On 22-25 March 1997, Manfred Jacob Kunststofftechnik, together with the SPE Thermoforming Division, hosted a three-day conference on thermoforming at the new technology center in Wilhelmsdorf Germany. The conference was patterned after the highly successful SPE Thermoforming Division conference held each September in the U.S.. Management and technical papers were presented the first day. The second day was given over to a very highly successful set of workshops. And the third day was a bus trip to Kiefel in Freilessing at the Austrian border. Owing to limited lodging and meeting facilities, the attendance was restricted to less than fifty attendees. Formers, extruders, machinery builders and mold makers represented the invited participants. This note reflects on the workshop concept.

Workshops

Four topics were chosen for discussion -Materials, Computer Simulation, Tooling, and The Dream Machine. The last topic was divided into thin-gage and heavy-gage. The topic leaders were invited experts in each of the four topics. The group was evenly divided into four diverse groups, and were led by a selected group leader. The groups were scheduled to move from topic to topic so that everyone had an opportunity to comment on and participate in each of the topic discussions. After all groups had discussed all four topics, the topic leaders assembled the diverse comments and presented a summary of the opinions and comments to the assembled attendees.

Materials Topic

I was the topic leader for the Materials topic. The following is an expanded version of the summary I presented to the assembled attendees.

  • Cooperation. It was agreed that currently, the level of cooperation between the former, extruder, compounder and resin supplier was based on polymer and conversion cost and the size of the order. There was no consensus as to how more attention and cooperation can be achieved, although it was pointed out that a better understanding about each others’ technical problems [e.g., communication] helps minimize adversarial attitudes.
  • Property/polymer consistency. It was the general consensus that many forming problems are caused by nonuniformity in polymer properties. It was thought that polymer producers do not consider thermoforming to be as critical or economically important a process as injection molding and therefore tend to relax polymer properties.
  • Thermoforming grade polymers. The general comment was that resin suppliers frequently recommend “extrusion grade” polymers for thermoforming applications. Since thermoforming has specific polymer requirements, resin suppliers should establish recommended “thermoforming grade” polymers.
  • Unified international material datasheet. It was felt that it is very difficult and at times, impossible, to select competitive polymers since many resin suppliers do not provide sufficient or adequate data.
  • Shrinkage and orientation. Lack of information about polymer shrinkage and sheet orientation was considered to be the most significant problem to processors. On several occasions, extruders stated that they would be amenable to an established standard or guideline on each of these subjects.
  • Test Mold. It was noted that several resin suppliers, mold makers and extruders had small shuttle presses for internal evaluation of their products. It was suggested that perhaps a simple mold design could be developed that all thermoforming elements could adopt as a guideline tool.
  • Responsibilities. It was noted on several occasions that there are at least four players in the materials area – the polymer supplier, the compounder, the extruder and the former. It was argued that the polymer supplier has the responsibility for knowing the effects compounding, extrusion and thermoforming processes have on the polymer properties. It was argued that the extruder has the responsibility for policing changes in these effects. And it was noted that the thermoformer has the responsibility for defining what polymer properties he (and / or his customer) needs.
  • Recyclability. There was a consensus regarding the importance of the effect recycled polymer has on the final forming characteristics of the polymer sheet. The group felt that it was solely the responsibility of the polymer resin supplier to provide technical support on the effect of various levels of recycled polymer on the forming and mechanical characteristics of the virgin polymer.

Action Items

In my summary, I proposed two action items to be initiated this year:

  1. Industry-wide thermoforming guidelines on
    • Datasheet content for thermoformers,
    • Orientation and shrinkage [including an accepted test procedure],
    • and Recyclability [as discussed above],
  2. A standardized thermoforming mold shape [5-sided box or false-bottom cup] so that sheet extruders, resin suppliers and thermoformers can compare formed sheet characteristics.

I suggest that the SPE Thermoforming Division be responsible for carrying out these two action items.

Jim Throne

27 March 1997

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