Pretreatment chemical replenishment system and method

Abstract

To provide a pretreatment chemical supply system capable of stabilizing the concentration of chemicals in a pretreatment tank for electrodeposition coating. [Solution] The system includes a pretreatment tank (31) containing a pretreatment agent containing chemicals for pretreatment of the workpiece (W) for electrocoating using the same type of component material, a pump (45) that operates in a timely manner to supply the chemicals to the pretreatment tank (31), and a control unit (37) that restores the concentration of the chemicals in the pretreatment tank (31) using the pump (45) in accordance with the weight of the workpiece (W) that has been pretreated, which is correlated with the surface area of ​​the workpiece (W).

Description

[Technical Field]

[0001] The present invention relates to a system and method for replenishing pretreatment chemicals used in pretreatment of products for electrodeposition coating. [Background technology]

[0002] As shown in Patent Document 1, conventional pretreatment methods for electrodeposition coating include a degreasing step, a surface conditioning step, a chemical conversion coating step, and the like.

[0003] In each of these pretreatment processes, the workpieces are immersed in a pretreatment tank containing a pretreatment agent. Maintaining a constant concentration of the chemicals contained in the pretreatment agent is useful for achieving uniform pretreatment. Therefore, in each process, chemicals are replenished after each treatment. For example, a metering pump is operated for a fixed period of time to replenish the chemicals after each workpiece treatment.

[0004] However, in pretreatment, multiple workpieces of different sizes may be treated consecutively. In this case, the amount of chemicals consumed varies depending on the size of the workpieces, and if a fixed amount of chemicals is replenished each time, the concentration of the chemicals in the pretreatment tank may vary. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2020-153006 Summary of the Invention [Problem to be solved by the invention]

[0006] The problem to be solved is the uneven concentration of chemicals in the pretreatment tank for electrodeposition coating. [Means for solving the problem]

[0007] The present invention provides a pretreatment chemical replenishment system including a pretreatment tank containing a pretreatment agent including chemicals for pretreatment of electrodeposition coating of workpieces made of the same constituent materials, a pump that operates in a timely manner to replenish the chemicals to the pretreatment tank, and a control unit that causes the pump to restore the concentration of the chemicals in the pretreatment tank in accordance with a weight that correlates with the surface area of ​​the workpiece that has been pretreated.

[0008] The present invention also provides a pretreatment chemical replenishment method for replenishing a pretreatment tank containing a pretreatment agent containing chemicals for pretreatment of electrodeposition coating of workpieces made of the same type of constituent material, the method comprising replenishing the chemicals to the pretreatment tank in accordance with a weight that correlates with the surface area of ​​the workpiece that has been pretreated, thereby restoring the concentration of the chemicals in the pretreatment tank. [Effects of the Invention]

[0009] According to the present invention, the concentration of chemicals in a pretreatment tank for electrodeposition coating can be stabilized. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a conceptual diagram of an entire electrodeposition coating line employing a pretreatment chemical supply system according to an embodiment of the present invention. [Figure 2] Figure 2 is a chart showing the chemical management items for each process in the pretreatment of the electrodeposition coating line shown in Figure 1. [Figure 3] FIG. 3 is a conceptual diagram showing the second degreasing step of the electrodeposition coating line shown in FIG. [Figure 4] FIG. 4 is a conceptual diagram showing the surface conditioning process of the electrodeposition coating line of FIG. [Figure 5] FIG. 5 is a conceptual diagram showing the chemical conversion process of the electrodeposition coating line of FIG. [Figure 6] FIG. 6 is a graph showing the correlation between the weight and surface area of ​​the workpiece. [Figure 7] FIG. 7 is a graph showing the correlation between weight and surface area of ​​frame components. [Figure 8]FIG. 8 is a graph showing the correlation between weight and surface area of ​​a pickup truck frame. [Figure 9] FIG. 9 is a graph showing the correlation between weight and surface area of ​​a medium / heavy truck frame. [Figure 10] FIG. 10 is a flowchart showing the supply of chemicals in each step of the pretreatment of the electrodeposition coating line of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0011] A pretreatment chemical replenishment system according to one embodiment includes a pretreatment tank 31, 49, 61, pumps 45, 57, 69, and a control unit 37. The pretreatment tanks 31, 49, 61 contain pretreatment agents 33, 51, 63 containing chemicals used for pretreatment of workpieces W made of the same constituent materials before electrodeposition coating. The pumps 45, 57, 69 operate in a timely manner to replenish the chemicals to the pretreatment tanks 31, 49, 61. The control unit 37 operates the pumps 45, 57, 69 in accordance with the weight of the pretreated workpiece W, which correlates with the surface area of ​​the workpiece W, to restore the concentration of the chemicals in the pretreatment tanks 31, 49, 61.

