Category: Medical

HORN Mastering Processes: Swiss Turning and Micromachining

 

Mastering Processes: Solutions for Micromachining and Swiss-type Turning

Outer diameters of 0.1 mm (0.004″), recesses of 0.5 mm (0.020″) and feed rates of 5 µm (0.0002″) – welcome to the world of micromachining! Screws for hearing aids, balance weights for automatic wristwatches or micro-turned parts for medical assemblies: Manufacturing such parts requires know-how, precise machines and special tools. With cutting depths of down to 0.01 mm (0.0004″), users place very high demands on the tools used. They include shiny surfaces and high dimensional accuracy of the components through the use of low cutting force. HORN has developed suitable solutions with the μ-Finish system for micromachining as well as with other tool systems and manufacturing processes for Swiss-type lathes.

The demands on the tools for micromachining with Swiss-type lathes are high. Due to the sometimes very small cutting depths, the tool edges must be very sharp in order to keep the cutting force as low as possible. However, the ground cutting edges are susceptible to microchipping. Even limited chipping in the range of a few µm at the cutting edge has a negative effect on the surface of the machined workpiece. Furthermore, the surface quality of the rake face plays an important role. To counteract built-up edges, the rake face must have good sliding properties. For this reason, it is finely ground or polished.

Changeover Accuracy of 2.5 µm

Clamping of the inserts is another important point in tool design. When machining turned parts of small diameter, the centre height of the tool must be precisely measured. Even slight deviations in centre height have a negative effect on the quality of the workpiece when machining the smallest diameters. In the best case, the machine operator should be able to turn the insert without having to readjust the centre height. With the μ-Finish system, HORN offers a changeover accuracy of +/- 0.0025 mm (0.0001″) when indexing a double-edged insert. This is made possible by the precise peripheral grinding of the insert in conjunction with the stable insert seat. In addition, the contact surfaces of the square shank toolholder are also ground, which has an effect on the holistic precision of the HORN system.

The grinding of a sharp, flawless tool cutting edge requires a lot of know-how. Grinding wheels with the finest grits, special new grinding techniques and a microscope with 400x magnification are necessary to ensure that the tool performs as required. In the process, every batch of the μ-Finish system produced is subject to 100 per cent inspection. Important quality assurance criteria are the tightly toleranced high surface quality of the rake and flank surfaces, the centre height and, in particular, the sharpness of the cutting edge. There must be no visually recognisable irregularities on the cutting edge with the µ-Finish system.

HORN presents itself as a holistic supplier of tools for all Swiss-type machining operations. The extensive insert portfolio can be easily adapted to the requirements of different processes in sliding-headstock turning. Close partnerships have been established with the companies Graf Werkzeugsysteme, Boehlerit and W&F Werkzeugtechnik to provide solutions for the interfaces between the cutting insert and the machine, including for ISO tools.

Broad Knowledge

Horn’s know-how does not only apply to cutting tools. The tool manufacturer also supports its customers and partners with knowledge of the correct application data and the development of new tool systems and manufacturing processes for sliding-headstock operations. This includes, for example, competence in driven tools, tool holders for backworking and entire tool solutions.

HORN Mastering Processes: Grooving

When Paul Horn introduced the type 312 indexable insert to the public in 1972, it was a small revolution in the grooving process. Horn was the first manufacturer ever to develop a tool system with a vertically mounted, three edged carbide insert for grooving. Today, the grooving process with indexable inserts is indispensable in modern manufacturing. Radial grooving, parting-off, face grooving and internal grooving to µ-precision are now part of everyday life in the machining industry. Paul Horn’s incentive at the outset was for the technical perfection of his products and the Horn company continues to set similar standards in tool technology for this machining process.

 

The 312 insert is still popular with users today. Horn has not stopped developing and optimizing successful product families. At the same time, Horn has completely integrated the value creation for its entire product range into its own production. The possible applications of the tool have grown considerably after the insert was originally used almost exclusively in the automotive industry. The “312” is intended for external machining and is used, among other things, for producing workpieces in the medical industry, in the manufacture of hydraulic components and for making everyday objects such as jewellery or ballpoint pens. However, it is not only the type 312 insert that has made the precision tool manufacturer known as a specialist for machining between the flanks. Numerous other tool systems followed the idea from 1972, which are now successfully used for grooving worldwide.

Basically, the grooving process involves a narrow cutting edge that penetrates the workpiece in a radial or axial direction. The art of grooving is, among other things, controlling the chip flow. Chip sticking, jamming or long, stringy swarf must be avoided in practice, as they have a negative influence on process reliability and can lead to tool breakage and damaged flanks. Depending on the material to be machined and the type of machining, Horn has developed different chipbreaker geometries that ensure reliable chip formation, control and breakage. Another important point for economical grooving is a sufficient supply of coolant. Where in the past cooling was external with the classic flood coolant, today modern tool carriers are used, mostly with an internal coolant supply. This ensures effective cooling of the shear zone between the tool cutting edge and the workpiece. For parting-off, Horn also offers a type S100 insert, which supplies the contact zone with coolant at high pressure directly through the insert. Tools are exposed to high loads during parting-off. The quality of the carbides used, the quality of the cutting edge and the insert coating also play an important role in reliable and economical parting-off.

