A method and an arrangement to monitor quality of a product made by using a crimping machine

Abstract

In the invention quality of a product made by using a crimping machine is monitored. A pressure curve of the product made by the crimping machine is monitored, and it is determinated whether the pressure curve is inside an allowed area. The product is accepted if the pressure curve is inside the allowed area.

Description

[0001] A method and an arrangement to monitor quality of a product made by using a crimping machine

[0002] Field of technology

[0003] The invention relates to arrangements to monitor quality of products made by a crimping machine.

[0004] Prior art

[0005] Crimping machines are used to make indentions and crimping connections for example to pipes. A product made by the crimping machine can, for example, be a pipe having a choke section, a crimp connection on a pipe, a hose coupling etc.

[0006] Crimping machines may use hydraulic pressure where the jaws of the machine are pressed hydraulically against the product to be made. Some embodiments use pneumatic pressure or mechanical / electric power elements to press the jaws towards the product. Power to provide pneumatic or hydraulic pressure can be achieved by a compressor using electric power or other power source.

[0007] In hydraulic crimping machines the measurement result of the pressure measurement of the hydraulic oil indicates properly the force required for work. As the object to be compressed is pressed, the pressure of the oil needed for the job and the amount of work required from the oil pump also normally increase. When pressing similar objects, the curves formed by successive pressure measurements are largely similar. Pressure curves that differ from each other tell about the differences in the objects to be pressed or the condition of the working methods, e.g. the positioning of the piece. The pressure measurement curve can therefore be used in quality assurance. The pressure value in the curve increases when the object is pressed further. So, an x-axis can represent the diameter of the product / object to be pressed. The more the product is pressed the smaller the diameter is. An y-axis can represent an oil pressure value. In order to allow some differences between the similar products, an allowed pressure curve area is used. The pressure curve of the pressed product must be inside the allowed pressure curve area in order to be accepted. Currently used pressure curve areas work well with relatively simple pressure curve shape, but not so good with more complex curve shapes. The curve shapes depend on the products to be made by the crimping machine.

[0008] Short description

[0009] The object of the invention is to provide a new method and arrangement to form a product specific pressure curve area, which takes into account product specific features better for crimping the accepted product. The object is achieved in a way described in the independent claims. Dependent claims illustrate different embodiments of the invention.

[0010] A method for monitoring quality of a product made by using a crimping machine according to the invention comprises steps of monitoring a pressure curve of the product made by the crimping machine; determinate whether the pressure curve is inside an allowed area; and accepting the product if the pressure curve is inside the allowed area. The method further comprises pre-steps of making at least one test piece of said product; producing a pressure curve for each test piece; determining several measurement points in the area of the pressure curve / s of the test piece / s; determining minimum and maximum values of the pressure curve / s of the test piece / s at each measurement point; determining an upper tolerance value and lower tolerance value, the tolerance values being zero or more; adding the upper tolerance value to said maximum values, and subtracting the lower tolerance value from said minimum values, and determining the allowed area by using said maximum values, added by the upper tolerance value, and said minimum values subtracted by the lower tolerance value.

[0011] A crimping machine arrangement to monitor quality of a product made by a crimping machine according to the invention comprises a monitoring unit to monitor a pressure curve of the product made by the crimping machine, and an evaluation unit to determinate whether the pressure curve is inside an allowed area, and accepting the product if the pressure curve is inside the allowed area. The arrangement further comprises a test computing module to produce a pressure curve for each test piece made by the crimping machine.

[0012] The test computing module is also arranged to determine several measurement points in the area of the pressure curve / s of the test piece / s; determine minimum and maximum values of the pressure curve / s of the test piece / s at each measurement point; determine an upper tolerance value and lower tolerance value, the tolerance values being zero or more, the upper tolerance value being added to said maximum values, and the lower tolerance value being subtracted from said minimum values; and determine the allowed area by using said maximum values, added by the upper tolerance value, and said minimum values subtracted by the lower tolerance value, the allowed area to be used by the evaluation unit.

[0013] List of figures

[0014] In the following, the invention is described in more detail by reference to the enclosed drawings, where

[0015] Figure 1 illustrates an example of an inventive arrangement;

[0016] Figure 2 illustrates a flow chart example of an inventive method;

[0017] Figure 3 illustrates a diagram example of a pressure area;

[0018] Figure 4 illustrates another diagram example of a pressure area.

[0019] Description of the invention

[0020] Figure 1 illustrates a schematic example of the inventive arrangement. It shows the invention very schematically, not showing, for example, all elements of a crimping machine 1.

[0021] A crimping machine arrangement to monitor quality of a product made by a crimping machine 1 according to the invention comprises a monitoring unit 6 to monitor a pressure curve of the product made by the crimping machine, and an evaluation unit 7 to determinate whether the pressure curve is inside an allowed area, and accepting the product if the pressure curve is inside the allowed area. The monitoring unit 6 is connected to a pressure sensor 4 in order to get measurements of oil pressure. The oil is pressurized, for example, in a compressor (not shown in the figure) and delivered 4A to a pipeline 3 connected to the jaws 2 of the crimping machine 1. The pressurized oil presses the jaws towards a product (not shown), which is situated in the crimping area 9 of the crimping machine 1 . The jaws 2 crimps the product in order to make a desired indention, crimp connection etc.

