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Creating High-Performance Assemblies with T-Slot Aluminum Extrusions

Today’s engineering managers are under significant pressure to design products that can evolve as fast as the needs of the customers they aim to serve. As a result, we see car platforms with a shelf-life of three years instead of five years become the norm. This new reality is significantly disrupting how end-products and supporting production equipment are being designed and manufactured.

Breanne 838cc05c38c0a6e5463d41a35eaf9f906baae66a3727cc65ff58be449642d9c9 Bre Hargreaves Head of Customer Success / Jan 5th, 2018

The imperative for faster machine design


Today’s engineering managers are under significant pressure to design products that can evolve as fast as the needs of the customers they aim to serve. As a result, we see car platforms with a shelf-life of three years instead of five years become the norm, and we saw electronic products adopt an obsolescence schedule of one to two years instead of three years. This new reality is significantly disrupting how end-products and supporting production equipment (i.e., machines) are being designed and manufactured.

At its highest level, a shorter product lifecycle means that the window to depreciate related production equipment is also shorter, creating a need for production assets that can be readily designed, deployed and repurposed at a low cost. Despite such pressure, custom industrial equipment is still being designed and manufactured like it was 20 years ago, relying on custom manufactured parts and welded structure assemblies. Those techniques are both time-intensive and costly. Modular hardware platform such as T-slot aluminum extrusions, could be a strong solution to faster machine design and build, but adoption to date has remained limited. It’s time to re-consider this decision.


Limitation of existing T-slot aluminum extrusion systems


An industrial hardware platform can be described as a coherent library of parts where compatibility is certified. For such platform to enable end to end machine design, while providing a significant gain in cycle-time and cost, it must include structural, motion and control components.

T-slot aluminum extrusions and associated assembly plates are often the foundation of such hardware platforms. In principle, such extrusions could be used for various applications; ranging from test rigs to assembly jigs to machine frames. That said, much of industrial equipment still relies on welded structure assemblies, which have a long lead-time and are costly to design and manufacture due to the workmanship involved.

Limited adoption of T-slot aluminum extrusions appears to be driven by technological reasons. Focus group research conducted with engineers working in automotive, aerospace and engineering services industries highlighted nine common issues with existing T-slot aluminum extrusions, as seen below in Exhibit 1. Suboptimal performance in terms of structural rigidity and assembly tolerances has been the biggest impediment to a wider adoption of T-slot aluminum extrusions.


Poor length and angular tolerances on assemblies

Since having been introduced into the industry, aluminum extrusions have used assembly plates combined with T-slot bolts and nuts to create complete assemblies. Unfortunately, gains in assembly speed using this method have come at the expense of assembly tolerances, with the T-slot bolt acting as the locating device between the assembly plates and extrusions. The clearance fit on plate holes and T-slot width lead to angular misalignment of up to ± 0.50mm per 25mm length, well below the accepted standard in several industries.

Poor strength-to-weight ratios

Because of the T-slot groove on each face, aluminum extrusions tend to have a lower rigidity then equivalent square tubing made of aluminum or steel. Such limitations have led to aluminum extrusions mostly being used for light-duty applications.

Exhibit 2. An example of a commercially available extrusion, where the T-slot bolt acts as the locator between the assembly plate and extrusion

Achieving high performance assemblies with T-slot aluminum extrusion


Our recent engineering task force has demonstrated that poor assembly tolerances and strength-to-weight ratios of T-slot extrusions could be resolved with an improved extrusion design.

Achieving greater assembly tolerances

To ensure the precise positioning of one extrusion to the next, the interface system between T-slot extrusions and assembly plates had to be rethought.


Exhibit 3. Self-positioning interface based on “V-Shaped” T-slot groove
Exhibit 4. “V-Shaped” T-slot groove and corresponding assembly plates

For example, an interface system based on a specially-designed, “V-shaped” T-slot groove acting as a part locator with the corresponding assembly plates (which include the male version of the “V-shaped” locator) could significantly reduce observed angular misalignment. Our engineers have shown that this self-positioning interface system allows for an angular tolerance less than ±0.04mm per 25mm length at each angular node, a 12X improvement vs. commercially available T-slot extrusions system.

Improving strength to weight ratios

Our engineering task force, through material distribution algorithms, demonstrated that strength-to-weight ratio of T-slot aluminum extrusions could be improved by up to 10% vs. commercially available products. Those improvement are achieved with the same amount of material used. (see moment of inertia by surface unit in Exhibit 5).

Translating such optimized extrusion profile into the reality of industrial equipment implies lower structural deflection by up to 30% (see max deflection in Exhibit 5).

Exhibit 5. Benchmarking of common extrusion profiles

Conclusion


Shorter product lifecycles are creating pressure for custom industrial equipment to be rapidly designed, deployed and repurposed at low cost. Fortunately, modular hardware platform, centered around T-slot aluminum extrusions, could enable significant cost and lead-time gains over custom machined parts and welded assemblies. For such performance to materialize, those modular hardware platforms must solve for reduced assembly tolerances and higher structural rigidity.

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