RU2717804C1 - High-frequency processing method of structurally complex articles from polymer materials - Google Patents

Abstract

FIELD: machine building; physics.

SUBSTANCE: invention relates to a method for high-frequency processing of structural-complex parts, which is, for example, a polyamide separator of a roller bearing. Proposed method comprises embracing the part by high-potential and earthed electrodes of operating capacitor connected to high-frequency generator and applying pressure thereto. Part is covered by electrodes on top, bottom and inner side surfaces of partitions, thus creating a spatial circuit of 2 × n working capacitors. In order to achieve uniform heating of both structural-complex elements and conical elements of the products design, gaps are also provided, which create air capacitors in places where high-frequency action is required to be changed. Taking into account dielectric properties of air (ε = 1.000570), it can be stated that exposure to polymer (polyamide ε = 3.0–3.6) in places with an air gap (depending on gap size) reduces high-frequency exposure. All capacitors are simultaneously connected to generator, thus forming potential difference between adjacent electrodes and between upper high-potential plate and electrodes connected through lower contact group to lower grounded plate, and lower grounded plate and electrodes connected through upper contact group to upper high-potential plate. Heating is performed to polyamide recrystallization start temperature. Then, generator is switched off on turning the part about its axis by one electrode to heat unprocessed surfaces.

EFFECT: method allows uniform heating to restore strength characteristics of all elements of design of bearing separator made from polyamide.

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Description

The proposed method relates to the processing of parts from plastics, in particular from polyamide.

80% of emergency stops of the rolling stock of Russian Railways OJSC are connected with the failure of axle boxes, one of the main elements of which are bearings with polyamide cages.

The problem with separators made of polyamide is their hydrophilicity. Water absorption reaches several percent (in some cases up to 8%) and significantly affects the strength and toughness. The deformation-strength characteristics of polyamides are restored after drying of the samples (see the book “Technical properties of polymeric materials”: Uch.-sp., Village / V.K. Kryzhanovsky, V.V. Burlov, A.D. Panimatchenko, Yu. V. Kryzhanovskaya. - St. Petersburg, publishing house "Profession", 2003, pp. 43-44, 110).

Therefore, the task is to create an effective technology for drying polyamides, using high-frequency processing, ensuring the restoration of the necessary mechanical properties of critical structural products, including all parts of bearing cages made of polyamide.

A known method of drying is presented in patent RU No. 2338135, IPC F26B 7/00 (claimed on November 7, 2008, publication date: November 10, 2008).

This patent describes a method for drying sodium iodide.

The essence of the method includes: preliminary dehydration of the feedstock to a mass fraction of moisture of 5-7%, cooling to a temperature of 60-65 ° C and final drying with the supply of electromagnetic field energy and a medium pressure of 25-30 mm Hg The final vacuum drying is carried out in an atmosphere of carbon tetrachloride vapor.

It is possible to develop a similar method for removing high humidity from polyamide separators in vacuum when applying electromagnetic field energy, but the cost of the installation will be very high, and the high costs of operation and maintenance will make it uncompetitive.

It is also known "Device for dielectric heating of long material" (patent RU No. 2073315 MAK Н05В 6/46, filed March 11, 1993, publication date: February 10, 1997).

The essence of the device is that for dielectric heating of a long material, it contains two identical long flat electrodes between which there is a heated material, two output terminals of a high-frequency generator, located opposite the middle of the length of the electrodes symmetrically relative to them, and two identical groups of conductors connecting the output terminals of the generator , one of which is connected to a common bus, with the corresponding long electrodes. They are connected in an identical way symmetrically with respect to the ends of the electrodes and at equal distances along the length of the electrodes, while the distance from the ends of the electrodes to the nearest ends of the conductors is half the distance between adjacent ends of the conductors. The conductors are made in the form of a symmetrical, with respect to the common bus, n-stage m-channel branching system with identical parameters of the conductors in each stage. Two conductors of the first branching stage are arranged symmetrically relative to an additional conductor shielding them from the common bus, both ends of which and the middle of one conductor of the first branching stage are connected to the common bus. An inductive element is connected between the middle of the other conductor of the first stage connected to the output terminal of the generator that is not connected to the common bus and the middle of the additional conductor.

It is practically impossible to use this device for drying separators made of polyamide due to the bulkiness of the installation and the complexity of its manufacture. During operation, this installation requires a lot of time for preparatory work, adjustment of equipment and devices.

Closest to the proposed invention is the "Method of high-frequency processing of parts made of polyamide and a device for its implementation" (patent RU No. 2497673 IPC В29С 65/04, F26B 7/00), F26B 19/00, Н05В 6/46 (2006.01), claimed : 2011142701/05, 10/21/2011, publication date 11/10/2013 Bull. No. 31.

