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Wiring Fundamentals: Crimping

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Crimping

15.51

00:00 - Where every wire in our wiring harness ends, we're going to have to perform a crimp connection.
00:05 This will either be a splice connection to other wires, or a crimp connection to a connector pin.
00:09 Crimping performs such an integral part of the harness construction process and it can be such a common point of failure, that we need to look at it in detail.
00:18 This module will look at the crimp connections between a wire and a terminal pin, the common styles, the tools we need to perform the job, and how to test the crimp connection will remain reliable when in service.
00:28 When we make a connection between a terminal pin and a wire using a crimp join we deform the terminal in such a way that it traps and holds on to the wire with permanent pressure.
00:37 This requires that we're using a terminal pin which is designed to be crimped, along with using the correct tool to apply adequate pressure to complete the operation.
00:46 Every terminal you encounter when constructing a wiring harness will have a specific crimping tool specified for use to ensure a proper connection.
00:54 We deal with many different connectors when we're building a wiring harness.
00:57 Particularly if we're making connections to OEM electronics.
01:00 And in a perfect world we would own the exact specified crimping tool for every application.
01:05 However this is not feasible in the real world and we've found that there is sufficient overlap between the required tooling, that a small selection of reasonably priced general purpose crimp tools is all that is required to achieve a professional and reliable result.
01:18 There are two main types of crimp join we perform when building a wiring harness, they're known as closed barrel and open barrel.
01:24 A closed barrel crimp join is one where the bared section of copper wire is inserted into a cylinder which is then deformed around the wire to tightly grip it.
01:32 The cylinder completely closes around the wire, thus being called a closed barrel crimp.
01:37 An open barrel crimp joint is one where the wire is laid into a U shaped crimp connector, the upper tangs of the U joint are then folded down onto the wire to tightly grip it.
01:47 Open barrel and closed barrel crimps require different tooling, which we'll look at in a couple of demonstrations.
01:53 As mentioned in the connectors section of the course, the Deutsch DT range of connectors are a solid and reliable choice for use in automotive applications.
02:00 They're most commonly supplied with closed barrel terminal pins, and each range, DTM, DT, and DTP, accept different sizes of wire.
02:09 Because the closed barrel section of the different pins is a different size, in this instance, we do need a different tool for each size terminal.
02:17 At the professional motorsport level, a single closed barrel crimp tool can be used with different position heads to suit all three sizes of terminal.
02:25 But that single tool is many times the combined cost of the three individual tools that we have here.
02:31 We'll perform a demonstration using a DTM series connector, and a 22 AWG wire.
02:36 But the operation and procedure is the same for both the DT and the DTP connectors.
02:41 When we perform a crimp operation, the first step we have to do is ensure that our wire has been cut to the correct length.
02:47 We also need to make sure that the cut on the end is nice and straight.
02:51 All the copper conductor strands need to be the same length.
02:54 That way, when they're inserted into the terminal, none of them will be missed when the crimp operation is performed.
02:59 We then need to strip a section of the insulation that is long enough that when the wire is inserted into the terminal pin, there is approximately 0.5 to one millimetre of copper conductor strands showing.
03:12 From this point the aim is to get the terminal inserted into the crimp tool with the wire inserted into the terminal.
03:18 Now the order in which you're going to do this will probably change depending on the situation under which you're working.
03:24 When we're out here on the bench, I find it easiest to insert the wire into the terminal and then insert both into the crimp tool, but if you're working upside down, underneath a dash board, you might find it easiest to insert the terminal into the crimp tool, close it slightly to grip the terminal, and then insert the wire into the terminal.
03:43 Once you're at this stage you squeeze the handles together to complete the crimp operation.
03:47 Now this is a ratcheting crimp tool which means once you begin the crimp operation, it won't release until you squeeze them all the way and complete the operation.
03:55 With that done, we can remove the wire and terminal from our crimp tool, and perform an optical inspection.
04:00 What we're looking for here is that the crimp indentations are evenly spaced around the closed barrel and that they're all a uniform depth.
04:09 We then perform a tug test which is when we hold the terminal and we pull on the wire.
04:14 We put a fair amount of force on this as we want to be sure the wire won't withdraw from the terminal and if we can't get it to pull out here on the bench we can be fairly certain that it's going to be reliable when in service.
