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Analysis of crimping terminal and crimping process control

  • Categories:Company News
  • Author:线束智造
  • Origin:本文转载线束智造公众号
  • Time of issue:2020-07-20 10:15
  • Views:

(Summary description)BellmouthAftercrimping,abellmouthisformedontheedgeofthecorewirecrimpingframetobecomeacorewirefunnel.Thisfunnelreducesthepossibilitythatthesharpedgeofthecorewirecrimpingframewillcutorcutthecorewire.Thethicknessofthebellmouthofthecorewirecrimpingframeshouldgenerallybeabout1to2timesthethicknessoftheterminalmaterial.  BendingtestThebendingtestisamethodtotestthecrimpqualityoftheinsulationsheath.Webendthewirebackandforthseveraltimes,andthenevaluatethemovementoftheinsulationsheathandcorewirebundle.Asarule,thecrimpingoftheinsulatingsheathmustwithstandthewirebendsat60to90degreesinanydirectionseveraltimes.Whencrimpingthinwires,becarefulnottocuttheinsulatinglayerbehindthecrimpingpartoftheinsulatingsheath.  ConductorbrushTheconductorbrushisacorewirebundlepassingthroughthecorewirecrimpingframeandfacingtheterminalcontactarea.Duetothecorewirebundleprotrudingfromthecrimpingframe,themechanicalcrimpingforcecanallactonthecorewire.Theconductorbrushshouldnotextendtotheterminalinsertionarea.  CorecrimpingThecorewirecrimpingisthecompressionoftheterminalcrimpingframeonthecorewire.Thisoperationestablishesanelectricalpathwithlowresistanceandhighcurrentcarryingcapacity.  CorewirecrimpheightThecorewirecrimpheightisthedistancefromthetopsurfaceofthecrimpformedtothebottomradialsurface.Thisheightdoesnotincludetheheightoftheextrusion(seeabovepicture).Thecrimpheightmeasurementadoptsafastandnon-destructivemeasurementmethodtomeasurewhetherthecrimpingframeoftheterminalsurroundingthecorewireiscorrectlycrimpedtothecorewire.Themeasurementresultisanimportantindicatorinprocesscontrol.Whenformulatingcrimpheightspecifications,itisusuallynecessarytotakeintoaccounttheelectricalandmechanicalpropertiesofcrimpingfordifferentstrands,coatings,terminalmaterialsandelectroplatedwires.Althoughdifferentoptimalcrimpheightscanbeformulatedfordifferentstrandsandterminalplating,generallyonlyonecrimpheightisspecified.  TaillengthAftertheterminalisseparatedfromthecarriertape,theterminalheadisnotflatbutaprotrudingpart,whichiscalledtailcutting.Asarule,thetaillengthshouldbe1.0 to1.5 timesthethicknessoftheterminalmaterial(pleaserefertothespecificterminalspecifications).Ifthetailistoolong,theterminals(duetoimproperinsertion)willbeexposedoutsidetheconnectorplasticshell,ortheelectricalspacingrequirementswillnotbemet.Usually,atoolcanbesettomakethecuttingtaillevelwiththethicknessofamaterial.  