The essence of this method

This method solves the problem of high-frequency processing of a roller bearing cage made of polyamide by covering parts with high-potential and grounded electrodes of a working capacitor connected to a high-frequency generator, while applying pressure, while covering the workpiece with electrodes is carried out on the upper, lower and inner side surfaces of the partitions, creating spatial scheme of 2 × n working capacitors (where, n is the number of electrodes) simultaneously connected to a high astotnomu generator, thereby forming a potential difference between adjacent electrodes and between the top plate and the high-potential electrodes connected through the lower contact group to the bottom plate and the grounded plate and the lower grounded electrode, connected via an upper contact group of the upper high potential plate. Heating is carried out to the temperature at which polyamide recrystallization begins, which is determined by the occurrence of a step in the anode current readings on the ammeter mounted on a high-frequency generator, after which the high-frequency generator is turned off. Since the parts of the upper and lower rims located under the contacts of the upper and lower contact groups are not heated, the treatment cycle is repeated by turning the part, for example, a separator, around the axis by one electrode. Press pressure is carried out by connecting contact groups with electrodes and high-potential and grounded plates.

This method can be used to restore parts, for example, separators made of polyamide, but only of an extremely simple design. Over the past decade, the design of parts, such as separators, have undergone changes, for example, different thickness (conical) elements (partitions) have been created in the design of separators. In this regard, the proposed method does not allow uniform heating of such structural elements of products made of polyamide materials.

The task of the invention is to uniformly heat in order to restore the strength characteristics of all product elements, for example, bearing cages made of polyamide.

The objective is achieved in that a method of high-frequency processing of structurally complex products, for example, a polyamide cage of a roller bearing, involves placing the workpiece between high-potential and grounded electrodes of a working capacitor connected to a high-frequency generator, while applying pressure. The workpiece is covered by electrodes on the upper, lower and inner side surfaces of the partitions, creating a spatial 2 × n working capacitor circuit, where n is the number of electrodes, they are connected to a high-frequency generator, thereby forming a potential difference between adjacent electrodes and between the upper high-potential plate and electrodes connected through the lower contact group to the lower grounded plate, and the lower grounded plate and electrodes. Thus created, a spatial, from several pairs, circuit of working capacitors is connected through the upper contact group to the upper high-potential plate, heating is carried out to the temperature of polyamide recrystallization, and then the high-frequency generator is turned off. In case of asymmetry of the product, the part is turned around the axis by one electrode and the raw surfaces are heated. Uniform heating of different thickness (conical) product elements connected to a high-frequency generator, for example, partitions of a polyamide roller bearing separator, is achieved by creating air gaps between the products and the electrodes. The gaps are selected in such a way that, in all areas of different-thickness (conical) product elements, taking into account the corresponding geometric parameters of the different-thickness (conical) product elements, they form (on all machined surfaces) working capacitors of equal capacity. The invention is illustrated by drawings.

The figure 1 presents a diagram of a high-frequency processing of parts made of polyamide

The figure 2 presents a diagram of a high-frequency processing of parts made of polyamide (type A). (Bottom ground plate not shown).

The figure 3 presents a diagram of the high-frequency processing of parts made of polyamide (with the upper high-potential plate lowered)

The figure 4 presents a diagram of the high-frequency processing of parts made of polyamide, in the presence of air gaps (when the upper high-potential plate is lowered)

In FIG. 1, FIG. Figure 2 shows a diagram of the high-frequency processing of parts made of polyamide, which contains a movable upper high-potential plate (1) and a lower grounded plate (2); they are mounted on: a movable upper high-potential plate - an upper contact group (3), on a lower grounded plate - lower contact group (4).

The separator (5) consists of partitions (6), the upper rim (7) and the lower rim (8). Electrodes (9) are inserted into the separator (5). For uniform heating of the separator's structural elements of different thicknesses, air gaps (11) are provided between the electrodes (9) and the partitions (6). The press (10) is in a raised state.

In FIG. 3, FIG. Figure 4 shows a diagram of the high-frequency processing of parts and a method of forming working capacitors and the potential difference on them, formed as a result of a technological device for high-frequency processing of parts assembled and connected to a high-frequency generator (press (10) is in the lowered, operational state).

The method of high-frequency processing of structurally complex products from polymeric materials is as follows.

The working capacitor C _v and the potential difference on it U _v - are formed between the upper movable high-potential plate (1) and the lower grounded plate (2).

