Drying procedure

Abstract

Method for welding hygroscopic plastic parts, preferably pipe components, using a butt welding machine, wherein the two plastic parts are clamped and fixed in a coaxial position to each other by means of a clamping device, wherein the opposite faces of the plastic parts are flattened by means of an interposed planer, and the ends of the plastic parts are melted by means of an interposed heating mirror, wherein the heating mirror is disposed at a distance from the faces of the ends of the plastic parts to achieve the heat required for melting, wherein after melting, the ends of the plastic parts are joined, wherein the ends of the plastic parts are dried during fixation in the butt welding machine, wherein the drying is carried out by means of the heating mirror disposed between the ends of the plastic parts.

Description

[0001] Method for welding hygroscopic plastic parts, preferably pipe components, using a butt welding machine, wherein the two plastic parts are clamped and fixed in a coaxial position to each other by means of a clamping device, wherein the opposing end faces of the plastic parts are planed flat by means of an intermediate planer and the plastic part ends are melted by means of an intermediate heating mirror, wherein the heating mirror is arranged at a distance from the end faces of the plastic part ends in order to achieve the required heat for melting, wherein after melting, the plastic part ends are joined together.

[0002] Such methods for welding plastic parts are known from the prior art; however, thermoplastic materials that are not hygroscopic are used for this purpose.

[0003] US 5 241 157 A, JP H08 156102 A and WO 2016 / 102291 A1 disclose conventional welding processes in which the pipes do not need to be dried beforehand.

[0004] EP 0 899 083 discloses a method according to the invention; however, this method would not be suitable for hygroscopic plastics unless the plastic parts were dried beforehand. It is known from the prior art that such drying is carried out as a separate, preliminary additional step, usually in a drying oven, to ensure that the plastic contains little or no moisture, as this would cause moisture bubbles during welding. This requires a correspondingly high expenditure of time and energy to weld hygroscopic plastic parts together.

[0005] The object of the invention is to propose a method that makes it possible to weld hygroscopic plastic parts together without having to dry the plastic parts separately beforehand in order to dehumidify the plastic part.

[0006] This problem is solved according to the invention by drying the plastic part ends during fixation on the butt weld, wherein the drying is carried out by means of the heating mirror arranged between the plastic part ends.

[0007] In the inventive method for welding hygroscopic plastic parts, preferably pipe components, using a butt welding machine, the two plastic parts are clamped and fixed in a coaxial position relative to each other by means of a clamping device. The fixed plastic parts can be axially displaced by means of the clamping device in order to move to the different positions during the welding process. Preferably, a drive and a control system are provided for this purpose, which carry out the welding process according to the specified data. Fittings and / or pipes are preferably welded to each other as pipe components. After clamping or fixing the plastic parts, preferably with the clamping devices of the butt welding machine, the opposing end faces of the plastic parts are planed flat using a planer that can be inserted between them.Preferably, the plastic part ends are planed to a specific dimension so that the end faces define a zero point.

[0008] The planed plastic parts are then melted using a heating mirror that can be placed between them instead of the planer.

[0009] The heating mirror is positioned at a distance from the end faces of the plastic parts to achieve the necessary heat for melting. The welding process according to the invention is preferably carried out using an infrared heating mirror and is therefore contactless, meaning that the heat is transferred to the plastic parts by thermal radiation and convection.

[0010] Following the melting process, the plastic parts are joined together after the heating mirror in between has been removed.

[0011] To achieve a weld seam that meets the requirements, it is essential to ensure that the plastic part contains no or only minimal moisture. In the inventive method, the moisture is extracted from the hygroscopic plastic part so that it contains no moisture or at least only a small amount sufficient to achieve a weld seam that meets the requirements. This is accomplished by drying the ends of the plastic part while they are being fixed to the butt welding machine. This drying is achieved using a heating mirror positioned between the ends of the plastic part. The heat radiation from the heating mirror and the prevailing convection ensure that the welding zones of the plastic part ends are dried accordingly. By drying only the welding zones and not the entire plastic part, a significant amount of energy can be saved.

[0012] Preferably, the plastic parts are dried after planing. After planing, the plastic parts are brought to a precise dimension, meaning the exact position of the end faces is known and the distance between the end faces and the heating element can be precisely defined, thus allowing the heat transferred for drying to be regulated by the distance. Furthermore, pre-planing avoids wasting energy drying material that will be planed off later.

[0013] A preferred embodiment has proven effective when, for drying, the end faces of the plastic parts are positioned at a greater distance from the heating element than during melting. This results in a lower prevailing temperature at the end of the plastic parts compared to melting, without requiring adjustment of the temperature at the heating element.

[0014] It is advantageous for drying to occur before the plastic parts are melted. To prevent moisture bubbles from forming during the melting process, it is beneficial to remove the moisture from the plastic parts beforehand through drying.

