Note: This is part 1 of a two-part project.

For the second part, see here: Building a Low Cost Solder Fume Extractor - Part 2

Introduction

I’m sure I’ve created some really stinky projects, but this isn’t one of them. After the last project that sucked, I hope this is the last one to do so for a while : )

I’ve wanted a solder fume extractor for home use for ages – they are quite pricey though. In particular the ones that filter the fumes.

As an experiment I decided to see if it was possible to build one. While the result does not compare with high-end commercial extractors, it is better than nothing, and I feel it is slightly better than the low-cost desktop fume extractors which only remove some gasses and do nothing about the smoke particles.

This project is intended to greatly reduce the amount of fumes in the soldering iron vicinity, and the hope is that the particles are being captured in the filters and not being recirculated in the room, although I cannot currently confirm this. Anyway, for occasional home use, I think it could be worthwhile assembling such a device for maintaining your health while working.

I’ve given it the nose test, with the stinkiest flux that I own; provided the iron is close to the end of the hose, the smoke gets sucked up and I smell nothing until the iron is moved away.

The project is designed around the idea that a lot of electronics that is thrown out contains fans; examples include desktop PCs and servers. These fans can be used for this project. Some other key points about this project is that it uses reasonably cheap particle filters (intended for vacuum cleaners) and a fume filter as used in commercial solder fume extractors. The entire project is more an exercise in woodwork than in much electronics to be honest. It is an easy-to-make project because it uses very thin wood that is easy to cut!

It is compact enough that very little desk space is taken up; the box could be screwed to the underside of a desk and just the hose needs to be exposed.

Furthermore, since it is a custom project, it can be extended for additional functionality.

How Does it Work?

It basically consists of a hose, some filters and some fanssome fans stacked up behind the filters. By using standard sized fans intended for electronics/PC use, cost can be saved if you already have some handy.

The hose is an anti-static one, to prevent static electricity build-up from particles in the air. The one I used (known as a Festool 27mm hose, on ebay it can be searched as Festool 452384 Suction hose D 27 antistatic - D 27 MW-AS) is a spare part intended for workshop dust extractors for machine tools. Cost could be saved by using a non-anti-static hose.

The filtering capability is in three parts; filter A is closest to the hose and is a basic thin sheet that filters large particles, followed by filter B which is a HEPA filter for small particles, followed by filter C which is a carbon filtercarbon filter for removing some gasses. Filter C is closest to the ingress/air inlet of the fan.

Filters A and B are vacuum cleaner spare parts therefore they will not be as good as the filters used in commercial solder fume extractors. Filter C, the charcoal filter, is an item that can be purchased as a spare for a low-cost basic single-filter solder fume extractor, so it should at least be as good as that product.

Filters A and B are quite dense whereas Filter C is like a very aerated sponge and you can see through it. When combined with such dense filters fans have to work harder to force air through. Pressure builds up (in this case a reduced pressure between the filters and the fan, since the fan is ‘sucking’ through the filters and not blowing) to the point that the fan works so hard that air flow is greatly diminished. To get around this problem, many fans are stacked up so that air can be sucked through without significantly reducing the airflow rate. I used four fans. The entire unit is powered from an external 12V mains to DC converter.

With hindsight it could also be possible to use a bathroom fan or other fan intended for connecting to ducting within a building. It didn’t occur to me at the time. Anyway, the PC fan approach does have a few advantages, such as they may already be lying around in an electronics lab, and they are low voltage (12V) so the project is easier from an electrical safety perspective.

Interior Construction

The diagram here shows the internal layout. There are a lot of wood pieces, so it helps to label them as soon as they are cut to prevent confusion.

Just to explain the diagram, it is constructed like a tube, with an air ingress side and an egress side. The ingress side is on the left side of the diagram.

The enclosure is designed for an exact fit around the HEPA filter because that is the largest component. It will drop into the tube from the left side until it hits the Filter Stop A/B pieces. The fan array will drop in from the right side of the tube, until it hits the Fan Ingress Surround.

Since the fans are smaller than the tube, they are centred inside the tube using the Fan Support A/B pieces.

The small pieces marked Support Block could be omitted, but are used for strength.

The Egress Frame A/B pieces are used to provide some thickness for attaching the Egress End Plate (not shown on the diagram).

The four sides of the tube (only two sides are shown in the diagram) are glued together permanently. The design was created such that the filters and the fans are removable for servicing by unscrewing the respective end plates of the tube.

Perhaps a speaker enclosure could be repurposed for the outer shell to save some effort.

Cutting the Wood

The enclosure is based on 4mm thick poplar plywood. It is available as 3-ply. It has the properties that it is rigid but slightly springy, very flat and stable, and cuts easily, and can be very quickly sanded to size with a sanding block and 150-200 grit paper. It came in convenient 300x210mm sized sheets as a pack of 10. and the sides were already very square, which makes accurate marking and cutting easier.

As mentioned after cutting it can be sanded for precise trimming if the wood is cut slightly too large; the wood is so soft that it takes just seconds to smooth out. Note you’ll need a dust protection mask and eyewear to work well on this project.

A square is mandatory for this project, because some accuracy is needed for the cut pieces. The ones in DIY stores are not fantastic (in my opinion) for this, I prefer a small metalworking square. With a sharp pencil you can mark (for cutting and sanding operations) to sub-millimetre accuracy,  and then during assembly, by looking at the gap between the square and the workpiece, it is possible to get an extremely precise 90 degree alignment.

With such easy precision, it will all fit together well, not much harder than flat-pack furniture (I long for the day IKEA sell flat-pack soldering fume extractors).

