RU2778925C1 - Plastic pallet fitting method - Google Patents

Abstract

FIELD: material processing.

SUBSTANCE: invention relates to the processing of plastic products and can be used to restore the shape of plastic pallets used in the electrochemical processing of parts for various purposes, in particular to the method for fitting plastic pallets. The method includes placing the product to be fitted between the surfaces of technological parts, two-stage compression in a coupling device with threaded elements, heating and cooling. Moreover, the product is installed on the fitting plate through levelers of equal thickness, the product is heated by heating the levelers in contact with it to a temperature of plus 55°C to plus 60°C. At the same time, the product is fitted by alternating localized thermomechanical effects on its zones with the greatest deformation according to the following algorithm: touching the product with the beam of the coupling device in the zone of the greatest deformation, heating the levelers, creating a clamping force with the beam by tightening the threaded elements of the coupling device. Further, reheating of the levelers is carried out, creating a clamping force with a beam by tightening the threaded elements of the coupling device with a torque equal to the tightening torque at the first loading or exceeding it by no more than 10%, holding the product in a compressed state for at least 120 minutes and removing the compressive load, dismantling the product.

EFFECT: expanding the range of sizes of products to be fitted by using a beam of a coupling device of the desired length and simplifying the fitting method by eliminating the need for holding the product in the coupling device at a given temperature.

3 cl, 1 dwg

Description

The invention relates to the processing of plastic products and can be used to restore the shape of plastic pallets used in the electrochemical processing of parts for various purposes.

In various branches of mechanical engineering, including machine tool building, plastics are widely used, in particular, caprolon, from which not only finishing parts are made, but also body parts of technological installations, for example, pallets, plates, etc. This also applies to equipment for electrochemical processing, where the use of plastics is due to their resistance to electrochemical corrosion.

In operation, plastic parts often lose their original shape, which is associated with the presence of residual stresses after machining during manufacture, as well as with the influence of various operational factors, in particular, mechanical and thermal loads. The loss of the original shape can be the cause of a partial or complete violation of the function of the part and the product as a whole. As a rule, it becomes necessary to restore the original shape of the parts, that is, to edit them.

A known method of repair, in which the curvature of parts is eliminated by cold editing with the help of clamps and special devices. The straightening of dented surfaces is carried out with a punch. In the process of punching, alignment is achieved by knocking out the concave part of the part until the correct shape is obtained (Shadrichev V.A. Fundamentals of automotive technology and car repair. Textbook. - L .: Mashinostroenie (Leningr. department), 1976. - 560 pp. 373).

It is known that it is not recommended to hit parts made of caprolon with a hammer, sledgehammer, etc. (Processing of caprolon. [Electronic resource]. URL: http://www.kaprolon-alvis.ru/obrabotka_kaprolona.html (date of publication: 04/22/2012)).

The disadvantages of the known solutions include the impossibility of using it to restore the shape of products made from caprolon.

The closest in terms of essential features - the prototype of the claimed invention - is a method of thermal straightening of parts made of sheet metal and a device for its implementation, including placing the product to be straightened between the surfaces of technological parts having a given shape, two compression cycles in a clamping device with threaded elements, heating and cooling (A.C. SU 1433037, publ. 20.12.2005. Bull. No. 35). According to a well-known solution, as technological parts, in particular, a package of straightening plates is used, between which the straightened product is placed. The straightened product is sheets of thin-sheet rolled products. A package of straightening plates with rolled sheets located between the plates is installed between the base plates. The clamping device is made in the form of a cylindrical cup, a threaded cap with a central hole and a faceted turnkey head and a plunger located in the central hole. At the same time, straightening plates and base plates are located inside the glass between its bottom and a threaded cover with a plunger. The known solution provides for holding at a given temperature, subsequent cooling and two cycles of compression of the straightened product: before heating and after cooling.

The disadvantages of the known solution include the fact that its use is limited by the dimensions of the straightened products: with an increase in the dimensions in terms of sheet metal, an increase in the inner diameter of the cylindrical cup, the diameter of the plunger, and the thread in the cover is required. In addition, exposure at a given temperature after heating involves the creation of isothermal conditions, that is, the exclusion of heat removal from the straightened product and a technological device for implementing the known method. This complicates and increases the cost of the device.

The technical objective of the present invention is to create a method for straightening plastic pallets (hereinafter referred to as products) that does not require thermal insulation of the product and is not limited by the size of the product.

The set technical problem is solved through the combined application of the following solutions:

- installation of the product on the correct plate through straightening plates of equal thickness;

- editing the product by alternately localized thermomechanical impact on its individual zones;

- the implementation of thermal effects on the product by heating to a predetermined temperature of the straightening plates in contact with it;

- use as a clamping device for the implementation of the mechanical action of the beam in contact with the product in the zone of its greatest deformation through a straightening plate made of a metal material;

- performing thermomechanical action according to the proposed algorithm.

The method of straightening plastic pallets (hereinafter - products) proposed as the present invention is illustrated by a drawing and includes the following technological transitions:

a) installation of the product 4 on the correct plate 1 with the concave side to the correct plate 1, through straightening plates 3 of equal thickness, placed in the places where the product 4 touches the surface of the correct plate 1;

b) touching the product 4 by the beam 2 of the tie device in the zone of greatest deformation,

c) heating the straightening plates 3 to a temperature from plus 55°C to plus 60°C;

d) creating a pressing force by the beam 2 by tightening the threaded elements 22 and 21 of the clamping device with a given moment;

e) reheating the straightening plates 3 to a temperature of plus 55°C to plus 60°C;

f) creating a pressing force by beam 2 by tightening the threaded elements of the tie-down device with a torque equal to the tightening torque at the first loading or exceeding it by no more than 10%;

g) exposure of the product in a compressed state for at least 120 minutes;

e) removal of the compressive load, dismantling of the product.

