When looking at injection molding cavity pressure sensors, the sheer number of products to choose from can be a bit overwhelming. In order to choose the proper sensor for your application, it’s vital to fully understand all of the options and what will work for your specific project.
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Some sensor selection considerations include:
We’re going to focus on the type of sensor technology.
There are two main types of sensors: strain gage and piezoelectric (piezo).
Strain gage sensors have a full or partial Wheatstone bridge strain gage sensing element (fun fact: it inspired our logo). When force is applied, the gage is deformed causing its electrical resistance to change. The resulting changes in current is interpreted by a process control system (such as CoPilot) where it can be displayed in graphical format.
Piezoelectric sensors have a quartz crystal in the sensor that, when force is applied, emits an electrical charge. This electrical charge is amplified to a signal that can then be sent to a process control system (such as CoPilot) where it can be displayed in graphical format.
Both technologies are reliable, and we recognize benefits each may have over the other depending on the application; however, we have identified strain gage sensors as our preferred technology for several reasons. Let’s review the benefits of strain gage sensors and why they are preferred in most scenarios.
Let’s review the benefits of strain gage sensors specifically and why they might be a good option for your application.
Contamination is any outside substance that causes inaccurate data readings. It happens when debris, water, or moisture sneaks into the electrical sections of a sensor system, greatly skewing the data.
Piezo sensor systems as a whole have many locations that can be exposed to contamination, causing drift in data and potential failure of the sensor itself. An example of this is any connection point, either at the sensor or on the side of the mold.
Strain gage sensors are highly robust and are inherently immune to all but the most severe forms of contamination. This means you can rest assured that your hardware is collecting accurate data.
It’s important to take into consideration how hot you will be running your mold. Each sensor head has a maximum temperature that it can withstand—going above that will cause damage to your sensor and inaccurate data. Piezo sensors can withstand up to 392°F (200°C), whereas some strain gage sensors can withstand up to 425°F. That means they can be used in a wider array of machines and applications without risk of damage to the sensor head.
Strain gage cables are permanently mated to the sensor head, providing more shielding against ambient electrical currents or build up through the tool. Each connection point for the Piezoelectric sensors is a break in the shielding, which may allow stray electricity to interfere with the picocoulombs of signal generated by the piezoelectric crystals under load. This signal interference is then magnified by the signal amplifiers necessary to boost the crystals’ generated current to a level detectable by modern computers (such as process control systems).
A frequently overlooked benefit of strain gage sensors is the ability to diagnose the health of the sensor while it is installed in the mold. The readings from a strain gage sensor at rest can determine whether a cable has been crushed during installation, the sensor is improperly installed, or the sensor has been overloaded or damaged. On the other hand, piezo sensors only provide very limited data for diagnosing sensor problems. This can be helpful in detecting problems in the tool room before the mold is installed in the press, saving significant downtime if a problem occurs.
One of the biggest things that sets strain gage sensors apart from piezo is that they are a lower cost option with the same data quality as a piezo sensor. When looking at equipping all of your molds with multiple sensors per mold, the savings add up fast. Though this is important, we want to make sure that you’re receiving the proper equipment for your application based on all factors, not just cost. But if those align, this is a huge benefit and win for your budget.
Overall, strain gage and piezo sensors are very comparable in performance and final data displayed on a process control system. Their resolution and accuracy are in line with one another, and they both offer a large array of sensor head sizes. Strain gage sensors offer a more robust design that is more likely to provide accurate data, ease of debugging, higher temperature threshold options, and a lower cost solution with comparable results.
Injection molding is the process of injecting molten plastic into a mold cavity in order to produce a part that is of the shape of that cavity. It is suitable for parts that need to be mass-manufactured, without the need to customize each part differently.
Almost every product we manufacture for our customers will get to a stage where additive manufacturing methods become insufficient and costly in the long run. Getting into injection molding is a serious undertaking and requires a few steps before any investment is made in the actual molds.
