Mack Blog

Gas-assist molding, which utilizes nitrogen gas pressure to form a part fully, offers significant cost-saving advantages while expanding design and manufacturing options for injection-molded components.

Traditional plastic processing delivers cost benefits through repeatable, high-volume production, but gas-assist molding furthers these savings. External gas-assist introduces a micro-thin layer of nitrogen gas during the packing phase, replacing the traditional holding phase. This reduces the required pressure to pack out a part, leading to lower molding pressures of 1-2 tons/in² and reducing clamp force requirements. As a result, manufacturers can utilize smaller, less expensive presses and achieve substantial cost savings.

Beyond press tonnage reduction, external gas-assist enables modifications to traditional part designs, such as increasing rib-to-wall ratios and allowing thicker ribs. These optimizations minimize differential shrinkage and reduce distortion, which in turn lowers scrap rates and enhances manufacturing efficiency. The primary trade-off is the need for more intricate tool design to seal gas from the external environment, but these initial tooling costs are often offset by long-term production savings.

Enhancing Aesthetics, Performance, and Efficiency with Internal Gas-Assist
Internal gas-assist molding is an effective solution for producing thick parts with high aesthetic quality. Unlike the external gas-assist method, which shapes the outer surface, internal gas-assist introduces gas within the part’s geometry, creating a hollow channel through the thick region. This process forces the resin against the external walls, resulting in a packed-out appearance while maintaining structural integrity.

By evacuating resin from the center of the thick section, internal gas-assist enables the molding of extremely thick features without compromising surface finish. The removal of excess material can reduce part weight by 20% to 30%, which may be beneficial for applications where weight reduction enhances performance. Lighter parts can also contribute to lower freight costs, particularly in industries where shipping expenses are influenced by weight.

Additionally, because there is less material to cool, cycle times may be reduced compared to molding the same geometry as a solid part. Since press cycle times are often driven by the thickest areas of a part, this effect can contribute to overall process efficiency, potentially leading to higher throughput and some cost savings in production.

While the technique allows for superior aesthetics and the ability to mold challenging geometries, it does require more intricate tool design. As with external gas-assist, the increased tooling complexity and associated costs must be considered when determining the best approach for a given application.

Optimizing Production Efficiency
Gas-assist molding not only lowers manufacturing costs but also optimizes production efficiency by simplifying part design and reducing complexity. By integrating this process, manufacturers can produce lighter, more structurally sound components while using fewer resources and less energy. The long-term savings in materials, energy consumption, and equipment costs make gas-assist molding a valuable investment for cost-conscious manufacturers.

What is Cast Urethane?

Cast urethane is the process of pouring liquid polyurethane resin into a rubber mold to create a part. It is a cost-effective alternative to injection molding, making it ideal for low-volume production and prototyping.

Benefits

Low-cost tooling and design iterations with minimal rework expenses allow programs to scale from low to high volume before committing to capital tooling investments. Because rubber molds can be easily modified, design adjustments can be made quickly, making this an ideal process for prototyping.

Additionally, cast urethane is a great alternative to thermoforming, as it allows injection mold-like design details to be cast directly into the part.

Cast urethane molding is well-suited for both small and large, intricate parts. Each mold can be reused up to twenty times, making it a versatile option for short-run manufacturing.

By leveraging 3D printing to create master patterns, Mack Prototype can produce high-quality molds in weeks rather than months. Urethane molding serves as a bridge to full-scale injection molding, enabling customers to refine their designs with a production-like process at low cost before committing to high-volume production tooling.

Drawbacks

The cast urethane process requires parts to set and cool within the mold, resulting in a slower production rate of approximately one part per day. However, multiple molds can be used simultaneously to increase output, allowing for faster batch production.

Why Mack Prototype?

Mack Prototype has extensive experience with cast urethane molding, from small components to large, complex parts. The team pays close attention to detail and ensures high-quality results, prioritizing clear communication and collaboration throughout the production process, making adjustments as needed to meet our customers’ requirements efficiently.

For Lucas Osorio, Mack Molding has been more than just a place to work – it’s been a foundation for personal and professional growth through all the stages of his life. From a young temp in the finishing department to a Program Manager back in the heart of Vermont, Lucas’ story is one of ambition, resilience, and gratitude.