There are a lot of pieces that need to be cut, so it is important to label each cut piece so it doesn’t get confusing.

A few lengths of square section wood (preferably hardwood) dowel is also needed; I used 12x12mm section.

The pieces of wood that are required and all dimensions are listed below. This only applies if the same HEPA filter and fans are being used otherwise the values will need to be adjusted.

Since there is lots of symmetry many of the pieces are needed in quantities of 2.

4mm thick plywood (all dimensions in mm):

12x12mm Dowel (all dimensions are in mm):

Large Circular Holes Technique

The Internal Fan Surround needs a 115.5mm diameter hole. To do this, find the centre of the the wood and then draw a circle of 115.5mm diameter using a compass. Next, drill small (3mm approx.) holes just inside the circle. With a knife or small jigsaw, the centre can be cut out. It will look ugly, but it is very quickly sanded to a neater finish. Sandpaper can be wrapped around any convenient cylinder (I used a small round paint can) and then the wood can be sanded against it. The result was better than expected with about 5 minutes of sanding.

Holes for Electronics

One of the Side A pieces can have all the holes for the connectors, LED and power switch. The diagram here shows the measurements I used. The ‘Aux’ connector is a mini DIN socket; it will be used for extending the functionality at a later date!

The DC socket is a usual 2.1mm barrel connector socket for power. The Earth connection is made with a 4mm banana socket.

I made the holes centred 26mm off the egress side edge.

Assembling the Enclosure

The photo here shows most of the main assembly complete; at this stage the insides are visible, before the final side is glued on top.

I followed these steps in order:

1. First assemble the four Egress Plug A/B pieces into a frame and gluing it, one joint at a time. PVA (wood) glue was used. The square is used to ensure the frame has perfect 90 degree angles.
2. Assemble the Ingress Plug pieces in the same way.
3. Next, draw lines on the Side A/B pieces, where approximately the Fan Support Blocks are desired. I chose to position them centered, 80mm apart.
4. The Egress Plug assembly was glued onto a Side B piece
5. The Ingress Plug was temporarily clamped into position (don’t glue it, we will use it just as a support for now)
6. Next, a Side A piece can be glued into position (don’t glue to the Ingress Plug, as mentioned use that just as a support for now).
7. The Fan Support A/B pieces can now be glued into place, using the Support Blocks as needed.
8. At this point the Fan Internal Surround can be glued on two edges and fitted into the assembly.
9. Glue the second Side A piece into position (don’t glue to the Ingress Plug)
10. Glue the Fan Support A pieces
11. Remove the Ingress Plug assembly which was just clamped into position
12. Glue the Jig Piece long edge to the Jig End
13. Next, using the Jig Piece/Jig End as a spacer, glue the two Filter Stop A pieces, and one of the Filter Stop B pieces. The Jig Piece results in the Filter Stop A/B pieces being exactly 39mm off the ingress side edge of the Side A/B pieces.
14. Test that the four fans (taped together) comfortably but snugly fit into the assembly up to the Fan Internal Surround (see photo below).
15. Test that the HEPA filter (Filter B) comfortably but snugly fits into the assembly, and hits the Filter Stop A/B pieces.
16. Remove the filter and fans, and glue on the final remaining side piece (Side B)
17. Glue the final Fan Support B pieces (trim them first slightly to have some room for wiring), and the remaining Filter Stop B piece.
18. Glue the Ingress Plug to the Ingress End Plate
19. Now the Ingress End Plate and Egress End Plate can be screwed to the main assembly!

The photo here shows the fans being tested for fit; they are taped up together and they they should easily slide in from the egress side.

The HEPA filter (Filter B) was also checked for fit:

The filter has a rubbery lip which mates with the side of the Filter Stop A/B pieces, creating a nice seal. The filter will be held in place firmly when the end plate, the Ingress Plate, is screwed on. The idea is that the filters are removable simply by unscrewing the Ingress Plate.

The photo below shows how this will work; there are four retainer pieces called Filter Retainer A/B, and they will not be glued, they will just be inserted into position and then the dowel assembly and the end plate will push against the retainer pieces to keep them in position. The dowel assembly will be glued onto the end piece, and will be screwed to the main assembly from the sides.

Constructing the end plates (Ingress Plate and Egress Plate)

Like the internal Ingress Surround piece, the two outer end plates need circular holes cut. They were cut using the same method as before (mark out the circular shape and then drill lots of small holes, cut out with a knife and then sand it into a circular shape). The Ingress Plate needs a 27mm diameter hole (to suit the hose) and the Egress Plate needs a 125mm diameter hole.

The Ingress Plate needs to connect to the hose. A really elegant solution was found by luck; there is a stepped vacuum hose adaptor available from Clas Ohlson. It can be used as-is, or shortened. I shortened it. Epoxy resin glue will be used to secure the hose adaptor to the Ingress Plate (but first paint the wood; see Part 2).

Next Steps

Part 2 will cover the rest of this project. It will involve painting the wood enclosure, and adding in the wiring, final assembly and then testing it out!

Summary

In a desire to reduce solder fume gasses and particles inhalation, this project seeks to filter it all out using parts such as vacuum cleaner filters and PC fans. The wood enclosure was easy to cut and assemble because it was made from very rigid but thin plywood. The final design can be unscrewed from either end, for serviceability.

If you’re interested, click on the Bookmark link for a reminder for Part 2, which will follow shortly!

(EDIT: Here is Part 2: Building a Low Cost Solder Fume Extractor - Part 2 )