Extrusion(outreach)Crimpingcausesabductionatthebottomofthewirecrimpingframe.Thereasonfortheabductionisthegapbetweenthepunchandtheanvil.Iftheanviliswornortheterminalisover-punched,itwillcauseexcessiveabductionofthebottomoftheterminal.Ifthepunchandanvilaremisaligned,ifthefeedingadjustmentfunctionisturnedoff,andifthedistanceoftheterminalbeingdraggedisnotenoughortoolarge,anunevenextrusioneffectwilloccur.  Insulationcovercrimping(stressrelief)Insulatingsheathcrimpingcanprovidesupportforthewiresothatthewirecanbeinsertedintotheplasticcase.Italsohelpstheterminaltoresistvibration.Theterminalmustgraspthewireasfirmlyaspossible,butmustnotpressthroughtheinsulatingsheathandtouchthecorewire.Thecriterionforjudgingwhethertheinsulatingsheathispress-fittedornotissubjective,dependingontheconnectionanduseoccasion.Forspecificapplications,werecommendthatyouperformcorrespondingbendingteststodeterminewhetherthestressreliefabilityprovidedbytheinsulationcrimpingisqualified.  InsulationcovercrimpheightThecrimpingheightoftheinsulationsheathisusuallynotspecifiedbecauseoftheexistenceofvariousinsulationsheaththicknesses,materialsandhardness.Mostterminalsaredesignedtoaccommodatemultiplespecificationsofwires.Iftheterminaliswithinitsapplicablerange,itmaynotbeabletocompletelyembracetheinsulatingsheath,oritmaynotbeabletoholdthewiretightly.Butinthiscase,thecrimpingoftheinsulationcoverisusuallyqualified.  1.Ifthewireistoothick,theinsulationsheathcrimpingframeshouldholdatleast88%ofthewire.2.Ifthewireistoothin,theinsulatingsheathcrimpingframeshouldholdatleast50%ofthewireandholdtheheadofthewirefirmly.  Tocheckthecrimpingsectionoftheinsulationsheath,cutthewirefromthebackoftheterminalsothatthecutsurfaceisflushwiththebackoftheterminal.Afterdeterminingthebestcrimpsetting,recordthecrimpheightoftheinsulationsheath.Theoperatorcancheckthecrimpheightoftheinsulationsheathaspartofthesetupprocedure.  EndpositionofinsulationsheathThispositionisthepositionoftheendoftheinsulationsheathinthetransitionzonefromtheinsulationsheathcrimpingpointtothecorewirecrimpingpoint.Inthistransitionzone,thelengthofthecorewireshouldbethesameasthelengthoftheinsulationsheath.Thepositioningoftheendoftheinsulatingsheathshouldensurethatthereisaninsulatingsheathundertheentirelengthoftheinsulatingsheathcrimpingframe.Ontheotherhand,theinsulatingsheathmustnotextendunderthecorecrimpingframe.Ifcrimpingwithadesktopcrimpingmachine,theendpositionoftheinsulationsheathisdeterminedbythewirestopandstrippinglength.Ifanautomaticwireprocessorisusedforcrimping,theendpositionoftheinsulationsheathisdeterminedbythein/outadjustmentofthecrimpingmachine.  StrippinglengthThestrippinglengthist

