In its production facility, complex parts are machined to high accuracy on a Mazak VCN 530C vertical machining centre and through the addition of a 2-axis CNC rotary table from Switzerland-based Peter Lehmann AG, the company can machine parts on five sides using five axes.
Loesch’s managing director Michael Loesch explains: “We are more than just a metalcutting service provider. We are best described as an innovative partner to a number of renowned businesses, primarily supplying ideas, developments and our own products.”
Mr Loesch emphasises that his relatively small company with a staff of ten is underpinned by nearly 70 years of experience in the development and manufacture of high-precision mechanical parts and components. The company has participated in several research projects conducted by universities and major partners from the industry, implementing the insight gained from the projects into market-ready products.
Loesch's product range covers three main areas: (1) testing equipment for the automotive industry – in particular specific components for engine and brake system test benches; (2) handling devices and components for plasma powder and laser cladding; and (3) measuring and testing equipment for the pharmaceutical, cosmetics and chemical industry.
“Our expertise in these areas is extensive and we not only apply it to the manufacture of parts, but also to their mechatronic requirements,” Mr Loesch adds. “Of course, metalcutting is an essential core competence because all complex, important parts are manufactured in-house.”
“Although parts can be processed on a 3-axis machine, this approach requires special clamping fixtures for angled surfaces and bores – and multi-sided machining always requires the re-clamping of parts in different positions. This is both time-consuming and detrimental to accuracy. From a technical and productivity perspective, 5-axis machining is definitely the best option.”
However, a true 5-axis machine wasn’t an option for Michael Loesch: “Rocker-mounted rotary tables are usually pretty small – but the alternative was to spend a lot more money on a larger machining centre,” he reveals.
Such a solution also entails interfering edges which require a raised fixture for the workpiece or at least longer tools – both of which reduce stability, promote vibration and ultimately reduce precision and machine performance.
A 3+2-axis approach is less expensive while offering a greater flexibility: “For us the Mazak VCN extended by the Lehmann rotary/tilting table is the perfect solution,” Mr Loesch enthuses. “It even leaves enough room to accommodate two more vices on the machine table, thus providing further clamping options for simpler workpieces.”
With the Mazak VCN 530C, Michael Loesch believes he and his team have the best machine available in its class. Cycle times are short thanks to the 42m/minute feed rate, excellent acceleration/deceleration and rapid 2.8 second tool changes.
Durable linear roller guides ensure consistent machining accuracy along all axes. The machine was specified with a 40x tool magazine, a 18,000rpm high-speed spindle and a Knoll 70 bar high-pressure system, reducing machining times for deep-hole drilling by up to 90%.
To the Loesch team, the 1,300 x 550mm table was of particular importance as it can accommodate the Lehmann CNC rotary table and still provide enough space for two (125mm) vices.
3D CAD data of the CNC rotary table was submitted to the team beforehand, so a matching workspace concept could be established via the in-house CAD system.
The 2-axis Lehmann T1-510520.RR TOP2 rotary table is 711mm long, 301mm wide and 250mm high. It clamps workpieces of up to 340mm in diameter which is more than enough for Loesch which mainly processes small to medium-sized workpieces up to cube edge dimensions of around 150mm.
A torsional rigid system was a key requirement so the decision was made for a clamped counter-bearing: “Besides copper, brass, aluminium and bearing metals, we often process stainless steels which cannot be roughed without this option,” Mr Loesch affirms,
With this in mind, clamping torques of 800Nm (maximum) in the fourth axis and up to 4,000Nm in the fifth axis were compelling features.
Precision is also of paramount importance to Loesch. Also, precision is a core value at LOESCH. The indexing accuracy (Pa) specified by Lehmann of ±17 arc/seconds and ±21 arc/seconds (fourth and fifth axis) as well as the average repeat accuracy (Ps) of ±2 arc/seconds respectively were verified Loesch onsite using a calibration cube. The results actually exceeded the specification.
In practice the high positioning speed of the rotary/tilting table is another significant benefit: “If possible we use one single tool, e.g. a chamfer milling cutter, to execute all operations in sequence, turning and tilting the workpiece than repeatedly changing the tool.”
Programming with the Mazatrol SmoothG is another highlight: “In the past, 3+2 machines could only be programmed for 5-axis operation using G-Code – a tedious procedure if workpieces are complex. Now, we can use the Mazatrol programming system which is really user-friendly,” Mr Loesch says.
“This required up-front collaboration between Lehmann and the Mazak control system developers but the result was well worth the effort. I can now program our VCN 530C with its 2-axis rotary table just like a 5-axis Mazak Variaxis which reduces programming to a fraction of the time. The productivity gains are significant – particularly for single and small-series parts. Typical batch sizes for us about between 20 and 200 pieces.”
Next on the agenda is an automated system to feed the VCN, but the Lehmann rotary table is already ahead of the game because it offers media channels to facilitate the remote control of automatic clamping systems.
“The force clamp on the rotary table is already pneumatically controlled and the two vices on the machine table will then be converted from manual to hydro-pneumatic operation,” Mr Loesch concludes. “This will allow us to fully machine all six sides without any manual intervention. This is definitely the way forward for us.”
Peter Lehmann www.lehmann-rotary-tables.com
Loesch T-P-L Mechatronics Systems www.loesch-tpl.de