Process for cooling workpieces

Abstract

A method for cooling workpieces (5), wherein a workpiece (5) is subjected to a fluid flow by means of at least one nozzle (411, 412), the fluid having a temperature lower than the surface temperature of the workpiece (5), wherein a data line (44) is connected to at least one surface contact temperature sensor (43) arranged on the workpiece (5), and the surface temperature is monitored by means of the surface contact temperature sensor (43, 431, 432), wherein the surface contact temperature sensor (43, 431, 432) is left on the workpiece (5) after cooling has ended, the data line (44) is disconnected from the surface contact temperature sensor (43, 431, 432), and the surface contact temperature sensor (43, 431, 432) is used again during a later analysis of the workpiece (5).

Description

[0001] The present invention relates to a method for cooling workpieces. State of the art

[0002] In order to machine workpieces with micrometer precision, for example, on a machining center, they must be brought to the specified base temperature of the machine before machining due to material expansion when the temperature changes. They must also be brought to a specified base temperature of the machine before any machining process can begin, for example, before any analysis of the workpiece, such as micrometer-precise measurement on a coordinate measuring machine for possible adjustments to the machining center.

[0003] Today, workpieces, which often come from pre-processing processes such as cleaning, at temperatures of up to 60°C, are brought into the further processing rooms or into upstream rooms at the same temperature and stored there for up to 24 hours, depending on the component size, wall thickness, and material, until further processing. During this process, the workpieces gradually adapt to the specified ambient temperature. DE 10 2014 101 874 A1, for example, concerns a manufacturing system with multiple machine tools. This system features a wet cleaning device to enable measurements to be taken on cleaned workpieces.

[0004] However, cooling leads to a time delay between the pre-processing process and the machining process or measurement. Production release can only be granted after the temperature has been reliably adjusted. Otherwise, there is a risk of rejects being produced while the measurement results are available. Furthermore, a significant amount of space is required to store the cooling workpieces. Furthermore, they are unavailable for further processing steps until they have completely cooled down.

[0005] DE 10 2016 100 613 A1 relates to a system for performing work on a workpiece. This system has a front chamber in which workpieces are stored on a workpiece conveyor. A robot is provided to remove the workpieces from the tool conveyor. Beforeward, the workpieces are cooled by blowing air taken from an air conditioning system through a ventilation opening. The workpieces rest on temperature sensors that monitor their surface temperature.

[0006] DE 689 04 980 T2 concerns the cooling of workpieces manufactured by formative buildup welding. A workpiece rotates and is cooled in the direction of rotation after a welding head by means of a cooling head. This cools the surface of the workpiece with a cooling fluid stored in a tank.

[0007] DE 601 10 713 T2 relates to a machine tool with room air conditioning. This is arranged in the machine tool system, in which a thermostatic chamber encloses the machine tool, so that the air temperature in the chamber is adjusted to a desired temperature.

[0008] DE 10 2009 031 018 B4 describes a modular machining system with an air-conditioned product module. Air is supplied from an air conditioning system inside the product module. A workpiece is referenced and adjusted relative to a tool interface using a positioning device.

[0009] DE 37 29 644 A1 describes a method for determining the temperature of workpieces in flexible manufacturing systems. For this purpose, a temperature sensor is attached to a workpiece and connected to the housing of a transmitter module. This transmitter module is arranged on a pallet for transporting the workpiece. DE 10 2004 013 361 A1 also describes how the temperature of a workpiece can be measured using a measuring probe and the temperature information can then be transmitted wirelessly.

[0010] DE 40 39 336 A1 discloses a method for rapid workpiece temperature measurement on coordinate measuring machines. A temperature measuring head is brought to a workpiece by means of a measuring arm and a rotary / pivoting device.

[0011] US 2008 / 0 198 900 A1 discloses a temperature measurement system. Extendable temperature sensors are arranged along a mold filled with molten metal, between spray nozzles that cool the metal by spraying it with water. These sensors are only moved toward the mold in the presence of a metal strand.

[0012] It is an object of the present invention to provide a device and a method that enable faster cooling of workpieces. Disclosure of the invention

[0013] This object is achieved by the method according to the invention for cooling workpieces. Here, a workpiece is exposed to a fluid flow through at least one nozzle, the fluid having a temperature lower than the surface temperature of the workpiece, in particular lower than the surface temperature in the area targeted by the nozzle. As a result, the workpiece cools more quickly than would be possible in a conventional cooling process through heat exchange with the environment. The surface temperature is monitored by at least one surface temperature sensor. In this way, it can be determined when the surface temperature corresponds to the desired target temperature of the cooling process.

