Chapter 32: ISO/TS 15066 |
Summary |
This chapter examines ISO/TS 15066, the technical specification that established the biomechanical foundation for power and force limiting in collaborative robot applications. Originally published in 2016, this document represented a philosophical shift in industrial robotics safety: rather than insisting on physical separation between humans and robots, it asked a deceptively simple question---if contact occurs, what level of force can the human body tolerate without pain or injuryThe answers, derived from biomechanical research, became the quantitative backbone of collaborative safety. As of 2025, these requirements have been formally incorporated into the revised ISO 10218 standards, marking the end of ISO/TS 15066 as a standalone document and the beginning of a new era in which power and force limiting is treated as a fundamental design consideration rather than a specialized technical specification. |
This chapter explores the origins, principles, and practical applications of ISO/TS 15066 across multiple industries. Rather than dwelling on the technical formulas that underpin the standard, we focus on how manufacturers, integrators, and end users have applied its principles in real-world settings---from automotive assembly lines to food processing facilities to healthcare environments. By understanding both the theoretical foundations and the practical implementations, readers will appreciate why this technical specification proved so influential that it was absorbed into the primary international standard for industrial robot safety. |
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1. The Origins of a New Safety Philosophy |
1.1 The Question That Changed Everything |
For decades, industrial robot safety followed a simple principle: keep humans and robots apart. Fences, light curtains, and interlocked gates served as the boundary between the controlled world of automated machinery and the unpredictable world of human workers. This approach worked well for traditional industrial robots, which were large, fast, and powerful enough to cause serious injury or death if contact occurred. |
But as robot technology evolved in the early 2000s, a new class of machines emerged. These robots were smaller, lighter, and equipped with sensors that allowed them to detect unexpected contact and stop quickly. Engineers began to ask whether physical separation was truly necessary in all cases. If a robot were designed to be inherently gentle---limited in speed, force, and momentum---could it safely share space with humans without a protective barrier |
The philosophical breakthrough came during discussions within the ISO committee responsible for industrial robot safety. As Roberta Nelson Shea, Convenor of the ISO Industrial Robot Safety Working Group, later explained, the committee asked: 'If an application will not hurt and injure a human, why not allow contact' This question inverted the traditional safety paradigm. Instead of assuming that contact was inherently dangerous, the committee explored the conditions under which contact could be acceptable---provided it did not cause pain or injury. |
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1.2 The Publication of ISO/TS 15066 |
The result of these deliberations was ISO/TS 15066, published in 2016 as a technical specification. Its full title---*Robots and robotic devices --- Collaborative robots*---belied its narrow scope. The document applied specifically to industrial robot systems and supplemented the requirements already established in ISO 10218-1 and ISO 10218-2. It did not apply to non-industrial robots, though its safety principles would prove useful in other robotics domains. |
The significance of ISO/TS 15066 lay in its specificity. Previous standards had discussed collaborative operation in general terms, identifying techniques such as safety-rated monitored stop and speed and separation monitoring. But they lacked the data-driven guidance needed to evaluate whether a particular application was truly safe. ISO/TS 15066 filled this gap by providing biomechanical thresholds---quantitative limits on the force and pressure that different parts of the human body could tolerate without pain or injury. |
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1.3 From Technical Specification to International Standard |
For nearly a decade, ISO/TS 15066 served as the definitive reference for power and force limiting applications. Robot manufacturers cited its limits in their documentation. Integrators used its thresholds to validate their safety designs. And end users, sometimes without realizing it, benefited from the protection it afforded. |
The 2025 revision of ISO 10218 marked a significant transition. Rather than maintaining ISO/TS 15066 as a separate document, the ISO committee incorporated its requirements directly into the main standard. As one analysis noted, 'the new edition of the standard (Part 2) partially incorporates the content of this technical specification'. The biomechanical thresholds that had once been guidance in a technical specification became normative requirements within ISO 10218-2:2025. |
This integration signaled that power and force limiting was no longer a specialized technique for a niche category of robots. It was a mainstream safety approach, applicable to any robot system designed for collaborative operation. |
