After 45+ years in the empty container leak inspection industry, here are five more of the top frequently asked questions, and the answers, our subject matter experts receive in the field.
Leak Inspection Systems for Empty Plastic Containers
Empty plastic containers are manufactured in high volume to keep up with demands. Inevitably some containers will have defects that will cause leaks once the bottles are filled and shipped. Inline leak testing equipment tests plastic bottles as they move through the production line and automatically reject those with defects. By performing empty container leak inspection you identify issues before containers make it down the production line, minimizing the potential of recalls associated with container quality.
1. What are the different considerations when testing different types of plastic?
Whether it be PET, HDPE, or an application that includes post-consumer resin, the material is an important consideration when deciding what leak detector and options are right for your application.
Polyethylene terephthalate, PET, is typically the fastest process when high volume and low changeover applications present themselves. To ensure proper handling, change parts are available for high-speed rotary leak detection platforms and include rail and conveyor options to provide smooth transitions.
High-density polyethylene, HDPE, speed is typically not as fast, but different defects can present themselves. One of them is a “choke” neck, which is a defect that is not visually seen unless an inspection inside the neck of the bottle is executed. A choke neck probe can inspect for this on every bottle and has multiple options to ensure this defect is found before it finds its way to a customer’s production line.
No matter what material, the addition of post-consumer resin will increase the probability of defects and contamination, therefore making the inspection of every bottle on the line critical to reducing the risk of sending defective bottles to the brand owner.
2. What are the different factors I should consider when leak testing an odd bottle shape?
Odd bottle shapes frequently present handling concerns on production lines, but these concerns can be reduced with planning.
First, a vacuum conveyor will help many bottles stay upright, especially those that are tall or unstable.
Second, consider the conveyor layout. Avoid drastic speed changes and use side to side or offset transfers to reduce bottle tipping when going from one conveyor section to the next. Side belt transfer systems can also help.
Additionally, offset necks can cause a bottle to tip when a test probe is applied to the finish, so choosing a leak tester with tooling to control the bottle may be the best approach.
Finally, reverse tapered bottles will tip when backlogged, and extreme oval designs will shingle. So choosing a moving head leak detector without tooling can effectively test odd-shaped bottles while in motion on the conveyor, without creating a backlog.
3. What causes different types of defects in plastic containers?
Materials, handling, or machine setup, and component-wear can all be causes of defects in plastic bottles.
Holes are one type of defect that can be in any area of the bottle and can be caused by contamination in the resin, uneven heating, or uneven plastic distribution.
Holes along the parting line can be from worn molds, or from worn or misadjusted deflashing setups.
Gate cracks are a common defect in PET bottles and are often from low temperatures in the gate or worn or misaligned blow pins.
“Short shots” are a type of defect that can appear in the finish of the preform. Causes of short shots include blocked channels or improper setup at the injection molding stage when the preform is made before the bottle is blown.
Seal surface defects can also be caused by improper setup or worn components in a trimmer.
Many of these defects are random, so sampling checks may not be enough to prevent your customer from receiving a defective bottle. 100% inline leak inspection can protect your inventory from defects.
To learn more about the different types of plastic defects and how to prevent them, head on over to our blog by clicking here.
4. Where in my production line should I place my leak detector?
When deciding where on your production line to place your leak detector, there are a few things to consider.
First, consider if you have any secondary processes, like trimming or flaming. You will want your leak detector placed after these processes because they could create a defect.
Next, consider if you are using an anti-stat application process. If you are, it will be advisable to have the leak detector placed after this process for sanitary reasons. It is recommended to have the anti-stat system on its own conveyor to minimize the potential for this material to be introduced into the leak detector.
Finally, consider if there is a labeling process. It is advisable to make sure the leak detection is done prior to the labels being applied, as a label could possibly plug or mask a hole.
Depending on what type of leak detection system and platform is being utilized the leak detector can also provide the opportunity to separate or stage bottles for other downstream applications like vision, labeling, or end of line automation.
While each application and line are unique, ALPS Inspection is here to discuss where the best placement on your line is to maximize your line’s efficiency.
5. Why is container handling important when selecting a leak detector?
Container handling is an important consideration when selecting a leak detector because it can affect the efficiency of the entire line.
On rotary and many multi-head linear leak testers, the handling provides control of the containers as they move through the machine and test cycle.
Having custom-designed timing screws and handling components that match each container’s design and application considerations will allow for fewer jams, smoother flow, and more time in the test cycle.
During a line changeover, time spent changing, or adjusting the leak tester handling parts, is time the line is not running. Having container tooling components that can be quickly removed and installed without the use of tools, helps keep that time to a minimum.
Likewise, setup errors can waste time on the startup. Having handling parts that are designed to reduce adjustments and having the few needed adjustments by scales or counters reduce the potential for errors, which helps get the line back into production quicker.
Have a question that you don’t see answered above, contact us and one of our leak inspection experts will be in touch.