Design of Experiment DeMaCo

For the validation of the developed methodology, a design-of-experiment exercise was carried out. Different process variants, mold filling strategies, consumables, fiber/resin systems, and the opportunity for automation were explored in theory before different configurations were manufactured and validated against each other.

Demonstrator A (sailing boat)

The mockup of the sailing boat was milled externally in PIR foam. The targeted production quantity and the specification required a gelcoated polyester tooling which was produced in-house. The mold was finished in October 2012, just in time for the third users committee workshop. During this workshop, a first dinghy was produced together. Subsequently, a series of 8 sailing boats was produced, using

  • different process parameters
  • different infusion strategies
  • different fiber/resin systems
  • different stiffening strategies (rigid honeycombs, infusible 3D-core honeycombs, stiffeners)
  • different consumables

Demonstrator B (tram nose)

The mockup of the tram component was milled from a casted block of Ebaboard 105. Targeted production quantity (100 – 200 pcs) and the specifications required a composite mold and countermold. Both were produced within the research consortium. The mold was finished in February 2012. Subsequently, a series of 10 tram noses were produced, using

  • different process parameters
  • different infusion strategies
  • different gel coats
  • different fiber/resin systems
  • different core materials (monolithic/no core, combi mats, infusible Soric honeycombs)

Demonstrator C (control arm)

The design of the RTM mold was challenging. First, it was a rather complex shape in combination with a complex shaped core. Second the included bushings (using Teufelberger’s T-igel inserts) needed an additional set of tooling inserts in order to keep the longitudinal tolerances at a minimum. Third, the consortium decided to design the part “net-shape”, avoiding post-processing such as trimming of the part. As the investment for the tooling was quite substantial, a flow simulation was carried out in order to verify the infusion strategy. Several design iterations led to quite some delay in the milling of the tooling. Therefore, the first of the 16 prototypes were produced as late as April 2013. These prototypes included:

  • different preform strategies
  • use of bushings with/without pins
  • polyester, vinyester and epoxy resins
  • different temperature and pressure settings on mold and resins

Evaluation

After manufacture, an evaluation was made in terms of production times and costs. This evaluation included material costs (incl. material waste), depreciation of equipment, tooling costs, labor, etc. The result was used to validate the cost models.