Today's machining tolerances are held extremely close on multilumen and multi-layer medical tubing through the use of state-of-the-art production equipment and processes. Any misalignment of the tools may be exaggerated in the final product output.

With this in mind, clean parts, especially with sealing and locating surfaces, are key to product performance. These surfaces receive the most care and attention during manufacturing and are the control surfaces that ensure uniformity throughout the tubing. It is important to note that precision-machined alignments are affected by even a speck of dirt measuring only a few thousandths of an inch.

Deformities can also affect performance. Burrs, scratches, and scrapes are usually a result of careless handling or storage of equipment. Double- and triple-layer extrusion heads pose an even greater challenge for maintenance. The number of sealing and centering surfaces multiplies and can magnify the results of dirty tools.

If the head is disassembled in order to change compounds and tips and dies, foreign matter can be introduced. Any residual materials must be thoroughly removed. Physical tool damage often occurs during this phase due to mishandling and poor storage techniques. These are highly precise parts, but can also be heavy and bulky to remove by hand.

Proper Maintenance

For proper maintenance a dedicated work cart should be reserved exclusively for extruder head maintenance. This cart along with a supply of spare components and hardware is easily justified, especially when examining the potential cost savings that result from well-maintained tools. The work area must be clean and organized. When maintaining tools, it is important to use a vise with soft jaws, such as copper. In addition, use special equipment, such as tip removal tools, etc. Standard tools include wrenches, soft-faced hammers, etc. Maintain a supply of soft, clean rags, and use cleaning solutions in spray bottle. Use spare parts as suggested by the tooling supplier, properly organized and stored. The equipment’s repair/maintenance manual should be readily available. A small surface plate is essential to provide a true flat surface, and a set of appropriate gauge and tip pins will be needed for initial tool location adjustment. Finally, all proper lifting aids, including overhead hoists and hydraulic lifts, should be easily accessible. In most situations, the head and tooling will still be at elevated temperatures; therefore, lined gloves are needed when handling.

Many extruders experience downtime because of poor or damaged tooling and excess maintenance time, which is costly in terms of time and money. Some start up quickly and make scrap, whereas others start up and run a product oversized to hold minimum tolerance. They waste 10–20 percent of the material, which can run from 50 to 90 percent of the product cost.

To prevent mishaps, it is essential to ensure that the operators have help for heavy parts and awkward situations. Because many surfaces and edges are hard and even brittle, dropping a part or striking parts together can damage the part. Tools should be stored in a dry, clean area, preferably in a dedicated area with soft surfaces. Tools should be segregated so that they do not come into contact with each other, and tools and instruments should be cleaned thoroughly before storage.

Purpose-built tooling, which should be available from the supplier, should be used to facilitate disassembly. The cost of these tools is easily offset by potential damages, frequently caused by use of improper equipment such as hammers and drifts.

Medical Design Briefs Magazine

This article first appeared in the March, 2017 issue of Medical Design Briefs Magazine.

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