Make a Good Dupont Pin-Crimp EVERY TIME!

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Introduction: Make a Good Dupont Pin-Crimp EVERY TIME!

About: Electrical Engineer by training; Electronics Nerd before it was fashionable.

Anyone working with an Arduino, Raspberry PI, Beagle Bone, or any other multi-circuit-board project has become familiar with .025 X .025 in, square post pins and their mating connectors. The male pins are usually mounted to the circuit board with board to board wiring accomplished through mating connectors and wiring. These connectors usually consist of female pins that are individually crimped onto the wires which are then then inserted into multi-position connector shells.

These connector pins, also commonly called “Dupont Pins,” and are manufactured by AMP, Tyco, Molex, Samtec and a myriad of others.

Crimping Dupont female pins onto a wire requires a special crimping tool, precise techniques, and lots of time and patience! When I first started home-crimping these pins, I found that only about 1 in 10 came out right, with the rest defective in one way or another.

Thankfully, a few soles before me posted documentation, a few Instructables, and some YouTube videos that helped me get a started. Even at that, it took lots of trial and error and many crushed, damaged and unusable pins before I was able to get my failure rate under control.

Over time I studied my problems and came up with this guide and document to share some common crimp problems and solutions. In particular, you will see a very simple “Pin-Guide Tool” that you can make that will precisely position and hold the female Dupont pin inside of your hand crimping tool throughout the whole process. By using this Pin-Guide and a few other basic ideas, you too I can get a good crimp every time!

Step 1: Tools and Parts Needed

Above you can see the items you will need. Although not shown, a good wire stripper is also required. Take care in selecting and using the stripper as you will see soon, consistent strip length, free of nicks, is crucial to good Dupont pin crimp results.

Step 2: What Goes Wrong?

I studied my many failed crimps in an effort to figure out what was going wrong. I came up with the DEFECT TABLE shown above. This table helped me determine the root cause(s) for each defect which in turn, led me towards solutions.

While I don’t claim this list to be a 100% comprehensive, it does represent a good summary of my most common reoccurring problems.

Step 3: Wire Strip Length

The figure above shows the anatomy of a Dupont pin.It is seen that the total length of wire going into the pin should not exceed .2 in (5.0 mm). This means that when the wire is correctly and precisely positioned in the pin, the optimum wire-strip length is only 0.10 in (2.5 mm). A shorter strip length will compromise the conductor crimp while a longer strip length will either cause the wire to penetrate into the pin too deeply or lead to a degraded insulation crimp. For these reasons, I conclude that strip length is critical to achieving a good Dupont pin crimp.

  • While I’m sure there are precision wire strip tools out there, I don’t have one. Therefore, I check each strip length and carefully trim away any excess wire whenever my stripped length is too long.
  • As a reminder, take great care not to nick any of the conductors during the strip process as this will compromise the quality of the finished connection.

Tip: I found that recycled stranded-wire Ethernet cable is a good source for the interconnect wire.

Step 4: Pin Positioning Inside the Crimp-Tool

Improper pin-positioning within the crimp-tool tool was also a major reason for many of my crimp defects.

Perhaps I am just ‘all thumbs’, but once I thought I found the best spot to place the pin inside the crimper, I rarely seemed able to get it there. Furthermore, even when my pin placement was perfect, I frequently found that the pin would be pushed out of position or even rotated as a by-product of inserting the wire into the pin.

To solve this problem, I came up with a “PIN-GUIDE” tool. The Pin-Guide tool is nothing more than a strip of male pins onto to which the female pin to be crimped is placed. While simple, this Pin-Guide provides many benefits.

  1. The Pin-Guide provides a ‘handle’ for the pin so that placement into the crimper jaws is easier.
  2. The Pin-Guide precisely sets the position and depth of the pin relative to the crimper jaws. This serves to locate the CONDUCTOR-CRIMP zone and INSULATION-CRIMP zone in exactly the right spots within the crimp dies.
  3. Since the Pin-Guide ‘stays in place’ during the crimp cycle. it prevents the female pin from twisting, sliding, or moving while inserting the wire or performing the actual crimp cycle.
  4. The Pin-Guide also provides a ‘wire-stop’ that keeps the wire from going too far into the center of the female pin and obstructing the Mating-Pin Zone. Note that this fault only revealed when you find that you can’t plug the finished connector assembly onto the male PCB pins!

The Pin-Guide is easily fabricated from a 4-pin strip of male pins. The key to success however, is precisely setting the pin depth.

Step 5: Making the Pin-Guide

It’s easy to use the Pin-Guide. Just cut the female Dupont pin from the carrier and place it onto the Pin-Guide.

Step 6: Loading the Pin-Guide

Step 7: Selecting a Crimp Port

The SN28-B crimp tool has three different crimp-ports. Each port has a slightly different die shape and will form the pin differently. As noted in the figure, I found that I get the best results using “port 1” with wire up to and including AWG 22 Ga; I do not get good crimps with 22 Ga wire in position 2. Your results may vary however, as each crimp tool is adjustable; your setup maybe different than mine.