Lucas grew up in Bennington, Vermont, with a deep love for the Green Mountains. After attending Mount Anthony Union High School, he started his journey at Mack’s Headquarters as a temp. It didn’t take long for Lucas to realize something important:

“I quickly realized this is something I could be very passionate about,” he said.

He gained experience on the manufacturing floor at Mack HQ and eventually became a Finishing Technician. Lucas’ early days at Mack were foundational, sparking his ambition to learn and grow.

In 2013, Lucas took a leap of faith. He moved to South Carolina to join Mack’s Inman facility, a decision that he calls “the best I ever made.”

“If I had stayed in my comfort zone, I wouldn’t have had the ambition I needed to grow,” he explained.

Starting as an Associate Manufacturing Engineer in the engineering department, Lucas contributed to projects for the non-automotive transportation market on the Automated Paint Line. He later became Quality Manager, a role that tested his leadership and broadened his perspective.

But growth doesn’t always follow a straight path. In 2022, Lucas took a career break. He and his wife, Daydrielane, moved to Jamaica, where they purchased land with plans to build a new life. Though the idea was exciting, it turned out to be more of a place to vacation than to settle.

After a year, Lucas reconnected with the team at Inman and stepped into the role of Document Control Manager. He was happy to return to Mack but soon faced difficult news: several family members were diagnosed with cancer. His mother, aunt, and grandmother all needed more support.

Lucas knew it was time to come home.

“I realized over the last six months that family here was going to need me,” Lucas reflected. “Mack’s support team was incredible, and I’ll always be grateful to Bryan Campbell and the team down South for helping me build my career. I’m very proud of the work we have done.”

Back in Vermont, Lucas found his place once again – this time as a Program Manager working with Business Unit Director Natasha Moses. Now he and his wife are living in Pawlet, Vt., with their sons Shiloh, 8, and River, 6, as well as their four-year-old daughter, Willow-Bliss.

While the call of family drew him back to the Northeast, it’s a role he’s always aspired to, combining program management with customer relationships while being surrounded by the mountains he loves.

“Every day, I drive to work and see the beautiful countryside,” said Lucas. “I think about how grateful I am to be back here.”

Reflecting on his journey, Lucas appreciates how far he’s come. When he first joined Mack at 20 years old, he knew little about manufacturing or the professional world.

“I couldn’t imagine Mack would develop me into a professional with a family,” he noted. “It’s more than I could hope for.”

Lucas credits Mack’s culture of support, mentorship, and opportunity for helping him grow. His journey is a testament to how Mack Molding’s footprint – its people, facilities, and values – creates opportunities not just for professional development, but for building a life.

“I bleed Mack blue,” Lucas said. “I believe in the support, the company, and the idea of what Mack should be. The reputation carries weight, and it’s nice to know that your work and ethics are paying off.”

From the mountains of Vermont to South Carolina and back again, Lucas Osorio’s story is about ambition, family, and finding the right place to grow – both personally and professionally.

Where might your career with Mack Take you? Start your journey today at https://www.mack.com/job-opportunities.

Mack Molding’s plastic injection molding and contract manufacturing experts are counting down the days until MD&M West 2025, taking place Feb. 4-6, 2025, at the Anaheim Convention Center.

The team is excited to hit the road, joining 1,700 exhibitors and more than 13,500 attendees from 50+ countries in 300,000 square feet of space highlighting solutions for every stage of the product development lifecycle.

Please join Mack by using the promo code INVITE974915 when you register online to get a free expo pass or save 20% on the conference. Of course, do not forget to stop by and see the Mack team at Booth No. 1539. We look forward to sharing our abilities as a full-service contract manufacturer with specialties in plastics design, prototyping, plastic injection molding, sheet metal fabrication, machining and turnkey system assembly.

We will also have representatives from wholly-owned Mack Group subsidiary Mack Prototype on site to introduce visitors to rapid manufacturing services designed to take products from prototype to production, including 3D printing and additive manufacturing, cast urethane molding, plastic injection molding, CNC machining, and an NPI Launch Lab.

