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New technologies in mould manufacturingHighest among the challenges of designing and building moulds is maintaining customer requirements, along with reducing costs while maintaining quality. A strong collaboration of the right processes - from design to trials and acceptance of the part needs to be worked out in parallel to produce ‘first time right’ results. This can be made possible with CAD, CAM, machining with the right machines and tools. ■ Gibson Manthopil

May/Jun 2012 | EM

M ould manufacturing kicks off by using CAD to design all the parts modelled fully in 3-D.

3-D software have the capacity to design complex moulds and also the capability to check the design at different stages. The varying shapes used in product designs today, cause split lines to become more intricate and difficult. Working in 3-D solids enables many of the manufacturing issues to be identified upfront, allowing the designer to detect potential collisions,

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Gibson Manthopil Asst General Manager NTTFgibsonm@nttf.co.in

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verify correct shrink values and determine whether parting surfaces are manufacturable. 3-D modelling and having a concurrent engineering process with standardisation and simulations in design is the key for quick deliverables. With a complete design in 3-D, a fully detailed and consistent model is maintained throughout the design and manufacturing processes, so that changes can be quickly and reliably incorporated from design to manufacturing and assembly. The solid or surface model

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New technologies in mould manufacturing

data that is produced for both split line and cavity creation during the mould design, if properly used can cut the programming time and lessen errors caused by human oversight and drawing misrepresentation.

Complete design in 3D

The aim is to digitally capture all the essentials of moulds and the mould making process and have a virtual mould built according to the standards and run it with all kinematics to prove that it functions in the virtual environment before the mould is even built. Advanced motion simulation technologies built within the CAD environment provide designers with the benefits of complete visual representation of mould kinematics and comprehensive collision detection, including automated recognition for mould components like lifters, sliders and ejectors.

Among other things, 3D modelling of the complete mould allows:■ to check flow, cool and warp analysis

of the part based on the design of the mould

■ to design complex moulds and check through intervention inspection

■ standardisation of parts■ parts to be directly imported from a

huge database of standard components, from many different vendors

■ synchronisation across design and manufacturing

■ reduce errors caused by human oversight and drawing misrepresentation

■ people on the shop floor to see exactly what they are building

Concurrent engineering

One of the key features of quick turn around in mould making is concurrent engineering. It can drastically shorten mould design time, as multiple design tasks can be performed simultaneously. For example, one designer may work on the cavity side while another works on the core side or one designer can finalise ejection while another designs the manifold and hot drops or one designer is finishing waterlines while another begins pulling electrodes. Manufacturing and assembly work can start while the design details are still being worked out, further compressing product delivery times. Machine operators can view the tool paths and clearly understand the production process, eliminating the need for excessive documentation. In the assembly area, toolmakers can access the data online to do preliminary checks and verify dimensions, saving valuable engineering time.

Conformal cooling

Efficient cooling of the mould is an important aspect for the quality of the product, influencing both the rate of the process and the resulting quality of the parts produced. Soft wares like mould flow, VISIflow provides tools that validate and optimise the design of plastic parts and injection moulds, and study the plastic

injection moulding process. The results provide thermal imbalances in the mould to help the designer work on efficient cooling options. Conformal cooling helps to create cooling/heating configurations within a tool that essentially follows the contour of the tool surface as thin/thick sections of the part may dictate for optimal thermal management. The objective typically is to cool or heat the part uniformly. Cooling channels are designed to follow the shape of the cavity and core, reach hot spots, and promote temperature uniformity in the plastic materials being moulded. Conformal cooling provides a tremendous advantage in mould tooling through significant reductions in cycle times.

5- axis machining

Majority of mould shops still use 3-axis VMCs and the advancements in machine tools, speeds and feeds, tool paths, tooling and control features during the last few years make this the perfect time to reconsider integrating a 5-axis machining center into a mould manufacturing facility. Technology enhancements have encouraged mould manufacturers to integrate 5- axis machining into their operations. Simultaneous 5-axis machining is particularly pertinent if a shop does deep cavity moulds or tall core moulds. The ability to use shorter tooling with 5-axis machining reduces the deflection of the tool, increases surface finish quality, significantly reduces the need to polish

Cut section of inserts with conformal cooling Thermal profile differences between conformal cooling and traditional cooling

May/Jun 2012 | EM

May/Jun 2012 | EM

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> more @ click | EM00663Further information at www.efficientmanufacturing.in

the mould, and in many cases, eliminates the need for EDM operations. With shorter tools, one can push faster with increased feed rates and take heavier cuts. The CAM system is important, but how the machine tool’s control handles the part program also matters. The multiple advancements in control technology in the machines improve surface finish, increase productivity and accelerate machining time. A few important points in a 5-axis machine is to consider machine configuration to ones needs, repeatability and accuracy and control features like tool centre point management (TCPM), toolpath linearisation, automatic safe repositioning (ASR).

EDM with graphite

When there comes a time, to decide whether to use graphite or copper electrodes in a shop, it’s important to look at the bigger picture. Graphite material machines very easily - one can mill it, grind it, turn it, drill it, tap it, even file it to whatever shape wanted. Another advantage of graphite is that it doesn’t burr. One can put it on a graphite high-speed mill and cut out complex shapes and forms, and once its cut it’s finished - with no deburring. The new high-speed mills that are sold today are specially designed to machine graphite totally enclosed with a vacuum system to remove all of the dust and there are some machines that can even cut square internal corners. Recent advancements in

the technology behind low-wear capability have drastically improved the machining speeds with low-electrode-wear application settings. In instances where it used to take three or four electrodes to produce a complex mould cavity with multiple ribs, today’s low-wear functions can reduce that amount to one, maybe two electrodes. Such a scenario brings forth major cost savings on milling additional electrodes, especially ones with highly difficult shapes.

3-D, non-contact scanning for inspection

3-D scanning is emerging as a viable tool for design and manufacturing applications. Advantages over CMMs are the thoroughness of the data set and the ability to inspect pliable parts. The dense point cloud that 3-D scanning outputs provides a complete description of the object. This means that every feature is measureable and that all variances are captured. Since 3-D scanners are non-contact, soft, pliable parts present no challenges. Where a CMM’s touch probe would deform such a part and nullify inspection data, 3-D scanners will return inspection data for moulded rubber, silicone and elastomeric parts. 3-D scanning also offers robust investigation of individual features. Using 3-D scanning software, features in question are measured to produce both tabular data, like a CMM report, and visual mark-ups that flag measurements that are out of tolerance. For

mould makers, this technology is key. It not only gives a complete depiction of a part, it also speeds up the entire project by reducing time for engineering documentation, inspection and analysis.

Ultrasonic polishing

The tool in an ultrasonic handpiece reciprocates at 21,000 to 25,000 strokes per second and produces a stroke length of only 1 to 5 microns. This allows the polisher complete finger tip control when polishing even the minutest details on even 40-64HRC tool steel. It comes equipped with numerous clamps that will accommodate tools—from small/fine diamond files to conventional fine grit stones—as well as ceramic stones and brass laps, which are used in conjunction with diamond compound. When intricate and precise finishing work on hard materials—like heat-treated moulds/dies, carbide dies and punches with fine edges and very narrow slots machined by an EDM is required, to consider using an ultrasonic polishing system makes sense because it can reduce finishing time by as much as 40 to 50 per cent.

While these best practices have proven to help many mould makers, the key to success is applying the strategies and processes and picking up the ideal machines that are right for one’s business. ■

Graphite electrode for speaker grill & finished core after EDM with HQSF Graphite electrodes for intricate EDM operations