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2. Understanding the Biomechanical Basis of Safety |
2.1 The Human Body as a Design Constraint |
The central insight of ISO/TS 15066 was that safe human-robot collaboration requires understanding the human body not as a generic obstacle to be avoided, but as a system with specific tolerances. Different parts of the body respond differently to applied force. The palm of the hand can withstand substantially more pressure than the face or neck. The back and shoulders tolerate higher forces than the fingers or forearms. |
The technical specification organized these tolerances into two categories of contact: quasi-static and transient. Quasi-static contact occurs when a body part becomes trapped or clamped between the robot and another surface. These are sustained contacts, where the robot continues to press against the human. Transient contact, by contrast, involves a brief impact---the robot strikes the operator but does not maintain pressure. The allowable limits for transient contact are generally higher than for quasi-static contact, reflecting the body's greater tolerance for brief impacts compared to sustained compression. |
2.2 The Role of Contact Geometry |
Beyond force magnitude, ISO/TS 15066 introduced pressure as a critical safety parameter. A given force distributed over a large contact area produces lower pressure than the same force concentrated at a sharp point. This principle has profound implications for robot and end-effector design. Rounded edges, compliant surfaces, and geometries that distribute contact forces over larger areas all contribute to safety. |
The standard's emphasis on pressure explained why a robot's gripper design matters as much as its motion control. A gripper with sharp finger tips could produce dangerous pressure concentrations even at relatively low force levels. The Robotiq Hand-E gripper, for example, underwent specific testing to verify that its grip force remained below the threshold for hands and fingers when equipped with standard overmolded fingers. This kind of verification became standard practice for end-effectors intended for collaborative applications. |
2.3 Beyond Force and Pressure |
While force and pressure constituted the core of ISO/TS 15066's quantitative framework, the technical specification also addressed other hazards. Sharp edges and protrusions were to be minimized throughout the system. The reasoning was straightforward: if a human were to impact the robot even when it was not moving, the result should be no worse than walking into a wall. This seemingly modest requirement had significant implications for the design of robot arms, end-effectors, and the fixtures and workholding devices that populate collaborative workspaces. |
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3. Power and Force Limiting in Practice |
3.1 How Power and Force Limiting Works |
Power and force limiting is one of four collaborative operation techniques recognized by ISO 10218, alongside safety-rated monitored stop, hand guiding, and speed and separation monitoring. Its distinguishing feature is that it permits contact between human and robot, provided that contact does not exceed the biomechanical limits established in the standard. |
Implementing power and force limiting typically involves three complementary strategies. First, the robot is designed with low inertia---its moving mass is minimized, reducing the energy that must be dissipated in a collision. Second, speed is limited, since kinetic energy scales with the square of velocity. Third, the robot's control system continuously monitors force, either through joint torque sensors or by deriving force from motor current. |
When contact occurs, the robot must detect it and stop before the applied force exceeds safe limits. This requires both sensitive detection and rapid response. The safety control system must meet specific performance levels---typically PL d or SIL 2 for speed monitoring functions---to ensure that the protective function operates reliably. |
3.2 The Validation Challenge |
Determining whether a specific application complies with ISO/TS 15066 limits involves either empirical measurement or theoretical analysis. Empirical validation uses certified measurement devices to record actual forces and pressures at all critical points in the workspace. This approach provides direct evidence of compliance but requires physical testing that can be time-consuming and costly. |
Theoretical analysis, by contrast, uses the formulas and data provided in the standard to calculate maximum allowable speeds and forces for a given robot configuration. This approach is faster and less expensive but relies on assumptions about contact dynamics that may not reflect reality in all cases. As one analysis noted, the standard's model assumes fully inelastic contact during collisions---an assumption that is 'highly conservative' and can result in overestimation of the forces involved. |
In practice, integrators often combine both approaches, using theoretical analysis to establish initial safety parameters and empirical testing to verify that actual forces remain within limits. The 2025 revision placed greater emphasis on application-specific validation, requiring that each collaborative setup be assessed based on its particular environment, use case, and configured safety functions. |
