3D printed moulds: a viable option?

3D printed moulds: a viable option?

Assume there is a problem which every body is talking about. Let’s say you have a concept idea on how to solve the problem. But the traditional subtractive method of manufacturing is expensive an time consuming to implement your conceptual solution. More over you need to be able to operate all the machines to do it your self.

What if there is a new invention which allows you realize your concept idea sooner and cheaper? That new invention is called 3DP (three dimensional printing)!
This technology allows you build objects cheaper and at a much sooner rate than the traditional subtractive method of manufacturing. Moreover it takes little effort to be able to use or operate that machine.

The traditional mould making for a vacuum infusion process techniques are expensive and time consuming. Traditional mould making heavily relies on subtractive processes by methods such as cutting milling and drilling which leads to high investment in machines and the use of costly materials. There has been a significant development in the automation of composites over the past decades to increase efficiency, however, these has never been enough. Therefore, introducing new capabilities that significantly enhance optimizing today’s mould making techniques is very essential. Additive manufacturing technology has a great potential in solving today’s mould making issues.

Inholland Composites, together with other ten Small and medium-sized enterprises started to make a research on how to automate the vacuum infusion process. One of the research topics considered was ‘Developing a first time right, one-off mould for vacuum infusion process using 3DP’. The main goal of this project is therefore to replace the traditional subtractive method of mould making system by the latest and most efficient technology. The main question that this project has been focused answering is “How can 3DP be fully applied in making a mould for Vacuum infusion process?
To answer the main question a mould for a Canoe paddle blade of dimensions 550x250x25mm has been considered for this project. The limited build volume of the Ultimaker type of printer at hand made it impossible to print the mould at once. Other type of bigger volume printers such as the robot arm 3D printer have been investigated. However samples printed with the robot arm have found to be not applicable for vacuum infusion process. The reason behind was that the surface quality of those samples where extremely rough and not air-tight. Therefore a decision was made to use the Ultimaker -2 type of 3D printer for this project.

The canoe paddle blade mould was designed in two parts, upper and lower mould parts. Therefore each side of the Canoe paddle blade mould was printed in a total of three individual sections. These individual 3D printed mould sections where then assembled together to make the complete mould. Visual inspection of the surface of the mould showed that it was not smooth enough to be directly used for Vacuum Infusion Process (VIP). Besides permeability tests made to the assembled mould showed that the mould was found not air-tight. However test made to individual 3D printed mould section proved that they were air tight. Therefore a backup structure was made to prevent the air leakage. Test made afterwards showed that the mould was air tight & could be applicable for VIP. But the issue related to the surface quality of the assembled mould had to be solved. Therefore the 3DP mould was wet-sanded until the desired surface quality is achieved.

Finally the 3D printed mould had to be verified if it is applicable for vacuum infusion process. To prove that the mould is viable, a product was made from the 3D printed mould using vacuum infusion process. First product made using the printed mould had some little defects on the surface of the product. Inspection made afterwards showed that the problem was not the mould itself but the fibers used during VIP. The second product made with the same mould but different type of fiber showed significant improvements in the quality of the surface compared to the first product.

An expert in vacuum infusion process was involved during the product making of the final test. This time one side of the product has shown good improvements compared to the previously made ones. However the quality of the other side of the product made using the second part of the mould showed no improvements at all. Careful inspection made afterwards showed that the second part of the mould was getting deteriorated because of multiple use. As a consequence resin was flowing into the inner core of the mould during injection. It should be remembered that the mould has never been changed during the whole testing process. This proved that the inconsistencies in the product quality of the earliest tests was due to one’s poor experience in vacuum infusion process, not the 3D printed mould itself.

The biggest issues related to large 3D printed mould for vacuum infusion process are:

  • Surface quality
  • Air-tightness
  • Limitations in build volume

The surface quality issue could involve lots of parameter, such as type of the printing material, choice of the 3D printing technique, type of slicing software and so on. This makes 3D printed mould difficult to be directly applicable for vacuum infusion process (VIP). However these problems does not make 3DP technology unfit for vacuum infusion process. Therefore with careful planning and proper execution of these plans makes medium sized 3D printed moulds could still be applicable for vacuum infusion. The plans which could lead to the possible solution of making 3D printed mould for vacuum infusion are discussed in (ref).

Besides the limitations in build volume, the Ultimaker-2, FDM type of 3d printer have shown to be applicable for medium sized mould of about 60x30x5cm. Simple shapes of large mould of size 20x4x2m and beyond could be possibly printed with large 3D printers such as the robot arm. However for airtight and smooth surface finishes with complex shapes the robot arm type of 3d printers need to be further upgraded.

Large mould, exceeding the Print volume can be made by splitting the mould into multiple sections and assemble them afterwards. However making a careful slicing strategy is important so as to achieve the desired strength, accuracy and surface finish. Proper assembly and suitable post processing steps are therefore crucial to the overall quality of the 3D printed mould surface. The Air tightness issues caused at the joints can be solved by making a backup structure to the mould. Putting the whole mould in a plastic bag during vacuum infusion could also solve the problem.

3D printed moulds might not be directly applicable for vacuum infusion process. However this depends mainly on the surface quality of the end product the mould is intended to produce. High quality smooth surface finish can be achieved through post processing . This could include sanding or polishing the 3D printed mould surfaces.

Answer to the main question could be summarized in the following three simple steps.

  1. Large moulds, bigger than the Build Volume of a 3d printer can be made by dividing the mould model in to sections which will later be carefully assembled.
  2. Desired Surface quality can be achieved by wet sanding (post processing). However this depends on the type of printing material, for some materials could absorb water.
  3. A 3D printed mould can be made air tightness by making a backup structure as a reinforcing material. A mould sealer could also be applied to the mould surfaces and put the whole mould into a plastic bag during VIP.

time-lapse of vacuum infusion using 3D printed mould

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