With injection molding, you can make parts using materials such as:
Acrylics (PMMA)
ABS
Nylon polyamide (PA)
Polycarbonate (PC)
Polyethylene (PE)
Polyoxymethylene (POM)
Polypropylene (PP)
Polystyrene (PS) or High Impact Polystyrene (HIPS)
Thermoplastic elastomer (TPE)
Thermoplastic polyurethane (TPU)
For more Injection Molding Gaugeinformation, please contact us. We will provide professional answers.
Thermoplastic rubber (TPR)
The working principle of the injection molding is as follows,
The feed material is heated to its melting point.
Liquid material is forced through an injection port to fill a formed cavity (mold) at high pressure.
As the material cools, it solidifies into the shape of the mold. The finished product is then removed from the mold and the cycle repeats.
Injection molding is costly in the short run but economical in the long run. Injection molding has a low defect rate average of 5%. On average, 500 pieces can be produced daily. The average turnaround time from mold design to production is 35 days. If you need detailed lead time predictions for your project, please contact us.
The maximum size depends on a multitude of factors, but shouldn't be a concern for those making products in the realm of IoT hardware.
One reason why we say it's crucial to run the whole NPI process for each new project is because of the lock-in that comes with opening a mold. Once the mold is opened (manufactured), it's costly to make changes to the design. Keep in mind that the ownership of the mold belongs to you.
Coloring injection-molded plastics is simple, but getting it right exactly is challenging. Adding colors in the injection molding process can be done by adding dye pellets together with the initial resin pellets before melting the plastics into the mold. These dye pellets are to be adjusted according to your plastic of choice's natural color, which could range from clear, to brown or black.
Molds are hollowed out structures used to set the shape of the product to be made. These are typically made out of aluminium, steel, copper, and alloys. The material choice for these molds are different according to the product's material.
Tooling is the process of choosing the appropriate tools: jigs, gauges, molds, cutting patterns, and other equipment appropriate for the product being made. Different products require different tolerance and clearance, which plays a part in deciding on what tools are to be used. Other than that, the product's material is also a core factor to be paid attention to.
Silicon or silicon rubber molds are also commonly used in plastics injection molding since it's relatively cheaper than harder metal molds. Silicon molds are generally flexible, chemical resistant, with great tear strength. These qualities make them appropriate to mold polyesters, polyurethanes, and even low-melting point metals. These silicon molds are often made using SLS 3D printing, which we also support.
Hot runner systems are systems of heated components used in injection molds to inject molten plastic particles into the cavity of the mold.
Hot runner systems are heated to ensure that the plastic in the runners and gates remains molten. Since there are heating rods and rings near or in the center of the runner, the entire runner from the nozzle outlet to the gate of the injection molding machine is under a high temperature, the plastic in the runner is kept molten. It is generally not necessary to open the runner to take out the condensed material after shutdown. For this reason, the hot runner process is sometimes referred to as runnerless molding.
Advantages of Hot Runner System
The main advantage of having a hot runner system is that it has negligible remaininog feed inside the mold. This means, it also:
Save raw materials and reducing material costs.
Shorten the molding cycle and improving machine efficiency.
Fewer follow-up processes and increased automation: There's no need to trim the gate and recycle the cold sprue and further processes, which is conducive to production automation.
Consistent quality of injection molded parts in multi-cavity molds improves product quality.
Reduces the possibility of deformation of thin-walled products, since lower injection pressure is used.
Common situational use of Hot Runner Systems
When the overall size of the product is large or when the product wall is thin.
When the requirement for product appearance or precision is demanding.
When the product yield is high.
When the material used in the product is thermally sensitive.
When the product requires special materials, such as high viscosity, low stickiness, and high forming temperature materials.
If you want to see how different design decisions affect your product, use 3D Printing, if you have finalized your design and secured funds for a manufacturing batch, move to injection molding.
The primary difference between die casting and injection molding processes is that die casting deals with metals and their alloys, while injection molding deals with plastics and polymers.
If you want to learn more, please visit our website Plastic Injection Molds.