Our roots may be in plastic injection molding, but today Mack Molding is so much more. As a vertically-integrated product development and manufacturing partner, Mack is prepared to take your ideas from inception through prototyping to manufacturing. Whether you are interested in Mack Medical, Mack Molding, Mack Technologies, Mack Prototype or Synectic Product Development, the design function is part of a total product development solution geared toward reducing cost and time-to-market and our vertically integrated services have been organized to benefit your business throughout the product life cycle.

If you would like to schedule a specific meeting time in our booth, please contact your business development manager, or Jon Whitney, Vice President of Business Development at jon.whitney@mack.com or (802) 375-0714.

For 40 years, MD&M West has been connecting industry-leading suppliers with the latest products and technology, helping bring products from concept to market. We look forward to seeing you at this year’s event – and remember you can find us at Booth No. 1539!

In the world of injection molding, optimizing the quality of molded parts is paramount. Two critical factors that play a significant role in this optimization process are gate location and flow ratio. Properly understanding and managing these elements can make the difference between a successful, high-quality part and having an incomplete part that can’t be filled. Let’s delve into how gate location and flow ratio interact, and why careful consideration of these factors is essential.

The Importance of Gating in Injection Molding

Injection molding commonly utilizes six types of gates, each with its unique application:

• Direct Sprue
• Edge-/Tab-gate
• Fan-gate
• Sub-/Cashew-/Banana-gate
• Diaphragm
• Pinpoint (for hot drops)

The location of these gates can significantly impact the quality of the final product. For example, improper gate placement might cause early freeze-off, leading to short-shots or improper filling due to inadequate machine pressure. To mitigate these issues, it’s crucial to follow specific guidelines when determining gate placement:

• Place the gate at the part’s largest wall thickness.
• Ensure the gate is positioned to minimize the flow length.
• Consider the cosmetic implications of gate placement.

By adhering to these guidelines, the risk of defects is minimized, resulting in a higher-quality product.

Understanding Flow Ratio and Its Implications

Flow ratio, defined as the distance between the gate and the farthest point of the part in relation to wall thickness, is a key metric in ensuring proper part filling (Equation 1). Choosing the best gate type, location and quantity minimizes the flow length and optimizes the flow ratio. The industry standard, as provided by RJG, suggests that the flow ratio should be kept under 150. At Mack, however, a stricter standard of 100 is applied to provide an increased factor of safety.

Equation 1: Flow Ratio = Flow Length / Wall Thickness

A poor flow ratio can lead to several issues, including:

• Longer fill times
• Pressure spikes
• Compromised part strength
  • Formation of knit lines or seams, creating weak points

For instance, consider Figure 2, a part with a flow length of 21.753 inches and a wall thickness of 0.16 inches, resulting in a flow ratio of 135.97 . This falls within the industry standard, but to meet Mack’s more stringent requirement, a second gate might be added to lower the ratio below 100. In contrast, Figure 3 is a part with a 36.08-inch flow length would result in a flow ratio of 225, which is well outside acceptable standards and would require significant adjustments.

Balancing Gate Location and Flow Ratio

In some cases, sub-optimal gating methods or locations are necessary to preserve the cosmetic quality of the part or accommodate complex geometries. However, these compromises often lead to increased flow ratios. So, how can this challenge be addressed?

One solution is the use of flow leaders. These are raised paths—typically 1 inch wide and 1 millimeter (0.0394 inches) high with heavy drafting—that help manage the flow of material through the mold. Flow leaders reduce unwanted shear and air pockets, eliminate the need for multiple gates, and increase wall thickness, thereby lowering the flow ratio and reducing pressure spikes.

Improper gate placement, on the other hand, can cause several issues, including fill imbalance, air pockets, uneven cooling, shrinking, warping, and short-shots. The use of Moldex simulations can provide valuable insights into how different gate placements and flow leaders impact the filling process, helping engineers make informed decisions.

Conclusion

Understanding the relationship between gate location and flow ratio is critical in injection molding. By carefully considering gate placement, flow ratio, and the use of flow leaders, engineers can significantly improve the quality of molded parts. At Mack, we prioritize these factors to ensure that our products not only meet industry standards but exceed them, delivering high-quality, defect-free parts to our customers.

For more information on this topic, or any of your plastic injection molding needs, please feel free to reach out to us!