RU2557038C1 - Shear die for parts cutting from thick-wall rubber - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to machine building, particularly to production of assembly units and part made of thick rubber, over 20 mm, of various shape, and can be used in production of rocket engines. Shear die comprises plate with cutting element secured thereat composed of cutter unit, pusher to drive extractor for removal of cut parts and wastes. Note here that shear die is provided with extra lower side blade unit for cutting of parts from both sides arranged on mating side of upper blade unit. Two stiff thrust incorporated with said die guarantees the clearance which rules out contact between blade cutting edges to contact solely with rubber material. Blade sharpening angle is defined by claimed formula.

EFFECT: sharpening edges is decreased from 16÷18° to 6÷8°, ruled out breakage and blunting thereof, higher accuracy and quality of cut parts.

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Description

The invention relates to the field of engineering, where parts and assemblies of thick-walled rubber more than 20 mm of various profiles are used, and can be used, for example, in the manufacture of rocket engines.

Thick-walled rubber parts should have vertical shear walls and a profile with stringent geometry requirements. When the rubber thickness is more than 20 mm, the cutting of parts with a conventional knife stamp is accompanied by a wall tightening, as a result of which the cut surface is not perpendicular to the plane of the rubber sheet. In addition, the knife of the stamp at the end of the run abuts against a hard lining, which leads to blunting and chipping of the cutting edge of the knife (Zubtsov M.E. Sheet stamping, L .: Engineering, 1980, p.338).

In order to get away from wall tightening, in practice, the cutting of parts from thick rubber is carried out on machines for the mechanical processing of metals. This technology has serious drawbacks: low productivity and large waste material.

The technical result to which this invention is directed is the high purity of cut of the parts to be cut, a reduction in the sharpening angle of knives from 16 ÷ 18 ° to 6 ÷ 8 °, elimination of breakage and chipping of the edges of the cutting elements, production of parts from thick-walled rubber with vertical walls relative to the plane sheet providing high performance. Prior to the claimed technical solution for cutting non-metallic materials, it is recommended to take the value of the angle α 16 ÷ 18 ° (RTM 34-65 Stamps for cold sheet stamping. Calculations and design. M: Publishing house of standards, 1966, pp. 49-50).

This technical result is achieved due to the design of a knife stamp for cutting parts from thick-walled rubber. The knife stamp contains a stamp plate, a cutting element fixed in it, made in the form of a knife block, a pusher driving a puller to remove cut parts and waste. In this case, the knife stamp is additionally equipped with a lower knife block for cutting parts from two sides and is located on the counter side of the upper knife block. The presence of 2 rigid stops in the stamp guarantees a gap ensuring the exclusion of contact between the cutting edges of knives in contact only with the material being cut. The angle of sharpening of the knife is determined by the formula:

, где $$tg\alpha =\frac{b}{H}$$

where

b - knife thickness, mm;

H is the height of the sharpened part of the knife, mm;

, где $$H=\frac{S}{2}+X$$

where

S is the thickness of the rubber, mm;

X - allowance for knife regrind, mm.

The design of the knife stamp consists of 2 knife blocks - the upper 1 and lower 2, mounted respectively on the plates 3 and 4 with screws 5 and pins 6. The cutting edges of the blocks are centered by 2 guide pairs - columns 7 and bushings 8. Since cutting material is produced from 2 sides at the same time, the contact of the cutting edges should be excluded, which is ensured by the presence of 2 hard stops 9 in the knife stamp, which guarantee a gap between the edges of the knives of 1.5-0.2 mm. Removing the cut part and the waste is provided by pullers 10 and 11 and pushers 12 and 13.

The drawing shows a knife stamp for cutting parts from thick-walled rubber.

The stamp works as follows.

A knife stamp for cutting parts from thick-walled rubber works on a P-311 hydraulic press. In the open position of the press slider, the workpiece is placed on the cutting edges of the lower knife block. After the stroke of the press slide, with the upper knife block fixed on it, the part is cut from 2 sides simultaneously. The limitation of the stroke of the slider are hard stops 9 mounted on 2 columns 7.

After cutting the part and moving the slider up, the press traverse through the pushers 12 and the traverse of the knife stamp 14 by the puller 10 remove the part and move away from the upper knife block. Removing the part and the waste from the lower block is done by the press hydraulic cushion through the pushers 13 by the puller 11.

Example

We select a rubber plate 2F-1-MBS-S according to GOST 263-75.

1. The thickness of the rubber S = 30 mm;

The thickness of the knife is b = 2.5 mm. This value is taken constructively and depends on the thickness of the rubber S.

, где X - припуск на переточку ножа, мм, конструктивно принятый 3÷5 мм. Принимаем X=5 мм. $$H=\frac{S}{2}+X$$

, where X is the allowance for the knife regrind, mm, structurally adopted 3 ÷ 5 mm. We accept X = 5 mm.

; $$H=\frac{S}{2}+X=\frac{\mathrm{thirty}}{2}+5=\mathrm{twenty}mm$$

;

$$tg\alpha =\frac{b}{H}=\frac{2.5}{\mathrm{twenty}}=7^{\circ }10\text{'}\text{'}$$

2. Rubber thickness S = 40 mm;

Knife thickness b = 3.0 mm.

; $$H=\frac{S}{2}+X=\frac{40}{2}+5=25mm$$

;

$$tg\alpha =\frac{b}{H}=\frac{3.0}{25}=6^{\circ }\mathrm{fifty}\text{'}\text{'}$$

3. Rubber thickness S = 50 mm;

Knife thickness b = 3.4 mm.

; $$H=\frac{S}{2}+X=\frac{\mathrm{fifty}}{2}+5=\mathrm{thirty}mm$$

;

$$tg\alpha =\frac{b}{H}=\frac{3.4}{\mathrm{thirty}}=6^{\circ }27\text{'}\text{'}$$

Thus, the proposed design of a knife stamp for cutting parts from thick-walled rubber is such that the knives are in contact only with the material being cut, which allows to reduce the sharpening angle of knives from 16 ÷ 18 ° to 6 ÷ 8 °, eliminates breakage and chipping of the edges of the cutting elements and their intense blunting, and also improves the accuracy and quality of cut parts.

Claims (1)

A knife stamp for cutting parts from thick-walled rubber, comprising a die plate, a cutting element fixed therein, made in the form of an upper knife block, a pusher driving a puller for removing cut parts and waste, characterized in that it is further provided with a lower knife block, located on the reciprocal side of the upper knife block for cutting parts from two sides, and two rigid stops to form a gap that ensures that the cutting edges of the knife blocks and the con their beat with the material being cut, and the angle of sharpening of the cutting edge of the knife blocks is determined by the formula:

where
b is the thickness of the knife block, mm;
H is the height of the ground part of the knife block, mm;

where
S is the thickness of the rubber, mm;
X - allowance for regrinding of the knife block, mm.