The working capacitors of the partitions (6) C _{per1 ... n} , (Fig. 3), and in places of different thicknesses (Fig. 4, view B increased) C _{per1 ... n} = C _{b1 ... n} + C _{per1 ... n} + C _{b21 ... n} , equal in capacity due to the selected gaps where they are provided, or the same thickness of the material. Taking into account the dielectric properties of air (ε = 1.000570), it can be argued that exposure to the polymer (polyamide ε = 3.0-3.6) in places with an air gap (depending on the size of the gap) reduces the high-frequency effect. For example, in different thickness (conical) elements, the gaps were proportionally increased in those places where the thickness of the separator design is proportionally reduced. Thus, when exposed to product areas where increased gaps are provided, the intensity of high-frequency energy is reduced, and vice versa, where the gaps are reduced, high-frequency exposure and heating are more intense. Thus, heating in different thickness places of the whole element of the product occurs evenly. Thus, the potential differences of the working capacitors are also equal on all the different thickness (conical) sections U _{per1 ... n} formed between the electrodes (9) connected to the upper high-potential plate (1) and the electrodes (9) connected to the lower grounded plate (2 )

The working capacitors of the upper rim (7) C _{vol1 ... n} and the potential difference on them, U _{vol1 ... n} , are formed between the upper high-potential plate (1) and the electrodes (9) connected to the lower grounded plate (2). The working capacitors of the lower (8) rim are formed between the lower grounded plate (2) and the electrodes (9) connected to the upper high-potential plate (1).

Thus, all working capacitors C _v , C _{vol1 ... n} and C _{per1 ... n are} equal in capacity due to the selected gaps where they are provided, or the same thickness of the material, are connected in parallel, which allows processing of all structural elements connected to the electrodes separator, in one cycle.

The processing of parts made of polyamide is as follows. Between the movable upper high-potential plate (1) and the lower grounded plate (2), the workpiece (for example, a polyamide cage (5), a roller bearing) with electrodes inserted in it (9) is installed on the lower contact group (4). Top set the upper contact group (3). The press (10) is lowered onto the assembled technological device and the generator is turned on. The processing mode is controlled by the anode current indicator of the ammeter installed on the high-frequency generator. The tight fit of the upper (3) and lower (4) contact groups to the electrodes (9) ensures the design of the contacts of the contact group (curvature radius R) and the pressure on the contact groups by the press (10), and uniform heating of different thickness (conical) elements of the separator design provided by the created air gaps (11).

After connecting the device to a high-frequency generator at the points of contact with the electrodes (9) on the product surfaces, potential differences U _{per1 ... n are formed} on the separator different thickness (conical) partitions (6), taking into account the provided air gaps and U _{ob1 ... n} on the separator rims (5 ) in capacitors C _{per1 ... n} and C _{about ... n} . The electric field in the capacitors, including air capacitors C _{b1 ... n} , leads to uniform heating of the structural elements of the partitions (6) and the upper (7) and lower (8) rims of the separator (5), respectively. To heat parts of the upper (7) and lower (8) rims located directly under the contacts of the upper (3) and lower (4) contact groups, it is necessary to repeat the processing process by turning the part (separator) around the axis by one electrode. After which the part is removed and goes to the assembly.

The high-frequency processing method provides the evaporation of moisture from parts, thereby increasing the dielectric constant of the material. Given that the dielectric constant of materials is proportional to humidity, heating continues until increased humidity is maintained. Due to the low thermal conductivity of the polyamide when heated to the temperature of the onset of recrystallization, the bulk of the material will not be removed from the crystalline or vitreous state.

A series of experiments was carried out on drying the polyamide on the installation UZP 2500 in accordance with the developed method.

Example:

Separators of model 2726 of JSC Stepnogorsk Bearing Plant (former GP3-16) were used, with an operating time of more than 50,000 km (dismantled during the overhaul period, during a full audit of axleboxes in the Passenger Car Depot of Irkutsk, Russian Railways Railways). Bearing cages material - Armamide PA SV 30-1ETM. The processing time varied from 50 to 200 sec, at a nominal value of the anode current of 0.6-0.7 A, controlled by an ammeter installed on a high-frequency generator, the fabricated electrodes made it possible to provide gaps in different thickness (conical) places of the partitions from 0, in places of the greatest thickness , up to 2.5 mm in place of the smallest thickness of the conical partition of the separator.

The results are presented in table. 1

From the above data it can be seen that the relative humidity at the initial rates of 5.5% after processing decreased to 0.9%, and the strength characteristics increased by 7.4%, which allows us to conclude the practical significance of this method.

Claims (1)

A method of high-frequency processing of products, for example, a polyamide cage of a roller bearing, comprising placing a workpiece between high-potential and grounded electrodes of a working capacitor connected to a high-frequency generator, while applying pressure, the workpiece being covered with electrodes carried out along the upper, lower, and inner side surfaces of the partitions, creating spatial scheme of 2 × n working capacitors, where n is the number of electrodes, they are connected to to a co-frequency generator, a potential difference is formed between adjacent electrodes and between the upper high-potential plate and electrodes connected through the lower contact group to the lower grounded plate, and the lower earthed plate and electrodes connected through the upper contact group to the upper high-potential plate, heating is carried out to the temperature of the onset of recrystallization polyamide, after which the high-frequency generator is turned off, the part is turned around the axis by one electrode and the untreated ones are heated overhnosti, characterized in that the heating elements of uniform articles such as conical baffles polyamide separator roller bearing is provided by creating air gaps between the products and the electrodes selected in such a way that all parts of the surface of articles of produce equal working capacity capacitors.

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