In a variation to our usual routine the group visited local company Zenith, who are involved in product design, prototyping, toolmaking and injection moulding. Owner Kevin McLeod gave a very informative tour and practical explanation of the equipment and processes involved. Kevin himself is a toolmaker by trade but has been involved in plastic moulding now for over 20 years.
He described how different materials and their differing properties affect how they are dealt with. The temperature used to heat the materials has to be exactly right otherwise the product will not form properly. For example the moisture in plastics can cause problems when heated. Many of the machines used are now mechanised which gives much more flexibility and once the settings for a particular job are input they can often be left to run on their own.
When Kevin first started working in this area the machinery took some time to warm up and perform effectively whereas now the correct heat can be achieved quite quickly and a constant steady temperature can be maintained.
Unlike steel, a variety of different textures can be achieved on plastics and of course a variety of different colours. We looked at the pellets of coloured dyes which can be added during the moulding process – a certain number of grams of colour to a specific amount of plastic has to be measured out exactly to get the right hue. And adding colour can add cost: black is the cheapest colour, while red is the most expensive. One container held pellets of recycled coat hangers which are used to produce drums for welding wire and frequently shipped abroad. Bits of plastic which Zenith don’t use in the finished products are usually recycled.
As well as the high temperatures involved in the processes a lot of force is also needed in order to shape plastic. For these reasons safety is paramount and various guards and checks are built into the equipment itself and also how they are used. Misuse of the machinery could cause very serious injury. Such safeguards are not always to be found in other countries which is one reason why costs for foreign manufacturing can be lower. Even so, in spite of such costs often drawing business abroad, Kevin pointed out that manufacturing abroad does not suit all customers or all products – it is not always the case that sending a job abroad will make it cheaper. A job requiring a lot of assembly work, for example, would probably be cheaper if manufactured in China. If assembly work is not a big part of it then the cost may not be any lower than if done here. Many customers also find it easier to deal with a more local company and particularly if problems arise it can be inconvenient and expensive for the customer to have to travel abroad in order to deal with that problem. An interesting point was that some products which are manufactured abroad can actually be stamped “Made in England” if assembled here.
We looked at different cutting tools capable of creating very precise holes and shapes down to very specific measurements. Getting the settings right on such equipment is obviously critical. Zenith can be involved in the full process from designing to finished product and Kevin showed the group some of the CAD design programs used and the various products they have taken through the process.
Many thanks to Kevin from the Leeds inventors group
Zenith Plastic Developments Ltd,3 lister hill,Horsforth,LS18 5AZ tel:0113 2590380 http://www.zenithplastics.