The experimental project HPS4MAN, awarded during the last edition of A&T, comes from the need to combine several aspects – such as ergonomics, collaborative robotics, quality and process control – in a single solution. Together with some more partners, the Veneto-based company BNP has developed and tested, at its production site, a double adaptive workstation for bonding carbon tubes with aluminium bushings. So far, such a complex and subjective task has been done manually.
by Carlo Pettenon
BNP srl, located in Cittadella (PD), is an SME that provides ergonomic solutions for manufacturing companies. The key element within BNP is the well-being of the operators, through the design and manufacture of products that help improve their working conditions.
One family of products made by BNP is that of adaptive workstations, designed to adjust certain ergonomic parameters according to the characteristics of the operators.
A second family of products manufactured by BNP concerns the “torque reaction arms”: these products are used by all companies that have manual assembly activities in which operators use screwdrivers that produce torque during tightening; the torque reaction arm prevents the effect of torque from affecting the operator’s wrist, arm or shoulder, resulting in an injury or occupational disease.
The main issues
Among the most used torque reaction arms are the telescopic ones, made of 3 carbon tubes with different diameters “joined” by aluminum sliding bushings. The major problem is given by the friction in the sliding of the carbon tubes with the aluminium bushings. This depends on the precision of the couplings between the bushings and the tubes that determine their sliding. To date, such a task is purely manual but the precision of operators is not enough to ensure a degree of accuracy that might avoid possible reworking of the piece. A second issue is the difficulty of having complete product traceability, achieved so far through the assembly of two subgroups made in two different factories at different times.
The first one concerns the bonding of bushings and pipes; the second one concerns the bonding and fixing of terminals.
Ergonomics, collaborative robotics, quality and process control
The experimental project named HPS4MAN comes from the need to combine aspect related to ergonomics, collaborative robotics, quality and process control in a single solution.
This project has brought to the making of a double adaptive workstation (Figure 2) devoted to assembling bonding carbon tubes with aluminium bushings. So far, such a task has been done manually, as it is quite complex and subjective. The project was carried out by BNP srl, together with Sogea srl, Milper sas and Damo srl, with the support of the University of Padua through its HIT centre. The experimental workstation has been tested at the BNP production site itself, in order to be sure that the targets set by the same company are achieved.
The solution developed by the project partners
The station recognizes the operator by reading a badge and configures some parameters according to the operator’s characteristics, such as height of the workbench, light intensity and language of the HMI panel. Also through the reading of a barcode, the software, connected to the ERP, recovers the work orders, going to set the work cycles involving a collaborative robot.
The robot retrieves a bushing from a special pallet, checks its size, places it in front of the operator (at an ergonomic height, Figure 3) and starts a rotation that facilitates the operator in the activity of glue coating.
When the operator has finished spreading the glue, he gives the OK signal to the robot in order to continue the cycle through a contact on one of its axes. The robot places the bushing in the tube, previously set in a special position (Figure 4), making an insertion preceded by a probing operation, necessary to identify the perfect centre of the tube (this activity cannot be performed by the operator). The insertion is done by rotating the bushing to allow a better glue distribution. The insertion is then completed by the operator, who checks that the bushing reaches the right level. In this way, a high-quality product is obtained.
The advantages: all activities can be monitored
Through the use of both devices (smartwatches, in particular) and a specially developed algorithm, the workstation monitors the level of operator fatigue, sending signals to the robot that changes its speed, thus helping the operator to recover energy.
The station is double and allows the simultaneous monitoring of two operators: the robot can thus help the most tired operator.
The software architecture includes a “manager” workstation, installed on a server that allows remote monitoring of production progress as well as monitoring of any anomalies on all connected workstations through its own IP. Real-time monitoring is carried out both on these workstations and on the one in the second plant. An “operator” licence is installed on each workstation to guide the operator step by step through all the activities to be carried out, as well as to manage process traceability.
From the workstations, any alerts are reported via e-mail to the production manager, who can also intervene remotely to check for any problems.
The software that manages the cell
A characteristic of the island is that it is able to manage robot collisions and restart permissions through the software on the work cell, the same that guides the operator in assembly operations, avoiding using the teach pendant of the robot, which is difficult to use by an operator who does not have skills in robot programming.
The software on the workstations reads the kanban code of the components to be assembled (barcode reader), starts a supplier order from the ERP, proceeds with batch registration and connection to the processing bubble. At the end of the machining process, it proceeds again with the reordering of the components used by kanban; in this way, the entire production is always under control and there is no risk of missing components for subsequent processing.
All the processed orders are communicated to the software that forwards the data to the ERP, allowing a connection between these assembled groups and the activities that will then be done in the second plant for the second subgroup, ensuring production efficiency.
The system monitors the times of each process stage and allows for the elaboration of statistics.
Each station is equipped with its own IP, allowing suppliers to connect to provide assistance on the workstations themselves.
Repeatability of results
The solution implemented can be applied to certain contexts, according to the issue to be faced. Highly repetitive and stressful manual activities. The system makes it possible to monitor the operator’s tiredness in order to adapt to his needs to ensure a constant production and avoid the onset of pathologies on the operators. The presence of robots that can perform some of these activities also improves the product quality. Traceability. The system allows the traceability of the activities carried out at different times and in different places. Traceability can be by serial number or batch number, depending on the type of production. The system also allows the printing of labels at the end of the process: all the information concerning the cycle is linked to the labels. Monitoring. The system also allows remote monitoring, as well as the management of statistics on each stage (processing times, rejects, setup times). In this way, the production manager can have control at any time of what is happening, connecting, for example, with their smartphone or tablet. Supplier management. The system allows the automatic reordering of components to their suppliers, thus ensuring continuity in production.
Management of activities in subgroups. The system allows the management of activities for subgroups, also realized in different locations and at different times. Through the “manager” workstation, it will be possible to get the management of the overall process as well as the overall production statistics.