[0022] The monitoring unit 6 is also connected to a position sensor / s 5 in order to get position data of the jaws. The position sensor / s can also be a virtual sensor / s, in which case the positions of the jaws are calculated from other available data, like oil pressure data, a pressing time, geometry data of the jaws etc. The position data can used to indicate how much the jaws are crimped the product. For example, if the product to be made is a pipe having a choke, an initial diameter of the pipe and the diameter of the choke section of the pipe can be monitored through the crimping process. In other words, dimensional change of the product can be monitored.

[0023] So, the monitoring unit has information from the oil pressure used for crimping and the dimensional change of the product. These can be used to provide and monitor the pressure curve of the product. As said above, the x-axis can represent the diameter of the product / object to be pressed and the y-axis can represent the oil pressure, or vice versa. The pressure curve must be inside the allowed area in order that the product is accepted by the evaluation unit 7 Otherwise the product is rejected.

[0024] The arrangement further comprises a test computing module 8 to produce a pressure curve for each test piece made by the crimping machine. Test pieces are not to be sold. They are used to obtain a product specific pressure curve properties. Figure 3 shows an example 30 of the pressure curves 31 , 32, 33 of three test pieces. The x- axis indicates the diameter of product in millimetres during the crimping process, and the y-axis indicates used pressure in bars.

[0025] So, the test computing module 8 is also arranged to determine several measurement points 36, 37 in the area of the pressure curve / s of the test piece / s, and to determine minimum 39, 311 and maximum 38, 310 values of the pressure curve / s of the test piece / s at each measurement point. The measurement points are preferably uniformly pitched, but spacing can be ununiform as well. Further, the test computing module 8 is arranged to determine an upper tolerance value and lower tolerance value, the tolerance values being zero or more. In the example of figure 3 the upper tolerance value is five bars and the lower tolerance value is two bars. A user may insert the tolerance values into the arrangement, for example using a touch screen or another device, or the test computing module 8 is arranged to utilize a predetermined tolerance data, which is a product type specific. The predetermined tolerance data can be in the memory of the arrangement.

[0026] The upper tolerance value is added to said maximum values, and the lower tolerance value is subtracted from said minimum values by the test computing module 8. The module 8 also determines the allowed area by using said maximum values added by the upper tolerance value 38A, 310A, and said minimum values subtracted by the lower tolerance value 39B, 311 B.

[0027] The tolerance added maximum values 38A, 310A, are connected to each other by lines in order to form an upper border line 34. Correspondingly, the tolerance subtracted minimum values 39B, 311 B are connected to each other by lines in order to form a lower border line 35. The area between the upper border line 34 and the lower border line 35 is the allowed area for the pressured curves to the products to be made. The allowed area is used by the evaluation unit 7.

[0028] Figure 2 illustrates a flow chart example of the inventive method. The method for monitoring quality of a product made by using a crimping machine according to the invention comprises steps of monitoring 28 a pressure curve of the product made by the crimping machine; determinate 29 whether the pressure curve is inside an allowed area; and accepting 210 the product if the pressure curve is inside the allowed area.

[0029] The method further comprises pre-steps of making 21 at least one test piece of said product; producing 22 a pressure curve for each test piece; determining 23 several measurement points in the area of the pressure curve / s of the test piece / s; determining 24 minimum and maximum values of the pressure curve / s of the test piece / s at each measurement point; determining 25 an upper tolerance value and lower tolerance value, the tolerance values being zero or more; adding 26 the upper tolerance value to said maximum values, and subtracting the lower tolerance value from said minimum values, and determining 27 the allowed area by using said maximum values, added by the upper tolerance value, and said minimum values subtracted by the lower tolerance value.

[0030] As can be seen the arrangement according to the invention utilizes the inventive method. There can, for example, be 50 - 100 measurement points in the area of the pressure curve / s of the test piece / s. A used measurement interval, dimensional change of the product and a product type information may be used for determining the number of the measurement points.

[0031] It is possible that there is at least one section in the area of the pressure curve / s of the test piece / s wherein a section specific upper and lower tolerance values of the pressure curve / s of the test piece / s at each measurement point in the section are determined. The section is not the whole area / range of the pressure curve. In this way a section specific upper border line and a lower border line can be formed. Figure 4 illustrates an example 40 of an allowed pressure curve area 41 , wherein a section between 21 - 20 mm dimensional change has a section specific upper and lower tolerance values of the pressure curve / s of the test piece / s are used. In the section the upper tolerance value is 10 bars and the lower tolerance value is 10 bars. In other words, the allowed area is larger in the section than in the rest area of the whole allowed area 41 between the upper border line 42 and the lower border line 43. As can be seen product specific properties can be taken into account accurately during a dimensional change process. At some phase / s during the crimping the criteria for an allowed product can be more loose, and at other phase / s more stringent. Also the section specific tolerances can be user insertable into the arrangement, or the predetermined tolerance data stored in the memory of the arrangement. Naturally, the method according to the invention can have this function. There can, for example, be 1 - 8 sections in whole area of the pressure curve.