[0014] The device is preferably located in an air-conditioned room, and the process is preferably carried out in the air-conditioned room. This allows an ambient temperature to be specified, which serves as the target temperature for the cooling process. Furthermore, the air conditioning prevents a layer of heated air from forming on the workpiece surface during cooling, which would delay the further cooling process.

[0015] In principle, any medium that can flow toward the workpiece at high velocity can be used as a fluid. However, air is preferred because it can be easily extracted from the workpiece's environment.

[0016] The flow preferably takes place at a flow velocity of at least 0.3 m / sec, particularly preferably at least 0.5 m / sec, most particularly preferably at least 1.0 m / sec.

[0017] In a preferred embodiment of the method, the at least one nozzle is configured to extract air as a fluid from an air-conditioned room. This air already has the target temperature of the cooling process. If air is extracted as a fluid from the air-conditioned room using such a device in one embodiment of the method, the flow to the workpiece is preferably continued for a predeterminable period of time after its surface temperature has reached its ambient temperature. This ensures that not only the surface of the workpiece but the entire workpiece reaches the target temperature of the cooling process. Immediate termination of the flow after the surface temperature has first reached the ambient temperature, on the other hand, would result in the surface temperature rising above the ambient temperature again, since the workpiece surface would be heated up again by the warmer workpiece body.

[0018] In another preferred embodiment of the method, the at least one nozzle is configured to extract air as a fluid from a cold air source in the air-conditioned room. Such a cold air source is typically arranged in the ceiling of the air-conditioned room, where it cools air drawn in from the room to below the current temperature of the room. Cold air is therefore understood to mean air whose temperature is below the temperature inside the air-conditioned room. By returning the thus cooled air to the room, the temperature of the room can be reduced. If, in one embodiment of the method, air is applied to a workpiece using such a device, the air applied to the workpiece is preferably continued until its surface temperature has dropped below its ambient temperature. Subsequently, the system waits until the surface temperature has risen to the ambient temperature.This can involve further airflow over the material, using air taken from the air-conditioned room and thus at the target temperature for the cooling process. This takes advantage of the fact that the air from the cold air source, whose temperature is below the ambient temperature in the air-conditioned room, enables rapid cooling of the workpiece surface below this ambient temperature. Subsequently, the surface temperature of the workpiece quickly adjusts to the ambient temperature due to its even higher core temperature. This process enables even faster cooling of the workpiece than can be achieved by blowing warm ambient air alone.

[0019] The at least one surface temperature sensor is a surface contact temperature sensor.

[0020] The device used in the method has at least one data line configured to be connected to a surface temperature sensor arranged on the workpiece. A data line is also understood to mean a wireless data connection, for example, via radio. The surface temperature sensor is left on the workpiece after cooling is complete, with only the data line being disconnected from the surface temperature sensor. The surface temperature sensor is then reused for a subsequent analysis of the workpiece.

[0021] The air-conditioned room is preferably a climate tunnel. As such, it can connect a production facility for the workpiece with an analysis facility for the workpiece. The analysis facility is, in particular, a measuring unit and can, for example, contain a coordinate measuring machine. After production, the workpiece can then be cooled in the climate tunnel and then transported to an analysis facility for analysis. This enables continuous production of workpieces. Short description of the drawings

[0022] Embodiments of the invention are illustrated in the drawings and explained in more detail in the following description. Fig. 1 shows a schematic side view of an apparatus used in a method according to a first embodiment of the invention. Fig. Figure 2 shows a schematic side view of an apparatus used in a method according to a second embodiment of the invention. Fig. 3 shows a diagram of cooling times of workpieces in a conventional cooling process and according to various embodiments of the method according to the invention. Embodiments of the invention

[0023] A device for cooling workpieces used in a first embodiment of the invention is described in Fig. 1. A production facility 1, designed as a machining center, has a passage into an air-conditioned room 2, which has the shape of an air-conditioning tunnel. Air cooled to 17°C from a cold air source 22 is fed into the air-conditioned room 2 via a ceiling inlet 21 in order to reduce its internal temperature to a predetermined value of 20°C. The air-conditioned room 2 is connected to an analysis system 3, which is also air-conditioned and which in this case contains a coordinate measuring machine. The device 4 is arranged in the air-conditioned room 2. A conveyor belt 11 can transport workpieces 5 from the production facility 1 through the air-conditioned room 2 into the analysis system 3. The workpieces 5 have a temperature in the range of 55°C to 60°C when they leave the production facility 1. Before they are transported further to the analysis system 3, they are cooled to 20°C in the air-conditioned room 2.

