Fluid power machining solutions

Axial piston machines convert hydraulic energy into mechanical energy or vice-versa
Axial piston machines convert hydraulic energy into mechanical energy or vice-versa

Tooling expert Mapal has carefully examined critical components used in the fluid power technology industry and their requirements for machining.

One example of this is the axial piston machine. Its series production and the machining of its different components pose a variety of challenges both for processes as well as individual cutting tools. However, Mapal specialists say they have developed a solution that reduces machining time for a cylinder block part alone by 19%.

Types of axial piston machines perform different tasks in closed and open hydraulic circuits, but they all convert hydraulic energy into mechanical energy or vice-versa. They are used in modern agricultural harvesters and tractors, as well as in heavy road, construction and mining machinery.

“Manufacturers of axial piston machines produce them in mid to large sizes,” says Tobias Stolz, component manager for general machining at Mapal. “A high degree of accuracy is required to machine their individual parts.”

Mapal is an expert in combining high quantity volumes with precision and has been able to improve processes considerably and save costs for clients in the fluid power sector. It also has all the products in its portfolio required to completely machine the individual components.

This made the axial piston machine an obvious choice for Mapal as a component maker to focus on. Its experts developed a model process which was successfully put into practice (with individual adjustments where required) for clients.

With a combination of specially designed specials and economical standard tools, Mapal can fulfil all requirements for fast and precise machining of components in axial piston machines
With a combination of specially designed specials and economical standard tools, Mapal can fulfil all requirements for fast and precise machining of components in axial piston machines

An axial piston machine is made up of a housing, adjustment unit, port plate housing and cylinder block. When machining the housing made from EN-GJL-250 cast iron, which provides protection for the unit, the machining of the oil leak countersink feature is key.

For this, Mapal recommends a modular boring tool which is particularly economical due to the TTD replaceable head drill and indexable inserts. Milling cutters from the NeoMill range are used to machine the housing’s various surfaces.

“This a special feature that we can offer Mapal customers,” Mr Stolz says, referring to the combination of specially designed custom and economical standard tools.

Standard tools are used for the most part to machine the adjustment unit made of EN-GJS-400-15 graphite iron, the axial piston machine’s control instrument. Mapal recommends solid carbide drills from its Mega-Step-Drill family for the threaded bores. In addition, FixReam reamers and HPR replaceable head reamers are used for the fine machining of various bores.

The third component, the port plate housing, is the axial piston machine’s connection plate and therefore the pressure and suction connection to other parts in the hydraulic circuit. It is usually made of either EN-GJL-250 or EN-GJS-400-15 materials. In this case interrupted cuts and partially thin-walled component segments pose challenges during machining.

“We machine some of the bearing seats and rotor bores with multi-stage, specially designed boring tools with indexable inserts that ensure high-quality bores even in difficult conditions,” says Mr Stolz. “As for the last component, if there is a challenge when it comes to machining axial piston parts, then it definitely has to be the cylinder block.”

The cylinder block is at the heart of the axial piston machine and is manufactured from either steel (C45 or 42CrMoS4) or spheroidal cast iron (EN-GJS-500-7 or EN-GJL-400-15). Through the movement of the pistons and oil, this component performs the machine’s main function. For it to work, the piston bores have to be machined with pressed-in liners.

An axial piston machine fundamentally consists of the following components (from left): pump housing, cradle adjuster, control plate holder and cylinder block
An axial piston machine fundamentally consists of the following components (from left): pump housing, cradle adjuster, control plate holder and cylinder block

“One customer was struggling with high costs manufacturing cylinder blocks,” Mr Stolz explains. “A great deal of effort is required to ensure the defined surfaces are between Rz 27 and 37µm, as well as the liners maintaining tolerances for roundness, straightness and parallel alignment of 3µm. Our experts developed an economical process with the customer where machining time was reduced by 19% per part in total.”

The customer machines the pressure and suction kidney with the OptiMill-Uni-Pocket solid carbide milling cutter as part of this new process which supports the boring process via inclined plunging. The machining of these inlets and outlets consequently does not require any other tools.

The Tritan-Drill step drill geometry offers similar benefits when pre-machining the piston bores. The spot face that is normally required is dispensed with and thanks to the sharp cutting edges, the bottom of the bore also does not have to be deburred.

The multi-stage Mapal fine boring tool ensures optimal quality before the brass bush is pressed in. It is not only precise during machining but also particularly efficient and economical thanks to the HX insert’s six cutting edges. These three tools alone reduce machining time by 19% compared to the previous method.

“We offer customers economical processing solutions to their machining challenges – for all functionally relevant parts in the fluid power industry,” Mr Stolz concludes.

Mapal
https://mapal.com/en-int

Company

Mapal

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