Compressor assembly is flexible and collaborative

In a “dark” corner of the refrigerator, which few people know about, there is an element without which this household appliance would just be “a shoe cabinet”: we are talking about the compressor. For many European refrigerators, this technology is the result of Italian expertise and synergy: first and foremost, BDG, active on the electromechanical and electronic components market; BAI, a company based in the Varese area which helps companies automate their production processes, with tailor-made solutions designed around their needs; finally, ABB, whose Italian subsidiary has been a partner of BAI for ten years and whose know-how in collaborative robotics is well established. These three companies have together created a robotic cell for the assembly of refrigerator compressors, with the aim of making the production system more efficient: the result is a safe and ergonomic solution. Carlo Del Grande, Managing Director of BDG, and Lorenzo Barison, CEO of BAI, spoke to us about this solution.

The cooperation between the two Lombardy-based companies BAI and BDG has been going on for 30 years: “It all started with our fathers, who were running our respective companies at the time,” Lorenzo Barison and Carlo Dal Grande commented. A long-standing trust, therefore, which has withstood the generational change. BDG was founded in 1954 and specialises in the production of electronic and electromechanical components, particularly for the white goods sector. BAI, on the other hand, specialises in the automation of industrial processes for which, together with partner companies, it designs and manufactures handlers, in-line or rotary table machines, robotic systems, control systems and robot guidance with cameras, suitable for the handling and assembly of consumer products and large series components. “BDG gave me the opportunity to design my first machines and automations,” Lorenzo Barison recalled. The collaboration between these two companies evolved over the years, and today they face the new challenges presented by the market together. One of these is the creation of a robotic assembly line for refrigerator compressors, for the assembly of the terminal block on the compressor through a single production cycle. We noticed,” Carlo Del Grande explained, “that many parts were still being manufactured manually, even though customers would have preferred an automatic line, so they started asking us at BDG for a business case to discover the advantages of automation. The objective was an automated assembly of electrical components and connectors with cables on the refrigerator production line: a critical operation from a quality standpoint, as an incorrectly inserted connector or an inadequately tightened screw could cause major problems for end-users. “To create an optimal solution for these requirements, however, we needed other skills besides our own,” Del Grande stated. When he had to start working on this project, Carlo Del Grande had no doubts and called in Lorenzo Barison of BAI. “After explaining the characteristics they were seeking for this line,” Lorenzo Barison explained, “we immediately thought of a third player, and therefore additional know-how, that is, ABB. We have been working with this robot manufacturer for about ten years, and we appreciate their after-sales response capacity, which is fundamental for us system integrators. We did not know what kind of robotics solution they were going to suggest to us, but we turned to them knowing that they would give us the best response to what we were asking for”. ABB therefore supplied its YuMi single-arm cobot, capable of assembling small parts and with part feeding systems, in short cycles and even in small batches. “The ideal choice for us,” Lorenzo Barison commented.

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The functioning of the line

Going into detail, this robotic cell is designed to be able to load two types of products in parallel: the first is the battery-operated MIT terminal block with automatic vibrator loading; the second is the plastic connector with integrated cable, previously prepared on an accumulation conveyor which leaves the cables exposed on one side of the conveyor. The YuMi cobot deals with the handling of the two objects, their insertion and the subsequent insertion of the compressor. The compact configuration of the MIT terminal block allows it to be assembled on the compressor in a single operation, optimising time. “The added value of this line,” Barison continued, “is that it handles the finished part keeping it straight, that is, there is no need for manual insertion or reinsertion of the part: everything is left to automation”. The integrated artificial vision of the YuMi cobot checks the correct insertion point with reference to the position of the compressor, then ensures correct assembly. An additional load cell also allows the verification of the exact value of the insertion load. The cobot enables a centred, accurately controlled and extremely repetitive operation, with no interruptions. “The integrated vision,” Barison explained, “helps to identify the three pins present in the compressor, to understand where the centre is and therefore the clamping area, and to verify the alignment of the connectors. The presence of the camera on YuMi provides complete traceability of the components and all the information of the production batch; it is able to read the code of the terminal block to ensure the correct correspondence with the right compressor, according to the bill of materials, so as to avoid the risk of wrong components”. The great flexibility of ABB’s collaborative robot not only allows it to process on the same line products for different customers, therefore with sometimes very different geometries, but also to perform different actions and steps depending on the batch. “There are product versions,” Barison explained, “where it is necessary to fix a screw: in this case the cobot inserts the part into the compressor, fixes the screw and then takes the connector. A third option is to use a clip, made by BDG, instead of a screw, which enables the terminal block to be fixed more quickly”. This line, in short, consists of the cobot with integrated artificial vision, two or three supply lines depending on the presence of the screw or the clip. It can be inserted into a compressor production line, but also into an internal refrigerator production line: “The production of refrigerators,” Barison explained, “consists of an assembly of a semi-finished product, that is, the compressor, and an assembly of the complete object, that is, the refrigerator. It is the end customer who chooses where to put it”.