[0012] The workpieces W made of the same type of constituent material are not limited as long as there is a correlation between the surface area and the weight, but in one embodiment, the workpieces W may be mainly made of plate material. Also, the workpieces W made mainly of plate material may be of multiple types with different sizes.

[0013] Various pretreatment processes can be adopted, but in one embodiment, the pretreatment process may include at least a degreasing process and a chemical conversion process.

[0014] In one embodiment, a pretreatment chemical supply method supplies chemicals to a pretreatment tank 31, 49, 61 that contains a pretreatment agent 33, 51, 63 containing chemicals for pretreatment of electrodeposition coating. This pretreatment chemical supply method supplies chemicals to the pretreatment tank 31, 49, 61 in accordance with a weight that correlates with the surface area of ​​the workpiece W that has been pretreated, thereby restoring the concentration of the chemicals in the pretreatment tank 31, 49, 61. [Example]

[0015] [Pretreatment chemical supply system] Fig. 1 is a conceptual diagram of an overall electrodeposition coating line employing a pretreatment chemical supply system according to an embodiment of the present invention. Fig. 2 is a diagram showing chemical management items in each process of pretreatment in the electrodeposition coating line of Fig. 1. Fig. 3 is a conceptual diagram showing the degreasing process 2 of the electrodeposition coating line of Fig. 1. Fig. 4 is a conceptual diagram showing the surface conditioning process of the electrodeposition coating line of Fig. 1. Fig. 5 is a conceptual diagram showing the chemical conversion process of the electrodeposition coating line of Fig. 1.

[0016] As shown in Figure 1, unpainted workpieces W (see Figure 3), which are products that have been pressed or otherwise processed, are transported to the electrocoating line by an overhead conveyor 1. Note that a general overhead conveyor 1 can be used, and is only conceptually indicated by arrows in the figure.

[0017] The workpieces W range from large and small truck frames made mainly of plate materials made of the same type of constituent material to other small parts. Multiple types of workpieces W of different sizes are transported in sequence and are electrocoated on the same line. In the figure, the workpieces W are also shown only conceptually.

[0018] In this embodiment, the workpieces W are a mixture of three types: frame parts, small truck frames, and medium / large truck frames. However, the workpieces W may be a mixture of two or more types. Examples of the same type of component material include steel plates. Therefore, the size and weight of the workpieces W are correlated, and as a result, the surface area is correlated with the weight. The same type of component material may be plate parts made of the same material and having similar thicknesses.

[0019] The electrodeposition coating line has, as pretreatment processes, a preliminary degreasing process 3, a first degreasing process 5, and a second degreasing process 7. In the following description, the preliminary degreasing process 3, the first degreasing process 5, and the second degreasing process 7 may be referred to as degreasing processes 3, 5, and 7.

[0020] Preliminary degreasing process 3, degreasing 1 process 5, and degreasing 2 process 7 are processes in which a degreasing agent is sprayed onto the workpiece W as a pretreatment agent, or the workpiece W is submerged in the agent to degrease it. By sequentially going through preliminary degreasing process 3, degreasing 1 process 5, and degreasing 2 process 7, press oil, iron powder from welding, and other dust are also removed.

[0021] Next, the workpiece W is washed through a first water washing step 9 and a second water washing step 11.

[0022] After cleaning, the workpiece W undergoes another pretreatment process, the surface conditioning process 12. In the surface conditioning process 12, the workpiece W is subjected to a surface conditioning treatment to improve the performance of the chemical conversion coating in the next process and shorten the processing time. In the surface conditioning process 12, the workpiece W is immersed in a surface conditioning treatment agent as a pretreatment agent. This surface conditioning process 12 creates crystal nuclei for, for example, zinc phosphate crystals on the surface of the workpiece W.

