Extrusion Asia Edition 1-2018

• 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 handl- ing. Today, tubing manufacturers compete with companies all over the world. To be a successful and profitable company, qua- lity and efficiency are essential. This is especially true in extru- sion, 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 spe- cification, 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 thick- ness 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 cover- ed after cleaning. Also, tools should be segregated so that they do not come into contact with each other. And tools and all in- struments should be cleaned thoroughly before storage. For disassembly of tools, it is imperative to use purpose-built tool- ing to facilitate disassembly. Here are some useful tips: • Clean the equipment while it is still hot as the residue is easier to remove • When cleaning a dual compound crosshead, (plastic and rubber) clean the plastic tooling first; the rubber second • Never use steel tools • Do not use open flames Recommended cleaning tools and materials include: • Brass pliers to grip material and aid in pulling • Brass scrapers • Brass bristle tube brushes (ideal for cleaning holes and recesses) • Brass rods • Copper gauze for cleaning and polishing exposed round or conical surfaces • Copper knives for removing residue from recesses and other hard-to-reach areas • Compressed air, which is more effective for releasing plastic, but also aids in rubber removal • Using fresh, clean rag. • Cleaning oven. If no temperatures are specified, do not exceed 850 degrees F (454 degrees C). Don’t quench tooling to cool, as this could affect tooling hardness, concentricity and tolerances • Purging compounds – several are offered to purge the extru- der screw/barrel of residual polymer and rubber compounds Removing Excess Material for Optimum Machining Efficiency Clean parts are critical to extrusion tooling performance and quality manufacturing. This is especially true for the sealing and locating surfaces – that control uniformity of the production process. For general maintenance of the tools, before storage or tooling changeover, a thorough cleaning and removal of the excess material assures the preci- sion machining alignments required to produce end products to the precise tolerances. Equipment should be cleaned while it is still hot, since residual polymer and rubber will be easier to re- move. Be sure to follow all MSDS recommendations when heating the tooling. Thermal gloves are used to protect the hands from the heated tooling surfaces. A brass scraper, as well as a brass or copper wool cleaning cloth are recommended be- cause they are soft enough not to scratch the surface. Make Tool Cleaning Easier The quickest way to remove the die is to employ the pressure of the extruder to push it out. Clean the body by using an air com- pressor and brass pliers so that the material cools down which increases the melt strength, making it into one-lump versus an elastic, gummy-like substance that is harder to remove. Cleaning the body feed port using compressed air and brass pliers to simultaneously cool and remove the excess residue from the feed ports. This procedure is followed by brushing with a round brass brush that polishes the surface. The flow area of the 51 mm flange adapter should be cleaned by care- fully using a brass brush. Examine all surfaces for any irregularities such as burrs and scratches since these must be repaired before the head is reas- sembled. Most manufacturers recommend using a hand polish- ing stone to remove the offending burr. Follow stoning with a light application of 600-grit emery cloth if necessary, but avoid rounding edges that are intended to be sharp. Flat sealing sur- faces can also be cleaned using a stone, followed by a 600-grit emery cloth. Place the cloth on a clean, flat surface, preferably a surface plate, then apply friction in a circular hand motion un- til the area is clean and even. The parts in question should all be hardened steel alloys and will not be adversely affected using these methods. Inconel, monel and Hastalloy ® are typically not heat-treated, requiring special care and handling to avoid any damage. Don’t Overlook Repairs Tooling maintenance helps ensure a quality extruded product – one that meets dimensional specifications, maintains the speci- 18 挤压工具 Extrusion Asia Edition 1/2018