The accuracy of die and mould determines the accuracy of the parts manufactured with them.
Rapid changes in models are pushing manufacturers of die & mould to constantly meet frequent product changes in their clients’ products, turn to shorter production runs, lower inventory levels while achieving higher productivity. Evolving new generation technologies like hard machining and complex profiling on multi-axis machining centres are the norm of the day. Manufacturing Today looks at the machining methods and new developments in design analysis, inspection techniques and complex programming systems of die & mould manufacturers.
Traditionally, moulds have been expensive to manufacture. So for economic reasons, they were usually used in mass production where thousands of parts were being produced. Moulds are typically constructed from hardened steel, pre-hardened steel, aluminium, and/or beryllium-copper alloy. The choice of material to build a mould from is primarily one of economics; steel molds generally cost more to construct, but their longer lifespan will offset the higher initial cost over a higher number of parts made before wearing out.
Pre-hardened steel moulds are less wear resistant and are used for lower volume requirements or larger components. The steel hardness is typically 38-45 on the Rockwell-C scale. Hardened steel moulds are heat treated after machining. These are by far the superior in terms of wear resistance and lifespan.
Vikas Taneja, vice-president, marketing, Jyoti CNC Automation Ltd, says, “Foreseeing the demand, we have developed fully vertically integrated manufacturing facilities to produce critical components under one roof such as foundry, sheet metal shop, paint shop, sub-assembly, assembly and state-of-the-art ‘Leonardo Da Vinci’ research & development centre and other allied manufacturing facilities. We have especially developed in-house high-speed motorised spindle up to 18,000rpm & special belt driven spindles with ceramic bearings up to 10,000rpm, which delivers higher torque during roughing operations and higher speeds during finishing.”
Tool Metal stamping, casting and plastic injection molding are popular production methods for die and moulds. Physical phenomena like part shrinkage and spring back make it difficult to precisely match the CAD geometry. For instance, in automotive, Nikon Metrology uses the iterative manufacturing process to monitor LC or XC laser scanners, which outperform tactile inspection in terms of measurement point count and inspection productivity. Colour maps generated in focus inspection visualise CAD deviation, providing powerful insight to avoid trial and error. Tool wear or accidental damage may call for repair rather than replacement. As original CAD may not outdated or missing, 3D scanning is a valid solution to reverse engineer the original tool.
Prasad Kokje, industry manager, TaeguTec, says, “In our state-of-the-art manufacturing and R&D facilities, TaeguTec is in continuous collaboration with the industry, including die and mould makers, to provide complete solution from rough to finish stages along with facilitating higher material removal rates and achieving excellent surface finish. Our efforts are also directed towards minimising cutting time as well as non-cutting time given existing machining setup towards reduction in overall production cost.”
Accurate and efficient machining of die and mould is essential provided the programmer is familiar with toolmaking concepts. Here are some areas that the programmer needs to have a good knowledge of:
Moulding area: The programmer needs to be aware of the areas of the die that will form the cavity for the material. Different strategies may be required if the cavity form is to be polished to reduce machining marks and save polishing time. Also material may need to be left in the cavity area if the component finish is sparked.
Visible and non-visible parts of the moulding: It is useful if the programmer knows which areas of the mould will produce visible areas on the mould. Then the machining parameters can be adjusted to save machining time on non-visible areas and produce a finer finish on visible areas.
Shut-off faces: Extra care must be taken when machining shut-offs (especially drop shut-offs and slide entries) to select cutters and strategies that ensure correct sizes are maintained. Too much material removed here can be disastrous.
Split lines: Edges where the moulding form ends and the split face starts must be absolutely crisp and sharp if split lines and flash are to be kept to a minimum. It is essential not to allow cutters to roll over these edges, so special strategies must be employed to cut these areas.
Hardening: If the die is to be hardened after roughing, then the programmer needs to judge whether the die will distort in the hardening process and allow for this in the roughing parameters.
Frequent product changes, shorter production cycles, lower inventory and higher productivity levels are the need of the hour. To meet these challenges, TaeguTec is continuously innovating latest-generation high feed machining solutions for die and mould makers to shorten production runs. In the long term, die and mould makers should invest on suitable machines which can run on 15K-20K+ mm/min federates and direct driven spindle technology for rough machining and high speed spindles to produce excellent surface finish in D&M finishing.
So with the right technological tool at hand, such as 3D parametric solid modelling, rapid tooling and high-speed machining, etc, what are the changes in the business model of tool-making? Kokje says, “Effective synchronisation of 3D modelling software plus state-of-the-art machine tools along with latest-generation cutting tools can produce great results in die and mould manufacturing with minimum lead time and excellent quality parameters. With new generation of cutting tool grades, we can work efficiently on higher hardness material as well as high speed machining which in turn helps D&M makers to achieve shorter delivery times and increased die life.”
TaeguTec has recently introduced the new four-cornered ChaseFeed (SBMT 09) insert line with a high positive helix cutting edge and is perfectly suited for smooth machining applications. It is particularly effective for machining areas of less than 1.2mm depth of cut with very high feed rate, providing higher material removal rates in longer-approach applications as well. The SBMT 09 inserts are available in three geometries: ‘M’ for optimum machining in steel and general machining; ‘ML’ for stainless steel, heat resistant alloy, low power machining in unstable and long overhang situations. And ‘MR’ for high hardness machining and interrupted conditions.
Other key features of ChaseFeed include its ability to generate lower cutting force compared to double sided inserts, and greater insert thickness for better endurance under high feed conditions.
In terms of the short term and long term strategies for die and mould makers and looking at the increasing demand in the Die & Mould Sector, Jyoti CNC Automation has designed and developed die-mould series: VMC Performance DM Series & K Mill Series to cater to its valued clientele in this segment.