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4. Industry Applications: Automotive Manufacturing |
4.1 The Downtime Imperative |
The automotive industry has emerged as one of the largest adopters of collaborative robots, driven by a compelling economic rationale. When a traditional industrial robot malfunctions, the entire production line in its vicinity must stop to allow human workers to intervene safely. In automotive manufacturing, where production lines are tightly synchronized, this downtime can cost more than two million US dollars per hour per factory. |
Collaborative robots offer a solution to this problem. Because they are designed to operate safely alongside humans, a cobot that encounters a problem does not require halting the entire line. Human workers can address the issue while other operations continue. This flexibility translates directly into cost savings and production continuity. |
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4.2 Seatbelt Assembly with Universal Robots |
A representative application comes from the automotive seatbelt manufacturing sector. Researchers at a university in Ecuador conducted a detailed study of cobot implementation for a bar pressing station in seatbelt production. The application involved handling small metal components weighing approximately 1.2 kilograms, a task well within the capabilities of a compact collaborative robot. |
The selection process demonstrated the practical application of ISO/TS 15066 principles. The research team evaluated several models from Universal Robots, ultimately selecting the UR3e for its compact design and three-kilogram payload capacity. The end-effector choice fell to the Robotiq Hand-E gripper, which offered a grip force range of 20 to 185 Newtons and could be modified with custom finger designs to access the required areas of the product. |
The safety analysis considered the effective mass transmitted through the gripper during operation. Rather than simply using the total product weight, the researchers calculated the mass supported at each contact point based on the gripping geometry and force distribution. This granular approach---consistent with ISO/TS 15066's emphasis on contact-specific analysis---resulted in a safety factor that ensured secure gripping without exceeding force thresholds. |
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4.3 Adhesive Application with Thermal Hazards |
A more complex automotive application illustrates how ISO/TS 15066 principles extend beyond force considerations. Researchers in Germany studied a collaborative robot performing adhesive application, a task that introduced thermal hazards alongside mechanical ones. The glue gun operated at internal temperatures reaching 190 degrees Celsius, creating a burn risk for human operators. |
The safety concept combined multiple protective layers. For the mechanical aspect, the team used compliant, rounded end-effector geometry with elastic interfaces to reduce tool-surface pressure. For the thermal aspect, they integrated a multi-layer heat shield combining thermally insulating polymer with reflective aluminum foil. Without shielding, external nozzle surfaces reached temperatures between 110 and 125 degrees Celsius. After installing the heat shield, accessible surfaces dropped below 50 degrees Celsius---consistent with touch-temperature criteria for short-duration contact. |
The validation testing involved 90 operational cycles across three human proxy configurations, measuring both force and temperature. The most critical transient event, involving contact with a face proxy, produced a peak force of 63 Newtons---below the applicable limit of 65 Newtons. All measured values remained within ISO/TS 15066 thresholds, demonstrating that the combined mechanical and thermal protections achieved compliance. |
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5. Industry Applications: Electronics and Consumer Goods |
5.1 The Electronics Assembly Challenge |
The consumer electronics industry presents particular challenges for collaborative automation. Products are small, often fragile, and subject to rapid design changes. Production volumes fluctuate, and the mix of products manufactured on a single line can change frequently. Traditional hard automation struggles with this variability; collaborative robots, with their easy reprogramming and flexible deployment, offer an alternative. |
ISO/TS 15066 compliance is particularly important in electronics assembly because workers and robots often share highly constrained spaces. Circuit board assembly, quality inspection, and device testing are tasks where human dexterity and judgment complement robot precision and consistency. The ability to work side-by-side without safety fencing enables configurations that would be impossible with traditional industrial robots. |
5.2 The Hand-E Gripper Compliance Verification |
The Robotiq Hand-E gripper, widely used in electronics assembly applications, provides an instructive example of how ISO/TS 15066 limits translate into component-level verification. The gripper's manufacturer conducted specific testing to confirm that the device maintains quasi-static grip force below the 140 Newton threshold for hands and fingers specified in the standard. |
