Split Topic: Crimping 0.1" Molex connectors for PWM/CAN cables

This kind of thing is great. But for teams that can’t find exactly what they need, it’s not hard to make your own. Get a good crimper made for the pins you will use, a bunch of pins of both polarities (may only need one type these days), and an assortment of different housings. There are many places to get these, here are a couple:



It’s usually very helpful to get a good crimp tool, and to practice. Also get the right type of wire.

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This is way easier said than done for 0.100" pins. What are some of your favorite sets?

The one I linked does a nice job – the main thing is to get a crimper specifically made for the exact pins you use (it’s possible to pick out another, but the generic crimpers tend to do a very poor job on these). These are not cheap – the one I linked is probably overkill, there are cheaper options. Fortunately, pretty much all signal wires on an FRC robot can be done with the same pins/tool.

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So what you’re saying is… crimpin’ ain’t easy?



This is the hard part. Molex 70400 / SL family look like good parts with appropriate performance standards, but I’m not seeing a set of tooling listed in the 70400 Spec or SL Catalog links at Digikey.
The only tools you’re directly linking to are sold at Hansen, but I assume the Hansen Hobbies “Deluxe Crimper” is the generic kind of crimp you’re warning against?

The Hansen one is probably decent but I can’t personally vouch for it. I know the universal crimpers that are fine for larger terminals don’t work. Here’s a link for a tool I know works very well, but is not cheap (Molex 638258800): https://www.digikey.com/product-detail/en/molex/0638258800/WM10405-ND/4576391 ($362.53).

Here’s a page with all the tools (crimper, insertion tool, extraction tool). You don’t really need an insertion tool, but an extraction tool is handy if you want to move pins around without just making new cables.

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We switched from latching molex to just a small zip tie around every PWM pair this year(zip ties fit nicely in the space freed by the missing wire) and didn’t have a single issue. When we were using the latching molex we’d run into failed crimps even when we had lots of practice making them.


Our team has had nothing but problems with low cost ratcheting crimpers - including the ones from Hansen hobbies. I tend to find a lot of the cheap ones either have a bad die to begin with, or wear our very quickly making it easy to make bad crimps.

We’ve had success with this crimper in particular when crimping the Molex SL series (thanks Jersey Voltage!). They are manual which means its a two step process, but its pretty easy to learn to use, and allows you to inspect the crimp after each step.

Edit: I realize I’ve now promoted custom crimping in a thread promoting new pre-made cables. Even with incrementally better tools, buying pre-made is WAY better than crimping. Buy where you can, crimp where you must.


I’ve always hated crimping those pins. Years ago, after expressing displeasure to another mentor, he said he’d take them to JPL and get one of the techs to do it. Those didn’t come out that well either. I’ve bought cables ever since.


We’ve used the Hansen Hobbies Deluxe ratcheting crimper on the Hansen Hobbies pins. My strategy is to use precision needle nose pliers to first slightly form the strain relief “wings” over the wire insulation to hold the pin onto the wire. Then the assemblage us placed into the large side of the crimper die and crimped, then into the small side of the die and crimped again. It’s about a 90% success rate this way. They come out acceptable. Not as good as factory crimps done with a more precision tool, but plenty acceptable. It does bend the pin slightly which I manually straighten with my fingers.

We also have the red handled crimpers from Hansen. I find them difficult to use and not great.

We also have the JST SM series pins and official JST crimpers. It’s a different crimper for male and female and around $500 ea, it’s no small investment. But, they work absolutely flawless. There’s a reason good crimpers cost a lot. I will say though too, due to the cost, these get kept put away, and are only used with supervision/authorization.

Finally, we got the Molex 638111000 on FIRST Choice. Haven’t had a chance to try it on anything yet. I think it may not go small enough for CAN or PWM wire.

Most teams are better off purchasing ready made cables of different lengths, in bulk.

For the years I was the electrical mentor for a team my son was on, I was able to teach students to make PWM cables of an acceptable quality (zero failures during the season). It took a lot time training them using some training aids I borrowed from my workplace and a lot of time doing QC work and getting them to fix the bad ones. I believe we used the crimper sold by Hansen at the time. The one linked by @Will_Toth may be a safer bet since it has the QC of Molex behind it.

Even at the places I worked that were capable of making their own wiring harnesses, only certain staff were asked to do the small stuff like the PWM cables.

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