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Holimaker Produces 100s of Prototype and Pre-Production Parts With 3D Printed Injection Molds

French startup Holimaker aspires to make plastic manufacturing accessible by fabricating micro-industry tools for plastic processing. Their core product, the Holipress, is a manual injection molding machine that enables engineers and product designers to process plastic parts on their desktop in low quantities for prototypes, pilot-production, or even limited series of end-use parts. 

Holimaker offers feasibility studies for their customers, using 3D printed molds for fast and affordable turnaround. This allows their clients to quickly and affordably prototype designs and validate final manufacturing conditions during the pilot production phase of new product introduction. By using the same manufacturing method including mold design and materials, these parts can be tested in the field and ensure the designs are ready to be produced at scale. The 3D printed mold designs can then be easily adapted for tool-grade steel during mass production.

Holimaker uses 3D printed injection molds in 80% to 90% of their projects today. We met with the managing director Aurélien Stoky and the marketing director Vivien Salamone to understand how they combine both technologies. 

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Low-Volume Rapid Injection Molding With 3D Printed Molds

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Why 3D Print Injection Molds?

Traditionally, injection molds are fabricated via expensive industrial methods such as  CNC machining or electrical discharge machining (EDM). For smaller part quantities though, the cost, time, specialized equipment, and skilled labor required to fabricate the mold out of common tooling metals and with these traditional manufacturing methods introduces barriers to the process, often making injection molding at this scale unobtainable for many companies. Leveraging 3D printing to fabricate injection molds for prototyping and low-volume production significantly reduces these barriers compared to metal molds, while still producing high-quality and repeatable parts.

The Holipress next to the Form 3 printer.

The Holipress next to the Form 3 printer.

"The blocker in injection molding is to manufacture the mold. In order to democratize injection molding and make it accessible to everyone, we had to find a complementary technology to produce our mold. Desktop printing was a perfect fit for this. We combine the flexibility of 3D printing with the productivity and quality of injection-molded plastics," said Stoky and Salamone.

The main advantage of this alternative process is to shorten the time from concept to production while delivering a series of parts in traditional thermoplastics. Thanks to the Holipress, they can produce small series of prototypes and pre-production parts to test the final material and production line that will be used in mass production, and even produce limited volumes of end-use parts. And thanks to desktop stereolithography (SLA) 3D printing, they can make it happen in a few days with very limited equipment and without the need for skilled operators.

Pre-production prototypes of these football crampons were injection molded in 3D printed molds using three different thermoplastics, POM (180°C), PA 6.6 (270°C), PP (210°C).

Pre-production prototypes of these football crampons were injection molded in 3D printed molds using three different thermoplastics, POM (180°C), PA 6.6 (270°C), PP (210°C).

With 3D printed molds, Holimaker’s team can dramatically shorten the lead time for mold production and iterate new designs to optimize the geometry within a single day.

"We often design the mold in the morning, print it during the day and we can test the injection in the afternoon to modify the design and start a second print overnight. With a traditional method, we would need to machine the mold again which would take weeks," said Stoky.

Holimaker has looked into alternative ways for mold making. For orders over a thousand parts, they would employ a machined aluminum mold, but for smaller quantities, they run the press on 3D printed molds. In some cases, they combine both: for large volumes with demanding geometries, they machine the outside of the mold and 3D print the insert, which is replaced over time. 

See how manufacturing solutions provider Multiplus combines machined aluminum frames with 3D printed molds.

In-house 3D printing has also allowed them to venture beyond the limitations of machining techniques. In many projects, they achieved complex mold designs that would be difficult to manufacture traditionally, enabling their customers to innovate even more. 

“In terms of geometry, some of our projects could not have been done without 3D printing," said Stoky.

The Process Step by Step

Design

Usually, the team iterates on three to four models per project in order to optimize the design. They follow the general molding and design for manufacturing recommendations, such as including draft angles. They mostly work on small parts, and add 0.1 mm vents and 0.5 mm runners. 

In addition, they respect a few 3D printing rules such as including chamfers to help to remove the part from the build platform, including centering pins to align the mold halves, and adding notches to assist opening the mold with a screwdriver. They usually use 10 mm thick molds and avoid thin cross-sections. Parts that are only 1-2 mm thick cannot endure the high temperatures.

Various injection mold designs in Formlabs’ PreForm print preparation software.