This verification process illustrates an important principle: the maximum grip force of a gripper cannot be used directly to assess compliance. The force transferred to a human body part during contact is lower than the commanded grip force, due to damping effects and the compliance of the contact interface. Specific testing is required to determine the actual force that would be experienced in a pinching scenario. Robotiq's testing confirmed compliance for the standard configuration with overmolded fingers, while noting that variations in fingertip shape, material, or sharp edges could affect results---a reminder that ISO/TS 15066 compliance is application-specific, not a blanket certification. |
5.3 Market Maturity in Electronics |
The electronics industry has reached a relatively high level of collaborative robot adoption compared to other sectors. Industry analysts note that commercial maturity in electronics is higher than in most other industries, with cobots deployed across tasks ranging from picking and placing to machine tending and inspection. This maturity reflects both the suitability of collaborative robots for electronics assembly and the industry's willingness to adopt new automation technologies. |
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6. Industry Applications: Food and Beverage |
6.1 A Growing Market |
The food and beverage industry represents a middle tier of collaborative robot adoption---not yet as mature as automotive or electronics, but growing steadily. Analysts identify picking and sorting, palletizing, and packaging as the primary tasks where cobots are finding traction. |
The food industry presents unique constraints that interact with ISO/TS 15066 requirements. Hygiene considerations limit the materials and surface finishes that can be used on robots and end-effectors. Washdown environments require protection against moisture ingress. And the products themselves---often irregular, fragile, or variable in shape---demand grippers with sophisticated sensing and control. |
6.2 Palletizing and Packaging Applications |
Palletizing is a fundamental task in food and beverage operations, traditionally labor-intensive and physically demanding. Collaborative robots are well-suited to this application because the task is repetitive, the payloads are moderate, and the speed requirements are within cobot capabilities. A cobot performing palletizing can operate continuously with minimal supervision, and its power and force limiting design means that accidental contact with a human worker is unlikely to cause injury. |
The rise of high-mix, low-volume production has made collaborative robots increasingly attractive in packaging. Consumers demand more customized products, leading to more frequent changeovers and greater product variation. Traditional automation struggles with this variability; collaborative robots, with their easy reprogramming and flexible deployment, can switch between tasks and handle product variation without extensive reconfiguration. |
6.3 Safety in Food Handling |
While ISO/TS 15066 provides the framework for ensuring safe human-robot contact, food industry applications introduce additional considerations. Sharp edges on end-effectors, for example, must be avoided not only for safety reasons but also to prevent damage to food products. The rounded, compliant geometries that reduce pressure concentrations during human contact also tend to be gentler on the products being handled. |
The integration of vision systems and force sensing allows collaborative robots to handle delicate food items without crushing them, while maintaining the ability to detect unexpected contact and stop safely. This combination of sensitivity to product and sensitivity to human contact is characteristic of well-designed food industry collaborative applications. |
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7. Industry Applications: Healthcare and Laboratory Automation |
7.1 An Emerging Sector |
Healthcare represents one of the most promising emerging sectors for collaborative robot deployment. The Bureau of Labor Statistics reports that healthcare employment constituted 9.3 percent of the United States workforce in 2022, and the industry continues to grow. Collaborative robots are being deployed for patient handling, surgical assistance, and laboratory automation---applications where the ability to work safely alongside humans is essential. |
The healthcare environment differs from industrial settings in ways that affect safety analysis. Patient handling involves contact with vulnerable individuals whose tolerance for force may differ from the healthy industrial workers on whom ISO/TS 15066's biomechanical data is based. Surgical assistance requires extreme precision and reliability. Laboratory automation involves repetitive tasks in controlled environments where human oversight remains essential. |
7.2 Laboratory Automation |
Laboratory automation has emerged as a particularly active area for collaborative robot deployment in healthcare. Tasks such as sample handling, pipetting, and analytical instrument loading are repetitive and time-consuming, making them candidates for automation. But laboratory spaces are often cramped, and the need for human oversight means that workers and robots must share the same environment. |
