Steve Ayre, managing director of the Oakham-based injection moulding specialist Rutland Plastics, says 3-D ‘printing’ technology has really come of age.
“We can use the multi-material capability of our latest ‘printer’ to create finely detailed truly functional models and prototypes. We are also developing a process for very small batch runs of plastic injection mouldings by printing a mould-tool cavity and saving the cost of a conventional steel or aluminium tool, thereby allowing us to significantly shorten the lead time from concept to production.”
Over the last six months, Rutland Plastics’ Objet Connex 350 — from Derbyshire-based SYS Systems Ltd
(www.sys-uk.com) — has made some 100 different printed models up to 342 x 342 x 200mm in single-cycle production. In addition, numerous repeat runs have been undertaken, many including design changes and improvements. These printed models have varied in size from 2mm in diameter ¥ 6mm long (with 0.3mm-diameter intersecting holes) to a sample electric-fence post produced in three sections that dovetailed together (to form a 1m single length with a 150mm-long steel nail in one end).
There are two key areas where 3-D printing is producing very practical aids to production and prototyping at Rutland Plastics. First there is the small-batch injection moulding service — in development — where mould tool cavities are 3-D printed and used for short moulding runs and trials. For these applications, the mould is placed in one of Rutland Plastics’ standard bolsters to produce an injection-moulded part. This approach offers significant savings in costs and time compared with the use of steel and aluminium mould tools for short runs.
“Secondly, the ability of the 3-D printing process to select or blend different materials from the 50 or so material types, grades and colours has been invaluable,” says Mr Ayre. “Our design engineer Simon Grainger can blend a variety of rigid and flexible materials — and transparent ones — in the same cycle.”
Simulating different materials
Mr Grainger says: “The resulting ‘composite’ materials can be ‘tuned’ to give specific values for tensile strength, elongation to breaking point and temperature ratings; we can even achieve various hardness values. This means we can easily simulate customers’ needs for polypropylene, ABS, transparent plastics, high-temperature plastics, and a wide range of rubber-like materials between Shore 40A and 95A. Moreover, we can produce wall sections as thin as 0.6mm and achieve general accuracy levels of 0.1mm; and larger models can be created by simply joining two or more ‘prints’ together.”
Rutland Plastics was set up in 1956 by Mr Ayre’s grandfather. At first, the company was mainly engaged in designing and manufacturing its own products — including toys and plastic flowers. It moved into sub-contract moulding in the 1980s after winning a major contract from a supplier to the UK gas industry; the contract was for producing pipe fittings using the jointly developed and patented process of electro-fusion — a method of joining MDPE, HDPE and other plastic pipes with special fittings that have built-in electric heating elements which are used to weld the joint together. The production of these fittings still accounts for some 40% of Rutland Plastics’ £8 million turnover.
Major investments
Investment has been continuous, and the company has progressively increased the size of its injection moulding machines; the largest have a capacity of 1,700 tonnes and can mould parts up to 1m square with a 38kg shot weight. These machines also feature integrated robotic automation. Today, Rutland Plastics has 100 employees (including three designers) and works three shifts over a five-day week.
Over the last 12 months alone, the company has invested more than £1 million in the business; this included the Objet Connex 350, a machine that Mr Ayre says is a must for any progressive moulding business wanting to have more customer involvement and win business when competing against overseas companies. “The printer is invaluable in supporting our ‘design for manufacture’ involvement with customers — an area that has been essential for retaining existing business and developing relationships with new customers. If we are involved in the early stages of a project, we can influence designs to reduce mould, material and process costs; and if needed, we can use the Objet machine to produce a prototype or sample from stock material in three days.”
Rutland Plastics also produces drill jigs and checking fixtures; these are made from stock materials and fitted with hardened bushes and location points as required. “Our 3-D printing capability allows us to produce these items far quicker than a conventional tool-room could achieve,” says Mr Ayre, who adds that the prototyping service is of particular benefit to clients when they make presentations of new products.
Typical of the components produced under the 3-D rapid-prototyping banner are scale models of parts such as ‘heavily detailed’ electronic cases, pipes and connectors, flow valves, keyboards, jigs for checking medical components, and fool-proof sockets to ensure the correct gas connections in a hospital. Components can also feature bar codes, logos and textures — and even hinges that can withstand repeated flexing.