Heating straightening plates 3 can be carried out by any method known from the prior art, for example, industrial hair dryer. The heating of the straightening plate 3 instead of the direct heating of the product 4 makes it possible to dispense with the exact positioning of the heating element (not shown in the drawing), which would be necessary with direct heating of the product 4 in order to avoid melting the latter. The temperature range proposed by this solution allows, on the one hand, to minimize the risk of cracking of the product 4 under mechanical loading, and, on the other hand, allows you to do without the use of control and measuring equipment, since it is the limit that a person’s hand can tolerate without protective fixtures. When performing heating, it is enough to touch the surface of the straightening plates 3 to control the temperature. If the operator feels that he cannot bear the touch for more than one or two seconds, the temperature has reached the desired value.

In the drawing, as an example explaining the implementation of the proposed method for straightening plastic pallets, but not excluding other options for completing the tie-down device, a tie-down device is shown, including, in addition to the beam 2, studs 21 and nuts 22, pressing the beam 2 in the direction of the correct plate.

The magnitude of the pressing force is determined by the applicant empirically for products subjected to editing in the conditions of its own production.

For threaded elements of the tightening device with Ml6x1.5 thread, the value of the tightening torque at the first loading is 5 kgf⋅m.

According to the applicant's experience, holding after the second loading is necessary not only for the straightening plates 3 to cool, but also for partial relaxation of internal stresses in the product 4.

The following are not subject to protection in this application:

- brand of material, geometric shape and thickness of straightening plates 3;

- method of heating straightening plates 3.

An example of the proposed method for straightening plastic pallets.

We carried out the editing of the pallet used in installations for the electrochemical processing of sprayer bodies of our own production. Pallet material: Block polyamide PA-6 (kaprolon) TU 6-05-988-87. The pallet is a box-shaped structure with dimensions of 618×420 mm and a height of 75 mm. The thickness of the bottom is 12 mm, the thickness of the side walls is 20 mm. In operation, the pallet is constantly washed with a brine solution with an admixture of electrolysis products, which has a temperature of about plus 40°C. The allowable deflection of the bottom is 1 mm. It has been established that after (6-7) months of operation, the pallet has an accumulated deformation (warping) with a bottom deflection of up to 5 mm.

The maximum deflection of the bottom of the pallet, on which the proposed straightening method was carried out, was 4.5 mm.

The number of straightening places (zones) on the pallet was 4: straightening was carried out for the bottom area along each side wall.

For straightening, a tightening device was used, shown in the drawing and including a beam 2 made of a hexagonal rod, and two studs 21 with an M16 thread with the corresponding nuts 22.

Leveling plates 3 were made of corrugated steel sheet 5 mm thick.

The straightening plates 3 were heated with an industrial hair dryer Interskol FE-2000.

The pressing force was provided by tightening the nuts 22 with a torque wrench. The tightening torque at the first loading was 5 kgf⋅m, at the second loading - from 5.4 kgf⋅m to 5.5 kgf⋅m.

The duration of the time intervals between successive transitions "c)" (first heating), "d)" (first loading), "e)" (second heating) and "e" (second loading) did not exceed 1 min.

The exposure after the second loading was from 115 min. up to 119 min. for each edit zone.

The largest bottom deflection after straightening did not exceed 0.5 mm. The total duration of the dressing operation was 470 min.

The use of the proposed method for straightening plastic pallets makes it possible to perform maintenance and repair of plastic pallets using a universal bench tool, without involving complex instrumentation, heat chambers and specialized equipment.

The technical result of the implementation of the proposed method for straightening plastic pallets is to expand the range of sizes of products to be straightened by using a tie beam of the desired length and simplify the straightening method by eliminating the need to hold the product in the tie device at a given temperature.

Claims (13)

1. A method for straightening plastic pallets, which includes placing the product to be straightened between the surfaces of technological parts, two-stage compression in a tightening device with threaded elements, heating and cooling, characterized in that - the product is installed on the correct plate through straightening plates of equal thickness; - heating of the product is carried out by heating the straightening plates in contact with it to a temperature from plus 55°C to plus 60°C; - dressing of the product is performed by alternately localized thermomechanical impact on its zones with the greatest deformation according to the following algorithm: - touching the product with the beam of the tensioner in the zone of greatest deformation, - heating of straightening plates, - creating a pressing force by the beam by tightening the threaded elements of the tie device, - reheating of straightening plates, - creation of a pressing force by the beam by tightening the threaded elements of the tie-down device with a torque equal to the tightening torque at the first loading or exceeding it by no more than 10%, - exposure of the product in a compressed state for at least 120 minutes, - removal of the compressive load, dismantling of the product. 2. The method according to p. 1, characterized in that the heating of the straightening plates is carried out with an industrial hair dryer. 3. The method according to the preceding claims, characterized in that when threaded elements with M16 × 1.5 thread are used in the tightening device, the tightening torque at the first loading is 5 kgf⋅m.

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