Grooving in Practice

A user produces a wide and deep groove in an aerospace component using the trochoidal grooving method. It is very well suited to the production of of deep, wide grooves where high metal removal rate must be generated.The machinists produce the component from 1.4548 (X5CrNiCuNb17-4-4), a steel with high corrosion resistance, strength and toughness. Roughing is carried out using a full radius Grooving insert S229 with a radius of 2 mm. The grooving process is designed as follows: The 30 mm wide and 15 mm deep (incremental) recess is trochoidally roughed using the full radius indexable insert with a cutting speed of vc = 140 m/min at a cutting depth of ap = 1 mm The programmed feed rate is fn = 0.25 mm -1. The finishing allowance is 0.2 mm. Finishing also involves using a cutting insert from the S229 system. The finishing operation is carried out from two sides with a 3 mm wide grooving insert. The corner radius is 0.2 mm. The total production time to complete the groove is less than two minutes.

 

Face Grooving in the Medical Sector

For the production of a thin-walled valve cover made of titanium for a cerebrospinal fluid shunt system, the SuperMini system type 105 is used. On one hand, the customer uses a tool for the face grooves and, on the other, a special tool for finishing the lid fit. For the narrow fit on the lid with a length of 0.5 mm, Horn had to design the SuperMini tool with a corner radius of 0.05 mm. The difficulty in machining titanium always arises from the dissipation of heat as well as the control of chips. For use as an implant, the user has strict criteria regarding the surface quality and the absence of burrs on the component. By optimizing the cutting paths with a CAM system, the experienced colleagues in the machining department were able to double the tool life from 1,000 to 2,000 components.

Although Horn’s tool portfolio has expanded considerably, not only in the area of grooving but for all applications in the field of demanding machining tasks, grooving and thus machining between two flanks is still considered the supreme discipline.

Looking ahead to the AMB 2022 trade fair in Stuttgart and IMTS 2022 in Chicago, Horn is presenting innovations and expansions in the area of grooving.

 

 

MAPAL – Miniaturised Clamping Chucks

Thanks to additive manufacturing, MAPAL now offers hydraulic chucks in miniature format with HSK E25 connection, for example for the direct clamping of tools with a diameter of 3 mm. These meet all the demands on chucks for the miniature sector with respect to radial run-out accuracy, balancing value, cooling lubricant supply and handling.

In order to guarantee perfect radial run-out accuracy, innovative clamping chamber systems are integrated into the new chucks that fit tightly against the shank of the tool. They are fitted with dirt grooves as protection against micro-soiling. The demanded balancing value is ensured thanks to the internal balancing geometries and supporting structures that also aid the optimisation of weight and strength. The miniature chucks allow homogeneous acceleration and deceleration of the whole tool system of chuck and tool for less loading of the spindle.

The innovative manufacturing method has also enabled the chucks for the miniature sector to be equipped with decentralised coolant outlets. These outlets are designed using parameters such as coolant pressure, setting dimension and spindle speed so that they deliver the cooling lubricant precisely to the cutting edge. In the best case, a metered total-loss lubrication system is achieved that eliminates the need for subsequent cleaning of the parts.

The new miniature chucks from MAPAL allow quick and simple clamping of the tool. Neither training courses nor high setup costs or expensive peripherals are required for implementation of the chucks.

New possibilities – not only for Tool Clamping

The new small hydraulic chucks also offer new possibilities for the clamping of workpieces. For example, for the clamping of artificial hip joint balls. Specially formed clamping chambers inside the chuck and a special outside geometry ensure that the balls are very precisely and at the same time gently clamped. Particularly in medical technology, topics such as reproducible precision are taking on enormous importance – and this is ensured during machining thanks to the new chucks.

Please contact us for more information.

 

HORN High Speed Whirling

 

 

HIGH-SPEED-WHIRLING
New technology for shorter machining times. Whirling and turning performed simultaneously saves time and reduces the material volume which has to be removed by whirling inserts. High feed rates shorten process time and increase productivity.

• Long tool life and excellent surface quality as a result of pre-turning the thread diameter
• Machine and Process Technology partners Index / Traub

Please contact us for more information on this new product.

 

 

 

Horn Thread Cutting Tools from M1 to M2.5

DCG thread milling cutters for M1 to M2.5

Thread Production in hard-to-cut materials

Horn presents new developments in the DCG thread milling system. Suitable for producing threads from M1 to M2.5 (metric ISO threads DIN 13–20), the tools extend the possible applications of the DCG series for the reliable milling of threads. They have extremely sharp cutting edges and are suitable for universal use thanks to their coating. The solid carbide milling cutters are available as standard up to a thread length of 2 x D. They demonstrate their special capabilities and efficiency when machining steels, stainless steels, cast iron, non-ferrous metals and in particular hard-to-cut materials used in the medical technology sector, for example.

DCG solid carbide milling cutters have been proving themselves in the production of threads sized from M3 to M12 for many years. As the single-row milling cutters can be used for different pitches, a high degree of flexibility is guaranteed.