tooling considerations
Rota Design balances the advantages, disadvantages and product design parameters in preparation of its recommendations for the type of mould to be used. There are a variety of options:
Cast aluminium
Cast aluminium moulds are predominant in many applications since it is relatively easy to replicate products with complex shapes and intricate detail.
A permanent pattern is required to define the basic mould shape and allowances for shrinkage during cooling of the casting have to be considered.
Parting lines are carefully defined and the negative shells are prepared. From these shells, foundry moulds are produced using special sand and ceramic materials. Finally the aluminium mould is cast.
The objective is to produce a thin and uniform wall thickness to optimise heat transfer.
CNC aluminium machined moulds
Rota Design is able to supply, where contractually agreed, the 3D CAD data to certain toolmakers direct input to a CNC machining centre in order to create a mould from a block of solid aluminium. This is a fast way of producing a mould in a cost effective manner, and with excellent accuracy.
Accuracy is important in the case of multiple moulds in order to minimise parting lines, especially where the product aesthetics are critical.
The surface of the mould may be acid etched to provide texture or features and various coatings are available to enhance performance of the mould.
Rota Design will work closely with the toolmaker, to an extent agreed with our client, with respect to design aspects and verification of the product design thus reducing time to market and providing a quality assured product.
Fast Cast ™ – a shortcut to casting
In the Fast Cast™ process, Maus GmbH take the 3D CAD design data direct from Rota Design and feed it to their NC machining centre.
From these data machine tool programs are produced to manufacture the foundry mould shells.
The foundry moulds are subsequently machined directly into prepared material blocks.
The advantage of this process is that it is unnecessary to manufacture traditional wooden patterns thus “leapfrogging” the process forward to the casting stage.
Fast Cast ™ is particularly cost effective when large castings are required.
For further information upon the Fast Cast ™ process contact Maus GmbH.
Fabricated moulds . . .
Moulds fabricated from bright mild steel plate, stainless steel or aluminum are commonly used.
Rota Design provide the plate development data for curves and complex shapes in a format ready for input into the laser cutting machine.
Large moulds may be fabricated using MIG welding, polished and sometimes coated with a smooth Teflon type finish.
This surface finish assists in releasing the product from the mould and provides a resilient surface to the mould thus extending its life.
Surface texture is difficult to achieve using fabricated moulds but inset embossed patterns for company logos etc may be included.
The image shows an example of a fabricated sheet steel tool for a modular pump chamber designed by Rota Design.
resin and non-metallic moulds
Polyester and epoxy resins in liquid form may be used to produce moulds, however, their relative life is short and thus are normally restricted to prototyping and short production runs, of say, 100 components.
Rota Design provides advice based upon experience and the best balance for any given product design and application.
mould coatings
A wide spectrum of coatings is now available; all with slightly different release properties.
A variety of effective alternatives to Teflon™ and other PTFE based coatings (including conventional release agents) should be considered for inclusion within the specification of your tooling.
Combining the permanent release functions of PTFE with the controllability of semi-permanent release agents, some coatings are available in standard, matt, metallic and ceramic coatings and may be specified for new moulds or used to refurbish existing moulds.
