Custom Plastic Extrusion Terms – Part Two
We hope you found part one of our four-part series on extrusion terms insightful. In the first of the series we discussed extrusion industry terms you may hear related to extruders and tooling for the extrusion industry.
In part two of our series, we are going to tackle the top 10 thermoplastic extrusion terms relating to ancillary or downstream equipment used to manufacture custom plastic profiles, tubing, and other hollow profiles.
Gravimetric Feeder– In part one of our series, we discussed that the hopper holds material that is fed into an extruder. These can be as simplistic as a steel “funnel” configuration that does little more than hold and feed material to very precise feeding systems that rely on gravimetric measurement to deliver accurate amounts of plastic material to the barrel and screw of the extruder. In tight tolerance situations, you will find many extrusion lines outfitted with this type of equipment. In the case of a custom color matched, single durometer extruded profile, you would have a natural color base compound and a color concentrate. This can be done with a gravimetric feeding system that feeds two materials to the extruder at the same time. When appropriate, a three-station unit can be used to feed in precise amounts of reprocessed plastic to manufacture the finished extruded profile in the most environmentally friendly way.
Vacuum Calibration– In our first part of the series, we compared plastic extrusion to pasta making. Both processes use “ingredients” that are fed into an extruder, conveyed down the barrel with a screw, and are forced out a die to make a specific shape. In the case of pasta, there is very little heat created during this process. However, to make plastic into a product using the extrusion process, both frictional and external heat are used. The heat forces the material through the extrusion die, then the manufacturer must captures the profile to maintain the overall shape and integrity of the profile during the cooling process. Water, other liquid coolants, or air can be used in the cooling process. Tolerance requirements may dictate that vacuum calibration (also called vacuum sizers) be built and used to capture the profile, using vacuum to hold the extruded profile in place during the cooling process. Most vacuum sizers today use water for heat removal.
Cooling Systems– Methods of cooling are dependent on the profile design. In some cases, a simple water-pan can be used to hold water or other coolant. This type of equipment is widely used in the extrusion of flexible profiles such as screen splines, extruded gaskets, and other smaller profiles. Another option is systems designed to hold guides and coolant. However, To manufacture more complex products (window lineal profiles, office partition base raceways, entry door seals, wood plastic composite components, wall protection corner guards & crash-rails, and other custom profile extrusions,) the extrusion manufacturer may use a calibration table. As the name implies, this is a very rigid stand that is designed to allow both vacuum sizing and water cooling tanks to be mounted for cooling and sizing purposes. The calibration stands vary in length to accommodate a wide variety of extruded plastic profiles. Typically, this type of stand has self-contained vacuum pumps along with both water and air supply with quick-change couplings to reduce set-up time during tooling changeovers.
Embossing or Texturing– Many extruded profiles you see have textured or embossed patterns on the exposed surface. The next time you are in a commercial building look at the extruded handrails and corner guards protecting the walls and corners in the building. Most of these products will have a pebble grain embossed pattern on the surface to add to the aesthetic appeal of the product, while offering the protection and durability high impact, rigid plastic materials provide. Another great example of textured, or embossed products are the baseboards or wire raceway covers on open office partitions. These panels are subject to abuse from foot traffic as well as cleaning equipment, and the textured pattern helps minimize cuff marks and scratches. Formtech has embossing equipment at both manufacturing locations. Patterns can vary from a typical pebble grain, to custom designs, or to wood grain textures resembling real wood.
Tape Applicator– Many plastic extrusions have double sided adhesive tapes, or even magnetic strips, applied to them for additional functionality. Some examples of this added functionality on extruded plastic profiles would include point of purchase display tags, Velcro®, automobile body side moldings, wall protection corner guards, and weather stripping. Anytime you here the term peel and stick, this is the added functionality the addition of pressure sensitive adhesive tapes can provide to your extrusion. Need to attach a vinyl extrusion to a piece of steel? Formtech can custom apply magnetic tape to the extrusion that will attach to a metal surface. You don’t need to attach to steel? Double sided foam and non-foam adhesive tapes specially formulated to adhere to a wide variety of surfaces can be applied to the plastic extrusion on an in-line process to maximize function and minimize cost. Formtech has considerable experience with tape application, and we have specially designed tape applicators that can be used for many custom extruded shapes.
