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Whether you are enclosing electronics, or mounting motors, sensors or switches, you often need to make plastic mounting components of equal size.

The following discussion covers a method to make components of the same dimensions.

Items required:

  • Desktop sander
  • C clamps
  • Construction material (1/4” acrylic plastic sheeting)
  • Double stick tape (DST) to attach the stop block to the fence

On the left side of the desktop sander image, we see a round vertical sanding disc with a perpendicular platform with miter; we will use this section of the sander to adjust the length, angle and width of manufactured pieces.

The miter keeps your work perpendicular to the sanding disk surface.

We are making a jig that will be attached to the miter; this jig will be the workhorse for plastic part production and duplication.

The jig is made from 1/4” acrylic plastic sheeting, available from Amazon.

Pieces of the jig are welded together with DCM, methylene chloride.

Use C clamps to firmly attach the jig to the sanding platform; 90 degrees to the sanding disc.

The following images show different views of the jig that we are making.

  1. Place the workpiece that we are copying on the jig’s bed and under the ‘stop block’.
  2. Use DST to attach the ‘stop block’ to the jig’s fence.
  3. Place an oversized length ‘push stick’ (new push stick) under the ‘stop block’ with the original work piece to the left.
  4. Turn on the sander and move the ‘push block’ to the right, advancing the workpiece into the ‘new’ push stick; slowly advance the ‘push block’ so the new ‘push stick’ is sized against the rotating sanding disk.
  5. When the ‘push block’ contacts the ‘stop block’, turn off the sander.
  6. We now have a properly sized ‘new push stick’.
  7. Place the original work piece aside for safe keeping, put a rough sized ‘new work piece’ under the ‘stop block’ to the right of the ‘new push stick’ we just made.
  8. Power on the sander, move the ‘push block’ with ‘push stick’ to the right advancing the new workpiece into the sandpaper; again, when the ‘push block’ contacts the ‘stop block’, turn off power.
  9. Repeat as many times as needed.
  10. Also make a 45-degree fixture for the jig to accommodate manufacturing pieces with 45 degree surfaces.

A push stick of correct length needs to be made for each ‘unique’ part.

Sizing our ‘Push Stick’

The push stick is now moved next to the push block. Here we size new 'work pieces’.

Make a 45’ attachment for 45’ part manufacturing.

Actual hardware used:

These acrylic pieces are welded together with DCM (Methylene Chloride).
Each piece made is exactly the same length as the original.

Keep your individual push sticks and the original work pieces for future use.

You can use: FR4, acrylic, wood etc. for your work material.

The sandpaper used is #80 grit.

Use dental picks to control ‘work piece’ movement next to the moving disc.

When using your ‘Hot Plate Preheat Station’ it can be awkward to position the PCB being soldered.

Make yourself a ‘hot plate soldering sled’ so you can more easily move your work around.

Silicone ears on either side keep your fingers from getting burned.

Cut the sled’s ears from a silicone cookie sheet.

If your ‘Hot Air Wand’ is centered on the hot plate, you can use the sled’s ears to move the PCB, so components are directly under the hot air jet.

After all PCB components have been soldered, turn the ears under the sides and move the sled to a location where the PCB can cool.

Aluminum is .064” thick.

After the hot plate gets to the 160 degree soak temperature, place the sled with PCB onto the heated surface.
After the PCB sits for the soak period, use hot air wand to finish component soldering.

For better control while soldering add a gatry to hold your hot air wand.

Use the silicone ears to move the sled when heating components for soldering.

Hot plate set to 160 degrees C, sled is ~10 degree less (150’C).

Set the air nozzle 1 cm above the components being soldered.

Set the Wand temperature to ~235’C and set the air speed to ~4.5.

When using regular tweezers, you often need to keep your hands free but need to keep the tweezers closed on what they are holding.

If you have a pair of ‘reverse tweezers’, this is easily accomplished.
Regular tweezers can be used to constantly grasp an item as seen below.

You need:

  • regular tweezers
  • 1.5 cm diameter heat shrink

Use a piece of heat shrink with a diameter large enough so that when shrunk still allows for slippage on the tweezer handle.