Various injection mold designs in Formlabs’ PreForm print preparation software.

Transitioning from a 3D printed mold for low-volume production to a machined metal mold for mass-production is seamless. Simple modifications to draft angles, gates, and air vent dimensions may be needed.

3D Printing

Holimaker’s team prints the molds, directly on the build platform at a 50 microns layer height. This orientation saves printing time and resin by not using support structures and the team also observed better dimensional accuracy on the mold surfaces after curing. If dimensional errors occur, it is usually on the outside of the block that they post-process with hand sanding to fit in standard metal frames that provide added support.

In general, Formlabs recommends Rigid 10K Resin and High Temp Resin for injection molding, but Grey Pro Resin can be an alternative in case of mold failure due to demanding shapes. If cooling time is not a priority, Grey Pro Resin is a good option to augment mold longevity. 

Holimaker favors Grey Pro Resin for most of their studies. This material has lower temperature resistance than High Temp Resin and Rigid 10K Resin, but it is less brittle and allows for a higher number of cycles for difficult geometries. Grey Pro Resin can also be drilled and handled repeatedly and can be used in a standard injection press. 

Injection Molding

The team uses the Holipress injection molding machine in all their studies. It is a small manual press, easy to use, and available at a tenth of the cost of an industrial press. 

These face shield clips were injection molded using PP (food-grade, 220°C).

These face shield clips were injection molded using PP (food-grade, 220°C).

The molds are placed into a prefabricated aluminum frame which holds the pressure better and ensures that the injection nozzle is not in direct contact with the printed mold.

With Formlabs printed molds, Holimaker injects a broad range of thermoplastics with different levels of hardness from Shore 40A to 90A, at a three to five minutes cycle time. The number of cycles per mold varies from about 10 parts for a PA injected at 270°C to 100s of parts for a PP, TPE, or POM injected at lower temperatures. Holimaker is developing an integrated cooling system to help reduce the cooling time before demolding. 

Results

The team chose SLA 3D printing from Formlabs for its part quality and ease-of-use.

"The quality of our injected parts is very good because the quality of the molds is very good. And when I start a print in the evening, I am almost sure to have a good mold ready the following day," said Stoky.

Stoky and Salamone had used another desktop printing technology before, but observed too much deformation on the prints even prior to injection. 

An eyewear frame manufactured using 3D printed molds.

An eyewear frame manufactured using 3D printed molds.

“Formlabs parts offer great dimensional accuracy and surface finish. If there is a dimensional error, it is very minor, and it is uniform on the three axes, therefore we can predict it and post-process it. With other desktop printers, we could not control the deformation," said Stoky.

The team also appreciates the simple workflow that is easy to learn and operate, including the automated post-processing tools Form Wash and Form Cure

Holimaker shared a few cases from their customers to give a better understanding of the part, molding conditions, and results of their feasibility studies.

CompanySmart PowerFERME 3DEyewear Manufacturer
ProductFootball cramponFace shield clipEyewear frame
NeedPre-production prototypes in different thermoplastics, to test on the field and select the final material for mass production. Test a solution to produce a series of 10,000s of parts in a short time.Test compatibility of eyewear materials with printed molds to produce a series of 200 frames
Materials injected POM (180°C), PA 6.6 (270°C), PP (210°C)PP (food-grade, 220°C)ASA (240°C), PA (240°C)
Number of parts for one mold6010070
Cycle time2 minutes2 minutes2 minutes
Project lead time1 week1 week2 weeks

Saving Time and Costs With 3D Printed Injection Molds

Using in-house 3D printed molds has resulted in considerable time and cost savings compared to outsourced machined metal molds.

Outsource Machined Metal MoldIn-House 3D Printed Mold
EquipmentHolipress, thermoplasticsHolipress, thermoplastics, Form 3 printer, Grey Pro Resin
Mold production time3-5 weeks1 week
Mold production costs4-5 X1 X

Rapid tooling with desktop injection molding and 3D printed molds enables Holimaker to rapidly produce small batches of thermoplastic parts on demand.

“We can shorten the time between the conception of the object and the injected part. We gain flexibility, and save time and money," said Stoky.

Download our free white paper or watch the webinar for a detailed process workflow, design guidelines, and other best practices for using 3D printed molds in the injection molding process and see additional real-life case studies with Braskem and Novus Applications.