If you’re a machine operator involved in extruding plastics, there are two important things that you need to be familiar with. First, you need to know how to use an extruder. Second, you need to know how to troubleshoot and maintain your extrusion machine. If you’re not conversant with these two things, then continue reading below.
How to Use an Extruder
If you do not know how to use an extruder properly, then the whole plant could shut down. That would mean lost production time. With that in mind, let’s take a look at the best practices when working with plastic extrusion machines and how to ensure safety.
A plastic extruder is designed to convert raw plastic pellets into long forms or profiles called “extrudates.” The plastic pellets are pushed through the machine by a screw, which melts them down as they pass down the barrel toward the die. These tips will help you ensure proper extrusion machine operation.
- Always confirm extrusion materials meet the required standards. Dry them if necessary and check to see there are no foreign particles that may cause contamination or clog the extruder die or nozzle.
- Before you can start extruding, check all parameters to verify they’re all properly set: these include heating and melting temperatures, screw speed, and other settings. For example, the RPM needs to be adjusted to match the material and other adjustments.
- Check all extrusion equipment such as water/air, electrical, and vacuum systems to ensure they’re working correctly. Check, also, the upstream and downstream devices such as material dryers, extruder feeding system, cutters, and pullers.
The work of a plastic extruder operator is not only monitoring the machine’s operation but also ensuring safety when using it. Extrusion machines contain hot parts, rotating components, and electrical systems. These can cause injuries. Therefore, in addition to knowing how to use an extruder properly, observe the following.
- Evaluate the extruder’s space to clear it of slip or trip hazards, loose or exposed wires, and other dangers
- Guards should be present near every danger spot around the extrusion machine
- Wear protective gear such as safety shoes, safety glasses, and gloves when overseeing the extruder operation
- Ensure safety with extrusion materials. For example, some temperature levels can cause PVC plastic to produce toxic HCL
Plastic Extrusion Machine Problems and Solutions
It’s important to know how to use an extruder safely and correctly. But equally important is understanding the problems associated with the machine. That said, here is a roundup of the most common extrusion machine problems together with their possible solutions.
Extruder Motor Not Turning
The extruder and its drive are energized but the motor won’t turn. Possible causes for this problem include low voltage, weak windings, and worn extruder motor parts such as brushes. Verify voltage to the motor by checking the power switches or controls. Some worn parts may need changing, including the motor itself.
A jammed extruder has the screw stationary. The reason could be drivetrain problems, using the wrong or misaligned extruder screw, and foreign objects blocking the screw’s rotation. In some cases, an extruder jam occurs if the temperature is too low or if there’s residual, plastic buildup in the barrel. Ensure correct temperature level and a clean extruder. Alternatively, you may allow the plastic time to melt.
Extruder Not Extruding
There’s no output at the extruder die. If you have the extruder not extruding, the issue could be a blocked feed throat or failed hopper coolers. It’s also possible that you’re using the wrong type of screw, or the extruder screw is broken. Check for any blockage in the hopper and screw channel. You may also check the hopper coolers to ensure the plastic isn’t melting too early.
You have the extruder leaking at the die or even from the breaker plate, causing an unsightly polymer mess. Two main problems could be responsible for that: loose die and adapter bolts or incorrect breaker plate installation. To stop the leaking issue, ensure any loose die bolts are properly tightened and that the extruder breaker plate is correctly seated.
Extruder Shuts Off On its Own
This extruder problem points to a blocked feed system or jammed screw, clogged screen, or improper machine setup. The extruder screw is also most likely worn. In all these instances, the extruder motor has to work harder, drawing more current and setting off circuit breakers and other protection systems. Ensure proper machine setup and a clean extrusion machine. Change screens on time, too.
If you understand how to use an extruder, you will easily be able to tell when it has developed problems. You will also be able to find the best means to fix them. Some extruder repair tasks involve changing worn parts such as screws and screens or breaker plate.
The repair of a plastic extrusion machine may also involve complex diagnosis and parts replacements, and require the help of a specialist. Extruder manufacturers and suppliers often offer the technical advice needed to troubleshoot the specific machine, sometimes also repair services.
Proper extruder maintenance can go a long way to prevent problems and their associated losses. It helps to ensure the machine is working at its highest efficiency level, in addition to averting unwanted downtimes. Keeping a plastic extrusion machine in good condition can mean doing many things:
For one, it could mean keeping the machine’s output at an optimum level. This can be achieved through regular cleaning of the extruder and refitment of worn and damaged parts in and around the screws. It helps to keep the extruder maintenance checklist.
How to Clean an Extruder
Most plastic extruder problems result from residual plastic jamming the screw or clogging the screen and causing the machine to stop working correctly. The good thing is that you can easily avoid that by routinely cleaning the machine. Extruder cleaning can be done in these two ways: using the resin and non-resin methods.
The resin method involves running a purging compound through the machine to remove residual plastic or buildup from previous processes. The extruder cleaning compound is commercially sold as a cleaning product. Alternatively, you can run a clear resin in the machine.
The non-resin way involves cleaning the extruder parts (screw, barrel, screen, beaker plate) manually. Extruder cleaning tools should not be abrasive or they will cause damage. Avoid using a blowtorch too, as it can damage the machine parts.
As an extrusion machine operator, you’re responsible for its working. Therefore, you want to know how to use it safely as well as correctly- and if problems surface, to be able to deal with them and ensure uninterrupted operation. We have all that covered in this section including the extruder troubleshooting tips. Next we will be a look at project ideas when using a plastic extrusion machine.