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Two interesting soldering videos on YouTube.

Flux comparisons:

Solder comparison:

It is interesting that adding silver to the solder mix gives a nice shiny finish.

I have used North American and Chinese solder and have not found much difference between their qualities.

However, I do prefer 63/37 and 60/40 Kester brand solder.

MG solder is okay, but MG plays tricks with winding the solder on a large diameter spool to make things look bigger than they are, buy solder by spool weight ;).

I am a fan of 'liquid' solder fluxes.

Jeezum Crow, Larry (A Vermontism) : I am WAITING for the BOOK!! Seriously, there are popular books out there which have crummy, low-contrast graphics. Your stuff is so excellent.

Now, about "you often need to make plastic mounting components of equal size." (Uh_Oh .. Terry Feels A Story Coming On)..

A few years ago I knew a guy who did something like this. Well, 62 years ago, actually.

He was making wood blocks out of rock maple. They were supposed to be exact sizes, because they were used in testing children's abilities at the Gesell Institute of Child Development at Yale University. (https://gesellinstitute.org/)

I went to this cool nursery school in New Haven when I was 4 or 5 years old (1945). They had the greatest wooden toys. And sometimes adults would play with you. Sometimes they had a game with a wooden board with different size holes in it. Some were square, some were round, some were triangular. They gave you some blocks and asked you to quickly put them through the holes. The blocks fit very exactly so you had to get them lined up just right to push them through the holes. They had some little clicky thing in their hand, but they didn't let you play with it.

So 12 or 13 years later my friend Jim Memery had a girlfriend named Britta, and her father was a machinist. He had a company that did "deep drilling", making barrels for aircraft machine guns. He helped us machine the stainless steel nozzle for the rocket engine we were building. When we were visiting his home workshop he was making small wood blocks. He had a jig that pushed them under a belt type sander. Each time he did a surface, he pushed the block farther and it went under a dial indicator. He wanted them to be within a thousandth of an inch. He had a metal cube he used as the standard, which was one inch within a ten-thousandth.

Suddenly I realized where I had seen those blocks before. "Oh, Yes.", he said, "these are for Yale and sometimes I make them for other Universities too."

I love wooden blocks and made them for my kids. Then their kids played with them. Now, each of my 14 grandchildren has a wooden block from me. It's not so exact but it has their name and birthday analog hand-carved on it. |500x375

|375x500

Terry
Yes kids and blocks go together. There is nothing like a good piece of hardwood sanded and given a nice waxed finish.


Further to post #724

Your old eye glass cases are great for storing delicate tools.

In situations where an accidental change in a potentiometer setting can cause catastrophic problems, change the potentiometer out for fixed resistors.

Make a resistor substitution board ahead of time to use it to determine what the values of these resistors should be.

All the standard resistor values (SMD 1026) have been placed on the substitution PCB.

One end of all the resistors are common and would represent the wiper on a potentiometer.

Female headers on the other side of the resistors would be the top and bottom terminals of our potentiometer.

In the images below, a $1.00 DC to DC Boost regulator is connected to a 12-volt computer fan.

Input to the regulator is 5-volt.

Cute, but wouldn't it be easier to set the pot to the desired output voltages, and then simply MEASURE it after it's been removed? (maybe even before it's been removed...)

The point is these are values which you can purchase off the shelf.

Since we are using ‘standard available’ resistors on the board, the selection process shows us final values that ‘will’ work.

And yes, you would set the pot first, remove it, then measure the resistances to get a ‘starting point’ for resistor selection.


For example: The potentiometer in this case was 107k.

The two associated resistances were 104k and 3.55k neither are close to what resistors are actually available.

The selected 100k and 3k gave an actual output voltage of 11.96 volts.


Now we can do a simple ratio too:

3.55/107= x/100

x=355/107=3.3k


It is important to point out to new people to do these modifications and possibly prevent intermittent problems that potentiometers can cause.

When using an ‘soldering iron’ along with Solder Wick to remove excess solder, there is a good chance you will damage or lift PCB pads.

Ideally you want to place as little pressure on the wick and solder joint as possible.

