Bearbeitungsanforderungen für Hydraulikverteilerblocks (Abmessungen, Form, Oberflächenrauhigkeit)

Today, we talk about the machining requirements of hydraulic manifold blocks from the size, shape and surface roughness of the block.

Should each dimension of the manifold blocks be marked with a tolerance?

The first question to throw out there is, does every dimension need to be considered for machining accuracy?

In fact, no, then what parts need to have machining accuracy requirements? Very simple, only the existence of assembly relationship, you need to pay attention to the machining accuracy, especially with the surface accuracy requirements.

Take our common shaft parts:

General radial dimensions will have precision requirements, because the need to cooperate with the corresponding hole (such as bearings and so on);

manifold blocks blueprint

In the axial direction, on the other hand, there is no fit requirement, so it is sufficient to keep the dimensions only free precision, i.e. no tolerance, because there is no fit in the axial direction.

manifold blocks blueprint

What are the machining errors?

The so-called machining errors include: dimensional error, shape error, and positional error.

  • Size error: the difference between the actual size and the ideal size after machining.
  • Shape error: can be further divided into macro-geometric shape error, surface roughness.
  • Position error: the deviation between the actual mutual position and the ideal position between the elements on the workpiece.

Just talk about error, not tolerance, is a kind of hooliganism, so what is the relationship between error and tolerance in the end?

The relationship between error and tolerance: tolerance is the allowable range of variation of error (emphasize, it is a range). As long as the error (error is a value, not a range) does not exceed the tolerance, then the part is qualified.

That is to say, the error is measured after people processed parts, while the tolerance is man-made in order to determine the workpiece qualified and unqualified and formulated a range, as long as the parts processed after the measurement of the error falls within this range, even if qualified, or else is unqualified.

Machining errors associated with manifold blocks

Valve block processing errors include dimensional, shape, positional errors, and surface roughness. Each aspect needs careful consideration during machining.

1、Dimensional error

As we know, the most machining element about the processing of the valve block is the hole, so what we have to pay attention to is the dimensional error of the hole.

The relationship between dimensional error, tolerance grade, and part size is shown in the table below:

manifold blocks blueprint

Among them:

  • IT12~IT18 for dimensions with no fit requirement;
  • IT11~IT12, for fit dimensions that are not so important;
  • IT9~IT10, used for fit dimensions with only general requirements;
  • IT7~IT8, for slightly higher precision fit dimensions;
  • IT6, for precision fit dimensions of important parts;
  • IT2~IT5, used for especially precise fitting dimensions of parts;
  • IT01~IT1, for standard high-precision gage level fit dimensions such as gauge blocks;

For manifold blocks, our hole diameters are generally between 3~30mm (that is, the basic dimensions in the leftmost column), so just focus on the parameters in the dashed box.

2、Shape and position tolerance requirements

  • The perpendicularity tolerance between the 6 surfaces of the valve block and each other should preferably be 0.05mm, and should not exceed 0.1mm;.
  • The parallelism tolerance between the relative surfaces (that is, parallel surfaces) is 0.03mm;
  • The flatness tolerance of each surface is 0.02mm;
  • The tolerance of perpendicularity between the thread and its fitting surface is 0.05mm.
  • The tolerance of perpendicularity of all holes to the end face on which they are located is 0.05mm;

3、Surface roughness requirements

Commonly used to evaluate the surface roughness of the parameter Ra, which represents the contour arithmetic average deviation (do not understand please ignore), note that its unit is um;

  • Ra50, Ra25, generally indicates the roughness of the rough surface, actually the raw material surface roughness;
  • Ra12.5, generally indicates the roughness of non-coordinated surfaces, such as shaft parts of the terminal shaft end face, chamfer and so on; of course, except for the chamfer in the hole of our cartridge valve.
  • Ra6.3, generally indicates the roughness of the unimportant surface, such as struts, brackets and other mounting surfaces.
  • Ra3.2, general parts with the roughness of the surface.
  • Ra1.6, said the tooth surface of the general gear, drive thread work surface, positioning pin hole.
  • Ra0.8, Ra0.4, indicates the roughness of the working surface that needs to be maintained for a long time.
  • Ra0.1, said the instrument track, cylinder piston rod and cylinder head contact surface roughness.
  • Ra0.05, highly demanding airtight moving parts.
  • Ra0.012, the surface roughness of standard high-precision gauges such as measuring blocks.

We through a “surface roughness comparison sample block” to visualize the understanding of different surface roughness is what kind of a state;

manifold blocks blueprint

Finally, we come back to the manifold blocks, whose roughness requirements vary from part to part:

  • The roughness of the surface of the valve block and the hole where the embedded hydraulic valve is mounted cannot be greater than Ra0.8;
  • The roughness of the sealing surface of the end pipe fitting and the O-ring groove is not greater than Ra3.2;
  • The roughness of general oil-through orifices must not be greater than Ra12.5.
  • The surface where the block meets the block must not have obvious scratches.
  • For the sake of aesthetics, the machined cast iron and steel valve block can be surface galvanized.

If you need manifold blocks, please kontaktieren Sie uns für Produktangebote. Wir freuen uns darauf, mit Ihnen zusammenzuarbeiten, um Herausforderungen zu meistern und gemeinsame Erfolge zu erzielen.

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