Safety has always been a priority for many manufacturers, but how has this affected machine productivity? Recent developments in the safety and ergonomics of press brakes have also resulted in significantly higher levels of productivity.
Safety and ergonomics are inextricably linked with productivity. The Oxford English Dictionary defines ergonomics as “the study of people’s efficiency in their working environment”. The use of press brakes is still a predominantly manual operation and global manufacturers are applying their safety and Ergonomic principles especially in markets where compulsory safety regulations apply.
Light guards
Some machinery manufacturers are being inventive and have integrated light guard systems into the machine’s control. This enables the light guard operation to be “programmed”, which can result in productivity benefits.
The primary function of a light guard is to inform the machine when an operator is in the danger zone. It is therefore evident that the machine can also know when the operator is out of the danger zone and can use this information intelligently.
An integrated light guard system can actually increase productivity by acting as a switch to ensure the machine is always ahead of the operator while maintaining a safe operating environment. This programmable light curtain allows the upper beam and back gauge to move to the next step without using the foot pedal freeing the operator to concentrate on handling the sheet. Furthermore, the servo-driven belt and pulley press brakes fitted with programmable light guards can carry out the bending of simple components without the operator even touching the foot pedal while maintaining the highest standards of operator safety.
Using the light guard as a switch means less fatigue of the legs making the operator less tired, more productive and less prone to accidents. These features alone can deliver significant reductions in cycle times and enable the use of light guards to be justified for their productivity advantages, with the positive “side effect” of improving operator safety.
Ergonomic machines
Many press brake operations carried out in the Asian markets are on small parts in high volumes. These often lend themselves to smaller machines and seated operators. As a result there has been an increase in the number of small machines on the market. It is however important for these machines to be ergonomically sound.
The higher-specification ergonomic machines are ideal for seated operation when manufacturing smaller components, though they retain the benefits of the standard press brakes, with large beam opening, long stroke and full back gauge capacity. They can be operated seated or standing, ensuring the operator has the most comfortable and most productive position at all times.
These machines have adjustable tables, seats and control panels all contributing to an ergonomically sound system with operator safety and comfort at the centre along with the resultant productivity benefits. Side tables can be fully or partially collapsed, enabling the operator to bend components while standing. This allows the machine to be used for larger sheet metal work as you would a regular machine.
Controls
Ergonomics does not just apply to physical attributes of a machine. The machine control can also be enhanced. The latest touch screen controls can be customised to suit individual operators. For example operators can have individual password access to the machine control. The system administrator can assign various levels of authority to each operator ensuring they only have access to that for which they are trained and have authorisation.
On logging in, for example, the control will revert to that operator’s preferred language, icons will be displayed for left-hand or right-hand operation, and the control will take up the desired height position. The most sophisticated systems are so ergonomically designed that only those icons which are relevant are displayed at any one time, and even the position of the icons are such that they are in the most practical position.
Some manufacturers offer machines with dual screens on the control. The dual screens are a useful option for companies wanting to have a paperless workshop and give operators access to additional information at the machine. This gives operators the ability to access many types of additional information without having to switch from the control screen.
The additional screen can be used for the following:
- To view files coupled to current bending projects, in formats such as DWG, DXF, PDF, JPG, PNG, BMP or WMV.
- To display custom applications like ERP, time management, etc.
- To create a paperless environment and prevent loss of information, which reduces errors by ensuring operators have all the information necessary.
It is even possible to view video on the second screen, which can show less skilled operators how to best handle complex and awkward products.
Tool set-up
Subcontracting companies are being asked to produce smaller batch sizes, leading to more set-ups per day. Consequently, anything that can reduce set-up times is an advantage. The major area to address here is tool set-up. There are an abundance of quick clamping systems available, but one stands out above others as it not only addresses the time issue but also improves safety and reduces operator fatigue.
The Wila clamping system can be fitted to most press brake brands can reduce set-up times by up to 70%. The tools are mounted into the machine vertically, as opposed to from the side, and safety clicks in each tool means that the operator can release the tool once it has been located in the top beam, leaving them free to lock the clamps.
In the hydraulic clamping version, all tools are clamped or released by the press of a single button. In addition the machine will not commence a bend until a safe clamping pressure is reached. This cannot be said for manual clamping systems, which can lead to accidents, tool damage and loss of production.
This version of tool clamping can be further enhanced with a system called Smart Tool Locator. This system of LED lights linked into the machine control can inform the operators where to place tools during the set-up process, and then during the bending process it illuminates the position where each bend is to take place.
This tooling system generally uses a tool length of 515mm, which not only allows a higher accuracy than the old fashioned 835mm system but also means the weight of the tools is much more manageable for the operator.
Right First Time
Increasing production demands and material costs means that operators are constantly under pressure to get the product “Right First time”. Often the problems are beyond the operator’s control such as variations in material thickness and tensile strength.
All batches of material vary in thickness and even the best machines can only work with the information provided. Thus if a machine is told the material is 1.0mm and it is actually anywhere between 0.9mm and 1.1mm, the end result will also vary.
Automatic sheet thickness measurement systems address this issue in a very quick way and can be used on all material types. The operator sets the thickness tolerance that is acceptable in the machine control. The sheet is presented to the device, which is adjacent to the back gauge fingers where it automatically measures the material thickness. If it is within thickness tolerance, the control will automatically adjust the programme and pinch point for the actual thickness rather than the theoretical thickness, resulting in a more accurate result. If the material is outside the set tolerance, the machine will not bend, reducing scrap and improving productivity. The whole process takes just a couple of seconds.
Where the tensile strength and spring back is also a problem, then a laser angle measurement system could be the solution. These systems automatically measure and correct angles during the bending process, ensuring every component is Right First Time.
When handling larger components that require a high level of accuracy, it is beneficial not to have to make corrections to bends that would require additional handling of awkward, large and heavy products, which is both a safety issue and causes the operator to tire more quickly. Two CNC-controlled laser sensors are mounted on either side of the machine table. The system continuously monitors and corrects the position of the Y-axis based on the required product angle and thus guarantees an end product of the highest angle precision. The system automatically adjusts the crowning and at the same time takes into account the spring back.
Both of these systems (Sheet Thickness & Laser Angle Measurement) improve quality and dramatically reduce handling and fatigue of the operator.
Material handling
For many products it is not the actual bending process that is a problem but more the handling of the material pre- and post-bending. Handling can pose significant safety issues and place unnecessary strain on the operators. In addition awkward and/or heavy products, if handled poorly, can also give quality problems. For this reason manufacturers are offering a range of handling and bending aids, some of which are CNC-controlled.
Each type of product poses different problems. For example very thin materials can be so flexible that they need greater support than a mere individual operator can provide. For heavier components the physical weight can make it impossible for manual operation and so a range of weight capacities is available.
Bending aids differ from sheet supports in that they follow and support the component during the actual bending process. CNC bending aids can be programmed to follow the component during bending, even pausing to allow for decompression of the material where heavy bending force has been applied. The speed of the aids is synchronised with the bending process, and is programmable to a speed that matches the operator’s capabilities. Some bending aids can even be detached and shared with other machines.
It is evident that productivity and operator safety can be improved by investing in some of the above-mentioned press brake options. The challenge for machinery manufacturers and users is to ensure that safety and ergonomics will be at the forefront of all product development.