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December 9, 1998

2 Min Read
xxxHow Many Different Parts from a Single Tool?

How many product variants can be moulded from one tool? Ken Symonds,design manager with Allibert Handling, the U.K. subsidiary ofFrench plastics group Sommer Allibert, says "How about 64?"But it could be more.

What Symonds refers to as his "baby" is an attachedlid, nestable container for secure distribution of goods, typicallyin the automotive and pharmaceutical industries. Its ancestor,launched five years ago, was a single-colour product. The firstsignificant variation along the evolutionary chain was to offertwo different heights-a third was added later-without removingthe tool from the press. Incorporation of a lock-and-link mechanismmeant that a job that could take all day was cut to a couple ofhours-simply a matter of taking one plate out and replacing itwith a thicker one. Symonds describes it as "a concertinaeffect."

The container's twin half-lids were then being moulded separately.To cut costs, Symonds proposed moulding both container and lidsfrom the same tool. But then, Allibert holds a patent on a single-barreltwo-colour process. Why not use this to create simultaneouslya container in one colour and lids in another? The attractionwas a run with a low break-even point.

At Allibert's manufacturing plant in Gloucester, the two-colourprocess is incorporated in an 850-ton Battenfeld moulding machine,which then had a hot runner system developed in-house by Allibert.This called for outside help since, if any complications emergedduring the later development of this increasingly elaborate project,their technical resolution would have been down to Allibert. SoMold-Masters was called in to modify one of its hot runner designsand then perform the necessary flow analysis and establish thepressure ratios.

Two-colour costs are competitive, since they are the same as singlecolour. Label holders on the box sides are created with "avery precise collapsing core mechanism," says Symonds. Twoother collapsing cores create special recesses in the containerto form the basis for a tamper-evident seal. A further 16 collapsingcores, eight on either side of the container, create engagementpoints for the hinge pins. Symonds says Allibert is the only companyto produce a box with twin lids that requires no additional hingesor axes.

Pins on the mould create small indentations on the container rimthat ensure the box is presented precisely for robot transferfrom the moulding machine.

But what about those variants? Symonds invites anyone of a mathematicalbent to work them out. Here's the range:

  • Lids the same colour as the container, or a differentcolour.

  • Two heights. (If a third became desirable, says Symonds,the Portuguese toolmaker would not need to see the existing mouldbut could respond simply to the data describing it. Fitting theadditional parts at Gloucester would take two days.)

  • Two bases-for stacking options.

  • With or without label holder on both long sides (ensuresidentical label orientation however stacked).

  • With or without document holder on both long sides.

  • With or without "pimple pads" which allow adhesivelabels placed there to be stripped away easily.

  • With or without a 1-mm-deep recess, on any or all ofthe four sides, to take a printed barcode.

  • With or without a base recess to take a smart card transponder

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