DE29908024U1 - Thermoforming tool - Google Patents

Description

"Thermoforming tool"

The invention relates to a thermoforming tool for producing molded parts from thermoplastic films or sheets. A new way of introducing ventilation slots makes it possible to produce the ventilation openings more efficiently overall. The larger overall ventilation cross-sections that are possible in this way result in a faster molding process. This enables higher production outputs and at the same time better molding sharpness. The tool according to the invention can be used in vacuum forming or in compressed air forming. The advantageous effect of the new ventilation is achieved in both processes.

Up to now, thermoforming tools have mainly been vented through small holes with a diameter of 0.4 - 0.8 mm or, if permitted, through slotted nozzles at the deepest points of the molded part contours. The hole diameter depends on the type of plastic and the molding process. It should be avoided as far as possible that vent holes or slots are visible on the molded part. The production of the small holes in particular was/is problematic, especially since this is usually done using small, hand-held drills. In order to keep the drilling depths low, larger holes are drilled from the back of the mold. This creates additional work. Another type of venting, known as slotted venting, is also known. This is usually carried out on molded part contours that allow tool division. The tool is then manufactured in several parts and is therefore more complex than in one part.

Fig. 2 shows a cross-section through a mold segment in which both ventilation via bores 4 and slot suction 5 via tool division in the mold base area are realized.

In the tool segment described below and shown in Fig. 1, modern processing methods such as wire cutting via spark erosion or laser are used to produce the ventilation slots. Wire cutting is preferably used as a more cost-effective method.

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Thermoforming tools, especially for the production of packaging, usually consist of several mold segments. The number can be up to 50; depending on the size of the molded part

and forming surface of the thermoforming machine. This fact requires the use of modern techniques with a high degree of automation to manufacture the tools.

The processing methods mentioned above allow the vent slots to be defined during the design of the tool using CAD systems, with the geometry data then being transferred to the control program of the processing machine. It is therefore possible to produce molds/mold segments from one piece and subsequently cut the vent slots into surfaces and contours, regardless of the shape of the molded part. The initial holes are made beforehand during milling, if the erosion machine does not have a drilling device. The slot width can be controlled, so that widths of 0.17 - 0.3 mm are possible. Marks on the molded part can thus be avoided. The wire cutting method also allows the slots to widen conically towards the bottom. This prevents clogging.

Of course, it makes sense to use the slot ventilation in the new design also for split tools, e.g. for inserted bases in the surface area.

Fig. 1 shows a mold segment with conical ventilation slots cut into the base area 1. Interruption bars 2 hold the tool segment together and at the same time act as thermal bridges for cooling. Cylindrical slots 3 with milled clearance are a common alternative.

The effectiveness of the mold venting is significantly improved by this design option. For comparison: a slot 0.2 wide and 10 mm long corresponds to 10 holes with a diameter of 0.5 mm.

Claims (2)

Protection claims 1. Thermoforming tool for producing molded parts made of thermoplastic material, characterized in that the vent holes are designed as micro-slots of limited length. 2. Thermoforming tool according to claim 1, characterized by downwardly conically widening ventilation slots.