[0023] Next, the workpiece W is subjected to another pretreatment process, the chemical conversion process 13. The chemical conversion process is a process for improving the corrosion resistance and adhesion of the coating using a chemical conversion treatment agent, which is a pretreatment agent. In the chemical conversion process 13, the workpiece W is immersed in the chemical conversion treatment agent, and a zinc phosphate coating, for example, is formed on the surface of the workpiece W.

[0024] The chemical conversion step 13 can also be zircon chemical conversion.

[0025] Next, the workpiece W is subjected to a water washing 3 step 15, a water washing 4 step 17, and a pure water washing step 19, and then to an electrodeposition step 21. In the electrodeposition step 21, the surface of the workpiece W is subjected to electrodeposition coating.

[0026] After the electrodeposition step 21, the paint and water are separated through UF water washing 1 step 23, UF water washing 2 step 25, and UF water washing 3 step 27.

[0027] Finally, the workpiece W is dried in a drying step 29, and the electrocoated workpiece W is discharged.

[0028] As described above, different pretreatment agents are used in the degreasing processes 3, 5, and 7, the surface conditioning process 12, and the chemical conversion process 13, which are pretreatment processes, and the supply of chemicals is controlled according to the weight of the workpiece W. The control items for the supply of chemicals in each pretreatment process are shown in the table in Figure 2.

[0029] Free alkalinity, pH, and activator concentration are controlled in degreasing steps 3, 5, and 7. If these values ​​are higher than the appropriate values, costs will increase, and if they are lower, there is a risk of poor degreasing.

[0030] In the surface conditioning step 12, for example, the surface conditioning density in the case of zinc phosphate conversion is controlled. If this value is higher than the appropriate value, it may lead to an insufficient coating amount, and if it is lower, it may lead to a decrease in the coating rate.

[0031] In the chemical conversion step 13, for example, in the case of zinc phosphate chemical conversion, the free acidity and zinc concentration are controlled. If these values ​​are higher than the appropriate values, it may lead to an insufficient amount of coating and increased costs, while if they are lower, it may lead to excessive sediment and insufficient amount of coating, respectively.

[0032] In the chemical conversion step 13, in the case of zircon conversion, the zircon concentration is controlled, and if this value is higher than the appropriate value, it leads to an increase in costs, and if it is lower, there is a risk of an insufficient amount of coating.

[0033] [Degreasing process] In degreasing processes 3, 5, and 7, a pretreatment agent is added to degreasing process 2 7, and the overflow from degreasing process 2 7 causes the pretreatment agent to be added to degreasing process 1 5, and the overflow from degreasing process 1 5 causes the pretreatment agent to be added to preliminary degreasing process 3.

[0034] Therefore, chemicals for the preliminary degreasing process 3, the first degreasing process 5, and the second degreasing process 7 are replenished for the second degreasing process 7, and the pretreatment agents for the first degreasing process 5 and the preliminary degreasing process 3 are managed by overflow.

[0035] As shown in Figure 3, the second degreasing process 7 employs a pretreatment chemical supply system and is provided with a degreasing tank 31 as a pretreatment tank. The degreasing tank 31 contains a degreasing treatment agent 33 containing degreasing chemicals as a pretreatment agent containing chemicals for pretreatment of the workpiece W before electrodeposition coating. The degreasing treatment agent 33 is a solution of degreasing chemicals, such as caustic soda and a surfactant.

[0036] The workpiece W is transferred to the degreasing tank 31 by the overhead conveyor 1. Specifically, the workpiece W is mounted on a paint hanger 35. The paint hanger 35 is transferred on the electrodeposition coating line by the overhead conveyor 1. Then, in the degreasing tank 31, the paint hanger 35 is lowered, and the workpiece W is immersed in the degreasing treatment agent 33.

[0037] The weight of the workpiece W mounted on the paint hanger 35 can be calculated from the current value of the driving electric motor when the workpiece W is lifted at the entrance of the electrocoating line. The current value when the workpiece W is lifted on the paint hanger 35 is input to a PLC (control panel) 37, which calculates the weight of the lifted workpiece W from this input current value.

[0038] The PLC 37 is a computer having a processor, memory, etc. The PLC 37 executes a program in the memory with the processor to control the electrodeposition coating line, including the transportation of the workpiece W, pre-treatment, and supply of chemicals (degreasing chemicals in the degreasing process) to the pre-treatment tank (degreasing tank 31 in the degreasing process).

