For Bufab Lann, chip disposal is an important element in the recently implemented process optimization. With a new system designed by Mercatus, the turned part manufacturer has made numerous improvements. Critical for these are, among other things, the conveyor lines for swarf trolleys that are based on the KNOLL TS-S transport system.
Bufab Lann, the leading manufacturer of turned parts in Sweden, creates a lot of chips, for this company headquartered in Värnamo, which employees 100 people, produces 40 million parts per year of steel, stainless steel, and various aluminum and brass alloys. Depending on the batch size, Bufab uses CNC lathes, multi-spindle automatic turning machines, and rotation transfer machines.
In order to feed the chips into recycling properly, Bufab had been using a centrifuge-based disposal system for more than 20 years. It consisted of several small central systems for the various types of material. The supplier of this system was Mercatus Engineering AB, the largest provider of systems for chip processing and cooling lubricant cleaning on the Swedish market. Herman Selin, Sales engineer and Head of department at Mercatus, reports: "We are in very close contact with Bufab and have supplied the company many systems of various sizes over the years. Furthermore, we provide service and maintenance in Värnamo.
Numerous possibilities for improvement
But even a well-maintained system is no longer state-of-the-art after more than 20 years. The wait times for the machine operator when emptying the swarf trolleys bothered the people in charge at Bufab, for example: it took several minutes before they had the empty trolleys back. This was time that they could use for quality assurance tasks or something else.
The previous centrifuge technology was also far from perfect, for it could only dry short chips reliably. This required an upstream sorting system that separates the end pieces of the rod material from the chips and a chip reducer that cuts the long serpentine chips down to the right size. Unfortunately, it happened frequently that end pieces were not sorted out and they caused sometimes significant damage to the shredder. The costs of this were one factor; worse, however, was the downtime for chip handling and the production downtime that this entailed.
Another fly in the ointment at Bufab Lann was the insufficient drying of brass chips. If with these very small chips, residual moisture is still more than one percent after degreasing, the chips compress in the big bag provided for removal due to their own weight. Oil leaks occur on the hall floor, and during subsequent transport, the recycler has to ensure that no oil gets into the environment.
New system for greater process reliability and productivity
All of these factors drove Bufab's decision to invest in a new chip disposal system. Once again, the trusted partner selected was Mercatus. Herman Selin and the planning team were very happy about this: "For more than six months, we worked intensively with our customer and various suppliers, considering a vareity of layouts, in order to find the optimal solution. In the end, we found it in a KNOLL transport system and a Steimel chip centrifuge system."
Mercatus has maintained an intensive partnership with KNOLL Maschinenbau, Bad Saulgau, for about 40 years. "Whether filter systems, chip conveyors or shredders – with KNOLL products, we know that the quality is high," emphasizes Selin. "This also applies for the transport systems that KNOLL has been producing for a few years. We were able to use these to provide optimal chip disposal."
New chip handling with buffer line
With the new system installed in summer 2018, the metal chips from all Bufab production can be degreased and sorted easily and automatically and collected in containers or big bags. Due to the production concept, the machine operators still have to push the swarf trolleys from the machine to the processing plant. However, the automation begins with the insertion of the swarf trolleys into one of two available conveyors. The employee uses a barcode to indicate which are the chips in question – whether steel, stainless steel, aluminum or brass. Usually, right after that, he can take an empty trolley from the return line back to his machine.
The conveyors consist of a 4.5 meter-long elevated KNOLL TS-S/TS-G transport system with a separator and non-return device. These can accommodate several swarf trolleys in a row and thus serve as a buffer zone. Patrick Hörmann, Project Manager at Mercatus, explains: "Because of the numerous machine tools at Bufab, it can happen that three, four or five employees arrive at the central system at the same time to insert swarf trolleys. Thanks to the buffer slots, the KNOLL transport system can balance out these production peaks."
The supplying KNOLL transport system is equipped primarily with straight-lugged chains. Only in the areas where employees are moving around are accumulation roller chains deployed. This provides assurance that the trolley remains standing – if it should come into contact with an employee.
