Automating Rebar Tying with Drone Technology

Numerous positions within the construction sector are categorized as “dull, dirty, and dangerous” and are considered suitable for automation. However, only a limited number are realistically achievable with current technological capabilities. A prime example is the essential, yet repetitive, task of rebar tying, which the startup SkyMul intends to fully automate through the deployment of drone fleets.

Understanding Rebar Tying

If you haven't worked with reinforced concrete, the process of rebar tying might be unfamiliar. Steel rebar, crucial for strengthening concrete floors, walls, and other structures, is temporarily secured during the pouring phase by being tied together at intersecting points. For substantial buildings or bridges, this can involve thousands of individual ties – a process traditionally performed manually.

The Challenges Faced by Rodbusters

Professionals specializing in rebar tying, known as rodbusters, possess a refined skill set. They expertly loop a short length of plastic or wire around rebar intersections, then twist and tighten it to firmly secure the rods in multiple directions. This work demands precision and efficiency, but it is physically demanding and repetitive. While professionals take pride in their work, the chronic pain resulting from performing this task repeatedly for extended periods is a significant concern. Consequently, rodbusters experience high injury rates and often develop long-term health issues.

Existing Automation Attempts

Automating rebar tying presents complexities due to the varied environments in which it occurs. A notable semi-robotic solution is the TyBot, a rail-mounted gantry system. While effective for bridges, its applicability to the 20th floor of an office building is limited.

Image Credits: SkyMul

SkyMul’s Drone-Based Approach

SkyMul, a startup in its initial phases, proposes a compelling solution: rebar tying performed by a fleet of drones. Considering the relatively low force required for tying and the advancements in computer vision technology, which now reliably identifies areas needing attention, this approach appears increasingly viable.

According to CEO and co-founder Eohan George, they assessed various robotic solutions, concluding that drones are the most practical option. Legged robots with the necessary dexterity are prohibitively expensive, while wheeled or tracked robots risk displacing unsecured rebar.

Image Credits: SkyMul

How the SkyTy System Works

The process begins with a mapping drone surveying the site to define boundaries. A subsequent, automated flight creates a detailed map of the rebar layout and identifies tie locations. A rodbuster technician then verifies this map, a process George estimates takes approximately one minute per thousand square feet of rebar.

The tying drones are then deployed, with the number determined by project needs. Each drone navigates to designated points, hovering and descending to position its tying tool – similar to those used by human rodbusters – to wrap, twist, and secure the rebar. Battery swaps are required every 25 minutes, allowing each drone to complete 70-80 ties. Currently, each drone performs a tie every 20 seconds, comparable to the speed of a human rodbuster.

Cost Savings and Business Model

Determining the precise cost savings and value generated by SkyTy is challenging due to varying labor costs. In regions where rodbusters earn over $80/hour, automation offers significant cost reductions. However, even in areas with lower wages – often less than a third of that amount – the inherent injury risks and resulting scarcity of qualified rodbusters create value through increased availability and reliability. SkyMul is refining its business model to capitalize on these varying conditions, with a likely scenario involving contractors leasing and eventually owning their drone fleets.

Image Credits: SkyMul

Additional Benefits and Future Plans

The system provides supplementary services, such as generating precise rebar maps that can be archived for future maintenance, quality control, and comparison with original plans. This could streamline logistics and potentially reduce project timelines.

SkyMul plans to initially target bridge construction, a less complex environment for drone operation. The U.S. bridge rebar tying market alone represents an estimated $30-40 million annually, providing a stepping stone for expansion into more challenging deployments and larger global markets.

The company is currently seeking funding, having progressed from research at Georgia Tech through the Comcast-NBC accelerator The Farm and receiving a National Science Foundation SBIR Phase I award. They have demonstrated the system and are preparing for a pilot program with a partner. While the construction industry is often slow to adopt new technologies, George is optimistic about attracting early adopters. Successful completion of initial projects is expected to drive significant interest among forward-thinking contractors.

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