Analysis of crimping terminal and crimping process control

(Summary description)BellmouthAftercrimping,abellmouthisformedontheedgeofthecorewirecrimpingframetobecomeacorewirefunnel.Thisfunnelreducesthepossibilitythatthesharpedgeofthecorewirecrimpingframewillcutorcutthecorewire.Thethicknessofthebellmouthofthecorewirecrimpingframeshouldgenerallybeabout1to2timesthethicknessoftheterminalmaterial.  BendingtestThebendingtestisamethodtotestthecrimpqualityoftheinsulationsheath.Webendthewirebackandforthseveraltimes,andthenevaluatethemovementoftheinsulationsheathandcorewirebundle.Asarule,thecrimpingoftheinsulatingsheathmustwithstandthewirebendsat60to90degreesinanydirectionseveraltimes.Whencrimpingthinwires,becarefulnottocuttheinsulatinglayerbehindthecrimpingpartoftheinsulatingsheath.  ConductorbrushTheconductorbrushisacorewirebundlepassingthroughthecorewirecrimpingframeandfacingtheterminalcontactarea.Duetothecorewirebundleprotrudingfromthecrimpingframe,themechanicalcrimpingforcecanallactonthecorewire.Theconductorbrushshouldnotextendtotheterminalinsertionarea.  CorecrimpingThecorewirecrimpingisthecompressionoftheterminalcrimpingframeonthecorewire.Thisoperationestablishesanelectricalpathwithlowresistanceandhighcurrentcarryingcapacity.  CorewirecrimpheightThecorewirecrimpheightisthedistancefromthetopsurfaceofthecrimpformedtothebottomradialsurface.Thisheightdoesnotincludetheheightoftheextrusion(seeabovepicture).Thecrimpheightmeasurementadoptsafastandnon-destructivemeasurementmethodtomeasurewhetherthecrimpingframeoftheterminalsurroundingthecorewireiscorrectlycrimpedtothecorewire.Themeasurementresultisanimportantindicatorinprocesscontrol.Whenformulatingcrimpheightspecifications,itisusuallynecessarytotakeintoaccounttheelectricalandmechanicalpropertiesofcrimpingfordifferentstrands,coatings,terminalmaterialsandelectroplatedwires.Althoughdifferentoptimalcrimpheightscanbeformulatedfordifferentstrandsandterminalplating,generallyonlyonecrimpheightisspecified.  TaillengthAftertheterminalisseparatedfromthecarriertape,theterminalheadisnotflatbutaprotrudingpart,whichiscalledtailcutting.Asarule,thetaillengthshouldbe1.0 to1.5 timesthethicknessoftheterminalmaterial(pleaserefertothespecificterminalspecifications).Ifthetailistoolong,theterminals(duetoimproperinsertion)willbeexposedoutsidetheconnectorplasticshell,ortheelectricalspacingrequirementswillnotbemet.Usually,atoolcanbesettomakethecuttingtaillevelwiththethicknessofamaterial.  Extrusion(outreach)Crimpingcausesabductionatthebottomofthewirecrimpingframe.Thereasonfortheabductionisthegapbetweenthepunchandtheanvil.Iftheanviliswornortheterminalisover-punched,itwillcauseexcessiveabductionofthebottomoftheterminal.Ifthepunchandanvilaremisaligned,ifthefeedingadjustmentfunctionisturnedoff,andifthedistanceoftheterminalbeingdraggedisnotenoughortoolarge,anunevenextrusioneffectwilloccur.  Insulationcovercrimping(stressrelief)Insulatingsheathcrimpingcanprovidesupportforthewiresothatthewirecanbeinsertedintotheplasticcase.Italsohelpstheterminaltoresistvibration.Theterminalmustgraspthewireasfirmlyaspossible,butmustnotpressthroughtheinsulatingsheathandtouchthecorewire.Thecriterionforjudgingwhethertheinsulatingsheathispress-fittedornotissubjective,dependingontheconnectionanduseoccasion.Forspecificapplications,werecommendthatyouperformcorrespondingbendingteststodeterminewhetherthestressreliefabilityprovidedbytheinsulationcrimpingisqualified.  InsulationcovercrimpheightThecrimpingheightoftheinsulationsheathisusuallynotspecifiedbecauseoftheexistenceofvariousinsulationsheaththicknesses,materialsandhardness.Mostterminalsaredesignedtoaccommodatemultiplespecificationsofwires.Iftheterminaliswithinitsapplicablerange,itmaynotbeabletocompletelyembracetheinsulatingsheath,oritmaynotbeabletoholdthewiretightly.Butinthiscase,thecrimpingoftheinsulationcoverisusuallyqualified.  1.Ifthewireistoothick,theinsulationsheathcrimpingframeshouldholdatleast88%ofthewire.2.Ifthewireistoothin,theinsulatingsheathcrimpingframeshouldholdatleast50%ofthewireandholdtheheadofthewirefirmly.  Tocheckthecrimpingsectionoftheinsulationsheath,cutthewirefromthebackoftheterminalsothatthecutsurfaceisflushwiththebackoftheterminal.Afterdeterminingthebestcrimpsetting,recordthecrimpheightoftheinsulationsheath.Theoperatorcancheckthecrimpheightoftheinsulationsheathaspartofthesetupprocedure.  EndpositionofinsulationsheathThispositionisthepositionoftheendoftheinsulationsheathinthetransitionzonefromtheinsulationsheathcrimpingpointtothecorewirecrimpingpoint.Inthistransitionzone,thelengthofthecorewireshouldbethesameasthelengthoftheinsulationsheath.Thepositioningoftheendoftheinsulatingsheathshouldensurethatthereisaninsulatingsheathundertheentirelengthoftheinsulatingsheathcrimpingframe.Ontheotherhand,theinsulatingsheathmustnotextendunderthecorecrimpingframe.Ifcrimpingwithadesktopcrimpingmachine,theendpositionoftheinsulationsheathisdeterminedbythewirestopandstrippinglength.Ifanautomaticwireprocessorisusedforcrimping,theendpositionoftheinsulationsheathisdeterminedbythein/outadjustmentofthecrimpingmachine.  StrippinglengthThestrippinglengthist