[0039] A degreasing chemical is supplied to the degreasing tank 31 from a degreasing chemical tank 41 via a pipe 43. A pump 45 and a flow meter 47 are installed in the pipe 43. The pump 45 and the flow meter 47 are electrically connected to the PLC 37.

[0040] The pump 45 is driven under the control of the PLC 37 to supply the degreasing chemical to the degreasing tank 31, which is a pre-treatment tank. The flow meter 47 measures the flow rate of the degreasing chemical supplied from the degreasing chemical tank 41 to the degreasing tank 31 by the driving of the pump 45, and inputs the measured flow rate to the PLC 37.

[0041] Therefore, in the degreasing process, the pump 45 is operated under the control of the PLC 37, which will be described later, in accordance with the weight of the workpiece W that has been degreased as pre-treatment, which correlates with the surface area, to supply the degreasing chemical from the degreasing chemical tank 41 to the degreasing tank 31. This restores the concentration of the degreasing chemical in the degreasing treatment agent 33, making it possible to degrease the next workpiece W.

[0042] It is preferable that the amount of degreasing chemical supplied is the same as the amount of degreasing chemical used. The amount of degreasing chemical used for the workpiece W varies depending on the surface area of ​​the workpiece W, and the surface area of ​​the workpiece W correlates with its weight. For this reason, in this embodiment, the amount of degreasing chemical supplied from the degreasing chemical tank 41 to the degreasing tank 31 is determined depending on the weight of the workpiece W, which correlates with the surface area of ​​the workpiece W.

[0043] [Tone process] As shown in Figure 4, the surface conditioning process 12 employs a pretreatment chemical supply system and is provided with a surface conditioning tank 49 as a pretreatment tank. The surface conditioning tank 49 contains a surface conditioning treatment agent 51 containing surface conditioning chemicals as a pretreatment agent containing chemicals for pretreatment of the electrodeposition coating of the workpiece W. The surface conditioning treatment agent 51 is a solution of surface conditioning chemicals, and the surface conditioning chemicals are zinc phosphate-based chemicals.

[0044] The surface preparation chemical is supplied to the surface preparation tank 49 from a surface preparation chemical tank 53 via a pipe 55. A pump 57 and a flow meter 59 are installed in the pipe 55. The pump 57 and the flow meter 59 are electrically connected to the PLC 37.

[0045] The pump 57 is driven under the control of the PLC 37, and supplies the surface preparation chemicals to the surface preparation tank 49, which is a pre-treatment tank. The flow meter 59 measures the flow rate of the surface preparation chemicals supplied from the surface preparation chemical tank 53 to the surface preparation tank 49 by driving the pump 57, and inputs the measured flow rate to the PLC 37.

[0046] Other steps are the same as the degreasing step.

[0047] Therefore, in the surface conditioning step, the PLC 37 operates the pump 57 in accordance with the weight correlated to the surface area of ​​the workpiece W whose surface has been subjected to pre-treatment under the control described below, and supplies the surface conditioning chemical from the surface conditioning chemical tank 53 to the surface conditioning tank 49. This restores the concentration of the surface conditioning chemical in the surface conditioning treatment agent 51, making it possible to perform the surface conditioning treatment on the next workpiece W.

[0048] As with the degreasing chemicals, the amount of surface preparation chemicals to be supplied from the surface preparation chemical tank 53 to the surface preparation tank 49 is determined according to the weight of the workpiece W, which correlates with the surface area of ​​the workpiece W.

[0049] [Chemical process] As shown in Fig. 5, the chemical conversion step 13 employs a pretreatment chemical supply system and is provided with a chemical conversion tank 61 as a pretreatment tank. A chemical conversion treatment agent 63 containing chemical conversion chemicals is stored in the chemical conversion tank 61 as a pretreatment agent containing chemicals for pretreatment of the electrodeposition coating of the workpiece W. The chemical conversion treatment agent 63 is a solution of chemical conversion chemicals, and the chemical conversion chemicals are, for example, zinc phosphate-based chemicals.

[0050] Chemicals are supplied to the chemical conversion tank 61 from a chemical conversion tank 65 via a pipe 67. A pump 69 and a flow meter 71 are installed in the pipe 67. The pump 69 and the flow meter 71 are connected to the PLC 37.

[0051] The pump 69 is operated under the control of the PLC 37 to supply chemicals to the chemical conversion tank 61 which is a pretreatment tank, and supplies chemicals from the chemical conversion tank 65 to the chemical conversion tank 61 .

