Robotic arm

Our flexible friends

Factory automation requires a partnership between robot, system provider and end user.

No sort of automation can ever provide a purely technological 'fix'. Relevant investment only provides a payback when the hardware involved is made to operate in a business context that is accurately costed and where staff are properly trained and understand what is required of them.

These factors are exemplified by a manufacturing cell that has been in operation for the past year at diesel engine manufacturer Perkins Engines.

The cell, which cost about £5m, is used to manufacture around 80,000 of the company's Type 400 D cylinder head each year. Previously, the units were supplied externally, but when the contract involved began to approach the end of its defined term the company decided to investigate bringing their manufacture in-house.

Accordingly, Perkins set up a 'six sigma' internal project team with a brief to formulate an in-house solution that would nevertheless be subject to competitive comparison with prospective external sources by the company's global purchasing operation. But, crucially for the success of the venture, the team selected two suppliers of automation technology - machine tool manufacturer Heller and robot supplier Fanuc - to be close partners in the venture.

Neither choice was based on mere cost, says Tony Green, manufacturing coach at Perkins. Instead the company selected the two suppliers after a rigorous analysis based on numerous factors including previous experience of working with them, quality of service and support and the fact that they had extensive facilities in the UK.

"We gave [the suppliers] the design and asked them to come back and tell us what would be required to make the units cost-effectively and to the required quality levels," Green explains. The outline scheme suggested by Heller and Fanuc was then refined on the basis of further input by Perkins' own engineering personnel until a final configuration for the cell was agreed.

Close contact

Operation of the cell starts with the delivery to it of pallets of cylinder heads after which a Fanuc R2000iA/165 robot equipped with one of the company's V500iA/3DL vision systems identifies the position of the heads and then picks them up using a magnetic gripper. After reorientating the head, the robot places it into a marking machine and then onto the cell's input conveyor system.

But the vision system provides additional benefits beyond unmanned loading of the cell. It also allows Perkins to use standard pallets, and eliminates the need for special jigs and costly containers. The robot is further utilised at the end of the machining cycle to load machined heads into a leak-testing machine and then restack them into a pallet.

The machining cell itself comprises six Heller machining centres - four for pre-machining and two for finish machining. Two washing machines then complete swarf removal. The machining centres are serviced by two of Fanuc's R2000iA/165 robots, each of which is capable of servicing the entire cell independently, thereby providing a degree of intrinsic back-up capability should either malfunction.

The staff members operating the cell also have an unusually high degree of familiarity with the equipment. Several of Perkins' own personnel were seconded to Heller's and Fanuc's UK sites in Redditch and Coventry respectively, in order to gain first-hand experience of how the equipment was constructed. Moreover, a number of Perkins' apprentices actually helped to build the machining centres that are now installed in Peterborough.

Green emphasises the importance of this degree of involvement on Perkins' own part in pre-installation activities. "There are obligations in both directions. We have to ensure that we are a good customer and that means being comfortable and familiar with what is being supplied to us."

Moreover, this underlying principle of active cooperation between Perkins and its automation suppliers has not ceased now that the cell is in use. Green says that there are still regular bimonthly meetings between key Perkins and Heller staff to review operations. There is also continuing, though slightly less frequent, contact between Perkins and Fanuc.

"The success of this project is down to partnership," he stresses. "It is the result of a ground-up development to ensure the cost effective machining of the 400D cylinder head. It has retained machining work in the UK, improved product quality and has further enhanced best working practice within Perkins Engines." 

Re-usability

Another key demand increasingly being placed on suppliers of automation systems by their customers is for flexibility and ease of re-use of installations. UK company DV Automation supplies custom-built installations for 'hemming' operations - the joining of panels of material to make more complex sub-assemblies such as car doors for customers in the automotive sector, both original equipment manufacturers (OEM) and 'tier-one' suppliers worldwide.

According to DV business manager Mark Schlanker, although Birmingham-based DV is a subsidiary of robot supplier Kuka, it also uses robots from other sources if they are specified by the client.

Schlanker says that the demand for re-usability of automated facilities is now commonplace. "Car manufacturers don't want to scrap existing production facilities when they introduce new models," he explains. But that does not mean that the capability is in any way easy to provide.

One major OEM, he says, has recently come to the company with a request that it find a way to enable the retooling for a new vehicle of a five-year-old hemming cell in a maximum of just two days. And this requires building a high degree of flexibility into manufacturing cells from the start. Realistically, therefore, says Schlanker, where a robot is concerned this will involve a combination of the reprogrammability of the robot with ease of retooling.

