East Midlands' Rutland Plastics (01572 723476) has embraced additive manufacturing for the production of jigs and fixtures.

The custom injection moulding company makes products for a wide range of companies and industries. Because each project is unique, Rutland must create complementary jigs and fixtures to position and hold each project's components during manufacturing operations such as assembly, gluing and drilling, in addition to measurement and inspection.

Traditionally, Rutland made approximately 100 new jigs and fixtures annually from aluminium on its two Bridgeport vertical machining centres. This process cost approximately £1,000 per piece, or £100,000 per year in total, while each new jig and fixture took three days to create. Identification labels and felt pads were manually added to the jig or fixture after production to prevent loss and accidental scratching of production parts.

3D PRINTING OFFERS MORE

Meanwhile, Rutland had purchased a Stratasys Objet350 Connex 3D printing machine from SYS Systems (01283 585955) to produce rapid prototypes, another service it offers. But it soon realised that the flexible system was also an ideal platform for creating jigs and fixtures. The company is now able to produce accurate jigs and fixtures having good surface finish and intricate details, and can now print them with sharp corners and deep contours previously impossible to achieve in milled metal.

The Objet350 printer's multi-material capability enables jigs and fixtures having a combination of rigid and flexible, as well as opaque and translucent features, to be made. For example, a fixture can have a flexible coating over rigid plastic to provide a non-marking, anti-slip surface, or a pliable interface that compensates for manufacturing tolerances. Multi-material printing can also be used for labelling purposes, to generate identification numbers and for alignment guides, while usage instructions can also be printed in process. This approach to labelling is simple, convenient and ensures that labels will not peel, fade or wash off. All of this is accomplished in a single build on the Stratasys multi-material 3D Printer, says Andrew Fulton, managing director of SYS Systems.

Although printing accuracy of 16 microns can be achieved, the printing process is sufficiently flexible to be able to incorporate metal inserts when better accuracy is required. Similarly, surfaces can be machined or ground to provide accurate datum points and machining locations.

"We don't have any more machining constraints. We can literally 3D print something that we couldn't have manufactured any other way," explains Simon Grainger, Rutland Plastics's design engineer.

The efficiency of additive manufacturing makes it practical to optimise jig and fixture designs and to increase the number of them in service, points out Fulton. Engineers can easily evaluate the performance of the tool and make quick, cost-efficient adjustments to designs, as needed. Also, the process makes it feasible to produce jigs and fixtures for operations where they have not previously been considered cost effective when produced by traditional manufacturing methods.

With its Stratasys 3D printer, Rutland has been able to significantly reduce the cost of producing jigs and fixtures. In total, the company's conversion to 3D printing reduced its per-fixture cost from £1,000 to less than £600, and from £100,000 annually to less than £60,000. It also allowed the firm to add 300 CNC machine production days back into its annual operations plan.

Finally, Rutland is able to produce customised jigs and fixtures in a single day. Now, engineers literally design a fixture during the day, print it overnight and have it ready for use the next day.

As 3D printing jigs and fixtures is so quick, Rutland could move towards a digital inventory concept. Rather than store a wide range of manufacturing aids when they are not in service, jigs and fixtures can simply be printed out as they are needed. This approach saves time, slashes costs for tool storage and reduces inventory control issues.

First published in Machinery, June 2015