[0052] The flow meter 71 measures the flow rate of the chemicals supplied from the chemical tank 65 to the chemical bath 61 by driving the pump 69 , and inputs the measured flow rate to the PLC 37 .

[0053] Other steps are the same as the degreasing step.

[0054] Therefore, under the control of the PLC 37 described below, the pump 69 is operated in accordance with the weight of the workpiece W that has been subjected to chemical conversion treatment as pretreatment, which is correlated with the surface area, and chemical conversion chemicals are replenished from the chemical conversion chemical tank 65 to the chemical conversion treatment agent 65 in the chemical conversion tank 61. This restores the concentration of the chemical conversion chemicals in the chemical conversion treatment agent 65, making it possible to perform chemical conversion treatment on the next workpiece W.

[0055] As with the degreasing chemicals, the amount of chemicals supplied from the chemical tank 65 to the chemical bath 61 is determined according to the weight of the workpiece W, which correlates with the surface area of ​​the workpiece W.

[0056] [Regression Analysis] FIG. 6 is a graph showing the correlation between the weight and surface area of ​​the workpiece.

[0057] In Figure 6, the horizontal axis represents weight x and the vertical axis represents surface area y, and multiple measurement results are plotted as a scatter diagram for different workpieces W: a frame part, a small truck frame, and a medium / large truck frame.

[0058] The regression equations obtained for three different types of work W through regression analysis based on this scatter diagram are as follows: y=0.0434x+1.8515(R 2 =0.9669)

[0059] According to the regression analysis in Fig. 6, the coefficient of determination R 2 It can be seen that there is a high correlation between the weight and surface area of ​​multiple types of workpieces W. Note that the thickness of the steel plate used as a constituent material may differ by several millimeters between different workpieces W, but the regression analysis in Figure 6 shows that there is no significant difference, and it can be said that they are made of the same type of constituent material.

[0060] Figure 7 is a graph showing the correlation between the weight and surface area of ​​a frame part. In Figure 7, the horizontal axis represents weight x and the vertical axis represents surface area y, and multiple measurement results of the frame part, which is the workpiece W, are plotted as a scatter diagram.

[0061] The regression equation for the frame parts obtained by regression analysis based on this scatter diagram is as follows: y=0.0482x+0.0626(R 2 =0.9659)

[0062] According to the regression analysis in Fig. 7, the coefficient of determination R 2 It can be seen that there is a high correlation between the weight and surface area of ​​the workpiece W as a frame part.

[0063] Figure 8 is a graph showing the correlation between the weight and surface area of ​​a small truck frame. In Figure 8, the horizontal axis represents weight x and the vertical axis represents surface area y, and multiple measurement results of the small truck frame, which is the workpiece W, are plotted as a scatter diagram.

[0064] The regression equation for the small truck frame obtained by regression analysis based on this scatter diagram is as follows: y=0.0361x+4.5679(R 2 =0.8012)

[0065] In the regression analysis of Figure 8, the coefficient of determination R 2 is sufficiently high, and it can be seen that there is a high correlation between the weight and surface area of ​​the workpiece W as a small truck frame.

[0066] Figure 9 is a graph showing the correlation between the weight and surface area of ​​a medium / large truck frame. In Figure 9, the horizontal axis represents weight x and the vertical axis represents surface area y, and multiple measurement results of the medium / large truck frame, which is the workpiece W, are plotted as a scatter diagram.

[0067] The regression equation for the medium / large truck frame obtained by regression analysis based on this scatter diagram is as follows: y=0.0371x+4.3218(R 2 =0.9973)

[0068] According to the regression analysis in Fig. 9, the coefficient of determination R 2 It can be seen that there is a high correlation between the weight and surface area of ​​the workpiece W as a medium / large truck frame.

[0069] The amount of chemical used in the pre-treatment of the workpiece W varies depending on the surface area of ​​the workpiece W as described above, but in this embodiment, it is assumed based on the regression equation above that it varies depending on the weight of the workpiece W. Under this assumption, the PLC 37 determines the amount of chemical to be replenished after the pre-treatment according to the weight of the workpiece W.

[0070] The regression equation of Figure 6 can be used for frame parts, small truck frames, and medium / large truck frames in general, and the regression equations of Figures 7 to 9 can be used for frame parts, small truck frames, and medium / large truck frames, respectively.

