrene, Vinyl, etc. Requires house hold oven and Shop-Vac style vacuum cleaner with 1 1/4" hose/adapter.

Vacuum Forming Explained in 3 Easy Steps: Step #1: Secure your plastic between the vacuum former's metal frames. Attach your Shop-Vac (not included) to the vacuum former. Place your model on top of the perforated aluminum vacuum platen. Step #2: Place the plastic in your kitchen oven and watch as it becomes soft and begins to sag. Align the metal frames with the vacuum former's guides and lower the plastic over your model. Step #3: The hot plastic forms an air tight seal around the vacuum platen's edges. Vacuum pressure pulls the hot plastic down around the model. After cooling for a few seconds the plastic part is complete.

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  Make your own prototypes, custom packaging, RC car bodies, or model rocket nose cones
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  Create custom molds for plaster or concrete, chocolate and candy, candles, and soap making
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  Forms Plastic Sheets 12" x 12" Up to 1/8" Thick (9 3/4" x 9 3/4" Usable Area)
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  Includeds detailed, step-by-step instructions along with sources for vacuum formable plastics
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  Requires house hold oven and Shop-Vac style vacuum cleaner with 1 1/4" hose/adapter

I think this looks like a higher quality hobby vacuum forming machine than some of the others sold on the market. The box looks to be well made and I particulary like that the platen area is metal. This results in better forming as it will transduce heat better. As for the price, it is very competitive. Other companies that sell inferior products also make you buy plastic with the machine at a very high price. You can buy plastic through many sources on the Internet, such as U.S. Plastics, much cheaper. I recommend using PETG (Vivak) for making chocolate molds.

See The Chocolate Mold Factory.com main pages for more instructions on how to use a vacuum forming machine like this.

CAD/CAM Software for Making Chocolate Molds - Delcam Case Study

Delcam software gives chocolate mould manufacturer a taste of success

Since 1999, Kaupert, a leading German manufacturer of chocolate moulds, has used Delcam software for the design of all its polycarbonate tooling. These moulds are produced using injection moulding or stamping tools, which are also developed with Delcam systems. Today Kaupert’s customers can expect delivery of their moulds in as little as six to eight weeks after confirmation of their chosen design – and so make an early start with the production of their own special chocolate creation.

Large-scale confectionery manufacturers like Lindt, Bahlsen, Storck, Kraft Foods and Master Foods are responsible for the greater part of Kaupert’s turnover. Its customers also include some traditional craft firms – confectioners, patisseries and chocolate-makers. For both sets of customers, particularly demanding standards of accuracy and surface quality must be met by those tool components that will later form the cavities in the chocolate moulds, and so have a decisive effect on the appearance of the chocolate wares that will be the end result.

Previously, the modellers created their artistic forms – Easter bunnies, Father Christmasses, hearts, flowers, animals, stars and a great variety of other designs – in the form of plaster models. Some 20,000 of these sculptures are stored as an archive resource. For most of them, injection moulding or stamping tools have already been created, making it possible for the designs to be reused.

When the tools are not available or when the design requires some modification, Kaupert’s designers and modellers use Delcam’s CopyCAD reverse engineering program to capture a computer model from the plaster original. The sculpting tools within the software then enable the user to add material to the CAD model or to pare it down to generate the final design.

The designers also use Delcam’s ArtCAM Pro engraving package to create new decorations for ornamental engraving and for writing on surfaces, usually for single-bar products. Data from CopyCAD and ArtCAM Pro can be combined with more engineering shapes developed with the PowerSHAPE CAD modeller through Delcam’s unique Total Modelling. With this unique approach, the user can process complicated 3-D reliefs, solid models and free-form surface models in a single system and on an equal footing.

PowerSHAPE also calculates both the shrinkage of the synthetic material and the effects of hardening on the chocolate shape, and so ensures that the confectionery that will be produced matches exactly to the designer’s intentions.

