Large machines seal the deal

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Specialist moulding and seal manufacturer TRP Sealing Systems relies on bridge type machining centres for accuracy and repeatability for in-house tooling manufacture.

Consistency of production cycles enabling extended unmanned running while maintaining accuracy and precise levels of surface finish and repeatability are critical to mould production at the Hereford headquarters of elastomeric rubber seal, gasket and moulding specialist.

The company has been able to maintain high levels of overall productivity during the last three years following the setting up of its own toolroom and the installation of a Wele large bridge-type (LB series) LB421 gantry machining centre.

Supplied by 2D CNC Machinery of Hinckley, the investment was critical to the business to bring often very complex mould production and refurbishment operations in-house as front line support to its seal moulding and gasket production.  Here, rubber mouldings weighing up to 5kg are produced in ‘made-to-order’ batches of up to 250,000 a year from mould tools that can vary in size between 300 mm square to 3,900 mm by 1,700 mm.  These variations in mould sizes are all now machined complete in a single operation on the Wele machining centre.

Said Quality Manager Jo Privett: “We design and develop each mould to suit the material specification which can also include cross-blended types, direct from customer supplied 3-D models or drawings of the gasket or seal they require.  This can be extremely demanding and often draws on our 35 years of production expertise where finished component thickness can vary between just 2 mm and 20 mm.  However, there are added complexities due to geometry applied to the form, special radii and especially transition between areas into both bottom and top halves of each mould.” 

To add to its specialist operational expertise, following measurement and material specification analysis, he said: “Final approval of the moulded component is always the result of a ‘fit-and-function’ application.”

This is why machining accuracy and especially consistency is important to TRP.  While the final moulded component can be to a tolerance of +/-0.15 mm, to ensure maximum production life from the mould, process sizes are normally maintained very close to bottom of the designed tolerance band which can mean within 0.08 mm.  However, even more demanding is that tolerances of form in the mould which can be as tight as 0.03 mm.                                                                         

Here, the accuracy and repeatability of the Wele LB421 has proven critical and is now well-proven, even when the 4,000 mm by 2,000 mm machine table is fully loaded with mould plates. These are retained in place using magnetic pads and tolerances have to be maintained across the whole table area. This is aided by the 15 tonne capacity table design that incorporates triple sets of ultra-heavy, linear roller guideways on the X-axis a major advantage for stable machining against most machines of this type which have only two.

Recently, following almost three years of continuous production, as part of the company’s regular quality audit, it was decided to lightly reskim the 1,225 magnetic pads which are fitted to the table.  These provide a datum and hold each mould in place giving total access to the top surface of the mould plate and eliminates the use of clamps.  When completed, the inspection report qualified the total area of the table had be machined within 10 micron.

Originally formed in 1981, TRP Sealing Systems has progressively grown to become a global business while still maintaining 80%of sales within Europe. It has set up manufacturing operations under Hereford’s control in China and India to serve the Asian and Middle East markets plus a facility in Romania. 

With customers in the automotive sector, it is also a regular supplier to electronics, biotechnology, food, medical, chemical, marine, power generation, oil and gas, aerospace and defence sectors.

An important part of its success is the advanced laboratory for compilation of material specifications and seal development involving the tailoring of special polymers to suit specific and often ground- breaking applications such as those required by chemical customers and to meet the latest environmental demands.  This ties in with its in-house tool design and prototyping service where the latest rapid prototyping equipment including laser and 3-D printing is installed.  There is also a facility to produce bonded metal components.

Previously TRP used external UK mould suppliers but now 99% of production is within the business.

www.trpsealing.com

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