Casting molds for Polyurethane

Written by Niels van Oostenbrugge

2nd April 2020

Kobato is specialized in applying polyurethane coatings and producing custom PU fittings for wear resistant applications . PU is applied in many industrial processes because of it’s tough and abrasion resistant properties. Coated steel piping of containers are made more wear resistant and free of corrosion by applying a PU coating.

When a product has to be coated with a 3mm wear layer very often Kobato uses a ‘contra-mold’ to controll the layer thickness. This contra-mold must have exactly the same geometry as the taget product, with the desired layer thickness as an offset. Previously they would machine this mold from a solid block of aluminum. Obviously this is quite costly (especially since it often regards small series and unique products) and the molds are heavy, resulting in logistic challenges during the various stages of the PU application.

Geprinte polyurthaan gietmal

One half of a 3d-printed casting mold

Together with the ceo and engineer Bart Rouwers Fiberneering developed a solution for practical and economically viable molds for complex geometry by the smart use of our FRP3D technology. The surface geometry of the 3d-printed molds are very similar to the machined aluminum molds, however with 3d-printing we are able to make the molds much lighter and produce at a fraction of the costs of an aluminum mold. The molds are printed in our Standard Blue X10 hars. Because FRP-3D is a light weight material (density of 1150 kg/m3) and we van print partly hollow structures the molds can be up to 20 times lighter than the aluminum version. This also offers significant benefits during handling through the factory as Bart Rouwers points out here;

“For molds such as the ‘egg carton mold’  (photo) we would previously have an aluminum mold made, costing approximately €12,000 and weighing over 150kg. Upon delivery by truck the unloading would be done by forklift, if Frank was available and wasn’t using it for other logistic chores. Also for the internal transport we would need heavy lifting equipment, such as the folklift and overhead cranes, to transport the mold to the various work locations (preparing mold with release agent, casting, releasing, cleaning, etc.). Especially the internal transport of these heavy molds would always cause delay since the lifting equipment is required in multiple locations within our factory and we only have Frank, one forklift and two overhead cranes to transport the items from one location to another.

Now a UPS courier hands over the mold in person, weighing approx. 5kg, and lasting for at least 200 castings. Frank simply ‘walks’ the mold along the various stations of the casting proces. It is much safer and saves us a lot of transport costs and lead-time”. – Bart Rouwers, Kobato BV.

The Fiberneering molds are mostly used for small series (up to 300 casting cycles), however when the casted product releases from the mold easily it is possible to use them for larger series.

Volgegoten mal

The assembled mold (green) filled with polyurethane (red).

 

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