Product Liability: Principles of the duty to warn

Lawyers also understand that certain risks are technically and structurally unavoidable. The user must be able to protect himself by behaving correctly, but at the same time he must be aware of the residual risk. For this reason, case law has given producers a duty to warn: The duty in this case is to further minimize the residual risk with the aid of operating instructions, warnings, symbols, training specifications etc. The principle here is that, wherever possible, a product should be designed to be safe and free from defects. The producer cannot therefore be content to overlook these options and simply refer to the hazards. The duty to warn refers to the residual risks that remain on a product even when every possibility has been exploited in its design and  manufacture.

Definition of the producer’s duty to inform should always be based on the least informed group. The greater the  extent of the potential consequential loss and the more concealed the danger, the more explicit the warnings must be. If the product harbors a health risk, warnings must be so explicit that the user deems the danger  plausible. In such cases, general guidelines regarding correct behavior are not enough; the threatened  consequences and health risks in the event of non-compliance must be described.

Indicating that the safety gap must be set correctly before using the machine and that this setting must be checked, is not enough. Appropriate warnings must make it clear that there is the threat of a serious hand injury if the safety gap is not set correctly.

There is no duty to inform where such information is evident to the general public or to specific user groups.

For example, it is evident and recognizable that a knife can cut.

The duty to warn also extends to obvious misuse of the product. However, the producer does not have to account for unreasonable, unforeseeable and improper use of his product.

Operating instructions should not only show the correct way to install or assemble the product, but must also provide separate warnings against incorrect hand movements that may be obvious and occur frequently.


By contrast, case law highlights that the producer can rely on a technically trained operator keeping to the dedicated specifications provided in the operating instructions. Thus, should a kneading machine operator attempt to open the lid seal by heating the modelling clay until excess pressure inside the machine removes the lid, this would be deemed “gross misuse”.

The warning against potential hazards arising from the product should be issued without embellishment at the point at which the user will expect to find it. It would not be right, therefore, to position information about potential product hazards in some hidden location within the operating manual. 

The producer must also take care to ensure that the user of the product understands the operating  instructions. So a significant factor initially is whether the user can actually read and which languages he understands. This immediately implies the question about the languages into which a manual’s safety guidelines should be translated. It goes without saying that the safety guidelines in an operating manual should always be translated into the language of the country in which the product will be sold. The producer cannot assume that the company responsible for international sales of a product in a particular country will also provide an  adequate translation, including that of the relevant warnings, into the respective local language.

Is this the only directive impacting suppliers and users of machinery?

No. There are a number of other directives, many dating back to the 1980's, that you need to be aware of. When creating the single market, the social partners agreed that protection of the Health, safety and Welfare of workers was a key value within the community. This led to the enactment of the "Council Directive 89/391/EEC of 12 June 1989 on the introduction of measures to encourage improvements in the safety and health of workers at work."

Another important directive is "Council Directive 89/655/EEC of 30 November 1989 concerning the minimum safety and health requirements of the use of work equipment by workers at work" (and subsequent amending directives 95/63/EC and 2001/45/EC). This directive impacts employers who use machinery and sets out minimum requirements for existing machinery and requires that all new machinery should meet the requirements of all applicable directives, including the machinery directive.

Q. Did the original directive result from the creation of the single market in Europe?

A. Yes, the single market depended on the elimination of barriers to trade between member states and enshrined protection for the freedom of movement of capital, people, goods and services. The Engineering and Machine building sectors were and are important sectors of the European economy. However, prior to the first machinery directive there were no common regulaions or standards for machinery supplied on the market. The aim of the EU in introducing the Directive 89/392/EEC and it's amending Directive 98/37/EC, generally known as the "Machinery Directive", was to ensure the free movement of the products within the scope by guaranteeing a high and common level of protection in the areas of health, safety and consumer rights.

Motion Control for Packaging Machines

In today's competitive atmosphere, shorter innovation cycles and flexibility are vital to packaging companies wanting to rise above the competition. We are continually hearing from machine builders and Original Equipment Manufacturers (OEMs) about these challenges and the complexities they bring to machine operator safety and the pressure to do this efficiently.


Further, this demand has resulted in the decrease of batch build and multi-pack runs and now requires machinery to produce multiple packaging variations from the same machine. Adapting to this means the ability to perform quick product changeovers while maintaining a high level of throughput productivity.

Ultimately this impacts the machine operator's ability to perform quickly and safely. This reality has driven the industry to look into alternative solutions. Automation, coupled with motion control is the key to accomplishing this. However, the increase in motion requires a robust safety system to monitor and control these added moving components. For safety processes to run quickly and smoothly systems require multiple axis controllers, additional motion control devices and they must meet industry standards.

When these modified systems are deployed properly you will achieve the required flexibility and observe an increase in the throughput of products. One last issue to accomplishing this is choosing the right safety products to fit system needs.

When looking for motion control products it is important to look at the overall picture. First of all, motion control is needed to manage the movement of any highly dynamic drives and camshafts, synchronization of a wide range of decentralized drives to keep manufacturing safe at a low cost and at a consistent quality. Second, quick setup and maximum flexibility, as well as the ability for automatic adjustment to product variances are essential. Finally, the handling and robotics of a packaging machine is as an integral part of a complete automation solution.

Any and all motion control products must include the following: PLC to control the machine, optimum movement management on decentralized drives for motion control and an individual safety solution customized with integrated software and tools that meet universal, local and federal legislations.

Packaging specific applications and motion control components should also be adaptable for individual requirements. The ability to join together safety and industrial standards is a crucial element in any motion application. Equally imperative, safety must be integrated within the drive to make sure that every law of motion is available, optional real or virtual master axes and all additional tools able to suit the task of a specific packaging machine.

It is important to note, that a control solution should also be platform-independent. Integrated soft PLC in accordance with IEC 61131-2, can fast scan time from < 50us for 1000 instructions and no adjustments are required to change platforms. Thus, all of the automation in one project with support for modular structures, large selection of field buses, extensive libraries, motion control, interpolation and OPC Server, can positively impact both safety and productivity.

In further examining comprehensive motion control functionality, always consider this indispensible checklist to discern the most important features within any motion control product:

• Virtual main shaft and cam synchronization

• Integral "flexible cam"

• Register control

• Web tension control

• Linear and circular interpolation

• Electronic camshaft and safe motion within the drive

When choosing safety products for your packaging machines choose a company that is aligned with your priorities and use the above checklist to ensure you're making the best choice possible.