  • Categories:Company News
  • Author:线束智造
  • Origin:本文转载线束智造公众号
  • Time of issue:2020-07-20 10:15
  • Views:
Information

Bell mouth
After crimping, a bell mouth is formed on the edge of the core wire crimping frame to become a core wire funnel. This funnel reduces the possibility that the sharp edge of the core wire crimping frame will cut or cut the core wire. The thickness of the bell mouth of the core wire crimping frame should generally be about 1 to 2 times the thickness of the terminal material.
 
 
Bending test
The bending test is a method to test the crimp quality of the insulation sheath. We bend the wire back and forth several times, and then evaluate the movement of the insulation sheath and core wire bundle. As a rule, the crimping of the insulating sheath must withstand the wire bends at 60 to 90 degrees in any direction several times. When crimping thin wires, be careful not to cut the insulating layer behind the crimping part of the insulating sheath.
 
 
Conductor brush
The conductor brush is a core wire bundle passing through the core wire crimping frame and facing the terminal contact area. Due to the core wire bundle protruding from the crimping frame, the mechanical crimping force can all act on the core wire. The conductor brush should not extend to the terminal insertion area.
 
 
Core crimping
The core wire crimping is the compression of the terminal crimping frame on the core wire. This operation establishes an electrical path with low resistance and high current carrying capacity.
 
 
Core wire crimp height
The core wire crimp height is the distance from the top surface of the crimp formed to the bottom radial surface. This height does not include the height of the extrusion (see above picture). The crimp height measurement adopts a fast and non-destructive measurement method to measure whether the crimping frame of the terminal surrounding the core wire is correctly crimped to the core wire. The measurement result is an important indicator in process control. When formulating crimp height specifications, it is usually necessary to take into account the electrical and mechanical properties of crimping for different strands, coatings, terminal materials and electroplated wires. Although different optimal crimp heights can be formulated for different strands and terminal plating, generally only one crimp height is specified.
 
 
Tail length
After the terminal is separated from the carrier tape, the terminal head is not flat but a protruding part, which is called tail cutting. As a rule, the tail length should be 1.0  to 1.5  times the thickness of the terminal material (please refer to the specific terminal specifications). If the tail is too long, the terminals (due to improper insertion) will be exposed outside the connector plastic shell, or the electrical spacing requirements will not be met. Usually, a tool can be set to make the cutting tail level with the thickness of a material.
 
 
Extrusion (outreach)
Crimping causes abduction at the bottom of the wire crimping frame. The reason for the abduction is the gap between the punch and the anvil. If the anvil is worn or the terminal is over-punched, it will cause excessive abduction of the bottom of the terminal. If the punch and anvil are misaligned, if the feeding adjustment function is turned off, and if the distance of the terminal being dragged is not enough or too large, an uneven extrusion effect will occur.
 
 
Insulation cover crimping (stress relief)
Insulating sheath crimping can provide support for the wire so that the wire can be inserted into the plastic case. It also helps the terminal to resist vibration. The terminal must grasp the wire as firmly as possible, but must not press through the insulating sheath and touch the core wire. The criterion for judging whether the insulating sheath is press-fitted or not is subjective, depending on the connection and use occasion. For specific applications, we recommend that you perform corresponding bending tests to determine whether the stress relief ability provided by the insulation crimping is qualified.
 
