Kemeling Kunststoffen robotizes thermal welding processing

The thermal welding of plastic board material is a nearly fully manual process, in which experienced professionals heat up both board parts with an electric extruder in a continuous motion and simultaneously add material. Kemeling Kunststoffen located in the Dutch town of Naaldwijk had the idea of having a robot perform the work and approached Valk Welding for this. Initially, the plastic welding robot was intended for the thermal welding of large, round fluid tanks, but by now, each free hour is also utilised for other workpieces. Managing director Robert Kemeling, “We continuously discover new applications.”

Kemeling Kunststoffen fabricates plastic containers, tanks, wells, boxes and casings for among other agricultural and horticultural applications, shipbuilding and yacht construction, water treatment and civil engineering, etc. Often for the storage of liquid and solid substances. 80% of the products fabricated by the company are made with flat HDPE board with a thickness between 6 and 30 mm. The boards are cut to size, shaped to contours, set and tacked using butt welding or thermal welding, after which the individual components are connected to an end product.

Self-developed concept
Robert Kemeling, “The high quality connection of the board parts requires a certified welder, while a robot can also be operated by a non-certified employee. However, knowledge at an undergraduate level is required for programming. For this reason, we worked out the possibilities of robot automation utilising students. We used a pre-owned robot in order to prepare a test set-up for the thermal welding of the HDPE board. This concept was worked out by Valk Welding to a set-up in which round tanks with a diameter of 3 m were thermally welded both from inside as well as outside on a support plate. The table rotates with a speed that the extruder can keep up with.

Valk Welding’s strength in particular lies in the translation of our concept to a working robot cell, with an emphasis on the control of the robot and the communication with the rotating table.”

Clean process without critical tolerances
In the course of the process, plastic is added from the coil while the extruder heats up the material of both board parts, causing the three elements to form a molecular connection that is particularly strong. Hessel Luiten, who accompanied the entire project as an graduate ‘industrial product designer’ intern and is now responsible for the programming and the entire robot installation, “It is a fully clean process, during which no vapours are released contrary to the welding of metal. Moreover, the tolerances are less critical. As long as the robot presses the extruder in the inclined position in the upright angle, the heating will be sufficient to melt the material. The majority of the knowledge and experience lies in how the dimensional losses that occur as a result of the melting can be compensated.”

Saving on labour costs
The greatest financial gain lies in the savings on labour costs and the ensuring of quality. Robert Kemeling, “The capacity of the production is increased because now a single operator works on two containers simultaneously. Moreover, work is performed in a constant, uninterrupted motion, which ensures high, consistent quality. Furthermore, the continuous handling of an extruder is a heavy load for the specialist.”

www.kemeling.nl