On the other hand, if you use a ‘hot air wand’ instead of an iron, there is no chance of damaging a PCB pad.

Tools and supplies needed:

  • Hot air Wand with a ~4mm nozzle
  • Kapton or heat resistant aluminum tape
  • 2 mm Solder Wick
  • liquid flux
  • ceramic tweezers (reverse)
  • IPA to clean up your rework

Before using your wand, to avoid overheating components, add Kapton or heat resistant aluminum tape to surrounding parts .

Cut a 2 cm piece of Solder Wick and place it in the ceramic tweezers.

Add liquid flux to the Solder Wick and melt some solder (~1mm) at the very end of the wick.

Add a drop of liquid flux to the solder joint being reworked.

Set the hot air wand to ~320°C at an air setting of ~4.5.

Heat the end of the Solder Wick and the solder joint you are going to rework.

Most of the heat applied to the wick stays in the wick as the ceramic tweezers are a good heat insulator.

When the solder on the end of the wick melts, sweep the wick back and forth across the solder joint.

As solder melts, insert the wick into the solder joint and let the wick do its job.

Cut off spent wick as necessary.

Since there is no mechanical pressure placed on the heated PCB pad there is almost no chance of damaging it.

After rework clean the solder joint with IPA.

Inevitably, we tip open bottles of fluids when they are filled with the worst possible stuff, Acetone, Lacquer thinner, glues, DCM, etc.

A magnet, and two cups can prevent a big mess.

We need:

  • A 1 inch ‘Rare-Earth’ ring magnet
  • Two tapered plastic medicine cups (Note: glass will shatter)

Since the ring magnet is open in the middle, any discontinuity on the bottom of the medicine cups will not tilt the magnet.

Got to get a new brush :frowning:

BTW plastic medicine cups are great for mixing epoxies and other glues.

‘Acetone’ is great at removing the most stubborn flux residues on your PCBs.

Make sure it does not affect your components and solder masks.

I have not found it harmful on PCB solder masks.

Many industrial flux removers are 50:50 Acetone and IPA.

‘Lacquer Thinner’ works well at removing flux buildup too.

One of the most useful bench tools I ve ever made :

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Also featured here : SUPERHOUSE CHANNEL

You just need a 3d printer and some very cheap extra parts.

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I do something similar with magnetic hold down clamps.

Currently the clamps have nylon standoffs as the leaver pull offs.

Someday these will be replaced with brass standoffs, then the logic probe wires can be connected to lugs at the brass tops.

You could add heat shrink on the stainless steel picks to insulate them.

When soldering, remember to use air filtration to remove flux fumes from the air.

See Amazon and eBay for reasonably priced air filters.

A noisy fan makes it much less likely that you will continue to use your air filter.

I replaced the noisy 120VAC fan in the unit below for the much quieter 12VDC computer fan.

A small booster fan gives you more distance between your work and the filter location.


If you do a lot of soldering, you might want to invest in a small HEPA room air purifier.

A small unit like the one shown is just right for a work bench.

Air Purifier is ~$90.00 and filters are ~$15.00 (6-8-month effectiveness), very quiet at low and medium speeds.


Almost no sound at speed setting 1, reasonable at setting 2.

Fan6.jpg


Commercial air filtration:

W A R N I N G
You can kill yourself if you connect a grounding strap to AC power mains conductors.


The discussion in this thread and the next is for information only. It is not suggested you follow the information presented because serious injury or death may result.


Electronic components can be damaged by static discharge.

Carpets, friction, insulated surfaces, and even body movement can build up high static voltages; this static can destroy your components.

A grounding wrist strap and a ground connection to your work surface discharges static voltages harmlessly to earth ground.


Ground straps often have a high valued series resistance between your skin and the metal alligator clip.

The resistance in the ‘wrist strap’ seen below is 1 mega ohm.

In the images below, the series resistor in the ‘work surface’ earth ground lead is 2.2 mega ohms.


For added safety, my workbench power outlets are on a ground fault circuit.


Underside of stainless steel work surface.
The stainless steel work surface is covered with teflon material.

Clear heat shrink encapsulates the 2.2 mega ohm resistor.

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