Extrusion International 1-2018

36 Extrusion International 1/2018 EXTRUSION TOOLING Tooling maintenance improves extrusion efficiency, enhances quality and boosts overall productivity for medical tubing applications By utilizing state-of-the-art production equipment and process- es, machining tolerances are held extremely close on today’s multi-lumen and multi-layer medical tubing. It is important to note that any misalignment of the tools may be exaggerated in the final product output. Clean parts, especially with sealing and locating surfaces, are key to product performance and suc- cessful end products. These surfaces receive the most care and attention during manufacturing and are the control surfaces that ensure uniformity throughout the tubing. Remember, precision-machined alignments are affected by even a speck of dirt measuring only a few thousandths of an inch. A human hair is about 0.08 mm, and since there are many such surfaces in a quality tool, cleanliness is critical. Checking of the tools for any deformities is also important. Burrs, scratches and scrapes are usually a result of careless handling and/or storage of equip- ment. 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. During changeovers, the head may be disassembled in or- der to change compounds and/or tips and dies. Foreign matter is usually introduced at this point and residual materials must be thoroughly removed. Physical tool damage often occurs dur- ing 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. Use of a dedicated work cart exclusively re- served and equipped for extruder head maintenance is recom- mended. This cart along with a supply of spare components and hardware is easily justified, especially when examining the po- tential cost savings that result from well-maintained tools. The following should be considered: • Maintain a clean, organized work area with soft and clean re- newable work surfaces • Using a vise with soft jaws, such as copper, and special equip- ment such as tip removal tools, etc. • Standard tools include wrenches, soft-faced hammers, etc. • Maintaining a supply of soft, clean rags • Using cleaning solutions in spray bottle • Using spare parts as suggested properly organized and stored • Keep handy your equipment’s repair/maintenance manual • Have a small surface plate to provide a true flat surface • Using a set of appropriate gauge and tip pins for initial tool location adjustment In most situations, the head and tooling will still be at elevated temperatures, therefore lined gloves are needed when han- dling. Today, tubing manufacturers compete with companies all over the world. To be a successful and profitable company, quality and efficiency are essential. This is especially true in ex- trusion, where material costs are usually much higher than labor costs. Like a racing car stuck in the pit, many extruders sit idle because of poor or damaged tooling, plus excess maintenance time. Overhead costs add up and losing money is the result. Some start up quickly and make scrap, whereas others start up and run a product oversized to hold minimum tolerance. They waste 10% to 20% of the material, which can run from 50% to 90% of the product cost. The tooling supplier goes to great lengths so that tips and dies are machined to a determined specification, ensuring perfect concentricity and alignment. The material is then distributed in the proper location as part of the finished product. In this example, with an improperly centered tool, a calculated out-of-tolerance area of 38 mm2 was derived. When the two surface areas were compared, the calculated material waste was 11.8% of the finished product. % wall = min. wall thickness max. wall thickness X 100. Get help for heavy parts and awkward situations: Surfaces and edges are hard and therefore somewhat brittle, so dropping a part or striking parts together can result in damage. Store your tools properly in a dry, clean area. These areas should have soft surfaces and each instrument should be covered af- ter cleaning. Also, tools should be segregated so that they do not come into contact with each other. And tools and all instru- ments should be cleaned thoroughly before storage. For disas- sembly of tools, it is imperative to use purpose-built tooling to facilitate disassembly. Here are some useful tips: Getting the Most from Extrusion Tooling