Flexibility and ergonomics

The challenge of flexibility was among the most important ones which BDG and BAI had to face. Connectors are a complex element to manage because of their geometric instability, because they are made of plastic with metal inside, and also because they “walk around” on a line with few indexing elements. ABB’s YuMi cobot becomes a fundamental element for the correct assembly and processing of the line. “The cable,” Barison explained, “brings with it irregularities which only robotics and artificial vision systems help us deal with, whereas first-generation systems would not be able to help us”.
Another instability which had to be taken into account is the very wide range of products to be processed: all customers have their own compressor, with its own specific characteristics, but it has to be produced together with others on the same line. Consequently, it is necessary to adapt to the different geometries of the compressors and refrigerators, the assembly methods of the electrical connection; only a flexible and versatile solution can compensate for these difficulties. Only a flexible and versatile solution can overcome these difficulties. “It is a cell which we see almost combined with the product,” Barison said, “perhaps a future development could be to sell the assembly system together with the product”.
At the same time, BDG wants to “flatten” the differences by creating standardised solutions, also designed to speed up production. “Many compressor manufacturers”, Carlo Del Grande stated, “relocated their production outside Europe, so we found ourselves dealing not only with customers who manufacture compressors, but directly with the refrigerator manufacturer”. BDG therefore responded to the needs of major appliance manufacturers to increase standardisation on their assembly lines, and in partnership with the major compressor manufacturers, a common design was created. “We kept it free,” Del Grande said. “Creating freedom means opening up to competition, of course, but at the same time it helps to simplify. We will thus create a system which each factory and line will be able to customise in a different way, with a combination of standardised elements”. This will also solve many of the problems faced by those who have to manage production differences and short notice requests. “In Europe itself, almost every country has its own cables; it is therefore difficult for a refrigeration specialist to have a large stock of products which can be customised at the last minute. This versatility we offer means that we always have products in stock for Italy, England, Germany and so on, which is crucial in a world where e-commerce represents a large share of sales and people want everything immediately. The more we automate, the better we will be able to react to this market which does not want to wait any longer”. Automating not only for the needs of customers, but also for those of the employees: it is now clear that in all sectors where robotics and automation have entered, there has been neither a worsening of working conditions nor a net reduction in human capital; on the contrary, companies which invested in automation also invested in new human resources, and improved the health of their employees. In all markets nowadays,” Del Grande explained, “there is a great need to eliminate as much as possible activities which are hard on their operators, especially those involving repeated movements and heavy lifting. If we think of the line we have been talking about, the work done by the cobot would be very difficult for a worker: the object, besides being sharp, is also difficult to insert quickly; an activity of this kind repeated for eight hours every day is very hard on the person, and also raises the risk of human error”. The cobot, therefore, also provides the certainty of error-free assembly, also counting the element of traceability which provides guarantees to the manufacturing company at insurance level and to the market where the product will be seen. “A collaborative robot,” Barison added, “allows operators, even though they may no longer be very young, to prepare the part and position it according to their own experience, but without the stress and force which must be applied to assemble it: humans are left with the ‘intelligent’ part of the job, while the cobot is left with the tiring part”.

Industry 4.0 and future developments

From a health and safety standpoint for human operators, the presence of a cobot also enables the distancing being imposed by the current Covid-19 pandemic. Restrictions and the exceptional situation are certainly giving a strong impulse to plant automation and technological innovation in an Industry 4.0 perspective. “Today the cobot is a mature, compact and safe product,” Barison commented, “which guarantees flexibility in any situation. Perhaps five years ago, when the first collaborative robots appeared on the market, this robotic cell would not have been successful; today, on the other hand, the idea of creating it with a traditional industrial robot would be unthinkable, because it would have a strong impact in terms of costs and project times”. The excellent synergy between the three companies, ABB, BAI and BDG, is certainly an added value: each brings along a strong know-how allowing them to create an innovative and efficient system. “Why did we choose BAI? – Del Grande explained – Because it knows our criticalities and problems very well: it knows that our product is damaged if it undergoes incorrect treatment, that assembly must be done in a certain way, and that the risk of bad contact must be limited. Why ABB? Because they have products which BAI trusts, and they are often already present or known to our customers; it is a perfect complement to the team”. The synergy between the three companies resulted in an innovative, but not ‘fixed’, robotic cell: what they have created can be modified and improved, depending on what the market demands. “At the moment,” Barison explained, “we have chosen the one-arm YuMi because it is ideal for the operations and timing we were interested in, but we do not rule out adding the second arm in the near future, if we are asked for different cycle times and assemblies with more screws. As we said, this is a flexible solution, so modifications are not out of the question, even those that we never even considered”.