Building Your Blow Mold:
Considerations for Product Development and Production Costs
Spurred by changing consumer demands, many of today’s high-volume markets are trending toward plastic containers instead of containers made of other materials. This means blow mold design has to meet more robust production requirements, while maintaining product quality and mold durability. Every customer benefits from the trend, because providers like Apex Plastics have geared up to handle these new requirements. No matter what volume you need, to fulfill crucial functional and aesthetic needs, it’s a benefit to have plastics manufacturing experts like Apex working hand-in-hand with you through the process.
In fact, over the course of more than four decades, Apex has earned its position as a leader in the plastic bottle industry. This is a direct result of close teamwork with our clients to deliver in the quantities they need at competitive prices, with the ultimate goal of manufacturing a product that is truly market competitive. When it comes to plastic bottles and containers, it’s easy to fit your need into the systems we’ve created. This article outlines the process we follow to produce quality extrusion blow molds for your projects and give you ideas to continue improving your products.
Product Development: First Identify Needs
To set up a successful blow mold production process, the first step is to define your critical part and production requirements by identifying a few key aspects of your part—in particular, symmetry, corner thickness, trim, and cooling time. Part complexity and volume have an important bearing on the most effective and least costly blow mold design to meet these needs. When evaluating your product, ask yourself the following questions and discuss options with your Apex representative.
Is your part symmetrical?
When a part is asymmetrical, we need to pay close attention to the way the part will eject, because the two halves of the mold cavity do not reflect each other. This causes the mold to release the plastic at different rates on different sides of the part, so we need to make allowances to achieve a clean part release. The asymmetry of a part also can affect wall thickness distribution, so we need to watch for areas that could be getting too weak or too bulky.
Does your part include tight radiuses?
Tight radiuses result in areas thinner than the main body, which can make them weaker. Wherever possible, large, smooth radiuses should be used to help maintain part integrity throughout the piece.
Will the plastic parison remain captive in the cavity or flash outside of the cavity?
A parison that remains captive results in a more attractive and more cost effective part. A part that must be flashed outside the cavity is costlier due to the addition of beryllium copper pinch plates, which adds additional costs to the mold and will require additional maintenance.
However, flash is unavoidable with some parts when you need to obtain proper wall thickness distribution to outlying areas. An example of such a part would be a spray bottle with a wide base and small neck opening. The parison must flash outside the neck opening, in order to get proper wall thickness in the body of the container.
Production Costs
Many factors contribute to the cost of producing a part. The blow mold manufacturing facility at Apex continually looks for ways to give you both maximum flexibility and cost efficiency, because even little adjustments can add up to a big difference in cost. However, the two major contributors to production cost are multiple mold cavities and cooling times.
Mold Cavity Size and Number vs. Production Needs
The size and number of cavities in a blow mold are largely determined by your output needs, and these are the primary factors in calculating mold cost. What is the anticipated annual volume of your product? More cavities generally return a lower piece price over time. However, additional cavities cost more at the outset of a project. Chances are that minimum order requirements and/or setup charges will increase with the number of cavities. Your Apex representative will work with you to evaluate all of these factors to determine how many cavities are required to meet your output needs.
Designing for Optimal Cooling Time
The next major consideration of production cost is mold cooling design. Molds are constructed with internal water paths to cool the part with chilled water. Until the part has solidified, it cannot be ejected from the mold, so cooling directly affects cycle time. A well-designed mold that properly cools the part decreases the time the part must stay in the mold, reducing overall cycle time and ultimately reducing the cost of the part.
Conclusion
A durable blow mold designed with precise cooling time and clean ejection is worth the initial investment of time and money, especially for high-volume outputs. We are constantly seeking to improve our processes and manufacturing capabilities in these ways and others to shorten your production runs. We look forward to using these finely-tuned capabilities to your benefit as we work closely with you to identify the best possible blow mold design strategies.
Understanding Raw Materials
Commodity Polymers: Choosing the Right Resin for Optimal Price, Process, and Performance
When selecting the proper resin for your plastic containers, you must examine raw material properties that will affect the nature of your end product. Do you need a plastic that is flexible or rigid? Transparent or opaque? Resistant to leaching? Does it need to withstand freezing temperatures or high heat? Apex Plastics produces in several thermoplastic polymers to meet each of these needs. The polymers we work with include High Density Polyethylene (HDPE), Low Density Polyethylene (LDPE), Medium Density Polyethylene (MDPE), and Clarified Polypropylene (CPP). All of our resins are FDA approved. To meet your specific requirements, Apex works with several different resin suppliers, and is always ready to provide a quote for a specific brand of resin for your project. If product compatibility is a concern, sample bottles may be requested for testing prior to production.
Available Resins
HDPE resin is very versatile, and used widely for manufacturing plastic bottles. Approved by the FDA, NSF, and USDA for direct contact, HDPE’s excellent resistance to attack by acids, alcohols, and bases makes it highly desirable in food and medical packaging applications.
This lightweight material is economical and impact-resistant. It provides an effective moisture barrier—perfect for medicine and toiletry containers, as well as milk and fruit juice bottles. In addition to being strong and watertight, plastic bottles made with HDPE are naturally translucent. They can be made opaque, but not glossy, with the addition of color. This kind of bottle is perfect when you are producing consumer personal care products that need to look appealing, such as lotions, shampoos, and astringents.
