How to successfully produce high-precision plastic parts

At Samaplast in Switzerland, tie-bar-less injection molding machines ensure greater efficiency and safety in the cleanroom. The contract manufacturer specializing in clinically pure medical technology operates three cleanrooms for injection molding where it produces high-precision molded parts, for example, the ZipFix: a connecting element similar to a cable tie for closing the breastbone after open-heart surgery. This sophisticated product is produced on a tie-bar-less hybrid machine. Of the 28 injection molding machines at the site today, only four machines still have tie-bars.  

Of all the medical technologies products made of plastic, implants pose the strictest requirements for the manufacturing process. ZipFix is also a two-component product, because at the end of the long tongue there is a curved needle to thread the tie through the tissue between the rib arches. Overview of the production of these high-precision plastic parts:

1. The needles are rinsed with ultrapure water in an airlock cleaning system, dried and fed directly from the cleaning chamber into the cleanroom. The needles are then manually inserted into the multi-cavity mold.

2. The needles are overmolded with PEEK on an ENGEL e-victory hybrid machine with electric injection unit and servo-hydraulic, tie-bar-less clamping unit in cleanroom design. High precision during injection and part removal guarantees maximum quality.

3. After the injection molding process, the ZipFix elements are removed by an employee, visually inspected, measured, laser-marked, and packed in sterile packaging. One benefit which tie-bar-less technology offers is improved ergonomics. There is no need for employees wearing protective overalls to bend down and reach between the tie-bars.

Advantages in the cleanroom were decisive for the tie-bar-less technology. Tie-bar-less machines and a barrier-free clamping unit keep the production of the high-precision plastic parts clean. The e-victory's hydraulic system is hermetically sealed. Samaplast uses only food-grade H1 oils, which are delivered to the ENGEL plant for initial filling. The ecodrive servo-hydraulic system ensures that the heat and particle load transferred to the cleanroom is reduced because no energy loss in the form of heat needs to be dissipated by the hydraulic oil. 

Flexibility in injection molding for medical technologies: as a contract manufacturer Samaplast needs flexible machinery. Only a few applications run continuously for several weeks. In contrast, some other products require just a few hundred parts per year. This results in frequent mold changes. Here too, tie-bar-less technology demonstrates its advantages. The extra freedom of movement in the mold mounting area makes it possible to mount very large molds on small injection molding machines. This efficiency factor is particularly beneficial in cleanrooms: the smaller the machine, the lower the emissions. The lower space requirement and reduced energy consumption with consistently high part quality result in lower costs.