Extrusion International 5-2023

56 Extrusion International 5/2023 EXTRUSION TOOLING pound restores polished surfaces g.) Compressed air, which is more ef- fective for releasing plastic, but also aids in rubber removal. Be careful not to force debris into recesses with compressed air h.) Cleaning solutions may be useful, so remember to use fresh, clean rags (used rags often have metal chips embedded in them, which may scratch polished surfaces) i.) Cleaning oven – for plastic only. Follow manu- facturer's recommendations. 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. j.) Purging compounds – several are offered to purge the extruder screw/barrel of residual polymer and rubber compounds Removing Excess Material for OptimumMachining Efficiency Clean parts are critical to extrusion tooling perfor- mance and quality manufacturing. This is especially true for the sealing and locating surfaces – that con- trol 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 precision machining align- ments 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 remove. 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 because 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 compressor 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 simul- taneously 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 2" (51mm) flange adapter should be cleaned by carefully using a brass brush. Examine all surfaces for any irregularities such as burrs and scratches since these must be repaired before the head is reassembled. Most manufacturers recommend using a hand polishing stone to remove the offending burr. Follow stoning with a light application of 600-grit emery cloth if nec- essary, but avoid rounding edges that are intended to be sharp. Flat sealing surfaces can also be cleaned us- ing a stone, fol - lowed 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 until 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 Has - talloy ® 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 specified minimum tolerance and is eco - nomically produced. Dirty, neglected and improperly adjusted tools contribute to excessive compound ap- plications, which in turn complicate maintenance of minimum thickness tolerance. Excess material results in unnecessary costs and these directly affect the profit - ability of your company and the relationships with your customers. The Important Final Step – Reassembly Working from your dedicated tool cart, follow the manufacturer’s instructions for reassembly. Give each component a final wipe down with a clean rag before installing. Even the smallest amount of grit, dirt and re - sidual material must always be removed. Use mechani- cal or manual assistance for heavy and awkward com- ponents to avoid unnecessary mishaps. Reapply anti seize compound to all fasteners if required. Tighten fas- teners to manufacturer’s recommended specifications as well as in the recommended sequence. This fastening sequence should be specified in the manual and is gen - erally in a star pattern. Tighten gradually until the prop- er torque is achieved to prevent distortion of the tool- ing. One of a die manufacturer’s main goals is to form a concentric cone as q u i c k l y and accu- rately as po s s i b l e