Automatic transfer to centrifuge system
The swarf trolleys inserted meet a crosswise line at the end of the buffer; it, in turn, was implemented based on a KNOLL TS-G transport system. The trolleys move to the centrifuges on it. When they arrive at the centrifuge, the chips are lifted and tipped into drums, which are then placed in the centrifuge. This way, the chips do not come into direct contact with the centrifuge or other mechanical components. "This keeps the system clean and wear-free," explains Patrick Hörmann, and he mentions another advantage: "Each batch of chips is assigned to an individual centrifuge barrel in which the chips remain until they are emptied into the appropriate container. We can therefore avoid mixing different materials."
Also important: the modern chip centrifuges are designed so that they can work with short and long chips. Even end pieces do not influence the result. Chip breakers or impact separators are therefore not required.
After centrifuging, the container with the degreased chips is brought to the appropriate collection containers via a portal. Currently, the turned part manufacturer uses two containers for steel, one for aluminum, and two additional ones for rust-free alloys. Furthermore, there are nine big bags ready for additional materials that accumulate in smaller quantities. Overall, with the new system, Bufab is able to process up to 14 different materials separately from one another.
An important function in the complete installation is the control of the KNOLL system. It not only ensures that the swarf trolleys reach the centrifuges with their freight, but also that the chips are emptied into the right container according to their type. Thanks to the transfer of the data to the centrifuge system, the software is also responsible for ensuring that the degreased chips land in the right container and that the emptied swarf trolleys find their way back correctly. In case of a breakdown of the KNOLL system, the entire system and then, after a brief period also production, would face serious problems. "The system works so reliably that we can guarantee very high process reliability," says project engineer Hörmann. "This is also why we like to use KNOLL products so much."
All requirements fulfilled
Bufab is very happy with the new Mercatus/KNOLL/Steimel system, as Bufab Production Manager Tobias Svensson confirms: "The drying results have improved immensely. We are now able to achieve an extremely low residual moisture of less than one percent, so we recover a lot of cutting oil. Cutting oil consumption has dropped by about 45%. Furthermore, we can transfer the chips to the recycling company dry and sorted by type, something that is evident from the greater reimbursement. The former minutes-long wait time has also been eliminated. The machine operator needs only 10 to 15 seconds in order to move his trolley into the system and remove another one from the removal conveyor."
In addition, the entire system – and especially the KNOLL transport system – is very robust. Mercatus employees perform preventative maintenance in a six-month cycle, whereby the share for the KNOLL components is at most one-tenth of the total effort. "We only have to re-tension the chains and check the sensors for damage," says Patrick Hörmann, who points out another advantage" "The KNOLL transport system is constructed in modular fashion. If Bufab should expand its production, we can easily add KNOLL modules and adapt the system to the new chip quantities."
Cooling lubricant cleaning and chip disposal specialist
From the very beginning, the family-owned Swedish company Mercatus, which was established in 1973, has concentrated on technical solutions for cleaning and recycling process liquids and components from the process industry. Today, the company employs 30 people and generates annual sales of a little more than EUR 10 million. Important company areas are chip handling and cleaning cooling lubricants for the metal-processing industry, as well as cleaning process liquids with membrane technology, evaporators and ion exchangers for industry, heating, and water treatment systems. Mercatus develops, builds, and supplies both small mobile equipment as well as complete systems. The company also provides service for the systems and complete after-sales service.
Mercatus Engineering AB
Box 84 (Hultsfredsvägen 33)
SE-598 40 Vimmerby
Tel.: +46 492 17100
Fax: +46 492 17128
Turned parts for all industries
Bufab Lann was established in 1943 and is now one of the leading European manufacturers of turned parts. The company employs approximately 100 specialists and state-of-the-art processing methods to manufacture customer-specific components made of steel, brass, stainless steel, and aluminum.
Bufab Lann is part of the Bufab Group, a trading company established in 1977, which offers its customers a full-service solution for the procurement, quality control, and logistics of C-parts (screws, nuts, etc.). The international company with locations in 28 countries employs more than 1,400 people.
Box 445 (Margretelundsvägen 8B)
SE-331 24 Värnamo
Tel.: +46 370 696900