Investment Cast Tyre Mould
Malcolm Nicholls Limited (MNL) were commissioned by a worldwide tyre manufacturer to aid them develop a radically different tyre mould design.
The CAD department at MNL started the project by converting 2D developments of the tread pattern into 3D solid models of tyre segments. To prevent harmonic road noise problems, differing segment widths are positioned around the circumference of the tyre, with up to 10 or more different widths being utilised in the 70-80 segments necessary to make up one tyre. The mould segments were designed direct from the tyre segments.
From the 3D data, 3D printed masters (*Quickcast™) were produced to enable the customers own foundry to produce aluminium castings of the tyre mould segments. Over various projects the customer used MNL’s different options for producing the required 3D printed masters, dependent upon the quantities required. These options are; quickcast SL patterns for investment casting; thick skinned shelled patterns for sand casting and solid SL patterns for ceramic gravity castings.
The close up view shows evidence of the build layers from the stereolithography process, these were left on the pattern purposely to aid venting of air during the injection moulding of the rubber.
*QuickCast™ is an SLA® build style trademarked by 3D Systems and was created to meet the needs of the Investment Casting industry. While 3D printing in general has greatly reduced time to market, QuickCast patterns for investment casting have had the most profound effect on this industry. QuickCast replaces the time consuming process of creating tooling to produce wax patterns, allowing the review of metal designs in days instead of months.
The QuickCast build style consists of a hollow SLA pattern with an internal hexagonal support structure that adds strength to the pattern, allows for easy drainage, and facilitates collapse of the pattern during thermal expansion to help avoid cracking the shell. QuickCast patterns provide several advantages compared to other direct patterns including low moisture absorption, high finish, dimensional stability and capabilities of producing large assemblies.