In Steyr, Austria, a subcontractor wanted to achieve an approximately 30 percent reduction in its component manufacture throughput time of 6 – 8 weeks. Adopting a “medium-long term strategy”, machines and process organisation were modified for this goal. A robotised milling cell thus became critical for faster and better production.
Long-term success depends on, amongst other things, modern manufacturing methods and the associated process know-how. The latter was Willibald Ebner’s principal asset when, in 1995, he decided to start his own business. Three years later, having laid sound foundations as a design and programming (3D) consultant, he launched into milling technology. He soon emerged from the stiff competition with a very good reputation. This was due not only to quality, but also to winning (three times) the “Austrian High Speed Machining Award” for one-off production.
Manufacturing the bodies of underwater cameras places extreme demands on precision during mounting and machining.
His company, ebner-tec, now has 20 workers producing components, injection moulding tools and electrodes. Despite the success, Willibald Ebner takes a pragmatic view of the future: “There are only limited expansion possibilities in our present premises and new construction would tie up too much capital for a long time. That is why we are trying to achieve one of our goals, 5,000 milling hours a year, through internal optimisation initiatives in, for example, logistics.”
Systematisation in the form of a pallet system and a robotised milling cell was a further example. It was expected that this investment would bring, in addition to streamlining, reduced personnel costs and the ability to create spare capacity.
When it comes to component manufacture, ebner-tec concentrates on workpieces no larger than 300 x 200 x 200 mm. Series are from 5 to 1,000. Subcontract work makes up around 50 percent of the parts, the other half being the company’s own product programme – underwater cameras. With the pallets manually loaded into a DMU 50 Evolution, an average of 3,500 hours was previously achieved. This was on the danger threshold and in screaming need of change – partly with an eye to the pressure on staff and partly because of the risk of being pushed into working with no time margins or production reserves.
“Automation of own production with fixed volumes was relatively easy to plan. However, this made it all the harder for subcontract work,” states Ebner when describing the start position.
Thus, the work procedures around the planned milling cell had to make provision for: a measuring station for presetting outside the machine; task-management shaping of milling programs; transfer of machining data to the machine; a workpiece magazine with at least 100 pallet places; and, a loading station. Pallet identification and establishing of offset values were also necessary in the measuring station and task management had to include simulation technology. Owing to the unpredictable subcontract volumes, a modular construction was an unconditional requirement for the integration of further pallets, magazines and gripping devices.
The compact rotating magazine has six planes, each of which houses 20 pallets. It takes barely 18 seconds to scan the entire magazine.
Thorough studies indicated that System 3R’s automation concept was especially suitable. Not only because it satisfied all the points in the requirements specification, but also because of the persuasive relationship between price and performance, the guaranteed ability to deliver spare parts, the clean interfaces between the units in the cell and the compact design. Indeed, this latter made it possible to place the robot next to the DMU machine and still have sufficient service space around the other machines – without moving any of the machinery.
Comprising a DMU 50 Evolution and a WorkMaster, the milling cell was taken into operation in May 2007. Barely three weeks had been required for installation, operator training (where the software’s structure and use received special attention) and start-up.
“The open architecture is suitable for current ERP solutions. This spared us any interface problems,” states Ebner. He emphasises: “Installation passed off with no great problems. A few ‘tuning glitches' were rapidly overcome.”
With 120 pallet places in the rotating magazine, WorkMaster has the capacity for unattended operation throughout the night – whatever the series size. Ebner comments: “With automatic changing, annual machine hours rose to 6,000.
” The 75 kg lifting capacity is more than sufficient for safe and reliable handling of the parts the company produces. If so required, the capacity could be easily upgraded to 150 kg. The rotating magazine can also be extended. Thus, with no significant fuss, the cell can be adapted to changing conditions.
A great deal of the responsibility for efficient and profitable production rests directly with the operators. Working from the set delivery dates, they organise everything so that the quality-tested components are supplied on time.
While automation was taking place, a local network was integrated into the total concept. This means that the entire process chain can be controlled directly at the machine – from CAD (using SolidWorks) and CAM programming (using hyperMILL) to milling itself. All the way from planning to conclusion, information can be easily exchanged directly with customers via interfaces such as Parasolid, IGES, STEP, SAT, VDA, DWG and DXF.
With their ID chips, the palletised workpieces are unerringly recognised. Even with chaotic loading, pallets are changed entirely in accordance with task planning.
The rapid changing is worth highlighting. Including scanning of pallet IDs, the “chip to chip” time is less than one minute. Besides the high process reliability that WorkShopManager has brought (through administration of machining programs, offset values, magazine positions, batch composition and transfer to the machine), Ebner has additionally found that the automated flow of work also promotes a relaxed work climate. This too has a positive effect on the company’s efficiency. That a pallet costs under 60 euros is yet another plus point that should not be kept quiet.
Using WorkMaster means that, despite the frequently tight deadlines, jobs can be organised very efficiently and flexibly. It is, for example, easy to change job priorities. The modularly constructed software guarantees that, even with chaotic loading, the machining program switches in the right tool at the right time – and puts it back again. Status reports via SMS bring additional safety in unattended shifts.
Ebner is convinced that the investment will make it possible to increase machine utilisation rates even further. He has already noted that the automated milling cell provides the production flexibility necessary for reacting quickly to customer wishes. It also creates time for other jobs. All of this helps to secure the company’s future.
Willibald Ebner uses the milling cell for both subcontract work and manufacture of the company’s own products – underwater cameras.
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Layout drawing:
WorkMaster & Deckel DMU50eVo linear
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