Seven rodless pneumatic cylinders have been incorporated into a giant plastic thermoforming machine for making the main body panels for static and touring caravans.

Seven rodless pneumatic cylinders have been incorporated into a giant plastic thermoforming machine just built by Format (UK) for making the main body panels for static and touring caravans. The cylinders provide the main axes of linear movement within the machine. Two feed sheet plastic into the forming chamber; two more remove the finished panels; numbers five and six provide the traverse movement for the lower heating element, and the final cylinder traverses the top heater.

'All seven drive cylinders are from Hoerbiger-Origa,' says Brian Waller, who founded Format nearly twenty years ago.

'This was a prestige order for us, and the machine will be expected to work very hard throughout its long life, so there was no thought of skimping on component quality.' In thermo- or vacuum forming, plastic sheets or panels are fed into a chamber and positioned just over a platen.

The chamber is sealed and the heaters positioned and activated to soften the plastic into a malleable state.

The air is then evacuated via vents in the bottom of the chamber, this having the effect of pulling the plastic down over the platen to form the finished product.

The heat is then reduced and the heaters retracted; after a short dwell time to allow the plastic to harden again, the product can be removed before the cycle is repeated to make the next product.

The technique is used in a great range of products, from packaging trays to door panels for double-glazing manufactures, shower trays, baths, suitcases, etc.

Caravan panels, forming the walls, roof and doors are too large to be easily handled manually and are also awkwardly flexible until fully cooled.

In order to achieve the hourly throughput volume required by the caravan makers, it was therefore necessary to automate infeed and outfeed to the chamber.

Format has designed and built many such handling systems, so knew that rodless cylinders were likely to provide the best solution.

'Standard pneumatic cylinders are inelegant because they are not load bearing so you cannot use them as structural elements of the system.

Additionally you have to design-in room for the rods when they are at full extension.

This makes for a much more costly machine that going for a rodless solution,' explains Waller.

Of the other forms of actuator, electric cylinders would not stand the heat, hydraulics are too cumbersome and expensive and linear motors nothing like robust enough.

Waller goes on to say that he has tried other makes of rodless cylinder in the past, but that just confirmed his loyalty to the Hoerbiger-Origa product range.

Many of the Origa cylinders he fitted into his earliest machines are still giving good service today.

Format is dedicated to the manufacture of plastic thermoforming machines, each one being bespoke to customer requirements.

In fact the company success is based on its bespoke design and build abilities: twenty years ago nearly all machines were standard designs imported from Germany or Italy, but the market was showing the early signs of wanting to move to bespoke systems because the techniques was moving from its small size/light weight product origins such as packaging trays into larger and larger panels.

One of the groundbreaking successes was the development of the Topper sailing dinghy, at the time the largest ever vacuum formed products.

'Local presence was vital for a bespoke operation in the 1980s, so we were able to win out over imports and get ourselves well established.

The Internet and email arrived at just the right time for us, as we were beginning to export.