JPS60118441A - Clamping block clamping and holding work to machine tool - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a clamping block for clamping a workpiece to a machine tool, especially a grinding machine, during machining of the workpiece.

Conventional technology When machining workpieces with machine tools, in particular when machining workpieces to be polished with @polishing machines, the clamping of the workpieces must be It is known to cast clamps into blocks, which serve as an aid in positioning and which hold the workpieces sufficiently unloaded during machining. Removing the mechanical load from the cast workpiece is extremely important for machining accuracy, especially in production @calendar polishing machines where high polishing pressures are applied to the workpiece during the polishing process. The clamping block and the workpiece cast into the clamping block for machining constitute a unit, herein referred to as a clamping unit. To produce the unit, this clamp is inserted into a workpiece (engineering mold), which mold is then cast together with the clamp material for the block. Zinc or zinc alloys are generally used whose thermal tensile modulus is higher than that of the material used to manufacture the workpiece, and the clamping is therefore carried out each time when the block (6) is cooled from the casting temperature to room temperature. Therefore, when tightening, the material of the block has a coefficient of thermal expansion larger than that of the workpiece material.
The clamping is therefore selected in such a way that after the workpiece has cooled down, it is fixed in the block without any play. In this case, the surface of the workpiece to be machined is located above the clamping block. A typical example of a workpiece that can be procured for processing on an abrasive machine in this manner is a turbine blade for an aircraft turbine.

The material for the turbine blades is a nickel-based alloy that satisfies the high requirements for turbine blade materials. As mentioned above, zinc or a zinc alloy is used as the material for manufacturing the fastening block that holds the turbine blades.

Zinc or zinc alloys have the disadvantage that their processing must be carried out at relatively high temperatures. Zinc is about 420
℃, which requires relatively high costs for injection molds and injection molding machines. At the same time, relatively steep temperature gradients occur during zinc die-casting on cold or low (4) temperature workpieces, which can lead to non-uniform injection of zinc into the die-casting mold and May cause uneven hardening of zinc. For this reason, high injection rates and rapid curing of the zinc are required, resulting in residual air inclusions, which lead to porosity in the cast body, which can deteriorate the stability of the cast body. Additionally, the clamping block must generally be provided with a breakage target location that allows the clamping block to split after processing without damaging the cast workpiece. Particularly for machining workpieces in manufacturing abrasive machines, where the workpiece and clamping are exposed to high mechanical loads, clamping has the disadvantage of reducing the stability of the block, which is called This is because the clamping under pressure of the abrasive discs must avoid deformations of the blocks and can lead to unacceptable dimensional deviations of the machined workpiece.

Problems to be Solved by the Invention 5 Therefore, the object of the present invention is to provide a method which can be manufactured at low cost with relatively little technical outlay and which nevertheless guarantees high stability and accurate dimensional cropping. The aim was to provide a clamping block that could be used and easily removed from the workpiece.

Means for solving the problem The above-mentioned problem is solved according to the invention in that the clamp consists of a block filled with plastic.

According to a preferred embodiment of the invention, it is particularly advantageous for the clamp to consist of a cold-curable multicomponent plastic. According to the invention, the materials for producing the clamping blocks are primarily styrene-epoxy resins, esters or acrylates, each of which has a high filler content.

According to the invention, as a filler, firstly up to 3.5 m
Sand and/or ceramic granules and/or powders (for example At2o3) with a particle size of m1 are suitable. The filler proportion in the plastic material may be up to 90%.

The injection molding method is particularly suitable for producing blocks of the plastic fastener proposed in the present invention.

A particular advantage of the invention is that the clamping blocks can be manufactured at significantly lower temperatures than are the clamping blocks made of zinc or zinc alloys. Plastics of the type usable in the invention are generally particularly processable in a temperature range around 200° C., which means that plastic fasteners keep the manufacturing costs of the blocks at a low limit. Furthermore, the clamping blocks made of plastic proposed in the present invention can be produced at significantly lower costs. At the same time, however, the clamping block provides the necessary stability for accurate and dimensional machining of the workpiece. Owing to the low processing temperature and adjustable curing time, a homogeneous injection of the plastic material into the mold is possible, at the same time avoiding air penetration leading to porosity of the formed body. can. The high filler content of the clamping block material results in strength values comparable to those from zinc die-casting, so that high-precision holding machining of clamped workpieces in the grinding machine is possible even under high grinding pressures. Furthermore, the material proposed for making the clamping block according to the invention is brittle at low temperatures, so that after machining the workpiece the clamping unit can be destroyed by cooling the unit to a low temperature. , this means that clamping from the machined workpiece results in a residue-free peeling of the block. Since a target breaking point is no longer required for this purpose, the clamping allows the blocks to be produced in larger quantities and the stability is therefore additionally increased.