[0015] Preferably, the drying process is dynamic, with the distance between the end faces of the plastic parts and the heating element being controlled based on the temperature at the end of the plastic part or in the welding zone. This ensures rapid temperature adjustment at the end of the plastic part and guarantees optimal drying conditions. Preferably, the drying time is also controlled accordingly. It has proven advantageous to have the data for the specific plastic parts stored in the control system, allowing the process to be carried out autonomously upon detection of the plastic parts. This means that the heating element preferably heats up to a predefined temperature, and the distances and dwell times at the respective positions of the plastic parts are adjusted according to the process steps.

[0016] It has proven advantageous that the ends of the plastic parts do not melt during drying. This prevents the formation of moisture bubbles, which would otherwise result in melting without prior drying. Consequently, the temperatures at the ends of the plastic parts are lower during drying than during melting. Preferably, the drying temperatures at the ends of the plastic parts are below the actual melting temperatures of the respective plastic.

[0017] It is advantageous to perform a zero-point check of the plastic part ends after planing to determine the spacing. This ensures that the position of the end faces is accurately determined and the spacing can thus be set precisely.

[0018] It has proven advantageous to keep the temperature of the heating element constant during drying. The drying temperature is regulated by the distance between the end face of the plastic parts and the heating element. Preferably, the prevailing temperatures at the weld zone of the plastic part are monitored by a sensor and adjusted accordingly by changing the distance.

[0019] Preferably, the temperature of the heating mirror is kept constant throughout the entire welding process. Since temperature changes at the heating mirror are slow to respond, other parameters such as distance and time are preferably adjusted to optimize the welding process.

[0020] It has also proven advantageous to determine whether sufficient moisture has been removed from the plastic parts by measuring their weight after drying, or by measuring their weight before and after drying and comparing these two values. Alternatively, a moisture sensor can be used to check the moisture content of the weld zone.

[0021] All design options can be freely combined with each other.

[0022] An embodiment of the invention is described with reference to the figure, although the invention is not limited to this embodiment. The figure shows: Fig. 1 a schematic representation of the process of the welding process according to the invention.

[0023] The in Fig. 1The drawing shows a schematic representation of the inventive method for welding hygroscopic plastic parts 1, preferably pipe components. Pipe components include not only pipes but also fittings and other components that can be welded together on a butt welding machine. Fig. 1The different steps of the process after planing are shown. Figure A schematically illustrates the arrangement of the plastic parts 1 relative to the heating mirror 2 during the drying step. It is clearly visible that the ends of the plastic parts 1 have a distance 3 to the heating mirror that is significantly greater than during the subsequent melting step B. Figure B shows that the distance 3 has been reduced to generate a higher temperature at the ends of the plastic parts, i.e., in the weld zone, by moving the ends of the plastic parts 1 closer to the heating mirror 2. Since the drying process is dynamic, the temperature in the weld zone is regulated by changing the distance 3 during the drying phase to achieve optimal drying and prevent melting.Figure C shows the position in which the melted plastic part ends were joined together after removal of the heating mirror, forming a weld seam 4. Reference symbol list

[0024] 1 Plastic parts / Plastic part ends 2 Heating mirror 3 Spacing 4 Weld seam

Claims

1. Method for welding hygroscopic plastics parts (1), preferably pipeline components, by means of a butt-welding machine, wherein the two plastics parts (1) are clamped and fixed in a coaxial position in relation to one another by means of a clamping device, wherein the mutually opposite end faces of the plastics parts (1) are planed flat by means of a planer which can be brought in between them, and the ends of the plastics parts (1) are melted by means of a heating mirror (2) that can be brought between them, wherein the heating mirror (2) is disposed at a spacing (3) from the end faces of the ends of the plastics parts (1), in order to achieve the required heat for the melting operation, wherein the ends of the plastics parts (1) are joined together after the melting operation, wherein the ends of the plastics parts (1) are dried while the plastics parts are being fixed on the butt-welding machine, wherein the drying is performed by the heating mirror (2) disposed between the ends of the plastics parts (1), characterized in that the end faces of the plastics parts (1) are disposed at a greater spacing (3) from the heating mirror (2) for the drying than they are during the melting operation.

2. Method according to Claim 1, characterized in that the ends of the plastics parts (1) are dried after the planing operation.

3. Method according to either of Claims 1 and 2, characterized in that the ends of the plastics parts are dried before the melting operation.

4. Method according to one of Claims 1 to 3, characterized in that the drying is carried out dynamically and the spacing between the end faces of the plastics parts (1) and the heating mirror (2) is regulated depending on the temperature prevailing at the end of the plastics parts (1), or the welding zone.

5. Method according to one of Claims 1 to 4, characterized in that the ends of the plastics parts (1) are not melted during the drying.

6. Method according to either of Claims 1 and 5, characterized in that, to determine the spacing (3) after the planing operation, a zero-point check of the ends of the plastics parts (1) is performed.

7. Method according to either of Claims 1 and 6, characterized in that the temperature of the heating mirror (2) is kept constant during the drying.

8. Method according to either of Claims 1 and 7, characterized in that the temperature of the heating mirror (2) is kept constant throughout the welding operation.

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