Complex fan wheel required for high-temperature, low-volume applications Vespa, an Italian luxury brand of scooters and mopeds manufactured by Piaggio, has gained a large following, and some of its vintage models are highly sought after for their bold design and unique riding experience.
However, wear and tear eventually lead to parts needing to be replaced, and owners sometimes struggle to find qualified replacement parts.
One of the most difficult parts to replace is the blower that pumps air into the Vespa’s engine compartment to cool the engine.
This fan runs at high speeds and is exposed to temperatures of up to 80 degrees Celsius as well as salt spray, dust and a number of other stress factors resulting from outdoor use.
In the spring of 2024, SK Industriemodell was approached by members of a local Vespa community who were looking for ways to source spare parts for vintage Vespas.
Top of the list of parts sought was the blower, and the community had looked at a number of alternatives for low-volume production without finding a solution that would provide the desired combination of cost, performance and quality.

Freeform injection molding enables 3-part batches of field-tested material SK Industriemodell is an experienced supplier to the automotive industry, where high heat tolerance is important for parts in the engine compartment.
PA6 GF30, a glass-filled nylon, is one of the industry’s gold standards for these applications, and SKI chose this particular polymer to achieve the required combination of strength, heat resistance and durability.
Freeform injection molding was chosen due to the complex design of the fan and the customer’s need for small-batch, on-demand injection molding.
The molds were printed using the Nexa3D XiP desktop 3D printer, with the soluble xMOLD tooling resin providing the necessary design freedom.
The first injection molded parts were delivered to the customer less than two weeks after the initial order was received.

Complex spare parts injection molded on demand from validated material With free-form injection molding, SK Industriemodell was able to supply spare parts on demand, in a quality that meets the requirements for high thermal tolerance and durability, and at an acceptable cost level. No minimum order quantities Freeform injection molding is ideal for small batch injection molding production due to its unique combination of simplicity, versatility and ease of run-in.
The first batch of 3 parts was produced with 5 shots, including the two shots required to set the parameters for the first round of injection molding.
And once the parameters are set, there is no need to run in the molds or parameters for subsequent productions.

Freedom in design The soluble xMOLD tooling resin used in the free-form injection molding process allows the molder to eliminate cores, slides and other molding interventions normally required for molding complex parts that drive up the cost, complexity and lead time of conventional injection molds. Versatility Another key benefit of solubility is that even materials that normally tend to stick to the mold surface can be easily demolded.
Soluble xMOLD molds have been successfully used in the injection molding of the full range of thermoplastics as well as metals, ceramics, silicones and a number of other thermoset materials. Precision Freeform injection molding utilizes the precision and high surface finishes of resin printing combined with the repeatability and process control of injection molding.
This combination has resulted in fans that can be used straight out of the mold without the need for post-machining prior to installation into the motor.

Delivery of injection-molded spare parts on demand The supply of spare parts is one of the biggest challenges in the manufacturing industry. Suppliers must either stock large quantities of parts to ensure availability or, alternatively, develop solutions for on-demand manufacturing if these solutions are capable of meeting part performance and other requirements. SK Industriemodell was able to use free-form injection molding to manufacture spare parts from a heat-resistant engineering polymer that has proven itself in similar applications. The parts produced met the performance and quality requirements and enabled SKI to supply a large customer base with cost-effective fans. At the same time, SK Industriemodell has demonstrated how xMOLD 3D-printed molds enable injection molders to use injection molding to produce complex parts in very small quantities that would normally be outside the domain of injection molding. This has enabled SKI to expand the range of injection molding services offered to include spare parts on demand, which is a very important business opportunity for the company.