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DL Series Plug: Sealing In Reliability

The following was first featured in Automotive Powertrain Technology International and Transmission Technology International.

In hydraulics, innovative product design is motivated by the need for a new function to reduce pain points or improve a current solution. The Lee Company’s automotive customers have told us that sealing cross-drilled holes in aluminum manifolds is a function they all need. These customers also shared that they seek new sealing solutions to reduce costs and weight, increase reliability, and enable easier installation and verification processes. Cost reductions can be achieved for each piece and via process improvements.

For example, reducing scrap and rework and eliminating secondary processes such as adding sealants, which may cause additional failure modes, can make the installation process more efficient. Automotive manufacturers want solutions for both low-volume and high-volume production, so it is a challenging set of issues to solve. With these needs in mind, The Lee Company developed a product to satisfy these requirements.

The DL Series Plug (patent pending) was born. It is a single-piece, stainless-steel expansion plug engineered to provide leak-tight performance in aluminum housings without using threads, sealants, or O-rings. The plug uses The Lee Company’s Drive Locking technology to reliably seal passages for life. This new locking-end design includes features that can be used for 100% verification that the part is properly installed, improving reliability in both low- and high-volume applications. The shallow length of the plug also provides several benefits for designers, including saved space, reduced manifold size and weight, and minimized dead volume.

An ideal method for verifying part installation for low-volume applications is visual inspection. The DL Series Plug’s locking end includes an Installation Indicator feature that will visibly flare out radially to touch the aluminum housing 360° around the part when installed. When there is no gap between the part and the housing, the part is fully installed.

For high-volume production, where hydraulic presses can be used, customers can additionally monitor the force and tool travel during installation to verify that the correct amount of force has been applied to the part and the tool has traveled the correct distance. An electric servo press- such as Promess – can provide detailed real-time force and displacement feedback for the highest verification level. With such a press, installers will know exactly when the part is fully installed. A vision system can also inspect the visual indicator. Multiple ways to verify the critical assembly process enable manufacturers to select the most appropriate application installation and verification processes.

Overall, the DL Series Plug helps automotive manufacturers reduce scrap, rework, and labor costs while improving reliability and lowering installed costs. Thanks to its compact size, competitive price, and ease of automated installation, the DL Series Plug meets the stringent demands of the automotive industry. The DL Series Plug is ideally suited for all applications where performance, quality, and reliability are critical to success. The Drive Locking technology used in this new locking-end design can also be leveraged by The Lee Company’s other products, such as check valves, pressure relief valves, and restrictors, to reduce costs for high-volume applications in aluminum.

If you have a cross-hole in your hydraulic manifold, seal it with a Lee Betaplug®. That’s the end of the story because only Lee Betaplugs are specifically engineered to seal cross holes in metal or plastic housings. This means they can be used in a wide variety of materials. Other solutions, such as ball bearings or bolts coated in adhesive, were never designed for sealing purposes and don’t offer 100% reliability. They fail under pressure – and sometimes they fail without any pressure.

The Lee Betaplug uses the market-leading aerospace design heritage of The Lee Company and applies it to the automotive market. Lee Betaplugs work without threads or sealants. Instead, they are pre-assembled, one-piece tapered expansion plugs designed to seal cross holes using the principle of controlled expansion. Lands and grooves on the outer diameter of the plug body bite into the housing wall during installation, creating leak-tight seals and ensuring retention. This single-piece design helps reduce costs, making the component cost-effective for mass production.

Lastly, the tapered design of the Lee Betaplug eliminates the need for tight manufacturing tolerances, which is ideal for high-volume applications. The matching tapers of the Betaplug and its installation hole create a perfect fit, eliminating the need for additional expansion. Since the size of the tapered pin precisely controls the Betaplug’s expansion, the amount of expansion and any resulting boss stress is completely predictable. This means that installation is repeatable – the same size plug will create the same stress, which is ideal for brittle materials or thin wall conditions. In short, no matter what kind of vehicle you’re making, Lee Betaplugs will undoubtedly help make it more reliable.

Further reference

The Lee Plug is simply the most successful method to seal drilled holes for critical applications. Over 150 million are used on aircraft, missiles, spacecraft, machine tools, downhole oil tools, molds – anything that requires a permanent leak-proof seal.

Lee Plugs are manufactured to exacting tolerances. Every process is precisely controlled. Critical dimensions are 100% checked, and others are statistically checked. All plugs and pins are 100% visually inspected. In addition, every lot of Lee Pins and Plugs is production acceptance tested. A representative sample of the mating pin or plug is performance tested to a Lee Company process specification for installation, leakage, pin retention, proof pressure, and thermal stability. Two certificates of performance (one for the pin lot and one for the plug lot) accompany every shipment of Lee Plugs. Go deeper into the precision of The Lee Plug with The Principle of the Lee Plug Performance.

Case Study

A leading automotive manufacturer struggled to find a cost-effective solution to reliably seal cross-drilled holes in transmissions and engines. The problem resulted in customer leakage complaints, high warranty costs, and internal rework costs, ultimately costing them millions of dollars and jeopardizing their reputation. Read more about their challenge and how The Lee Company plugs were the perfect solution: Helping One of the Largest Automotive Manufacturers Save Their Reputation and Dollars. 

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