Welcome to our site, in this article, I am gonna show you how to crimp molex micro fit terminals.
Step by step.
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1. Prepare materials and tools
1.1 Terminals (female and male)
The Molex Micro-Fit is a 3.0mm pitch wire-to-wire and wire-to-board connection system. Both female and male terminals has two version in wire size accommodation. One type is for AWG24-AWG20 wires, and the other is for AWG30-AWG26 wires. In our tutorial, we will be using terminals for AWG24-AWG20.
1.2 Terminal cutter
If you have terminals in loose pieces, then you won’t be needing a terminal cutter. If you recevied terminals from a Chinese manufacturer, mostly like it’s in reel package.
Then a terminal cutter is needed to cut off terminals from the carrier strip. If you don’t have a cutter, use a scissors.
1.3 Wires
Just don’t use AWG24-AWG20 for a terminal which is applicable for AWG30-AWG26 wires, or use AWG30-AWG26 for a terminal which is applicable for AWG24-AWG20 wires. We will be using AWG20 wires (UL1007).
1.4 Wire stripper
A wire stripper is a small, hand-held device used to strip the electrical insulation from electric wires. Feel free to use any stripper that does the work. We will be using IWISS FSA-0626B.
1.5 Crimping tool
A crimping tool (also called crimper or crimping plier) is the tool used to deform the material and create the connection. Feel free to use any crimper that does the work. We will be using IWISS SN-2549.
1.6 Connector housing
After crimping completed, the crimped wires will go into the connector housing (with correct orientation). Let’s have dual row 8 pin male and female housings for instance.
Make sure you are following the following crimp criteria. It is important to ensure the quality of crimping.
2. Definitions & crimping acceptance criteria
Following are definitions of anatomy of a crimp termination from Molex. Acceptacne criteria are closely followed (in red color).
2.1 Cut-off Tab Length
This material protrudes outside the insulation crimp after the terminal is separated from the carrier strip.
The cut-off tab length of molex micro fit terminal is 0.2-0.4mm.
2.2 Strip Length
The strip length is determined by measuring the exposed conductor strands after the insulation is removed. The strip length determines the conductor brush length when the insulation position is centered.
The wire strip length for molex micro fit terminal is 2.54-2.92mm. And avoid following symptoms.
2.3 Bell Mouth
It is formed on the edge of the conductor crimp acts as a funnel for the wire strands. This funnel reduces the possibility that a sharp edge on the conductor crimp will cut or nick the wire strands.
Bell mouth of molex micro-fit terminals is 0.2-0.4mm.
2.4 Conductor Brush
The conductor brush is made up of the wire strands that extend past the conductor crimp on the contact side of the terminal. This helps ensure that mechanical compression occurs over the full length of the conductor crimp.
There should be conductor brush, and it should not extend into the contact area.
2.5 Insulation Crimp (Strain Relief)
This is the part of the terminal that provides wire support for insertion into the housing. It also allows the terminal to withstand shock and vibration. The terminal needs to hold the wire as firmly as possible without cutting through to the conductor strands. The acceptability of an insulation crimp is subjective and depends on the application. A bend test is recommended to determine whether the strain relief is acceptable for each particular application.
The terminal needs to hold the wire as firmly as possible without cutting through to the conductor strands.
2.6 Insulation Position
This is the location of the insulation in relation to the transition area between the conductor and insulation crimps. Equal amounts of the conductor strands and insulation needs to be visible in the transition area. The insulation position ensures that the insulation is crimped along the full length of the insulation crimp, and that no insulation is crimped under the conductor crimp.
Equal amounts of the conductor strands and insulation needs to be visible in the transition area.
2.7 Pull Force Testing
Pull force testing is a quick, destructive way to evaluate the mechanical properties of a crimp termination.
Pull force testing results out of allowed range are good indicators of problems in the process. Cut or nicked strands in the stripping operation, lack of bell mouth or conductor brush, or incorrect crimp height or tooling will reduce pull force tests results. Wire properties and stranding, and terminal design (material thickness and serration design), also can increase or decrease the value of the results of a pull force levels.
Per UL486A, the crimped wires should pass the pull test at the following test value.
| Test Values For Pullout Test UL486A | |||
|---|---|---|---|
| Conductor Size | Pullout Force | ||
| AWG | mm2 | N | LBF |
| 30 | 0.05 | 6.7 | 1.5 |
| 28 | 0.08 | 8.9 | 2 |
| 26 | 0.13 | 13.4 | 3 |
| 24 | 0.20 | 22.3 | 5 |
| 22 | 0.324 | 35.6 | 8 |
| 20 | 0.519 | 57.9 | 13 |
| 18 | 0.823 | 89.0 | 20 |
| 16 | 1.31 | 133.5 | 30 |
| 14 | 2.08 | 222.6 | 50 |
| 12 | 3.31 | 311.5 | 70 |
| 10 | 5.261 | 356.0 | 80 |
| 9 | 8.367 | 400.5 | 90 |
3. Crimping process
3.1 Cut off terminals from carrier strip (reel)
Skip this step if you are using terminals in loose pieces. Keep cut-off tab length at 0.2-0.4mm.
3.2 Strip wire
The stripping tool we are using doesn’t have a wire stop. Thus we have to mark the strip point before stripping. The strip length is 2.54-2.92mm. So we mark at 2.73mm (average of 2.54 and 2.92) from the end.
Strip the marked wire, and use it as ruler to strip the rest wires. So you don’t have to mark every wire that needs to be stripped.
If the strands of wires scatter, use your fingers to twist them to centralize them for crimping process.
Check the stripped wires with your eyes under strip acceptance criteria.
3.3 Crimping
4. Inspections & test
4.1 Visual inspection
Go to crimping acceptance criteria and inpect the crimped terminals with your eyes.
4.2 Pull force testing
Apply an axial pullout force on the wire at a rate of 25±6mm (1±14inch) per minute.
When you are doing pull force testing, it is important that the jig or plier on the terminal side doesn’t grab the brush or conductor crmip area. And the jig or plier on the wire side doesn’t grap the insulation crimp area.
How to do pull force testing without professinal device or equipment?
You can use a plier to grab the terminal, and hang something that is 6KG (like a bucket with water ) on the wire. Then lift (when you feel the weight) the bucket from the ground by the plier at a very low speed. Once the bucket is off the ground, if it keeps for 10 more second, consider the test result is good.
It is not professional, but we can get a credible result from a credible mothed with limited resources.
4.3 Insert crmiped wires into connector housing (orientation)
The insertion orientation is that the lock of housing and seam of crimped terminals face the same direction. Both male and female apply.
That’s all about how to crmip moelx micro-fit terminals. What tips/points have I left out?
Let me know by leaving a comment.
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