 
Insulation cover crimp height
The crimping height of the insulation sheath is usually not specified because of the existence of various insulation sheath thicknesses, materials and hardness. Most terminals are designed to accommodate multiple specifications of wires. If the terminal is within its applicable range, it may not be able to completely embrace the insulating sheath, or it may not be able to hold the wire tightly. But in this case, the crimping of the insulation cover is usually qualified.
 
 
1. If the wire is too thick, the insulation sheath crimping frame should hold at least 88% of the wire.
2. If the wire is too thin, the insulating sheath crimping frame should hold at least 50% of the wire and hold the head of the wire firmly.
 
 
To check the crimping section of the insulation sheath, cut the wire from the back of the terminal so that the cut surface is flush with the back of the terminal. After determining the best crimp setting, record the crimp height of the insulation sheath. The operator can check the crimp height of the insulation sheath as part of the setup procedure.
 
 
End position of insulation sheath
This position is the position of the end of the insulation sheath in the transition zone from the insulation sheath crimping point to the core wire crimping point. In this transition zone, the length of the core wire should be the same as the length of the insulation sheath. The positioning of the end of the insulating sheath should ensure that there is an insulating sheath under the entire length of the insulating sheath crimping frame. On the other hand, the insulating sheath must not extend under the core crimping frame. If crimping with a desktop crimping machine, the end position of the insulation sheath is determined by the wire stop and stripping length. If an automatic wire processor is used for crimping, the end position of the insulation sheath is determined by the in/out adjustment of the crimping machine.
 
 
Stripping length

The stripping length is the length of the core wire that is exposed after the insulation sheath of the wire is stripped. When the end position of the insulating layer is in the middle of the transition area between the insulating sheath crimping place and the core wire crimping place, the stripping length determines the length of the conductor brush.
 
 
Crimping process control
 
 
The crimping process is a process of interaction among terminals, wires, tools, personnel, methods, procedures, and environmental factors. When this process is controlled, qualified crimping can be achieved. Quality control is an important part of high-quality crimping operations. Tool setting or inspection work will not take you too much time, but it will avoid thousands of dollars in losses due to rework or remanufacturing.
 
 
Deviation is a slight change from one crimp to another. There are two kinds of deviations: ordinary deviation or special deviation. Deviation usually affects the consistency of the crimping effect, and the deviation is caused by many small reasons. Common deviations are caused by inherent tolerances in the coiled wire or terminal. It is also due to the natural errors of the peeling and crimping equipment.
 
 
To reduce common deviations, the wire, terminal, and mold manufacturers are usually replaced.
 
 
Certain special circumstances can cause special deviations, which are irregular and unpredictable. If the mold loosened or the mold was damaged after the first few hundred terminals were crimped and the process was blocked, and we did not follow up and inspect the entire crimping process, the problem may not be discovered until thousands of terminals have been crimped.
 
 
Process Capability
 
 
Before using the new crimping tool for production, please research with the specific wire that will be used in production. The capability study is based on the assumption of a normal distribution (bell-shaped curve), and the study estimates the likelihood of unqualified measurements.
 
 
*PPM: parts per million of potential defects.
 
 
At least 25 samples should be taken during the crimping process. Calculate the average and standard deviation of the sample. The company below defines Cp (capability index). The value of Cp can range from zero to infinity. The larger the value, the stronger the capability of the process. Values ​​greater than 1.33 are considered acceptable values ​​for most applications.
 
