User Story

Plastro Irrigation : Moldflow

Plastro Irrigation was established in 1966 by Kibbutz Gvat in Israel. Starting as a manufacturer of plastic pipes and basic irrigation products, the company rapidly expanded and diversified its lines of products to become one of the world's leaders in the field of Low Volume Irrigation (LVI). The company is a full service company offering customers solutions to all their irrigation requirements. Plastro products include integrated and on-line drippers, Ray Je sprayers, sprinkler systems, foggers, misters, and other items.

Recently, Plastro engineer Zvika Einav solicited assistance from Gal Sherbalis, principal at GS Design, an independent plastics engineering consultant firm in Israel. Plastro needed to develop a thick part to be used as a dead weight in a new mist sprayer. The weight is constructed of two shells clipped together around a pipe. Einav was aware that thick "chunky" parts tended to warp and required long cycle time to produce. Further, more thick parts could have surface finish problems due to jetting during injection molding.

The following factors were considered:
  1. An optimal part weight needed to be determined.
  2. Manufacturing cycle time had to be as short as possible.
  3. Part shape had to be as straight as possible and if not the mating surface had to be concave.
  4. Cosmetically, the part surface appearance needed to be aesthetically pleasing.
  5. Part production was dependent upon marketing approval.
Sherbelis says, "Keeping these factors in mind, we went through a few iterations producing a geometry in parasolid format. Using Moldflow Plastics Insight (MPI), we performed a flow/cool/warpage analysis and studied the fill pattern, cycle time, and warped part shape. The geometry went through significant modifications until we obtained the final design that satisfied all specifications."

The project sequence and goals were not different from many similar projects done in the past, but what made this project special were the geometry and the analysis tools used. Sherbelis adds, "Most plastic parts have a shell-like shape with the length and width of the part being much larger than the thickness dimension. Shell-like geometry can be successfully analyzed by the midplane technique or it's off shoot the double skin technique.

"The part in question has a length width and thickness of the same order and could not be possibly analyzed by the midplane technique. Only full 3D analysis could accurately accommodate the part geometry. This was the first time I used MPI's full 3D warpage capability."

Since the analysis project, the part has been in production with satisfactory results that match the software predictions. See the part at

For more information about Moldflow, visit Visit for more information about Plastro Irrigation.

Author: Laura Carrabine

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Page last modified on October 12, 2004
Copyright 2004 by John Stark