Analogue visualisation steers 3D design

Paul Boughton

Design engineers do not think digitally - they think in terms of size, shapes and attributes, and even mathematical symbols in some cases. Whereas in the past they would have needed to write programs in languages like Fortran and C, modern software tools allow them to visualise their designs in terms they understand argues Boris Sedacca.

Formerly a topic for geeks and engineers, 3D printing was a godsend for the media in May 2013 when it was revealed that Cody Wilson, a 25-year-old law student and founder of the group Defense Distributed, successfully fired the world’s first gun made with a 3D printer in the US.

The gun was assembled from 15 separate printed components made from ABS plastic on a second-hand Stratasys Dimension SST 3D printer that cost $8,000 from eBay - only the firing pin was made from metal. Stratasys is the leading manufacturer of 3D printers for prototyping and manufacturing.

A little less dramatically but also in May 2013, Stratasys announced that French remote control systems manufacturer, Survey Copter, is using its 3D printing technology to produce prototype and short-run component parts for mini-unmanned aerial vehicle (UAV) systems, also known as drones.

Survey Copter is a subsidiary of Cassidian, which is the defense and security division of European Aeronautic Defence and Space (EADS) group. It designs complete remote systems for surveillance photography and video service applications for UAVs and other airborne craft, as well as for sea and overland vehicles.

Survey Copter designs and manufactures turnkey remote systems working in critical and severe environments/conditions at sea, in the air or over ground. These systems involve UAVs, robots, tanks and complex turret systems, as well as data transmission and target tracking devices.

24-hour prototyping

Having previously outsourced its prototyping requirements, Survey Copter asked Stratasys for an in-house solution that would reduce costs and ensure greater efficiency and autonomy, allowing the company the means to rapidly produce very small quantities within 24 hours.

Survey Copter has installed a Stratasys Dimension Elite 3D Printer and Stratasys Fortus 400mc 3D Production System, which offers nine production-grade engineering thermoplastics using Stratasys' patented fused deposition modelling (FDM) technology.

They are deployed in the production of component parts for the company's mini-UAV systems, including both helicopter and fixed-wing variants weighing up to 30kg and 10kg respectively.

Ranging from a few millimetres up to parts measuring 40cm x 10cm, these components comprise mechanical structures for optical turrets, structural elements of aircraft, battery compartment housing, supporting structure, as well as scale models.

Jean Marc Masenelli, managing director of Survey Copter, asserts that the ability to utilise different materials according to specific application needs offers key advantages for producing durable 3D printed parts.

“The Stratasys 3D Printer can produce parts with complex shapes, which allows us to produce parts of wide-ranging dimensions and hollow forms, as well as full honeycomb structures,” Masenelli explains.

Another Stratasys customer, Rutland Plastics, recently moved into rapid prototyping for customers to test products prior to committing to invest in a mould tool.

Presaging volume production

“Some customers will only want one or a few prototypes, but we can now also offer this to existing customers in the hope that if they get a prototype from us initially, it can later on be developed to full-blown injection moulding for volume production,” explains Stuart Lovett, marketing manager at Rutland Plastics.

“We also make parts for a pump that is used for draining central heating systems. The customer has just up-rated the pump motor and one of the parts we make has a filter with holes that allows water through. Now because of the up-rated pump, the customer wanted to increase the flow, so we came up with a redesign to the part, which had a filter with more holes.

“The customer was concerned that some of the water might blow out again because of the increased pump power, so we suggested that they build a prototype to test it. We produced one prototype with maximum flow and another prototype with smaller holes. They were then able to assemble both prototypes and attach them to the pump so they could test it and decide which way to go.

“As a result, they were able to go for the one which offered maximum flow because they could show that it worked. Had they not used a prototype, their only other option would have been to modify the tool and they would have probably chosen to play safe with the lower flow option. The ability to prototype has enabled them to improve the efficiency of the flow of the equipment.”

At Haughton Design, engineers develop designs through visualisation, 3D modelling and prototyping. The company offers specific expertise to mechanically focused clients such as FEA with a fully traceable design binder.

The company has provided prototype design and manufacture for a pipework and induction welding system called Strata from Aliaxis, global manufacturer and distributor of primarily plastic fluid handling systems used in residential and commercial construction, as well as in industrial and public infrastructure applications.

Induction welding

The brief was to design and develop a complete range of fittings for an innovative pipework system and then work with the client’s technology partner to mechanically design casings and fittings for a novel induction welding unit.

The project involved development of over 140 pipe fittings with fully defined CAD models and drawings. It also involved working closely through the research and development stage with the client and technology partner to integrate sophisticated electronics and systems to provide controlled fusion of composite plastic pipes and fittings.

David Mills, managing director of Haughton Design says: “We buy in quite a bit of rapid prototyping using 3D printing on general and special purpose products, like single mechanical parts or small batches if required. They are then tested to see if they perform as they should and then they can go to tooling.

“We use SolidWorks to produce the files for 3D printed polymer and metal parts. With polymers, if someone orders ten prototypes, we can print one from which to make a silicone mould and we can then cast the rest, or go to CNC machining.

“We look at the complexity of a product design and its accuracy, and then decide which 3D printing bureau to use for the prototype. We looked at the possibility of buying a 3D printer but because our requirements vary so much, it is not cost effective to buy in a machine that may quickly be out of date.”

Some projects may have large dimensions, which may limit the number of 3D printers able to do the job, while a medical device project may need high accuracy and this would impose different limits on available printers. Haughton Design has used 3D printing for about ten years and has benefitted from falling costs and improvements in materials.

“Design teams have tended to get smaller and if we spent £25,000 on a 3D printing machine we would need a big design team to keep it busy. Some of our larger customers have bought their own prototyping equipment but we could not afford to have such equipment lying idle.”

ARRK, One of the bureaux used by Haughton Design, provides a complete rapid prototyping service. Outdoor power products manufacturer Husqvarna called on ARRK to help develop a new rear collection lawnmower, the Flymo Multimo 360XC.

CNC prototypes

ARRK proposed an ABS fabricated CNC model and supplied a model Comprising 25 CNC components in ABS and clear acrylic to prove the design and fit of the components. Husqvarna conducted field trials to cut grass and confirm the performance of the lawnmower.

The use of ABS, with its high impact properties, allowed the lawnmower to endure the physical demands of the trials, which allowed the design team to optimise the cut and collection performance of the Multimo. ARRK was then commissioned to produce vacuum castings of all the components, resulting in 15 fully assembled lawnmowers being supplied.

"CNC services can still be classed as prototyping,” contends Marc Bouvier of ARRK Europe. “We also make dashboards for vehicle testing from selective laser sintering (SLS) powder-based rapid prototyping.”

ARRK uses CNC masters for its silicone tooling. The vacuum castings were produced using colour matched polyurethane resins that were as close to final production material as possible. The components were finished, textured, assembled and then delivered within four weeks. Husqvarna has since reported a very successful product launch which it says reinforced the Flymo brand in the market.

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