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A CNC machine allows foam fabricators to produce a typical order of 20 sample models in two days compared to the five days needed to cut the foam pieces by hand. In addition to saving time the CNC machine frees up engineers who previously had to pitch in and help cut foam pieces when a large quantity of samples were needed.

A company producing foam products used in the packaging of items such as electronics equipment and appliances moulds a full range of materials including expanded polystyrene (EPS), expanded polyethylene (EPE), expanded polypropylene (EPP), and copolymers such as GECET, ARCEL, and RMER. These raw materials are injected as beads into moulds then heated with steam, which causes them to expand and solidify into the finished shape.

The first task when a new product needs to be packaged is to work with one of the company's engineers to determine the appropriate material. Once this has been selected the engineer uses the customer's specifications and CAD geometry to develop a rough design of the foam part. The engineer specifies the material, size, and performance characteristics for the product and uses SolidWorks CAD system to create a 3D model of the initial concept. At this point most of the customer’s request between 20 and 30 samples for drops testing. Some customers have this testing done by the company while others prefer to take the samples and do the testing in-house.

Previously samples were produced by hand where an engineering assistant used a band saw, drill press or hot wire to cut the foam, working from the specifications on the CAD drawing. This was a time-consuming process whereby a typical order for 20 samples took a person about one week to produce. When a customer wanted an unusually large number of samples the work was spread out over numerous people including engineers.

This was clearly not the best use of engineering time and there was an additional drawback to producing samples by hand. Some of the shapes the customers needed were not possible to produce this way. For example where a part had a lot of complex geometry, impossible to shape it by hand. A third drawback was that the handmade models were not highly accurate since the process of cutting them required some interpolation between surfaces. This was acceptable to some customers, but others wanted greater accuracy. The answer was an Isel CNC router, which offered a perfect solution as the machine, was very accurate and robust, designed for production routing and drilling on a wide variety of materials including wood, plastic, MDF, solid surfacing materials, and non-ferrous metals. The specifications of the router selected included a working area for the router of 1500mm by 1250mm and z-axis height of 300mm, a vacuum hold-down table, 3.7Kw spindle and a raised gantry for large part clearance. The table features a rapid travel speed of 2000cm per minute, a z-axis cutting force of 900 Newtons maximum, resolution and repeatability of 0.013mm and 0.23mm per Metre absolute accuracy.

Now when a customer comes to with a request for a new product, the engineer creates the SolidWorks model as he did in the past, but instead of creating a drawing he exports the solid model directly into the system's CAM programme. Originally designed for metalworking this CAM program is also well suited for foam because of its ability to generate the most complex contours with little programming effort. In the CAM program, the engineer gives the command and the software creates the toolpaths for cutting the sample. The only additional input required be information such as feed rates and cutting speeds. Total programming time from when the model is imported into the CAM program until the system is ready to cut foam, ranges from 30 minutes to two hours depending on the complexity of the part.

After a piece of foam stock is fastened to the machine the operator hits the start button and the sample is then carved automatically. The machine does not require any supervision except to remove the finished piece and attach a new foam block to repeat the process. With this machine a typical order for 20 samples is completed in two days. Large sample orders no longer require the production assistance of engineers and the machine is simply kept supplied with stock until the order is finished.

The machine is very reliable requiring just regular lubrication due to the materials used in its construction; for example the machine uses anti-backlash ball screws. These screws have excellent power transmission due to the rolling ball contact between the nut and screws and this type of contact ensures low friction, low wear, and long life. The ball screws also make it possible to produce parts to the machine resolution of 0.013mm. In addition the machine is constructed on steel stress relieved bases with hardened steel linear ways. Ballscrews driven by servomotors offer the best precision performance, speed capacity, and machine longevity. This shaft-and-bearing system produces very smooth, play-free motion and is an extremely rigid system producing high-quality cuts.

The company now has confidence the company can take on many jobs no matter how complex the shape of their parts because the CNC machine imports CAD geometry replicating the shape exactly, regardless of the complexity. Furthermore they are no longer limited to just simple shapes.

Micromech is the UK systems and distributor for Isel, if you want to find out more about these cost effective, quality machines then visit our website at www.micromech.co.uk or contact Alan Spinks on 01376 333333 or email alan@micromech.co.uk for further details.

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