The toolmaker then generates programs for the company’s Micron and Röders milling machines with the PowerMILL CAM system. One of the strengths of the system is that it warns of possible sources of error in advance: collision checks, analyses of rest material, and machine tool simulations work together to ensure that in the subsequent machining process nothing is left to chance.

Chocolate Coin and Chocolate Mold Dies - Bauer Engraving Co.

If you are looking for a system to make chocolate coins, or want dies made for chocolate molds, you may want to contact Bill Bratt, owner of Bauer Engraving Co.  located in San Fransisco.  Bauer Engraving Co. makes many kinds of photoengraved dies, including those use for foil stamping, chocolate coin imprinting, and chocolate mold making.  In addition, you can buy a machine to make chocolate coins from Bauer Engraving Co.

Bratt, is part owner of a company called Image Development that manufactures machinery to imprint chocolate coins.  Bauer Engraving then can make the dies that go with the Image Development machine.  The lowest price machine (over $1,000), is a manually operated machine that stamps one coin at a time.  To make a custom chocolate coin, the dies are insterted into the machine, along with a blank foiled coin.  Using pressure, the machine will quickly press the die against the foiled chocolate.  As a result, the image is transferrred to the chocolate and foil.

Bauer Engraving can also make dies for use with making chocolate molds.  To make a chocolate mold, you must first have a model of what you want your chocolate to look like.  Then by various methods, including vacuum forming, silicone molding, plastic injection, and stamping, you can make a mold.  See the "How To" section on The Chocolate Mold Factory's main website for detailed information about these mold making methods.

To order dies is relatively simple.  You will need to send very clean black and white artwork to Bauer, or any other photoengraving company you want to use.  Any jagged edges will show up in the die.  As such, vector artwork is best.  Normally, anything black will be raised in your die, whereas, anything white will not.  Photoengraving is a chemical process whereby an image is transferred to a metal plate with a light sensitive coating.  Anything that is exposed to the light will harden.  The unexposed areas will wash away, leaving a plate with the image in relief.

Some other tips to consider if you are going to be making a mold from these dies (which I learned the hard way):

1. Make sure your lines are not close together. If your lines are not far enough a part, your mold making material will not be able to get down into the crevices.  This will cause a loss of your image in the mold.
2. If you want text to be recessed, it has to be quite large.  Otherwise, the metal etching will not be deep enough for the mold making material; also resulting in a loss of the image.
3. If you are going to be making a mold with multiple cavities, you may want to order all the dies at the same time.  Differences in the etching process can make significant changes in the final mold.  (For example, I had ordered one mold initially to test if an image would work because letters were very close together.  On first try it did work, and molded beautifully.  So I ordered the rest of the dies.  However, there was some minor change in the depth of the etching that made the new dies not work when I tried to mold them)
4. To save money, order multiple dies on one plate and cut them yourself.  If you have the photoengraving company cut them for you, you may lose the discount based on larger square inches.

Custom Carvewright or Compucarve 3d Model Files

CarveWright Woodworking System

Many people are catching on to the Carvewright or Compucarve CNC system. For the first time it is possible to do computerized carving without having extensive CAD/CAM knowledge. A Carvewright user simply saves a project to a memory card, puts the card in the machine, and the machine tells the user what to do.

There are many companies out there making computer files of models that can be purchased. You have to be careful if you intend to make molds with any of these files. Copyright infringment is a serious issue. Make sure the seller knows what you intend to do with any file you purchase so as to avoid problems.

If you want to use the Carvewright system to make molds with your own designs or with your customers designs and logos, there are companies who will make the 3d model files for you. One such company is Vector Art 3d, Inc. Besides STL and ArtCam files, Vector Art 3d can make custom 3d files for the Carvewright system. You can go to their website and get a quote. To get the quote they just need an image, whether it be a photo or drawing. The website says that they try to get all quotes done within 72 hours.

You also choose whether the design will be exclusive or open use. This is critical. If you do not want your artwork copied make sure you choose exclusive. However, if it doesn't matter, you can choose open use and the cost of making the file will be reduced. Open use means that they will sell your file to other users.