Optimising the design of plastic mouldings
Plastics Advisers 6 from Moldflow
Moldflow has built a leading reputation, bolstered by the acquisition of competitor C-Mold in April 2000, for tools to optimise the design and manufacture of plastic moulded parts.
Manufacturing tools target the problems associated with production planning and scheduling, machine set-up and process optimisation, monitoring and reporting.
Design optimisation tools fall into two product families; Moldflow Plastics Insight (MPI) for in-depth simulations and Moldflow Plastics Advisors (MPA) for design-centric analysis.
The comprehensive MPI range incorporates thermoplastic and reactive moulding processes including gas, co-injection, fibre orientation and microchip encapsulation modules based principally on mid-plane mesh analysis and more limited direct support for 3D models to handle difficult geometry and avoid the need to create a mid-plane model.
This level of detail is most appropriate to toolmakers and moulders and is often not necessary during the design of the majority of components so the Plastics Advisers range aims to deliver ease of use, accessibility and CAD integration for rapid analysis of components early during the design cycle.
Despite the reduced level of sophistication, MPA’s Part Adviser and Mold Advisor products enable significant optimisation when the cost of change is minimal before the tool is cut, increasing the chance of higher quality parts, minimising rejects and reducing time to market.
MPA is recommended for generally thin wall parts where the thickness < ¼ average length and width of any local section. Should limitations be encountered or further analysis required, MPA set-ups can be transferred directly into MPI although material information is not transferred. MPA can be run as a standalone application or as an add-in for popular solid modellers. Models in .stl format can be opened as standard, but the separately licensable Moldflow Design Link (MDL) now in version 3 allows STEP, IGES, Parasolid and Pro/E files to also be opened. Part Adviser is available as an add-in for Pro/E, SolidWorks, Catia, CoCreate, Solid Edge, Mechanical Desktop and Inventor but Mold Advisor only for the first three. The benefit of using MPA as an add-in is that simulations can be run and results viewed directly on the solid model, minimising the need to re-export the model to explore multiple design iterations. In Part Adviser the basic operating procedure is simply selecting a material, specifying the injection location, running the analyses and viewing the results. An extensive material database is supplied including supplier and trade names plus search tools enabling almost any material property to be specified as criteria. Materials can be edited or imported and commonly used materials can be added to a personal list for rapid retrieval. Other processing conditions include mould and melt temperatures and injection pressure and times. Rather than jump directly into a plastic flow analysis, it is possible to run a moulding window analysis to identify good processing conditions or material suitability. It is also possible to run a gate location analysis that presents a coloured map indicating locations most likely to give the best fill results although these do need to be assessed in relation to mould practicality. Once a flow analysis has been run, a confidence of fill map is displayed and results for fill time, injection pressure, pressure drop and flow front temperature can be selected. Each of these can be animated to observe the flow, with the ability to rotate the model view simultaneously if required. The plot scale spans the entire result range by default. If required the scale limits can be set numerically or on a slider in order to assess specific areas of the component in greater detail. Additional analyses that can be run after a flow analysis are cooling quality to identify modifications required to part geometry in order to avoid differential cooling that can cause warpage and sink mark analysis to indicate the likely presence and location of sink marks. The result summary indicates the percentage of the part prone to sinkage and a contour scale of the probable depth. Since sink marks are often a largely aesthetic issue, a shaded view approximation can be displayed although resolution makes overall part views more useful than detailed area analysis. Should the additional analyses be required, they can be run unattended after the flow analysis using a sequence analysis batch option. Air trap and weld line locations can be superimposed onto the result plots. By saving iterations of model analysis as individual files, multiple result plots of a part can be viewed simultaneously as tiled windows. Significantly these can be locked together so that the selection of a result type including interactive view manipulation will apply to all. In this situation the set scaling command shows a table of the range in each file and allows them to be synchronised to show directly comparable plots. A report generator wizard steps through the creation of paper based or HTML based reports incorporating plot animations. Options include the plots and details to include, image size and order of results. Reports can include one or more part analyses. Mold Advisor incorporates all Part Adviser functionality and adds tools to orientate or mirror parts for multi-cavity and family tools. By working along the additional tool bar, parts are orientated, the number of cavities, parting plane and overall tool size specified then runner and gates created. Runners can be generated automatically or manually and can be subsequently edited. An automatic gate sizing analysis estimates the best gate dimensions and automatically updates the model with the calculated dimensions. A wider range of available gate types minimises the customisation required and analysis with gates only allows their optimisation before adding the sprue and runners. MPA 6 even includes support for three plate moulds. A runner balance analysis can be run with the option to accept proposed modifications. Runners can also be imported from previous models and a library of standard geometric sizes for sprues, runners, and gates can be created for rapid reuse. Additional results include cycle time, clamp tonnage, and shot size. An additional feature of MPA 6 is the Moldflow Community Center, a set of web based tools accessible from within MPA. These include discussion groups with other users, issue and enhancement request reporting and assistance in the form of training material, FAQ's and Moldflow's Knowledge Zone to supplement the extensive information available in the installed help topics. In order to establish an informed view of product usage and possible enhancements, performance and usage logs are automatically forwarded to Moldflow unless specifically disabled in the preferences settings. Part Adviser is priced around £5,500 for a machine locked license and for an additional £1,00 a floating license with a Commuter option to allow a license to be checked out from the server for up to 30 days, typically for use on a laptop. A new native compressed file format is used to reduce disk space storage requirements. The two complementary products within MPA definitely put easy to use tools into the hands of part and mould designers. As with all analysis tools it is important to understand the results that are generated but the supplied support files and new web based resources make a significant attempt to inform both novice and expert users. Even for designers with extensive practical experience, the speed with which analyses can be run leaves little reason not to use MPA to spot potential problems at the point in the development cycle when changes can most easily be implemented.