ISO/TS 15066 provides the safety framework for these applications. The force and pressure limits for hands and fingers are particularly relevant, since laboratory workers frequently reach into the robot's workspace to adjust equipment, retrieve samples, or perform manual steps. A collaborative robot that stops safely upon contact, without exceeding the biomechanical thresholds, can operate in the same bench space as a human technician. |
7.3 Surgical and Rehabilitation Applications |
The intersection of collaborative robotics and healthcare extends beyond laboratory automation. Surgical robots that assist surgeons during procedures, rehabilitation robots that work with patients during physical therapy, and mobility assistance devices all operate in close proximity to humans. While many of these applications fall outside the scope of ISO 10218 (which is limited to industrial robots), the principles established in ISO/TS 15066 have influenced safety thinking in these adjacent domains. |
The standard's exclusion of medical robots from its scope reflects the specialized regulatory frameworks that govern medical devices. However, the biomechanical data and risk assessment methodologies developed for ISO/TS 15066 have proven useful in medical robotics as well, demonstrating the broader relevance of the collaborative safety framework. |
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8. The Integration into ISO 10218:2025 |
8.1 A Milestone in Standardization |
The incorporation of ISO/TS 15066 into the 2025 revision of ISO 10218 represents a milestone in the evolution of industrial robot safety. What began as a technical specification---a document with less formal status than a full international standard---has been elevated to a core requirement within the primary safety standard for industrial robots. |
This integration has practical implications. The biomechanical thresholds that were previously guidance in a technical specification are now located in Annex M of ISO 10218-2:2025, where the maximum quasi-static force for hands and fingers is specified at 140 Newtons. While this annex is classified as 'informative' rather than 'normative,' adherence to its limits has become the industry benchmark for safety validation. |
8.2 Terminology and Conceptual Shifts |
The 2025 revision also introduced terminological changes that reflect the maturation of collaborative robotics as a field. The terms 'collaborative robot' and 'collaborative operation' have been deprecated in favor of 'collaborative application'. This shift emphasizes that collaboration is not a property of a particular robot but of the way robots are deployed. Any robot, properly configured and integrated, can participate in a collaborative application. Conversely, a robot marketed as 'collaborative' is not inherently safe; safety depends on the application. |
This conceptual reframing aligns with the practical experience of integrators and safety engineers. The key question is not whether a robot is collaborative by design, but whether the specific application---including the robot, end-effector, workpiece, environment, and task---meets the safety requirements. ISO/TS 15066 provided the data and methodology for answering that question; ISO 10218:2025 provides the framework for applying it systematically. |
8.3 Global Harmonization |
The 2025 revision also marked a shift from a European-centric to a truly global standard. The 2011 edition had been adopted as a European harmonized standard, closely tied to European directives and CEN mandates. The 2025 edition functions as an international ISO document without mandatory regional endorsement, enhancing its exportability and facilitating broader application outside Europe. |
For manufacturers and integrators operating in global markets, this harmonization simplifies compliance. A safety design validated according to ISO 10218:2025 and its incorporated ISO/TS 15066 requirements is more readily accepted across jurisdictions, reducing the need for region-specific adaptations. |
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9. Practical Implementation Guidance |
9.1 Risk Assessment as the Foundation |
Despite the quantitative limits provided by ISO/TS 15066, compliance is not simply a matter of measuring forces and comparing them to tables. The standard emphasizes risk assessment as the foundation of collaborative safety. Each application must be assessed based on its specific environment, use case, and configured safety functions. |
A comprehensive risk assessment considers not only the forces involved in normal operation but also foreseeable misuse, fault conditions, and the full range of tasks that workers might perform in the collaborative workspace. The biomechanical thresholds provide objective criteria for evaluating whether identified risks are adequately controlled, but they do not substitute for the systematic identification of hazards. |
9.2 Design Principles for Power and Force Limiting |
Several design principles have emerged from practical experience with ISO/TS 15066 implementation. Rounded edges and compliant surfaces reduce pressure concentrations during contact. Limiting robot speed and payload reduces the energy that must be dissipated in a collision. Minimizing the moving mass of the robot arm and end-effector reduces inertia. |
