CIMdata PLM Industry Summary Online Archive
20 November 2008
Implementation Investments
WorkNC Cuts with Ultra Precision Diamond Bite Tooling
The Shinkoh Mold Co. Ltd, based in Kanagawa Prefecture, Japan has been a pioneer and leader in the manufacture of plastic injection molds since its formation in 1967. The bulk of its business is in the manufacture of molds for cellular phone display mock-ups. As part of its expansion plans, the company has launched a new ‘Prism’ project initiative with the aim of developing the expertise to offer nanotechnology ultra precision molds to its customers.
The WorkNC automatic CAM/CAD system was first installed at the company in 1999, for core plate manufacture. The key benefit was its rapid calculation speed, which cut program preparation times by up to 66%. At the time, Shinkoh Mold used another CAM system to program its cavity plates, but the programming time was so long that the machine tools were frequently idle, waiting for NC data. Detailed re-evaluation and testing of WorkNC’s capabilities by Shinkoh Mold’s engineers in 2005, when the software proved itself to be accurate and compatible with the cutting tools and machining centers used, led the company to switch all its programming to the Sescoi software.
Mr Kenichi Otsuka, President of Shinkoh Mold Co. Ltd, said, “When you select a CAM system it must be compatible with your milling machines as otherwise it will have a detrimental effect on your production levels. We carried out extensive testing which demonstrated that WorkNC was the best match for our Yasda and Makino machines. This was just one of the reasons we purchased additional seats of the software. WorkNC has delivered a 40% reduction in programming times for cavity plates. Now the milling machines are never idle waiting for NC data.”
Shinkoh Mold has developed seven predefined machining sequences in WorkNC: Cavity-Large, Cavity-Small, Core-Body, Core-Frame, Core-Slide, Small-Insert A and Small-Insert B. Mr Kazuya Fukushima, Shop Floor Manager, said, “These predefined sequences allow even novice programmers to generate high quality toolpaths by simply reading in the new model data and executing the toolpath. WorkNC’s batch mode calculation enables us to process toolpaths overnight ready for machining in the morning.”
The company makes extensive use of WorkNC’s Z-Level Re-machining toolpath, using it to re-rough the cavity and to remove excess material in corners, avoiding damage to the tool to be used in the following toolpath and minimizing cutter loads. To finish the cavity, Z-Level Finishing is used on slopes greater than 75 degrees, and Planar Finishing on more gradual slopes. Where a higher quality finish is required, Planar Finishing is used with the angle option of 45 degrees from X axis to minimize tool load.
Mr Kazuya Fukushima added, “WorkNC’s Contour Re-machining toolpath enables us to re-rough the whole part. We then use a trimmed Z-Level Re-machining path to reach deep cavities and to work with long tools without incurring excessive loads.” He continued, “WorkNC is easy to use, it requires very little training and experienced shop floor engineers can use it to store and share their practical knowledge with the NC programmers.”
The company is reducing the number of electrodes it uses and increasing the level of direct machining of each cavity. The benefits include cost reduction (half the cost of electrodes), 66% reduction in manufacturing times, sharper definition on edges resulting in improved quality and reduced polishing times. Mr Kenichi Otsuka added, “Possible is different from practicable. By standardizing our CAM processes in WorkNC we eliminate reliance on individual skill levels and achieve consistent results.”
Shinkoh Mold examined ways of reducing cutter marks on the cavity and minimizing tool load. Techniques employed include running the spindle for 30 minutes prior to cutting to avoid problems with expansion, keeping the spindle speed to 13,000 rpm to ensure consistent and repeatable expansion figures, and reducing approach angles to 1 degree to minimise cutter load. Combining these methods with WorkNC’s re-machining and finishing toolpaths has enabled the company to machine successfully with 0.2mm diameter tools 10.5mm long, which is a length to diameter ratio of 26, without deflection or damage. Mr Kazuya Fukushima said, “We used our standard predefined routines in WorkNC to produce these results, which prove that the software works well with smaller tools. WorkNC’s stability is outstanding, it can’t be beaten.”
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