The Microfinish Process
The highest level of component precision is a prerequisite for better performance, higher operational readiness, longer service intervals and efficiency with regard to the use of energy and raw materials. Performance is greatly improved by the optimal level of surface quality and shape tolerances. This is where the Microfinish process comes into play, which is also known as Superfinish, Finishing or Short Stroke Honing.
Schematic Representation
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Cylindrical and conical components are machined utilizing the plunge-cut or through-feed method (see figures A and B). The tools oscillate
linearly and the part rotates.
- For producing flat, spherically concave or convex surfaces on workpieces the tool and the component rotate. The angularity between
the axis of rotation of the tool and workpiece determines the surface profile (see figures D and E).
- Ball bearing tracks and other similar profiles are machined with tools that oscillate radially and the part rotates (see figure C). The combination of the motion of the tool and rotation of the part results in a generated profile, rather than a "formed" profile.
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Microfinish / Superfinish Saves Energy And Resources
The logic is compelling: if wear-and-tear is reduced, there is necessarily an increase in the service life as well as a simultaneous decline in friction. These savings in raw materials and energy can be achieved through the use of the Microfinish process.
Let's take a look at the surface changes in the above ball screw. Although the first windings have the appearance of being round, they display a high degree of profile roughness (left-hand image).
As soon as the Microfinish machining starts, the peaks in the roughness are removed: the wave troughs which have not yet been machined clearly stand out from the surfaces which have already been machined. These troughs, known as chatter marks, are the sign of fine waviness, which always lead to premature wear and tear (see middle image).
With progressive precision machining the proportion of the load bearing surface becomes ever greater, until it stretches across the entire raceway. This then leads to a noticeable improvement in the quality: the profile roughness has been completely removed, leaving the profile considerably improved (see image on right). This is the foundation for permanent, defect-free functioning and thus for savings in terms of raw materials, energy and production costs.
Microfinish In The Automotive Industry
In the automotive industry in particular, precision and minimal friction are requirements for greater performance, functional reliability, longevity and the careful use of energy and raw materials. The utilisation of Microfinish / Superfinish enables the manufacturing of defined, technical surfaces and work piece geometries, in order to minimise friction coefficients and improve the degree of efficiency.
The producible surface structures, which are often defined by the contact ratio and various specifications pertaining to surface roughness, can be adapted to requirements within the smallest of tolerances, and can be manufactured with proof of functionality. Micro-and macro-geometric defects in the pre-machining stage can thus be reliably eliminated.
Microfinish In The Anti-Friction Bearing Industry
The qualitative requirements for ball, cylinder and taper roller bearings have increased significantly. Priority criteria include the obligation to save energy, the extension of guarantee periods, increased load-bearing and the trend towards smaller dimensions and simultaneously increased service life.
Thielenhaus machines have been used in the Microfinish / Superfinish of roller bearing raceways and rolling elements for decades. Thanks to Microfinish / Superfinish machining, the roundness and roughness of the relevant anti-friction bearing surfaces are significantly improved, thus delivering the highest levels of quality. After machining, the anti-friction bearings also display a higher load-bearing capacity and longer service life, as well as lower noise emissions.
Microfinish In The Medical Engineering Industry
Modern joint surgery has witnessed medical successes, which just a few decades ago were hardly imaginable. Variations of endoprostheses, which have seen improvements in both form and service quality thanks to the Microfinish / Superfinish process, have also contributed to this success. This applies in particular to the technical optimisation of ball and socket joints.
The machining of these components leads to improvements in the micro-and macro-geometry, which are decisive for their longevity, as well as ensuring a high load-bearing capacity and a reduction in the specific surface load. The process also removes the amorphous layer, meaning that the healthy base material can be fully exploited in terms of hardness and durability. In practice, a further benefit can be seen in the increase of useful pressure characteristics in the outer layers.
Microfinish In The Medical Hydraulics / Pneumatics Industry
Typical work pieces include:
- Ball valves
- Sealing seats
- Pump pistons
- Pump rotors
- Pump gearwheels
- Pump covers and
- Pump pistons