HDPE is the safest plastic with regard to leaching, and is covered by most recycling services.
While HDPE containers protect their contents in temperatures below freezing, they should not be filled with products heated above 160 °F (71 °C) or products requiring a hermetic (vacuum) seal.
Similar to HDPE in composition, LDPE is less rigid and generally less chemically resistant, but more translucent. The flexibility of LDPE plastic bottles makes them the ideal candidate for product dispensing and squeeze applications, such as wash bottles or tubing for laboratory purposes. Containers made with LDPE can withstand sustained use at temperatures up to 176 °F (80 °C), and for shorter durations at higher temperatures.
While considered environmentally safe, LDPE is accepted in fewer recycling programs than HDPE products.
MDPE is less rigid than HDPE, but more rigid than LDPE. It is mainly used for products with characteristics typical of HDPE, while still offering flexibility.
Polypropylene provides a rigid, chemical-resistant container and excellent moisture barrier. Although not intended for high impact or cold temperature applications, a major advantage of polypropylene is its stability at high filling temperatures for hot-fill products, such as pancake syrup. Polypropylene bottles and jars also can withstand frequent autoclaving and steam-sterilization.
Polypropylene products are inherently opaque. However, many applications increasingly demand transparency, particularly in food packaging industries. For that reason, clarifying additives have been used increasingly in recent years. These additives remove opaque properties, making the plastic transparent and glossy, while retaining its original strength. Clarified Polypropylene—CPP—is comparable in clarity to glass, but more economical and less subject to physical shock.
Polypropylene is designated as a safe plastic product, and usually is recyclable wherever HDPE is processed.
Conclusion
Appropriate resin selection is a must from the beginning of your project. Apex will help you weigh all considerations that come into play when selecting materials, including shock absorption, heat and chemical resistance, cycle time reduction, secondary operations, regulatory compliance, aesthetics, and recyclability.
*This information is supplied for use as a guideline only. Information may vary under certain conditions. It is the responsibility of the customer to test the compatibility of each bottle for its intended use.
Parent Company PCE, Inc. Among ICIC and Fortune Magazine’s Inner City 100 WinnersAnnual ranking
showcases the 100 fastest-growing urban businesses in America
Annual ranking showcases the 100 fastest-growing urban businesses in America
The Initiative for a Competitive Inner City (ICIC) and Fortune magazine announced that PCE, Inc. was selected for the 2012 Inner City 100, a list of the fastest-growing inner city companies in the U.S. The Inner City 100 program recognizes successful inner city companies and their CEOs as role models for entrepreneurship, innovative business practices and job creation in America’s urban communities. Visit www.fortune.com to view the entire list.
ICIC is a non-profit research and strategy organization and the leading authority on U.S. inner city economies and the businesses that thrive there. Founded in 1994 by Harvard Business School Professor Michael Porter, ICIC expands inner city economies by providing businesses, governments and investors with the most comprehensive and actionable information in the field about urban market opportunities. ICIC’s unique knowledge and expertise about inner city success factors and thriving companies is developed from specialized urban networks and path-breaking research.
PCE, Inc. is a privately held corporation founded in 1993. It is structured into two distinct business groups to serve its customers: Plastics and Data Center Solutions. PCE Plastics Group has three divisions:
Apex Plastics
Apex Plastics, located in Brookfield, Missouri, is an FDA registered, ISO 9001:2008 registered plastics molding manufacturer, specializing in custom and proprietary blow-molded bottles, containers and shapes. Recently, Apex invested in a new molding machine and take-out system. This new machine will expand the cavity offerings to their customers and increase production capacity.
HTI Plastics
HTI Plastics, located in Lincoln, Nebraska, is an ISO 9001:2008 certified world leader in injection molded plastics, with more than 25 years of experience in consulting and manufacturing within the medical device, animal health and packaging industries. HTI’s high-speed machines and computerized systems are housed in an 83,000-square-foot, state-of-the-art facility.
Geist Plastics
Geist Plastics, also located in Lincoln, Nebraska, is an ISO 9001 certified company, focusing on custom plastic profile extrusions. Geist employs standardized quality control and lean practices. Founded in 1948, Geist was acquired by PCE in 1997, and continues on atrend of record-setting growth.
PCE’s Commitment to Customers: Demonstrable Quality and Service
With locations in the United States, Europe and China, PCE, Inc. is doing business on six continents, with solutions for every size of company, from just a few employees to hundreds of thousands of employees. PCE employees are committed to delivering customized solutions that exceed customers’ expectations.
Founder and CEO Sam Featherston believes service and quality are the characteristics of PCE that set the company apart from their competitors. These important focuses of PCE business begin with the company’s directors and trickle down through the entire staff. “I tell our associates we want to be the best supplier our customers deal with, regardless of category—from paper clips all the way to the most important component of their products. This goal is regularly communicated to all employees, and they see it also is communicated to our customers. It has become a part of our culture—a self-fulfilling quality essential to the way we do business every day. It’s obvious that our commitment to customers in these areas is what keeps them coming back, and we are proud of that.”
Featherston adds that PCE works toward quality and exceptional customer service in many ways throughout the manufacturing, sales and fulfillment processes. For example, the company continually seeks cutting-edge technologies and supports employees through education and cross-training. “These qualities and activities permeate what we do and are a major building block of PCE.”
For more information about PCE, Inc., go to www.pce.us.com. To learn more about ICIC, visit www.icic.org .