04:26 These Deutsch DTM terminals do also have an inspection hole right below this locking tab flange and you need to make sure that you can see the copper conductor strands through that hole, as that ensures the wire was fully inserted into the terminal when the crimp operation was performed.
04:41 With all those inspections performed, we can be certain that this is a reliable successfully completed crimp join, that will remain in service without issues for many years.
04:50 When we perform a crimp connection with an open barrel terminal, the process is a little different to that of a closed barrel terminal.
04:55 It's usually performed in two individual crimp stages.
04:58 The first is the smaller open barrel crimp section of the terminal which grips the copper conductor strands and provides the electrical connection.
05:05 The second is the larger crimp section of the terminal which grips the insulation jacket of the wire to provide strain relief.
05:12 Because we're going to use our general purpose crimp tools with multiple die sizes, we need to determine how we select the die size to use, and if the completed crimp joins are acceptable.
05:22 This is best looked at with an example, which we'll undertake using a 22 AWG TXL wire and a crimp terminal for an AMP super seal 1.0 connector.
05:31 This is a very common application in the industry as these connectors are favoured by many performance automotive companies, Link, Haltech and Motec for example.
05:40 Before we undertake the crimping operation on our actual wiring harness, we need to determine which of the die sizes our crimp tool has are the best to use.
05:48 This will mean performing multiple test crimps and examining the results.
05:51 The tool I've selected here is the one I use most commonly for open barrel crimps that don't include a wire seal.
05:58 Wire seals are an element we'll show in the next demonstration.
06:01 This tool has two rows of crimp dies, one side is for the first crimp stage that grips the copper conductors and the other side is for the second crimp stage that provides the strain relief.
06:11 We'll try a first stage crimp with each of the three available die sizes and examine the results now.
06:17 The procedure does begin the same way as our closed barrel crimp though.
06:21 We need to ensure that our wire has been cut to the correct length and that the cut on the end is nice and straight.
06:27 We want all of those copper conductor strands to be the same length, that way none of them will be missed when the crimp operation's performed.
06:34 So with that done, we can strip back a section of our insulation, and this needs to bare a length of copper conductor strands that is long enough that they protrude all the way through the smaller of the open barrel crimp sections here but that the larger of the open barrel crimp sections still lines up with the insulation so when we crimp it down it'll provide the necessary strain relief.
07:00 So with that lines up, we can have a look at the crimp tool we're going to use.
07:04 It's a general purpose crimp tool, of a non ratcheting type, so we can provide as much or as little pressure as we need, and we've got the three open barrel die sizes here, we're going to start off with the largest die selection, and have a look at the results.
07:22 So I like to install the terminal into the tool as it makes it very easy to hold it in place when we insert a wire, which we'll do now.
07:33 And want to make sure those copper conductor strands are all the way through the open barrel crimp section, and we can squeeze the handles and perform the crimp operation.
07:45 Now with that done we can have a good inspection and we can see straight away that it hasn't folded those open barrel upper tangs over evenly and it's providing no crimp whatsoever so that's not the correct die size for this terminal and wire combination.
08:04 We can get another terminal and move down to a smaller die size, and undertake the same operation.
08:13 So we'll install that into our tool.
08:18 Insert the wire all the way through that smaller open barrel section, and perform the crimp operation.
08:28 And on our initial visual inspection, this does look quite a bit better.
08:32 Those tangs of the open barrel crimp section have been folded over, and they do look like they're gripping the copper conductors.
08:38 So we'll perform our tug test.
08:42 That's one of the reasons when you're performing the tug test, you really do need to apply quite a bit of pressure.
08:47 This initially felt like it was going to hold but it did pull out with a bit of pressure applied and that is definitely something that would have happened when it was in service on the vehicle.
08:56 So we know this is another failure and that's not going to be the correct combination, the correct die size for this combination of terminal and wire size.
09:04 So we can get another terminal and try the next die size.
09:08 But I'm just going to trim this wire again as it's starting to look a little bit second hand.
09:14 Just strip our section of insulation back.
09:20 So install our terminal into our crimp tool and this time we're in the smallest of the die sections.
09:32 Our wire through that smaller open barrel crimp stage.
09:37 And apply pressure to complete the operation.
09:44 In our initial inspection this looks even better again.
09:47 Those upper tangs of the open barrel crimp section are folded over nice and uniformly and they're looking very tight.