[0032] Further it is possible that when making 21 the test pieces, a pressure curve of a test piece being clearly abnormal is not accepted, and a new test piece is made. The test pieces can, for example, be made 1 - 10 in order to get enough information to form the allowed area of the pressure curve.

[0033] The inventive arrangement can be produced as software, which is arranged to run in a crimping machine computer unit, having at least one processor and memory. A display, like a touch screen can also be used. Specific circuit boards can also be used. Although in the example of figure 1 the monitoring unit 6, the evaluation unit 7 and the test computing module 8 are illustrated separately, they can also be integrated to a one entity.

[0034] The invention provides an advanced method and arrangement to monitor the quality of the product made by a crimping machine. The crimping machine can be a type having jaws around the object / s to be crimped. A product specific property, especially in view of the crimping process, can be taken into account more accurately than in prior art solutions. Measurements and tolerances are adjustable for each product. The properties of each product can be taken into account more specifically in order to accept a crimping machine manufactured copy of the product.

[0035] It is evident from the above that the invention is not limited to the embodiments described in this text but can be implemented in many other different embodiments within the scope of the independent claims.

Claims

Claims1 . A method for monitoring quality of a product made by using a crimping machine wherein the method comprises steps of- monitoring (28) a pressure curve of the product made by the crimping machine,- determinate (29) whether the pressure curve is inside an allowed area,- accepting (210) the product if the pressure curve is inside the allowed area, characterised in that the method further comprises pre-steps of- making (21 ) at least one test piece of said product,- producing (22) a pressure curve for each test piece,- determining (23) several measurement points in the area of the pressure curve / s of the test piece / s,- determining (24) minimum and maximum values of the pressure curve / s of the test piece / s at each measurement point.- determining (25) an upper tolerance value and lower tolerance value, the tolerance values being zero or more,- adding (26) the upper tolerance value to said maximum values, and subtracting the lower tolerance value from said minimum values, and- determining (27) the allowed area by using said maximum values, added by the upper tolerance value, and said minimum values subtracted by the lower tolerance value.

2. A method according to claim 1 , characterised in that there are 50 - 100 measurement points in the area of the pressure curve / s of the test piece / s.

3. A method according to claim 1 or 2, characterised in that there is at least one section in the area of the pressure curve / s of the test piece / s wherein a section specific upper and lower tolerance values of the pressure curve / s of the test piece / s at each measurement point in the section are determined.

4. A method according to claim 1 , 2 or 3, characterised in that there are 1 - 8 sections.

5. A method according to any of claims 1 - 4, characterised in that 1 - 10 said test pieces are made.

6. A method according to any of claims 1 - 5, characterised in that when making (21) the test pieces, a pressure curve of a test piece being clearly abnormal is not accepted, and a new test piece is made.

7. A crimping machine arrangement to monitor quality of a product made by a crimping machine (1) wherein the arrangement comprises a monitoring unit (6) to monitor a pressure curve of the product made by the crimping machine, and an evaluation unit (7) to determinate whether the pressure curve is inside an allowed area, and accepting the product if the pressure curve is inside the allowed area, characterised in that the arrangement further comprises a test computing module (8) to produce a pressure curve for each test piece made by the crimping machine, the test computing module being also arranged to- determining several measurement points in the area of the pressure curve / s of the test piece / s,- determining minimum and maximum values of the pressure curve / s of the test piece / s at each measurement point,- determining an upper tolerance value and lower tolerance value, the tolerance values being zero or more, the upper tolerance value being added to said maximum values, and the lower tolerance value being subtracted from said minimum values, and- determining the allowed area by using said maximum values, added by the upper tolerance value, and said minimum values subtracted by the lower tolerance value, the allowed area to be used by the evaluation unit (7).

8. An arrangement according to claim 7, characterised in that there are 50 - 100 measurement points in the area of the pressure curve / s of the test piece / s.

9. An arrangement according to claim 7 or 8, characterised in that there is at least one section in the area of the pressure curve / s of the test piece / s wherein a section specific upper and lower tolerance values of the pressure curve / s of the test piece / s at each measurement point in the section are determined.

10. An arrangement according to claim 7, 8 or 9, characterised in that there are 1- 8 sections.

11. An arrangement according to any of claims 7 - 10, characterised in that when making the test pieces, a pressure curve of a test piece being clearly abnormal is not accepted by the test computing module (8).

12. An arrangement according to any of claims 7 - 11 , characterised in that the crimping machine (1 ) has jaws around the product to be made.

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