While the tool markings implies larger gauge wire may be used, I suspect that anything much larger than 22 Ga may not fit into the 0.1 inch spaced shells used for most Dupont pin connector assemblies.

Step 8: Loading the Dupont Pin Using the Pin-Guide Tool

As shown, with the female Dupont pin on PIN-GUIDE post #2, place the pin into the crimper jaws and close the jaws until they “click” and the pin is held in place. Be sure the pin is properly oriented and take care NOT to over compress the pin at this time as that will make wire insertion more difficult.

Step 9: Loading the Wire & Completing the Crimp

Next, carefully insert the stripped wire into the pin. As shown, be sure the wire is fully inserted and is not ‘hung-up’ during placement. While holding the wire in place, compress the crimper-handles to complete the crimp. Release and remove the completed crimp and perform a QC inspection.

After each crimp, it is important to perform a VISUAL INSPECTION as well as a QC PULL TEST of the pin-wire combination. A few examples follows that show you what to look for. Since the pins are small, I recommend you use a magnifying lens for all visual QC checks.

Step 10: Inspecting Your Work: Example A

Step 11: Inspecting Your Work: Example B

Step 12: Inspecting Your Work: Example C

Step 13: Loading Connector Shells

When the crimped pins are completed, they are easily inserted into the connector shells as shown. Pay attention to the photo details as pin orientation is important. Note that the pins will only lock-into the shell when inserted with the proper orientation.

Step 14: Summary of Pin-Crimp Steps

Step 15: Troubleshooting

As another aid to diagnose and trouble shoot common crimping issues, I offer the expanded trouble shooting table above.


CLOSING COMMENTS

This Instructable aims at helping you get solid, consistent Dupont pin termination results. I have focused on female-pins but similar steps can be applied to help you achieve good results for male-pins as well. I invite you all to review and tweak these ideas as you see fit to get them to work well for you.

Take care and Happy-Crimping!

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    42 Discussions

    0
    user
    sdw_nj

    7 months ago

    Interesting article. When I had to replace a end stop wire on my 3d printer and add a JST connector I first bought an IWISS crimper (https://www.amazon.com/gp/product/B00OMM4YUY/). I could be wrong, but my estimation at the time was that it just wasn't sized properly for what I was trying to crimp. There are two different sized sections - one to crimp around the insulation and one around the wire - but the one on the wire side was too wide causing the pin sleeve to be crushed. I found the PA-20 crimper from Engineer Inc. (https://www.amazon.com/gp/product/B002AVVO7U) that only crimps one part (insulation or wire) at a time. I think that simplifies the issue greatly.

    3 replies

    This is a pretty educational Instructable.

    I've had the PA20 style since around 1980 and IWISS style for several years and done literally thousands of crimps on 1/4"~6.3mm spade terminals using 14 ~18 gauge wire without a problem, the IWISS style being slightly quicker to use. Because I'd had pretty good results I got the smaller IWISS style.

    I found the same as you, the dies seem to be the wrong size and impossible to get a good crimp.I'll try adjusting them as I kinda like the way they work, holding terminals better with the locking ratchet compared to PA20 style

    Hi. Good to hear you are doing well with the PA20 tool. I find that when I am crimping big spade terminals with a pliers-style, 'non-locking' tool, the quality of the termination is highly variable. I sometimes have to go back and make a second compression pass if the crimp seems 'loose' or incomplete. Worst case, I end up soldering the terminal as well to be sure I have a solid connection.

    The locking-style crimp tool design came from the connector pin companies themselves. The logic behind them is that they are more 'operator independent'. That is, they only "unlock" after a complete crimp cycle has occurred and don't depend on operator judgement to determine when a crimp is 'tight enough'. This style of crimp tool only provides this assurance when 1) the correct-crimp-tool is used for the terminal being used, 2) a compatible wire is being used, and 3) the wire has been properly prepped.

    In a prior life, I worked in a manufacturing plant making products that ran at very high current levels. Correct wiring was key to success.
    Not only is the termination important, but all terminal block hardware had to be tightened to the correct torque specs. In these situations, a poor crimp or under tightened wire junction could lead to poor performance (ie: excessive voltage drops), and worst case, high temperatures and/or fires at defective junction!

    Take care.

    Hi. The pins I discussed in my Instructable were NOT JST connectors. I did a little more WEB research on JST pins and I agree with your assessment - the IWISS SN-28B crimper is not the right tool for "JST" connectors.

    A quick search on eBay for a "JST CRIMPER" came up with the SN-01B crimper tool. On eBbay the tool is described as follows:
    SN-01BM Crimp Plier Tool 2.0mm 2.54mm 3.96mm 18-28 AWG Crimper Dupont JST Molex .

    This is DIFFERENT than the SN-28B. Take a look at the SN-01B photos as several show some of the pins as well. Are these the pins you are using? It appears to me that the JST connector is shorter than the ones I have used and referenced in my article. I can see that the SN-28B may mangle the pin. Also, the JST connector pin may have different strip requirements as well - You will have to check that out.