09:54 If we perform our tug test, I can put quite a lot of force on that and it's not withdrawing from the terminal so we know that's gonna be held tightly.
10:03 The next stage of the crimp operation is very similar.
10:05 It's the larger section here that's going to crimp down onto the insulation jacket of the wire to provide our strain relief.
10:11 So it's a similar situation to what we've just been in.
10:14 We've got these round section dies here we're going to use and we need to determine which is the correct size.
10:19 So I'm going to start with the larger die size here, and line this all up in the crimp tool, and apply pressure.
10:31 Straight away here on our visual inspection we can see that those larger tangs of the open barrel crimp section haven't crimped down enough to grip our insulation jacket, so that's not going to be providing any strain relief, it's not the right size die for this application.
10:46 That terminal has been fully crimped now so we're going to have to cut it off.
10:51 And strip another section of insulation.
10:57 And with our last terminal here, we've determined that the first crimp stage is the smallest of the die sections here so we can quickly do that.
11:17 That's in there nice and solid.
11:19 And now we're going to try the smaller of the second open barrel crimp stages.
11:30 Get everything lined up, apply pressure.
11:37 And perform our visual inspection.
11:39 So we can see here that those upper tangs of the larger open barrel crimp section have gripped onto our wire insulation this time and they're gonna be providing good strain relief.
11:52 Everything looks nice and tight there, that's gonna be a good crimp join that'll be nice and reliable when it's installed in the vehicle.
11:58 So with those test crimps made and our die selection finalised, I would actually document that and I would store that documentation with these terminals as it means the next time I pull out one of these terminals I'll be able to go directly to the correct crimp tool and use the right sized dies the first time.
12:13 The next open barrel crimp demonstration we'll undertake is very similar to the last except we'll need to integrate a wire seal into the procedure.
12:19 So it begins exactly the same way, we want to ensure that our wire has been cut to the correct length and that cut on the end is nice and straight.
12:29 This is where the procedure differs slightly though as we need to install a seal onto our wire.
12:35 This can be done before or after you strip a section of insulation.
12:38 If possible I like to do it before as it avoids the problem of the copper conductor strands possibly poking through the side of the seal.
12:48 So we'll install that onto the wire, and I like to slide it a good distance down as it keeps it out of the way of the wire strippers.
12:57 So we'll strip back a section of insulation to expose enough of the copper conductor strands that they will protrude all the way through that smaller open barrel crimp section.
13:13 At this point we want to slide our wire seal back up to the very end of our insulation as that way when we line everything up, we can see our smaller open barrel crimp section is going to grip onto our copper conductor strands and our larger open barrel crimp section is going to hold onto the wire seal.
13:32 So with all that lined up, we can have a look at the tool we're going to use.
13:36 It's another general purpose crimp tool and off camera we have actually undertaken our test crimps to determine the size of dies that we need to use.
13:45 So I know for this first crimp stage it's gonna grip with the copper conductor strands, we need to use die size three.
13:52 So we'll go ahead and do that now.
13:55 Once again I like to fit the terminal into the crimp tool to hold it all in place.
14:00 And then get this lined up.
14:06 Making sure that the larger open barrel crimp section is lined up with the wire seal.
14:14 So with everything in place we can undertake our crimp operation.
14:21 And we can see from our visual inspection that that has folded over the tangs of the open barrel crimp section nicely, and with our tug test, excellent, that's not withdrawing from the terminal so we know that's a good crimp.
14:35 The next stage of the operation is very similar to the last demonstration except that the larger section of the open barrel terminal here is not going to grip onto the insulation, it's going to grip onto the wire seal and hold it in place.
14:47 So on our general purpose crimp tool we're going to use the round die sections here and from the test crimps we've performed, I know that we want to use die size one in this application.
14:58 So we'll go ahead and do that now.
15:06 And we can have a quick visual inspection and we can see that that has folded those tangs nicely onto that wire seal and if we hold, just grab just that wire seal, we can do a quick tug test, and it is held nice and tightly in place so that's gonna be a good crimp join.
15:21 Those three demonstrations should prime you to tackle the majority of crimp terminal connections you'll encounter when building your wiring harness.
15:29 As mentioned at the beginning of this section, we keep an up to date list of where to source the tools shown here in the wiring fundamentals section of our forum.