[0071] The regression equation in Figure 6 has a high coefficient of determination and can be applied to all workpieces W, eliminating the need to distinguish the type of workpiece W and making it easy to replenish chemicals after pretreatment.

[0072] By setting the amount of chemicals used relative to the surface area of ​​the workpiece W in the degreasing 2 process 7, the surface conditioning process 12, and the chemical conversion process 13, the relationship between the amount of chemicals used and the surface area of ​​the workpiece W is linked to the weight of the workpiece W, and the chemicals are replenished according to the weight, thereby optimizing the control items in the chart in Figure 2.

[0073] [Degreasing chemical replenishment control] FIG. 10 is a flow chart showing the supply of chemicals by PLC in each pretreatment step of the electrodeposition coating line in FIG. 1, in this embodiment, the degreasing step 2 7, the surface conditioning step 12, or the chemical conversion step 13.

[0074] In the PLC 37, the program in the memory is executed by the processor using a trigger such as a start switch signal, and the flowchart in Figure 10 is started.

[0075] In step S1, the process of "reading supply amount relative to weight" reads the supply amount of chemical relative to the weight of the workpiece W stored in the memory of the PLC 37. As described above, the amount of chemical used during pre-processing is correlated with the surface area of ​​the workpiece W, but since the surface area and weight of the workpiece W are also correlated, the supply amount of chemical is the amount of chemical used converted from the weight of the workpiece W based on these correlations.

[0076] The read supply amount of chemicals may be corrected using a correction coefficient. The amount of chemicals used in pretreatment may vary depending on changes in the pretreatment environment, such as temperature. To accommodate this change in the amount of chemicals used, a correction coefficient based on the change in the pretreatment environment is set in the PLC 37.

[0077] The correction coefficient can be set based on the correlation between the pretreatment environment and the amount of chemical used. Alternatively, the correction coefficient can be set based on the measured chemical concentration after performing pretreatment such as a trial run and replenishing the chemical.

[0078] The chemical concentrations are the concentration of the degreasing treatment agent 33 in the degreasing layer 31 in the degreasing step 2 (7), the concentration of the surface conditioning treatment agent 51 in the surface conditioning tank 49 in the surface conditioning step 12, and the concentration of the chemical treatment agent 63 in the chemical conversion tank 61 in the chemical conversion step 13.

[0079] In step S2, the "electrodeposition coating" process is executed. That is, the overhead conveyor 1 is driven by the PLC 37, and the paint hanger 35 carrying the workpiece W is transported sequentially from the entrance of the line. In response to this transport, the paint hanger 35 repeatedly rises and falls, and the workpiece W is sequentially subjected to the processes from preliminary degreasing 3 to drying 29.

[0080] In this treatment, as shown in FIG. 1, in the pretreatment steps of degreasing step 2 7, surface conditioning step 12, or chemical conversion step 13, a predetermined degreasing treatment, surface conditioning treatment, or chemical conversion treatment is carried out in a degreasing tank 31, a surface conditioning tank 49, or a chemical conversion layer 61 using a degreasing treatment agent 33, a surface conditioning treatment agent 51, or a chemical conversion treatment agent 63.

[0081] In step S3, a "weight value detection" process is executed. That is, for weight value detection, the current value of the electric motor used to drive the paint hanger 35 at the entrance of the electrodeposition coating line when it is lifted is detected in advance and input to the PLC 37. The PLC 37 calculates the weight of the lifted workpiece W from this input current value. As a result, the calculated weight value becomes the detected weight value.

[0082] In step S4, the process of "calculating the amount of chemicals to be supplied" is executed. That is, the PLC 37 calculates the amount of chemicals to be supplied from the weight of the workpiece W obtained in step S3. The PLC 37 calculates the amount of degreasing chemicals to be supplied in the second degreasing process 7, the amount of surface preparation chemicals to be supplied in the surface preparation process 12, and the amount of chemical preparation chemicals to be supplied in the chemical preparation process 13. In this case, the amount of each chemical to be supplied is calculated according to the weight from the amount of supply relative to the weight read in step S1.