The exemplary drawings show a typical clamping unit consisting of a turbine blade as the workpiece and a clamping block made of plastic.

The shown clamping unit 1 consists of a workpiece in the form of a turbine blade blank 2 and a clamping block 3 .

According to the invention, the clamping block 3 is made of plastic with a high filler (7) content and is manufactured by injection molding. The clamping block 3 advantageously consists of a cold-hardening multicomponent plastic containing up to 90% filler content. This tightening applies to plastics for manufacturing the block 3, such as styrene, epoxy resins, esters and acrylates. Fillers include primarily sand (5i02), ceramic granules or powders (eg At203), which have a particle size of up to 3.5 mm. If the tightening significantly increases the requirements for block 30 dimensional retention, the particle size of the filler should be selected to be small.

The shape of the block, which tightens the blades of the turbine blade 2 without any play due to material contraction during cooling, creates a defined stop surface for positioning the workpiece in the machine and ensures accurate machining of the turbine blank 2. The measurement points are selected to have the defined measuring points required for the purpose.

As shown in the drawings, the illustrated clamping blocks 3 do not have distinct breakage target locations. (8) Nevertheless, it can be removed from the finished turbine blade without imposing any mechanical or harmful thermal loads on the turbine blade. After the unit 1 has been processed into the workpiece, clamping can be carried out by exposing it to a cryogenic cooling bath which cools the block material below the embrittling temperature. Below the embrittling temperature of the plastic material, it separates from the turbine blade by light mechanical action. In this case, the tightening does not leave any residue of the block material attached to the blade surface. The low embrittlement temperature of the plastic material is achieved. For this purpose, a container with liquid nitrogen, for example, can be used as a cold bath, the temperature of which is in any case below the weakening temperature of the plastic material used.

The strength of blocks according to the invention made of filled plastic with a high filler content is comparable to the strength pj of blocks made of zinc or zinc alloys. Even under high polishing pressures, such as those that occur during assembly of turbine blades in production polishing, there is no need to fear deformation of the block with a clamp made of filled plastic, which would have an adverse effect on the dimensions of the finished turbine blade. .

In order to enable a permissible immovable positioning of the clamping block in the machine, the clamping block has positioning grooves 6 and 6' on its support surface 4, which correspond to the corresponding positions on the machine bed. Cooperative with positioning strips (not shown). Positioning g
6 and 6' extend perpendicularly to each other and the tightening fixes the unit 1 in a defined position on the table in cooperation with the aforementioned positioning strip, so that this form-locking positioning ensures a high precision of the workpiece. processing is possible even under high polishing pressure. Furthermore, positioning means are provided on the upper surface of the block 3 to ensure a positive shape-integrity positioning of the tightening unit in cooperation with an auxiliary member (not shown) acting from above. Good too. Such positioning means are
In the drawing, in the form of positioning strips 8 and 8' (11) are shown in dashed lines. The dimensions of the positioning means are shown unduly enlarged in the drawing for particular clarity.

[Brief explanation of the drawing]

The south side is a perspective view of a typical clamping unit consisting of a clamping block according to the invention and a turbine blade as a workpiece. 1... Unit with m 2... Turbine blade material 3
...Tighten with block 4...Support surface 6,6'...
・Positioning groove γ...Top surface of block 8, 8'...
・Upper positioning strip (12)

Claims (1)

[Claims] 1. The clamp for holding the workpiece on the machine tool during machining is a block, characterized in that the block (3) is made of filled plastic. The clamp that holds the workpiece to the machine tool is the block. 2. The fastening block according to claim 1, wherein the fastening block is made of a cold-hardening multi-component plastic. 6. A fastening block according to claim 1 or 2, consisting of styrene with a high filler content. 4. The clamping block according to claim 1 or 2, which is made of an epoxy resin with a high filler content. 5. A fastening block according to claim 1 or 2, consisting of an ester with a high filler content. 6. A fastening block according to claim 1 or 2 consisting of acrylate with a high filler content. Z. Clamping block according to any one of claims 1 to 6, characterized in that the filler is sand and/or ceramic granules and/or powder with a grain size of up to 3.5 mm. 8. A fastening block according to claim 7 characterized by up to 90% filler. 9. The tightening block according to any one of claims 1 to 8, manufactured by an injection molding method.