Your screw and barrel are among the most important and expensive parts of your injection or extrusion machine. If there is a problem with them it can shut down your entire process. Wear is one of the main issues you will face with your screw or barrel. Thankfully wear on the components is a slow process, but it can go unnoticed until their performance has been dramatically reduced. Feedscrew wear, in both extrusion and injection molding, is very similar. Most of the wear will occur in areas of high pressure, particularly in transition sections and the last few metering turns. So how can you tell if there is a problem?
1.) Burrs on your screw flights
Trailing side of flight: The high compressive force and angular motion of the flight relative to the barrel wall during rotation causes wedging and subsequently burrs on the side of the flight. Basically, the flight surface is torn off of the back of the flight in the compression or barrier section of the screw.
Both sides of flight: Misalignment puts tremendous pressure on the flight, as well as tearing and crushing, as the screw is forced to bend to follow the barrel bore.
2.) Polished or rounded flight corners
Extended wear from particles caught between the flight O.D. and the barrel wall, particle fracture, removal of lubrication, and impact cause abrasive wear that erodes the base screw material.
3.) Leakage flow during operation
Minor wear has little effect on overall machine performance; however, when the radial clearance between the screw flights and the barrel wall increases, leakage flow occurs. When this happens, you will typically see a reduction in throughput and an increase in melt temperature as the screw cannot maintain the correct pressure. This will force higher RPMs and energy consumption to maintain the desired production rate.
Without regular tool and machine maintenance, the quality of your plastic components will be negatively affected (as well as your project’s budget). Since the screw is inside the barrel, it can be challenging to know if there is a problem with either tool. Thankfully, keeping a close eye on your machinery, such as regular examinations of the screw flights or production output numbers, can give you a good idea of what may be happening.
How can we help you?
The doors have been open at Santa Fe Machine Works, Inc. since 1923, and for the past 45 years we have been dedicated solely to the manufacture and supply of new & rebuilt injection & extrusion screws, barrels & valves to the plastics industry. We also offer custom-tailored screw, barrel, and valve combinations, allowing our customer’s production goals to be met in the best, fastest, and most cost-effective ways possible. Our employees have over 200 years of combined experience in the plastics industry and are eager support your specific extrusion or injection needs. Have a question, need assistance, or looking for a quote? Contact us today!