[0024] The device 4 has two nozzles 411, 412. Air is sucked in from the air-conditioned room 2 through an intake opening 421. A workpiece 5 is exposed to this 20°C warm air via the nozzles 411, 412. A surface temperature sensor 43, designed as a contact temperature sensor, is already attached to the surface of the workpiece 5 in the production system 1. It is connected to the device 4 in the air-conditioned room 2 via a data line 44. The nozzles 411, 412 supply air to the workpiece 5 until the surface temperature sensor 43 measures a surface temperature of 20°C for a predetermined period of time. This predetermined period of time was determined empirically for the workpiece 5. The data line 44 is then removed, and the workpiece is transported to the analysis system 3 for measurement.During measurement, the surface temperature of the workpiece is again determined using the surface temperature sensor 43, which is connected to the coordinate measuring machine for this purpose. If deviations from the desired dimensions are detected, a processing machine in the production facility can be adjusted to avoid the deviations in the production of subsequent workpieces.

[0025] A device 4 for cooling workpieces, which is used in a second embodiment of the invention, is shown in Fig. 2 shown.

[0026] It differs from the device 4 according to the first embodiment in that it has a connecting line 422 to the cold air source 22. The nozzles 411, 412 can be supplied with air either via the intake opening 421 or via the connecting line 422. The cooling process differs from the cooling process in the first embodiment in that the surface of the workpiece 5 is first cooled to a temperature of 17°C with air from the connecting line 422. Subsequently, the workpiece is further exposed to air at 20°C from the intake opening 421 until the surface of the workpiece 5 has reached a temperature of 20°C. After this, the air flow is interrupted without further delay, the data line 44 is removed, and the workpiece is transported to the analysis system 3 for measurement.

[0027] In Fig. Figure 3 shows a bar chart illustrating how long it takes for a 60°C aluminum cylinder head, which leaves the production line 1 as workpiece 5, to cool to a temperature of 20°C at different flow rates. In a comparison example, in which no flow is applied, the cooling takes a period t of 7 hours and 58 minutes. It also shows how an inflow of 20°C cold air at flow rates of 500 m 3 / h, 700 m 3 / h and 1,000 m 3 / h using a method according to the first or third embodiment, the cooling time is shortened. Here, a volume flow of 500 m 3 / h, an inflow velocity of 0.3 m / sec, a volume flow of 700 m 3 / h corresponds to a flow velocity of 0.5 m / sec and a volume flow of 1,000 m 3 / h corresponds to an inflow velocity of 1.0 m / sec. In each case, the time it takes until the surface temperature of 20°C is first reached is specified. The further inflow over the empirically determined predetermined period is not included in the specified period t. A further reduction in the cooling time can be achieved by using a method according to the second or fourth embodiment, first inflowing with 17°C cold air and then another inflowing with 20°C cold air. This is shown in Fig.5 is represented by hatched bars. Here, too, the time it takes until the surface temperature of 20°C is first reached is indicated. The further flow of 20°C cold air is not included in the specified time period t. It can be seen that the cooling time can be significantly shortened using the methods according to the first or third embodiments. An even more pronounced shortening of the cooling time is achieved using a method according to the second or fourth embodiments, in which the workpiece 5 is first subcooled below the desired target temperature and then heated to this temperature.

Claims

[1] Method for cooling workpieces (5), wherein a workpiece (5) is subjected to a fluid flow by means of at least one nozzle (411, 412) whose temperature is lower than the surface temperature of the workpiece (5), wherein a data line (44) is connected to at least one surface contact temperature sensor (43) arranged on the workpiece (5) and the surface temperature is monitored by means of the surface contact temperature sensor (43, 431, 432), wherein the surface contact temperature sensor (43, 431, 432) is left on the workpiece (5) after cooling has ended, the data line (44) is disconnected from the surface contact temperature sensor (43, 431, 432) and the surface contact temperature sensor (43, 431, 432) is used again in a later analysis of the workpiece (5). [2] Method according to claim 1, characterized bythat the device is arranged in an air-conditioned room (2), wherein air is taken from the room (2) as a fluid. [3] Method according to claim 2, characterized by that the flow to the workpiece (5) is continued for a predeterminable period of time after its surface temperature has reached its ambient temperature. [4] Method according to claim 1, characterized by that the device is arranged in an air-conditioned room (2), wherein air is taken as a fluid from a cold air source (22) of the room (2). [5] Method according to claim 4, characterized by that the flow to the workpiece (5) continues until its surface temperature has dropped below its ambient temperature. [6] Method according to one of claims 1 to 5, characterized by that the workpiece (5) is cooled in a climate tunnel and then transported to an analysis system (3) and analyzed therein. [7] Method according to claim 6, characterized by that the climate tunnel connects a production plant (1) for the workpiece (5) with the analysis plant (3). [8] Method according to claim 6 or 7, characterized by that the analysis system (3) is a measuring unit.

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