Features

By using state-of-the-art production equipment and processes, machining tolerances are held extremely close on today’s multilumen and multi-layer medical tubing. It is important to note that any misalignment of the tools may be exaggerated in the final product output.

Double and triple-layer extrusion heads by nature have more sealing and centering surfaces.

Clean parts, especially with sealing and locating surfaces, are key to product performance and successful 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 0.003 in. (0.08 mm), and because there are many such surfaces in a quality tool, cleanliness is critical.

Checking the tools for any deformities is also important. 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.

During changeovers, the head may be disassembled in order to change compounds and tips and dies. Foreign matter is usually introduced at this point and 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.

Use of a dedicated work cart exclusively reserved and equipped for extruder head maintenance is recommended. 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.

Machining tolerances are held extremely close on today’s multi-lumen and multi-layer medical tubing.

The following should be considered:

  • Maintain a clean, organized work area with soft and clean renewable work surfaces.
  • Use a vise with soft jaws, such as copper.
  • Use special equipment, such as tip removal tools, etc. Standard tools include wrenches, soft-faced hammers, etc.
  • Maintain a supply of soft, clean rags.
  • Use cleaning solutions in spray bottle.
  • Use spare parts as suggested by your tooling supplier, properly organized and stored.
  • Keep handy the equipment’s repair/maintenance manual.
  • Have a small surface plate to provide a true flat surface.
  • Use a set of appropriate gauge and tip pins for initial tool location adjustment.
  • Make sure all proper lifting aids are available, including overhead hoists, hydraulic lifts, etc. In most situations, the head and tooling will still be at elevated temperatures; therefore, lined gloves are needed when handling.

Today, tubing manufacturers compete with companies worldwide. To be a successful and profitable company, quality and efficiency are essential. This is especially true in extrusion, 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 and 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 10–20 percent of the material, which can run from 50 to 90 percent 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.

Understanding Maintenance Procedures

It is important to get organized before you even start. Here are some examples:

  • Example 1 – In this example, with an improperly centered tool, a calculated out-of-tolerance area of 0.059 in2. (38 mm2) was derived. When the two surface areas were compared, the calculated material waste was 11.8 percent of the finished product.
  • Example 2 – Alternatively, if the percentage wall can be increased from 80 to 95 percent, a savings of about 12 percent of total cost can result. Savings will vary depending on the designs, of course.

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 tools properly in a dry, clean area — a dedicated spot for each tool is best. These areas should have soft surfaces, and each instrument should be covered after cleaning. Also, tools should be segregated so that they do not come into contact with each other. And tools and all instruments should be cleaned thoroughly before storage.

For disassembly of tools, it is imperative to use purpose-built tooling to facilitate disassembly. These should be available from the supplier. If they are not, consult with a reputable tooling house for replacements. The cost of these tools is easily offset by potential damages, frequently caused by use of improper equipment such as hammers and drifts.

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