 
Cp calculation formula: allowable error/6X standard deviation
 
 
Cpk (Process Capability Index) indicates whether the tested process can produce products less than the allowable error. If the process is set to the standard average value, the Cpk value is equal to Cp. If Cpk is negative, the average process value exceeds the specification limit. If Cpk is between 0 and 1, some six sigma distribution ranges exceed the allowable range. If the Cpk value is greater than 1, the six sigma distribution range is completely within the allowable range. The result calculated by the following formula, whichever is smaller, is the Cpk value:
 
 
Six Sigma is the goal of many companies because it represents almost zero defects. Whether a company is capable of reaching the level of Six Sigma depends on the general deviation of its manufacturing process; manual crimping tools produce greater deviations than using crimping machines and molds for crimping, and the table ends cause greater deviations than wire processing machines.
 
 
A part of crimping deviation is measurement deviation, which is caused by different measurement equipment and different measurement methods of the same measurement personnel. The crimp micrometer is more accurate than the representative caliper. The measuring instrument must have sufficient accuracy.
 
 
Two operators may use different methods to measure the same part. The same operator may use different methods when measuring the same part with two different gauges. Molex recommends conducting a gauge capability study to find out which part of the deviation is due to measurement errors. The miniature terminal is crimped to the thin wire, and the crimping height deviation range should be narrow, so as to maintain the tensile strength. The measurement error will increase the measured deviation value, thereby reducing the Cpk value.
 
 
If the data obtained from the production crimp is significantly different from the data obtained from the (tool) capability study, the capability of the crimp tool needs to be reconfirmed.
 
 
produce
 
 
Before the tool is ready to start production, its capability level needs to be determined. Many wire harness manufacturers only crimp hundreds or thousands of wires at a time. In this case, it is unrealistic and cost-effective to perform a 25-piece capacity measurement for each tool setting.
 
 
Visual inspection
 
 
The operator must follow the standard operating procedures to manually separate each bundle of wires, visually inspect the bell mouth, conductor brush, the end position of the insulation sheath, tail trimming and insulation sheath crimping, or use the intelligent pressure management system for detection.
 
 
Control icon
 
 
The crimp height is generally drawn as a control chart, because the crimp height measurement is a fast and non-destructive measurement and is critical to the electrical and mechanical reliability of the terminal. There are three main purposes for drawing a control chart. First of all, the number of samples collected for setting is usually small, so its statistical value is limited. Second, the occurrence of special circumstances that can cause consequences in the process is irregular and unpredictable, and there must be a means to record deviations in time. This can prevent thousands of termination joints from being scrapped after the operation is over. The third and most important point is that data is necessary to evaluate and improve the crimping process.
 
 
After setting up the tool and determining the wire diameter, use a single chart to record the wire color change, wire length change, terminal material change, or setting adjustment. Record the data points on the chart, and then adjust the crimp height. If the data is recorded after each adjustment, the crimping process can probably control the quality. The results may indicate that the process does not need to be improved, and the operator needs to make as many diagrams as possible. To manage the manufacturing process, the only truly effective and economical way is to understand, monitor and reduce the inherent sources of deviation in the manufacturing process. And every minute spent on setting up or adjusting is in vain.
 
 
What does this chart show?
 
 
The control limit of 5 samples for each measurement = the average of the readings of the 5 samples + 0.577X the average of the range of each measurement
 
 
It shows that the manufacturing process drifted during the 12th and 13th measurements. The reason for this deviation may be the replacement of wires, batch replacement of terminals, blockage of the crimping machine and damage to the mold, replacement of operators, or adjustments to the crimping of the insulation sheath. Since the measured value is still qualified according to the specification, will you stop the crimp production and adjust the crimp height?
 
 
It may be necessary to adjust the crimp height due to the offset caused by the replacement of the material during the manufacturing process. Deviations after clogging do not indicate adjustments, but need to pay close attention to the mold. The shift of operators in the manufacturing process does not mean that adjustments are to be made, but rather to evaluate measurement capabilities. The purpose of the control chart is to find out the cause of the offset to determine whether to adjust the process.
 
 
 
This article is reproduced in the public number of Wiring Harness Intelligent Manufacturing

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