In a continuous process like extrusion blow molding, pollution can adversely affect your company's profits. Blow molding often has bigger problems than other processes. Once the contamination begins, it is almost impossible to stop it without active intervention—usually by pulling a screw or using a scavenging compound. If you want to remain competitive, it is essential to effectively purify your thermoplastic processing equipment. Not only material changes occur more frequently, but waste disposal is more difficult (and more costly), and more and more customers require timely customized products. For many blow molding plants, reducing waste, time and costs are some of the most important factors in maintaining competitiveness. Many customers have reduced costs by more than 70% by using the right purification compounds, saving them up to tens of thousands of dollars each year.

Until recently, the most popular method of purging extrusion blow molding equipment was to use the next processed resin or regrind. However, in the long run, this method will result in longer cleaning times, higher reject rates and more residue accumulation.

Here are seven quick tips for using decontamination compounds to keep the decontamination operation as efficient as possible:

Tip #1: Do not use production resin to clean your machine

The production resin is not designed to be used in cleaning machines, nor is it a substitute for commercial cleaning compounds. Cleaning the blow molding machine with the next resin or recycled material is time-consuming and wasteful, and it is inefficient in removing color and carbon pollution. When you use recycled resin or virgin resin for cleaning, this material will form another layer on any existing resin, color deposits or carbonized material in the barrel and on the screw. Over time, these layers become additional sources of pollution, making purification more difficult. Once your machine resumes production, the carbonized material will eventually break away and contaminate your product.

Tip #2: Choose the right blowing compound for blow molding

In many cases, blow molding conversions are significantly shortened by the use of scavenging compounds because they eliminate residues and contamination. Choosing the right level will make all the difference. Extrusion blow molding head and accumulator are designed as low pressure area. The low flow or low pressure environment of extrusion blow molding makes certain areas difficult to clean. Since mechanical cleaning compounds require maximum pressure, they are not always the best choice for this application. Instead, try to use chemical scavenging compounds. When cleaning the extrusion screw, it is very important to use the correct product and cleaning process. Using the wrong chemicals or tools can damage the screws or die head and cause serious production problems.

The product grade you need depends largely on the resin being purged and its processing temperature. If your facility has pollution problems, your supplier may recommend a different grade. In addition to the processing temperature, the compound should also have a similar low melt index, which is more compatible with the resin.

The following is the typical melt index (MI or MFI) of blow molding resin:

LDPE: <2g/10 minutes HDPE: <1g/10 minutes PP: <2g/10 minutes

Another option is to use a purification concentrate like our PLUS Grade. PLUS Grade uses Asaclean's strongest cleaning ingredients to pressurize your processed resin. You can guarantee matching processing temperature and melt flow, because you are using your own production resin.

The blowing procedure of the extrusion blow molding process differs depending on the blowing product you use. If you are not sure how to clean the extrusion blow molding machine most effectively, it is best to contact your blowing compound supplier.

Tip #3: Practice preventive cleanup procedures

Many plastic processing companies use purification compounds only when absolutely necessary. But participating in this type of purification "process" can lead to reduced profitability and efficiency. Adopting preventive purge practices can not only save your facility from machine downtime, but also reduce scrap rates, customer scrap rates, and production line downtime. You can't wait until the last minute to run the purification compound, because by then you are already plagued by pollution problems or color streaks.

Regular use of cleaning agents can prevent contamination from the beginning. Normally, only one or two system volumes of purge compound are needed to prevent contamination. Most operators would rather plan for downtime related to cleaning than unplanned screws or head pulls. There are three main benefits of implementing a preventive maintenance plan and decontamination process in your facility:

• 1- Prevent color accumulation and carbon pollution

• 2-Reduce excessive purging time and material waste at the end of the production run

• 3- Limit the frequency of screw pulling and minimize the time and effort required to pull and manually clean the screws

Tip #4: Use the correct machine settings

In order to maximize cleaning performance, please follow the machine settings recommended by the supplier. Settings are very important. Asaclean's chemical scavenging compounds are an excellent choice for blow molding because they work through an endothermic (thermally activated) chemical reaction that causes the material to expand into those low-flow areas. Without the correct settings, you will miss the benefits of these compounds. Using the correct settings will activate your chemical cleaning for the best cleaning performance.

How the Midwest blow molding machine reduced waste by 21% and downtime by 30%

One of our purge specialists recently managed a cost-saving purge project at the Midwest EBM plant with a manufacturing engineering supervisor. They use translucent polyurethane (low-temperature processing) to blow-mold large air-bag components for residential and commercial applications. During the start-up process after the weekend shutdown, they have been struggling with random carbon spots.

According to production needs, they shut down the machine and restart it several times a month. Their goal is to reduce machine downtime and reduce the number of pounds scrapped at start-up. During the 2-month trial period, they conducted four independent tests with Asaclean E-level purification compounds to compare their performance with respected competitors. After these tests were completed, the manufacturing engineering supervisor provided us with a detailed data-driven report, which achieved good results.

Using the average of these trials, his report indicated that they had approximately 180 minutes and 215 pounds. The value of scrap parts for start-ups when using our competitors. After switching to Class E, they saw a major improvement and dropped to 130 minutes and 170 pounds. The value of scrapped parts. In the end, they saved approximately US$4,640 for this application for each machine in the factory.

Tip 5: Increase the heat of troublesome equipment

For machine parts that are difficult to clean, increase the heat in this area to 500°F (if the production resin is not sensitive to heat). When using the AASALEAN chemical grade, this will cause the endothermic reaction to occur where you need cleaning the most.

This is very common in extrusion blow molding systems with accumulators, where the accumulator head is the most troublesome area. First of all, be sure to pinch the gap on the accumulator head as much as possible to maximize the mechanical cleaning effect. In addition, the rollout speed is increased to the maximum security setting. Fill and empty the accumulator four to eight times, varying between 25% and 100% to ensure that the accumulator is clean. Finally, when replacing the cleaning material to reduce the amount of replacement resin, be sure to maintain these settings. When all cleaning appears to have been removed, restore the head gap, filling height, and ejection speed to production settings.

Tip #6: Use Asaclean to seal your machine every time you shut it down

In addition to regular and preventive maintenance purge, thermally stable purge compounds can also be used for temporary or long-term shutdown and sealing, especially during weekends or holidays. During the shutdown period, the oxygen in the barrel will cause the residual polymer to degrade and carbonize, delay the start-up and cause the machine downtime to be prolonged and scrapped. The thermally stable cleaning compound creates a "closed" environment in the barrel and promotes further cleaning during shutdowns.

Tip 7: Clean each extruder in a multi-layer system

A common mistake in extrusion blow molding is to clean only the contact layer, not the isolation layer or inner layer. However, materials used as barriers or inner layers may be more susceptible to degradation and contamination. Some processors use recycled materials as fillers or thickeners in the inner layer. Due to multiple thermal cycles on the resin, recycled materials can cause pollution. Make sure to clear every layer during each conversion to maximize quality and performance.

Using commercial cleaners can keep your blow molding machine clean and running smoothly, but only if you use them correctly. Keep these seven quick tips in mind, and your blow molding plant will remain competitive without any problems.

Take advantage of our remote consultation, trial and training via Skype, FaceTime or WhatsApp. Call 800.787.4348 or visit asaclean.com to request a free cleaning consultation.

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