The placement of the robot within the workspace also matters. Positioning the robot to avoid contact with sensitive body regions---particularly the head and face---can eliminate risks that would be difficult to control through force limiting alone. While ISO 10218 does not provide specific guidance on head protection, many integrators adopt a conservative approach, either fencing the robot to prevent head contact or positioning it such that contact with the head is geometrically improbable. |
9.3 Validation and Documentation |
The 2025 revision places increased emphasis on validation. The verification and validation domain has been revised to include new methodologies and a structured validation matrix, reclassified from normative to informative status. This matrix provides a systematic methodological guideline for assessing compliance with the requirements of the standard. |
Documentation of the validation process is essential for demonstrating due diligence. Records should include the risk assessment, the selection and configuration of safety functions, the results of empirical testing or theoretical analysis, and the rationale for concluding that the application meets the applicable limits. |
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10. Conclusion: A Detailed Summary |
10.1 The Legacy of ISO/TS 15066 |
ISO/TS 15066 answered a question that had troubled the robotics safety community for years: under what conditions can humans and robots safely share a workspace without physical separationIts answer---that contact is acceptable if it does not cause pain or injury---was simple in principle but required extensive biomechanical research to implement in practice. The technical specification provided the data and methodology needed to translate that principle into engineering reality. |
For nearly a decade, ISO/TS 15066 served as the definitive reference for power and force limiting applications. It enabled a generation of collaborative robots to move out of fenced cells and onto factory floors, laboratory benches, and assembly lines alongside human workers. Its influence extended beyond the industrial robotics domain, shaping safety thinking in healthcare, service robotics, and human-robot interaction research more broadly. |
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10.2 The 2025 Integration |
The incorporation of ISO/TS 15066 into ISO 10218:2025 represents both an ending and a beginning. It marks the end of the technical specification as a standalone document, but it also marks the beginning of a new phase in which power and force limiting is treated as a fundamental aspect of industrial robot safety rather than a specialized technique. |
The practical implications of this integration are significant. Biomechanical thresholds that were previously guidance are now embedded within the primary safety standard. The terminology has shifted from 'collaborative robot' to 'collaborative application,' emphasizing that safety is a property of the deployment, not the device. And the standard has become truly global in scope, facilitating international harmonization of safety requirements. |
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10.3 Applications Across Industries |
The chapters of this book have traced the application of ISO/TS 15066 principles across diverse industries. In automotive manufacturing, collaborative robots reduce downtime costs that can exceed two million dollars per hour while enabling flexible production. In electronics assembly, they work alongside humans in constrained spaces, handling delicate components with precision. In food and beverage, they perform repetitive tasks such as palletizing and packaging with consistent quality. In healthcare and laboratory automation, they support human workers in environments where safety and precision are paramount. |
Each application presents unique challenges, but they share a common foundation: the biomechanical limits established in ISO/TS 15066 and now embedded in ISO 10218:2025. These limits provide objective criteria for safety validation, enabling engineers to design collaborative applications with confidence. |
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10.4 Looking Forward |
As collaborative robotics continues to evolve, the framework established by ISO/TS 15066 and its successor provisions in ISO 10218 will face new challenges. Advances in robot learning, artificial intelligence, and sensor technology are enabling new forms of human-robot interaction that the original standard did not anticipate. The standard's deterministic validation protocols may need to adapt to systems with cognitive capabilities beyond their current scope. |
Yet the core principle remains valid: human safety must be grounded in empirical understanding of human tolerance. The biomechanical data compiled for ISO/TS 15066---the pressure limits for different body regions, the distinction between quasi-static and transient contact, the recognition that contact geometry matters as much as force magnitude---provides a foundation that can be extended and refined as technology advances. |
For the practicing engineer, the legacy of ISO/TS 15066 is a set of practical tools for designing safe collaborative applications. For the industry as a whole, it is a reminder that safety and productivity are not opposing forces. The most successful automation is that which enables humans and machines to work together, each contributing their unique capabilities, in environments designed for the safety of both. |
cs@easiersoft.com