    Good luck; hope this helps.

    Well done. I followed your guide and just did 4 perfect crimps after many previous failures. Using a pin guide makes all the difference. Nice clear instructions and the pictures are great.

    1 reply

    Thanks for your followup. Glad to hear it worked for you.

    0
    user
    dpeach

    7 months ago

    This was great. Thanks for writing it. I had my first attempt at DuPont cable crimping a couple of months ago. Eventually I got it to work well and I actually enjoy creating wires of just the right length. This guide would have helped back then. I am sure it will be a help to others in the future.

    Great guide. FWIW, I highly recommend using the "OK Industries" style wire stripper. It has a depth gauge that can be set for perfect strips every time. I've crimped thousands of dupont connectors and went through a similar journey to conclude that it starts with a perfect stripper and ends with a perfect crimper.


    https://www.amazon.com/Industries-Wire-Stripper-Adjustable-20-30/dp/B0015A7DBI

    3 replies

    Thanks for your idea. Your stripper suggestion, while a little pricey, looks pretty cool!

    Search around for best price. I think I paid about $22 for mine. The OK Industries ones are very high quality and worth the money if you do this all the time.

    Thanks for your feedback. I will have to look into the OK model.

    Very informative piece, thank you.

    I bought a very cheap crimping tool which looks a lot like yours, and found it has a peculiar problem - instead of curling the "conductor crimp" around into two neat humps, it pushes them down so I get a partial crimp with a gap in the middle and two little flanges on the the back. I made a quite a few of these before I realised there was a problem.

    So I bought another very cheap crimping tool of different design, which also doesn't crimp properly but does form the "conductor crimp" into a better shape.

    So now I start the crimp off with the second tool I bought, and finish it with the first one, the result being quite good looking crimps. Still not as good as the commercial ones, but far better than either tool on it's own (and still much cheaper than a decent tool which I simply can't afford)

    It's a good job I don't do many...

    2 replies

    Thanks for your feedback. If you regularly use Dupont pins, you will be well served to get a better tool. I think I paid less than $20 for the version I have and with some tender loving care (and a Pin Guide!) it works pretty well.

    I confess the pin guide is a really good idea - I may have to make one. Nine times out of ten I get the terminal in the right place though, by being very careful!

    This has got to be the very best most technical without being too technical guide to crimping dupont pins in the universe. I wish you were in charge of the various guides and manuals that either exist or should exist!

    1 reply

    Thanks for your comments. Sorry, don't know a think about the SN-48B; Hope someone else can give you some ideas.

    If it's a genuine SN-28B crimper, you will need a small mortgage to buy one.

    Really suspiciously cheap crimpers aren't worth buying, but there are some decent mid-quality crimpers that work really well.

    I bought one of these for the smaller Molex 0.1" pitch friction lock female headers and can't fault it. Japanese, decent quality with a choice of crimp sizes.

    https://www.amazon.co.uk/Universal-Micro-Crimping-Crimppins-Engineer/dp/B002AVVO7K/ref=pd_lpo_vtph_147_tr_t_2?_encoding=UTF8&psc=1&refRID=75A3K44F74HE2NVC6WKY

    I don't know how these connector companies can justify charging 3-figure sums for a crimper, but if your firm is buying it, so what

    1 reply

    Thanks for your comment. I agree that crimp tools from MOLEX or AMP are exceedingly expensive ($200-$400 or more). On the other hand, they do work well and tend to be more fool proof than the 'knock-off' varieties (like the one I have!) .

    0
    user
    KenC7

    7 months ago

    Hate to suggest something that might be simpler, but I get perfect crimps on these without the guide part. The wire strip length is important, as noted. I put the pin into my tool, close the tool part way, so it's not crimping yet but the pin is held, then gently pull the pin so it sticks out of the tool more. The crimp end will be in the tool completely, and the insulation crimp will stop on the anvil for the wire crimp. The tool will hold the pin in that position (just enough friction.) Put in your wire, making sure the insulation travels in all the way (it too will stop on the wire crimp anvil), position the cable so that the wire rests on the base plane of the pin (you can see this), and crimp.

    The only times this fails for me are when I didn't insert the cable fully, or didn't look to see the wire was laying flat on the base of the pin. If you get the wire strip length right, you can see - every time - that the insulation is far enough in and the wire is flat, because you won't see the wire going far enough or laying flat if you miss one of those two.

    One additional note for #13 - You may find at times that the pin goes into the shell easily at first, and then is *really* hard to insert the rest of the way. When the crimp forms on the insulation, sometimes it becomes too horizontal (flattened). If you give it a small squeeze with a pair of needle-nosed pliers to make it slightly less flat, it will often solve this problem without compromising your crimp.

    1 reply

    Thanks for your input. Good to hear that you've had good success with a simpler approach. I haven't had good success without the help of the Pin-Guide. Perhaps I just haven't terminated enough terminals to get good at it without some help from a simple fixture like the Pin-Guide..