Robots are, as Schlanker points out, intrinsically re-usable. Therefore, formal proof of ease of reconfiguration of a manufacturing cell is likely to become an increasingly important part of the tendering process on the part of system suppliers like DV. That could well mean enhanced importance for simulation tools that can demonstrate different uses for a manufacturing cell even before it is commissioned for the first time.

One customer already using a highly versatile hemming cell from DV is tier-one automotive pressings and components supplier Stadco, which operates a robotic installation at its plant in Coventry to hem bonnets and tailgates for its UK customer base. The cell comprises a single hemming station positioned around a Kuka robot equipped with a roller hemming head. The robot guides the hemming head around the part to form the hem joint, ensuring that the inner and outer panels of the component are properly closed to form a safety edge.

The cell has also been designed to handle a variety of model variants and, in addition, to be capable of expansion to perform other tasks. Stadco is already considering extending the cell's capabilities so it can operate dispensing equipment for sealants. "The trend for manufacturers to have several model variants all based on one chassis platform means this approach is more attractive due to its high flexibility and cost-effectiveness," Schlanker adds.

Flexibility

Meanwhile, Finnish company Fiskars, a leading global maker of sharp-edged metal implements including scissors and axes, has embraced robot technology to provide the flexibility it needs to produce multiple products with quick changeovers.

Robots, for instance, play an integral role in the manufacture of the 30 different types of scissors produced by the company. When parts are loaded onto a conveyor belt prior to heat treatment, they are first examined using a 3D vision system mounted onto an ABB IRB 140 robot. This enables the robot to pick the blades from a randomly scattered pile and then sort and orientate them so that they enter the heat-treatment process correctly.

The oven generates temperatures up to 1,050°C to ensure the perfect shape and hardness of the blades, which cannot be straight since the material being cut would wedge between the blades. But before plastic handles are added to make a pair of two-handed garden cutters, for example, the blades go through another two IRB robots that sharpen the cutting edges.

Even though many of Fiskars' products are superficially similar, they are not identical, posing particular manufacturing challenges. "We like to build the robot cells to be as flexible as possible so that we can switch the lines quickly or assemble several products at the same time," says technical director Carl-Olof Holm.

One recent product enhancement that is facilitated by robotic manufacture is the application of a PTFE coating to axe blades that makes the implements lighter and easier to use. On the axe production line, the blades are suspended from hangers and come in batches of 20 to a coating station where an ABB IRB 540 robot sprays the coating.

"This robot is so accurate that it uses 30 per cent less PTFE material than our previous system," Holm says. "Not only is it great for us financially, it has also made the process safer for operators and much more environmentally friendly."

Simulation

Another factor that is facilitating the take-up of automated manufacturing is the increasing ease with which its effectiveness can be assured beforehand through simulation - even with products whose market appeal is based in large part on the perception that they are intensively hand-crafted.

The labour-intensive process of hand-crafting premium vehicles at the factory of Bentley Motors in Crewe, UK, for instance, should not disguise the fact that behind the scenes the company makes extensive use of computerised data to drive automated systems. For example, Bentley has a strong design-to-manufacturing strategy based firmly on the use of 3D data. Bentley has over 400 Catia design and 30 Delmia manufacturing-simulation users at the factory.

Derek Harrison, product development systems senior manager at the factory, says the ability to create, use and share 3D design data in non-design situations as well as in immediate design tasks enables the company to work more collaboratively.

"Delmia enables us to see designs in a manufacturing context and visualise how components can be assembled," he says.

Virtual data can be analysed in great detail to define the most efficient production process methodology. Since this information is available during the design evolution process, even before designs are completed, designers and manufacturing engineers can share the same visual data and enjoy visibility of each other's work as it progresses.

Harrison says this methodology has enhanced the linkage of design and manufacture considerably because designs are optimised for manufacture very early in the design process, even at the conceptual stage. One example of this, he says, was in the conceptual design for an instrument panel, which enabled modifications to be carried out before mainstream design engineering was initiated. 

But the benefits do not stop there. "Line-side planning procedures have been greatly enhanced through the software's production simulation features," Harrison says. "Because these allow us to link with the engineering bill of materials and assembly specifics to the virtual build it is possible to tune the process sequence for maximum efficiency."

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