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Paperless mould tool design and manufacture

Paleman aims to advance the state-of-the-art in computer-
based support for mould tool design and manufacture, and
thereby make significant reductions in the lead time for
designing and manufacturing a mould tool.

Projects to be injection moulded are generally designed by one company (e.g. an automotive company) and the mould design and manufacture is subcontracted to a second company (a small mould making company). The product designer will generally have a different Computer Aided Design (CAD) system to the mould maker. The product designer requires a CAD system suitable for designing a component from the concept stage and which will allow a new design to be checked for assembly problems with other product designs. It is not always necessary to model every detail of the component however - merely those features of the component which affect style or method of fit with other components. Many details are typically omitted from the product designer's model. The mould maker, on the other hand, requires a CAD system capable of modelling every minute detail of the component (as every feature must be manufactured), but does not require strong functionality for styling or assembly modelling. The mould maker typically receives data from the product designer in one of the following forms: * as 2D drawings (on paper or electronically) * as incomplete 3D models (often some important surfaces, plus some 3D curves representing boundaries, or sections) * as complete 3D models (but usually from a different CAD system). In some cases the product model may be received in a 'host' CAD system format, but usually the transfer is via a standard neutral interchange format such as IGES, VDA-FS or STEP. The mould maker must go through the following (not necessarily exhaustive list of) steps: 1. Read the external product data into the local CAD/CAM system 2. Sort out what the data meant and repair any interchange problems. Research has shown that this stage takes a surprisingly long time. Models may consist of several thousand surfaces, and any structure present in the original model is generally lost due to the neutral interchange format used in the data transfer. 3. Find the split line (where the two halves of the mould will separate) and decide on split-surfaces. 4. Find undercuts and decide how to split the die blocks to provide moving side cores so that the component can be removed from the mould. This is a skilled task which is not currently supported by available software on the market. 5. Build a model of the mould die blocks which contain the inside and outside impressions of the product shape, but altered to allow for plastic shrinkage, draft (to allow the component to be removed from the mould), addition of the split-surfaces, etc. This is possible using commercially available software, but has enormous potential for improved software support. 6. Extract geometry from the external product model which describes ribs, bosses, etc. which will be sparked into the mould dies, rather than milled. This geometry is omitted from the 3D model of the core die block (so that it will be ignored when milling), and a set of 2D drawings of the electrodes required is produced. This process is not supported by commercially available software. 7. The rest of the mould tool is designed, generally in 2D. This involves deciding on the ejection and cooling systems and producing 2D drawings of each mould component to be manufactured. 8. The mould components are then manufactured. Often the basic components (plates, pillars, bushes, etc.) are bought in from standard mould catalogues. The plates will then requires many holes to be drilled (from information on the 2D drawings). This may be done manually or via CNC (though in this case the CNC programs are generally produced manually from the 2D drawings). The two main plates (the core and cavity die blocks) require 3D CNC milling, followed by EDM sparking for ribs, mounting bosses, etc. The milling is done by CNC, with the CNC program generated from the mould model by a CAM software package. This software typically requires the CNC programmer to visually inspect the cavity shape and manually sub- divide this into regions suitable for different machining strategies. Different strategies are required for flat(ish) areas, steep walls, corner fillets, etc. This is a skilled task. Use of an inappropriate strategy will cause a significant increase in the machining time required to provide a suitable surface finish. Most programmers are not sufficiently expert to make a good job of this process. Finally the EDM electrodes are manufactured. Electrodes for thin ribs are generally cut from sheet copper - often by EDM wire sparking. The CNC programs for this wire sparking are typically generated manually from the 2D electrode drawings. Milled electrodes may have a complex surface form (in which case the CNC programs are generated via CAM software from a 3D model derived from the mould cavity geometry), or they may (more commonly) have a simpler form (to tidy up sharp corners in the model which cannot be milled) in which case the CNC programs may be generated manually from 2D electrode drawings. There is enormous scope to improve support for the manufacture of mould tool components via generation of much more CNC information automatically from the mould model. 9. During this process the product designer will typically send several design modifications. These are often sent as a completely new component model, and the mould maker is left with the problem of determining what has changed and the effect that will have on the mould model which is already under construction. Current commercially available software does not provide support for this process. PALEMAN aims to support all the above mould design and manufacture stages (the numbers below tie up with those in the stages above). 1. Transfer of external product models is already available via IGES and other standard formats. PALEMAN will investigate the possible use of OLE4D&M (a 3D version of the OLE standard used to embed documents such as spreadsheets within other documents such as word processor documents under WINDOWS) to help in the sharing of product data between the product designer and mould maker. 2. PALEMAN will develop software to suppor the process of understanding, structuring and repairing external data. 3. PALEMAN will provide improved methods of generating split-surfaces. 4. PALEMAN wil research and prototype ways of supporting the process of decomposing a model into pieces to allow for sliding cores, collapsing cores, etc. 5. PALEMAN will provide methods of building the mould cavity/core models from the component geometry. In cases where the product designer and the mould designer are within the same company (or the same person), PALEMAN will provide software support for the design of complex shaped products by selecting features from a menu of choices - based upon an anatomy of surface features for a particular product family (e.g. a shampoo bottle). 6. PALEMAN will provide software support for the extraction of geometry for EDM sparking, and subsequent generation of CNC EDM programs semi-automatically from this data. 7. PALEMAN will provide improved support for the design of mould tools (other than the core/cavity shape), and in particular make use of this mould tool model to allow automatic generation of CNC drilling programs to manufacture each mould plate. 8. PALEMAN will seek to improve the automation of the manufacture of the core and cavity die blocks by aiding/automating the selection of an appropriate strategy for different surface regions. PALEMAN will seek to automate the CNC drilling of mould plates (see 7) and the CNC wire erosion of rib electrodes (see 6). PALEMAN will also investigate the use of rapid tooling technologies (e.g. layer manufacture, high speed milled prototypes) to manufacture tooling more quickly. 9. PALEMAN will seek to support the concurrent design and manufacture of mould tools alongside the design or redesign of the plastic component. Mechanisms which will be investigated to help this process are associativity between the component model and the mould model (both via IGES and OLE4D&M), differencing IGES models, and use of EDI via ISDN/Internet. It is hoped that use of the software resulting from this project by mould makers will result in: * reduced lead times (expected to be as much as 50%) * improved quality (due to reduction in manual mistakes creating and reading 2D drawings) * reduced cost (due to reduction in re-working because of mistakes or design changes).
Acronym: 
PALEMAN
Project ID: 
1 798
Start date: 
01-11-1997
Project Duration: 
36months
Project costs: 
3 280 000.00€
Technological Area: 
Market Area: 

Raising the productivity and competitiveness of European businesses through technology. Boosting national economies on the international market, and strengthening the basis for sustainable prosperity and employment.