Print, Pour, Perform; 3D Printing and BJB Materials
How and where to use BJB polyurethanes, silicones, and pigments alongside 3D printing technology.
The introduction of 3D printing has helped improve silicone moulds, offering, exceptional accuracy and complexity.
3D printing gives you the shape while casting silicones and polyurethanes give you the material. Put the two together and you can go from a CAD file to a batch of tough, flexible, or fire retardant parts in days rather than weeks.
This pairing is now standard from product design studios to Formula 1. This article walks through ways to combine a 3D printer with BJB silicones, polyurethanes, and foams, and where it pays off in automotive and motorsport applications.
Why print alone isn't enough
A 3D printer is brilliant at geometry but limited on material with most producing parts which are rigid or that carry layer lines and weak layer bonds. Rubbery seals, fire retardant parts, or producing multiple identical parts is a struggle with printing alone.
Casting fills the gap. Silicone moulds taken from a printed master can produce polyurethane parts which closely mimic engineering plastics and a single silicone mould typically yields 20 to 25 copies before replacing.
Simply: Print the idea, cast the product/part
How do you combine the two?
Option 1 - Print a master, make a silicone mould, cast in polyurethane
This is the workhorse method, also called vacuum casting or urethane casting. The printed part is the master mould, you don’t use it, instead you copy it.
What is vacuum casting?Vacuum casting is an alternative to low volume injection moulding, it is a process which involves pouring liquid resins or elastomers into a silicone mould in a vacuum environment, reducing the risk of air bubbles. |
In this method, the master is printed using a 3D printer and then sanded for a smooth finish as silicone will pick up any lines or imperfections. A mould box is then made around the master and liquid silicone poured over it. A translucent silicone like BJB TC-5015 is ideal for this as you’ll be able to see into the cavity allowing you to spot any trapped air during casting.
Once cured, the silicone is cut open and the master removed leaving an exact cavity. Casting polyurethane can then be poured into the mould and pigmented as you go.
This method allows you to create the same identical part in different hardnesses and colours easily and efficiently. It is also an economical option.
Option 2 - Print the mould and cast straight into it
This method lets you skip the master and instead design the mould and pour silicone or polyurethane straight in. An example of this are eggshell moulds.
What is an eggshell mould?An eggshell mould is a thin brittle mould, much like an actual eggshell which then has liquid injected into it. It's a sacrificial technique, intended to be broken to remove the casted part within. |
The eggshell approach is popular in motorsport applications, with thin shells printed, coated with release agent and then filling with PU or silicone. The shell is then broken away to release the part. This allows for creating grommets and seals in a single day.
This method is ideal for one off parts or awkward shapes.
Option 3 - Printed tools for composites and silicone intensifiers
This method involves using silicone as a tool, not as the finished part, instead it helps shape carbon fibre inside a mould.
Race teams make hallow carbon fibre parts such wings and fins by filling the inside of a closed mould with shaped silicone blocks called intensifiers. When the mould is heated the silicone expands, pressing the carbon layers tightly against the mould, forming the exact shape.
The printer can be used to make the intensifier mould, while BJB silicones can be used to make the intensifiers.
How to choose the right BJB material?
The best way to find the right material is to work backwards from the finished part, where is it needed and what does it have to do.
| What you need | BJB range | Why it works |
| A long lasting, accurate mould from a printed master | Platinum silicones (TC-5015 and TC-5150) | Low shrinkage, long mould life, translucent grades |
| A forgiving mould from a resin print | Tin cure silicones | Less sensitive to cure inhibition from printed resins |
| Rubbery or rigid prototype parts | F-1 series castable polyurethanes | 5 to 95 Shore A, tune hardness part by part |
| Padding, bolsters, crash pads | Flexible or self skinning foam (TC-277 and TC-284) | Soft, cushioned parts, TC-284 forms its own tough outer skin |
| Lightweight fill or pattern backing | Rigid foam | Closed cell, can be sanded, stapled or painted soon after demoulding |
What about for Automotive and Motorsport applications?
| Application | 3D Print | Cast with BJB |
| Seals, grommets, and gaskets for development and wind tunnel models | Eggshell mould or master | Platinum silicones or soft F-1 polyurethanes |
| Wind tunnel model parts | Master for a silicone mould | F1 series, tuned for stiffness and surface finish |
| Suspension bump stops and bushes (prototype and low volume) | Master or two part mould | Harder F-1 grades, around 60 to 90 Shore A |
| Cockpit and engine bay trim, caber guides, covers | Master mould | F-164 FR for self extinguishing behaviour |
| Composite wings, fins, and ducts | Intensifier mould | Platinum silicone |
| Padding and bolster prototypes | Mould | TC-277 or self skinning TC-284 foam |
| Lightweight patterns and fixtures | Printed shell | TC-300 rigid foam fill |
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A note on safety - Print and cast is ideal for development and testing but certified safety components (FIA regulations) need certified materials.
Speak to an Expert
Still not sure? Speak to our Technical Team for help picking the best BJB materials for your automotive, motorsport, or 3D printing application. Our team can not only advise on polyurethanes, foams, and silicones but also adhesives and sealants to cover all your production needs.
