Expert articles and guides on precision machining: from fundamental processes and the specific characteristics of challenging materials to practical topics such as cleanliness, tolerances and series production – drawn from the daily work of a premium supplier.
Turning is one of the most important machining processes: the workpiece rotates, a stationary cutting tool removes material and thereby produces rotationally symmetrical contours. How modern CNC sliding headstock and fixed headstock lathe centres achieve the highest precision.
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In milling, the tool rotates while the workpiece is fed in a defined manner – ideal for prismatic and complex geometries. A look at 5-axis machining, tool selection and the production of demanding contours.
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Grinding is the method of choice when the tightest tolerances and finest surface finishes are required. From cylindrical and centreless to surface grinding – this is how micrometer-range fits are created.
WeiterlesenStainless steel (V2A, V4A) boasts corrosion resistance and strength, but presents machining challenges such as work hardening and heat build-up. What matters when it comes to tools, cooling and cutting data.
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Aluminium is easy to machine – and yet the detail is crucial: the choice of alloy, tool geometry and optimal cutting parameters determine the surface finish and dimensional accuracy of turned and milled parts.
WeiterlesenTitanium combines high strength with low weight and excellent biocompatibility – but is difficult to machine. Low thermal conductivity and high reactivity require a great deal of experience in turning and milling.
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Technical ceramics withstand extreme operating conditions and are increasingly replacing metal and plastic. Their grinding is demanding and mastered by only a few suppliers – the effort is worthwhile.
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Turning is among the oldest and most important machining processes – and remains the backbone of any precision manufacturing of rotationally symmetrical components.
During turning, the workpiece rotates about its own axis while a stationary cutting tool is fed in a defined manner. At the point of contact, the cutting edge removes material in the form of chips, thereby producing the desired contour. The machining process can be precisely controlled via the depth of cut, feed rate and rotational speed.
All workpieces with a rotationally symmetric basic shape are turned – from shafts, axles and bolts to bushes and sleeves, as well as complex precision components with internal contours, threads and undercuts. Modern turn-mill centres combine turning and milling in a single setup, enabling even demanding geometries to be manufactured in one pass.
The machinery ranges from CNC sliding head lathes for delicate microscopic parts to fixed head and chuck turning centres for larger diameters. Driven tools, multiple turrets and automatic loading and unloading enable a high degree of manufacturing integration while maintaining consistent quality – even across larger production runs.
Milling is the process of choice when it comes to prismatic components and complex three-dimensional geometries that cannot be produced by rotation.
Unlike turning, here the tool rotates while the workpiece is fed in a defined manner. The multi-edged cutter removes the material step by step. Using the number of axes and path control, almost any contours, pockets, grooves and free-form surfaces can be produced.
On 4- and 5-axis machining centres, the component is machined in several planes simultaneously. This reduces repositioning, shortens process chains and increases accuracy because datum surfaces are maintained in a single set-up. This is a decisive factor for quality and cost-effectiveness, especially for components with a high vertical range of manufacture.
Tool geometry, cutting data and a stable clamping situation determine surface finish and dimensional accuracy. In the case of thin-walled parts, vibrations and heat input must be controlled in order to maintain form and position tolerances.
Where the tightest tolerances and finest surfaces are required, there is no getting around grinding – it produces fits and qualities that other methods cannot achieve.
During grinding, a rotating grinding wheel with a multitude of geometrically undefined cutting edges removes minuscule amounts of material. This achieves micrometer-level dimensional accuracy and surfaces with very low surface roughness – frequently as finishing work following turning or milling, especially in the case of hardened materials.
Particularly with implant components and highly stressed precision parts, the surface quality determines function and service life. By combining grinding with subsequent finishing processes such as honing and lapping, surfaces can be achieved that meet the highest requirements.
Stainless steel combines corrosion resistance, strength and suitability for hygiene – properties that make it indispensable for many industries, but make its machining challenging.
Stainless steel refers to steels with a high degree of purity; the well-known corrosion- and acid-resistant grades V2A (e.g. 1.4301) and V4A (e.g. 1.4571, 1.4435) contain chromium and nickel, which form a protective passive layer. However, it is precisely these alloy constituents that make machining more difficult.
Stainless steel is prone to work hardeningIf the cutting edge is not kept cleanly in engagement, the surface work-hardens and wear increases. The low thermal conductivity also leads to Heat buildup on the cutting edge. Both require coordinated cutting data, sharp tools and effective cooling.
From corrosion- and acid-resistant steels to duplex and super duplex materials and implant steels: the range of stainless steels is vast, and each grade has its own behaviour. Many years of experience in turning and milling is the prerequisite for precision parts that impress over the long term.
Aluminium is considered easy to machine – but that very fact is deceptive: surface finish and dimensional accuracy are determined by the details of the alloy, tool and cutting parameters.
The low material resistance permits high cutting speeds and makes aluminium an economical material for turned and milled parts. Its low weight combined with good strength makes it particularly attractive in aerospace, measurement technology and mechanical engineering.
The correct one alloy selection is the first step – from easily machinable free-cutting alloys to high-strength aerospace alloys, every material behaves differently. Also crucial are a sharp, polished tool geometry against built-up edges as well as coordinated cutting parameters to avoid burrs and achieve the best surfaces.
Aluminium is sensitive to thermal expansion and clamping forces. With thin-walled parts, a well-thought-out clamping strategy and process control are necessary to ensure that tolerances are reliably maintained even after unclamping.
Titanium combines high strength with low weight and outstanding biocompatibility – an ideal material for medical technology and aerospace, but one of the most demanding in machining.
The special properties that make titanium so valuable also make it difficult to machine. Pure titanium (e.g. ASTM F 67) and alloys such as Ti-6Al-4V ELI (ASTM F 136) are used wherever lightweight construction, corrosion resistance and biocompatibility are required.
With adjusted cutting data, suitable cutting materials and effective cooling, titanium can be machined safely and reproducibly. Laser welding is additionally used for permanently joined components. Especially for highly stressed implant components, the interplay of machining, finishing and surface quality is decisive – for internal surfaces, surface roughness values down to the range of a few hundredths of a micrometre are aimed for.
Technical ceramics withstand extreme temperatures, wear and corrosion, and are increasingly replacing metal and plastic – yet only a few suppliers have mastered their machining.
Materials such as zirconium dioxide (ZrO₂), aluminium oxide (Al₂O₃) or Macor offer properties that traditional materials cannot achieve: high hardness, electrical insulation, chemical resistance and dimensional stability even under high heat. This hardness makes grinding the only practical machining method.
Ceramics are hard and at the same time brittle. During grinding, the infeed and cooling must be selected so that no edge chipping and no micro-cracks occur. This requires diamond-tipped grinding tools, sensitive process control and a great deal of experience.
Because only a few finishers offer the grinding of technical ceramics, it is a true differentiator – and the right answer when metal or plastic reach their limits.
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