[0083] In step S5, the "pump operation" process is executed. That is, the PLC 37 controls the pump 45 to supply chemicals. Specifically, in the case of the second degreasing process 7, the degreasing chemicals are supplied from the degreasing chemical tank 41 to the degreasing tank 31 via the pipe 43. In the case of the surface adjustment process 12, the PLC 37 controls the pump 57 to supply the surface adjustment chemicals from the surface adjustment chemical tank 53 via the pipe 55 to the surface adjustment tank 49. In the case of the chemical formation process 13, the PLC 37 controls the pump 69 to supply the chemical formation chemicals from the chemical formation chemical tank 65 via the pipe 67 to the chemical formation tank 61.

[0084] In step S6, a process of "detecting chemical flow rate" is executed. That is, in the case of the second degreasing process 7, the flow rate in pipe 43 when replenishing the degreasing tank 31, in the case of the surface conditioning process 12, the flow rate in pipe 55 when replenishing the surface conditioning tank 49, and in the case of the chemical conversion process 13, the flow rate in pipe 67 when replenishing the chemical conversion tank 61 are successively measured by flow meters 47, 59, and 71, respectively. The detected flow rates are input to the PLC 37, which monitors them while storing them in its internal memory.

[0085] In step S7, the process "Does the chemical flow rate match the calculated chemical value?" is executed. That is, the PLC 37 determines whether the total flow rate detected in step S6 matches the chemical supply amount calculated in step S4. If the flow rate does not match the chemical supply amount (NO), steps S5 to S7 are repeated, and if they match (YES), the process ends. With the end of this process, the concentrations of the degreasing chemical in the degreasing tank 31, the surface preparation chemical in the surface preparation tank 49, or the chemical preparation chemical in the chemical preparation tank 61 are restored.

[0086] In this manner, in this embodiment, when the workpiece W is degreased, surface-conditioned, or chemically treated in the degreasing tank 31, the surface-conditioning tank 49, or the chemical layer 61, the degreasing chemical is supplied to the degreasing tank 31 from the degreasing chemical tank 41, the surface-conditioning chemical is supplied to the surface-conditioning tank 49 from the surface-conditioning chemical tank 53, or the chemical chemical is supplied to the chemical tank 61 from the chemical chemical tank 65, depending on the weight of the workpiece W.

[0087] Therefore, in this embodiment, chemicals are replenished in an appropriate amount according to the amount used, based on the weight of the workpiece W, which correlates with the surface area, and the concentration of the chemicals in the degreasing tank 31, the surface conditioning tank 49, or the chemical layer 61 can be restored.

[0088] In the above, chemical supply processing for degreasing steps 3, 5, and 7 was performed in degreasing step 2 7, but chemical supply processing can also be performed in the same manner in each of preliminary degreasing step 3, degreasing step 1 5, and degreasing step 2 7. [Explanation of symbols]

[0089] double work 21 Electrodeposition process 31 Degreasing tank (pre-treatment tank) 33 Degreasing agent (pre-treatment agent) 37 PLC (control unit) 45, 57, 69 Metering pump 49 Surface conditioning tank (pre-treatment tank) 51 Surface treatment agent (pre-treatment agent) 61 Chemical tank (pre-treatment tank) 63 Chemical conversion treatment agent (pretreatment agent)

Claims

1. a pretreatment tank containing a pretreatment agent containing a chemical for pretreatment of electrodeposition coating of workpieces made of the same type of constituent material; a pump that operates in a timely manner to replenish the chemicals to the pretreatment tank; a control unit that restores the concentration of the chemical in the pretreatment tank by the pump in accordance with a weight that correlates with a surface area of ​​the workpiece that has been pretreated; A pretreatment chemical supply system including:

2. 2. The pretreatment chemical replenishment system of claim 1, The workpiece is mainly made of a plate material. Pretreatment chemical replenishment system.

3. 3. The pretreatment chemical supply system of claim 2, The workpieces are of a plurality of types with different sizes, Pretreatment chemical replenishment system.

4. A pretreatment chemical supply system according to claims 1 to 3, The pretreatment step includes at least a degreasing step and a chemical conversion step. Pretreatment chemical replenishment system.

5. A pretreatment chemical supply method for supplying a pretreatment agent containing a pretreatment agent for electrodeposition coating of workpieces made of the same type of constituent material to a pretreatment tank containing the pretreatment agent, the method comprising: The chemical is replenished to the pretreatment tank in accordance with a weight correlated with a surface area of ​​the workpiece that has been pretreated, thereby restoring the concentration of the chemical in the pretreatment tank. Pretreatment chemical replenishment method.

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