Haul-Off– In extrusion jargon, you will hear many terms used to describe a puller, conveyor, or haul-off, which is used to pull and convey extruded profiles down the extrusion line before being cut to lengths you can see from the picture below, top and bottom cleats, or belts, are used to apply pressure on the extruded profile as it is being pulled downstream. The belts can be made from a variety of materials, including foam, silicone or even rubber. Careful adjustment is required to maintain the plastic extruded profile integrity, without distorting the shape as the product passes through the unit. In many cases an additional speed controller is located near the extruder so the line operator can speed up or slow down the haul-off when controlling the size of the extruded profile.
Cut Off Saws– Plastic extruded profiles are linear products, and must be cut to length before they are removed from the extrusion line and packaged. A traveling saw is used primarily with medium to large profiles. The traveling saw, or progressive saw, clamps onto the profile to move the cut-off saw downstream with the product until the saw can cut through the extrusion. Many traveling saws have the blade mounted above the profile, and cut down through the part much like a miter saw used by homeowners and contractors. Notice the progressive saw in the picture has the blade contained in the bottom of the unit, and it travels up through the plastic part. This can help control dust and saw chips more effectively when this type of saw can be used.
Fabrication Punch– The traveling saw has limitations, and is used only when extruded profiles are square cut at a 90° angle, or some consistent angle to make a trapezoid shape. This simplistic cut works for many customer applications where mill lengths are manufactured, or no additional fabrication is required. One of Formtech’s strengths is the capability to do additional, value added fabrication, both on an in-line and out-of-line basis. Many of the extruded products Formtech manufactures are components in OEM products. We strive to provide the extruded profiles completely finished when possible, including more sophisticated end cuts, holes, punch-outs and other fabrication that allows less labor and handling at your plant.
Fly Knife Cutter– Have you ever wondered how drinking straws are manufactured? These tiny tubes are extruded, and extrusion lines to manufacture these products run at speeds that can manufacture over 180,000 straws per hour. The only way to cut a plastic extrusion at this type of rate is to use what it commonly called a fly knife cutter. As the name suggests, the unit has one or more knives on a rotating wheel that cuts through the plastic extrusion as the wheel rotates. Many of these units are servo driven, meaning the blade can be extended to cut, and then retract at very high speeds. The blade, or blades, can also be fixed in an extended position to provide one or multiple cuts per revolution of the flywheel on the cutter. Fly knife cutters are typically used for small to medium size extruded profiles and can include cutter guides for very clean end cuts on the end product.
Digital Length Gauge– At Formtech, we would not consider our extrusion manufacturing facilities complete without digital read-out length gauges for our production and quality associates use during manufacture and inspection of your custom profile extrusion. We have this equipment in both the Fairview, PA and Athens, GA We believe that quality is defined by our customer’s expectations, and in the pursuit of superior quality, we emphasize the process of doing things right the first time. Extrusion dimensions are often measured in thousands of an inch, and we provide our teams with equipment that can accurately measure to this level. The operation of a digital length gauge is fairly simple. The measurement device is mounted to a very accurate set of linear rails, and the part is inserted onto the unit for measurement. One end of the plastic extrusion is held up to a fixed stop, and the rail on the opposite end slides along the linear rails until it contacts the other end of the extruded profile. The actual length of the part being measured is displayed on a digital read-out, with measurements showing to three or more decimal places. We involve and empower all our employees utilizing training, teamwork, and technology to the pursuit of superior quality. Pieces of equipment like the digital length gauges are tools we provide to back up this quality commitment.
We hope part two of our extrusion industry terminology review will help you better understand the extrusion process. Check back for parts three and four of our four-part series that will cover materials and processing.
We are anxious to work with you and your team on your next plastic extrusion requirement. Give us a call at 614-531-9954 or email at email@example.com for more information or a quotation.