Here's how to build a small air hockey table, that is both cheap and portable. As well as this, you can make it any size, depending on the box you use. A plastic box was used for simplicity; it means you can experiment with the air flow easily.
An air hockey table works by creating a cushion of air beneath the puck, so that it moves smoothly. As oppose to using an expensive blower, some old CPU fans were used. These are less powerful, so the table is scaled down.
Things you'll need:
►MDF, at least 6mm thick
►Plastic Storage Box
►Wooden borders, I used 1/4 cylinders
►1 or 2 powerful, brushless computer fans
►12V Power Supply, suitable rating for the fans (preferably with a 5.5 mm jack)
►Mitre saw/Mitre Box (only for the borders)
►Drill, with a 1.5mm / 2mm bit
►Silicone sealant, and/or tape
Step 1: Finding a Suitable Box
You should determine the dimensions of the box according to the fan(s) you are using. Make sure there is space to mount the fans (in terms of depth). See the diagram above. Choose a box that is suited to the fans; if it is too big then the puck won't float. The ratio between the length and the width does not matter, it is personal preference. Try to find a box that has straight sides and has a flat surface at the top, when the lid is removed.
Once you have chosen a box, you can discard the lid and mark out where the fans will go. You can either follow the above, or place them directly opposite. I selected fans with guards, so it did not matter, but be careful where you mount them if they don't have covers.
Step 2: Mount the Fans
First you need to cut vents for the fans. Use a jigsaw to cut this out, creating a hole for the blade with a suitable drill bit first. Remember that you will need to affix the fan to the plastic, so make the vent circular, leaving room for the mounting holes at the corners.
Alternatively, you can use a hole saw bit, with an appropriate diameter.
Drill holes at the corners, being careful with the alignment. Secure the fan with nuts and bolts (and washers if the plastic is weak). Check the orientation, it should be drawing air in from outside the box.
The fans can be on the outside or inside; though inside is preferable. If there is a gap around the border of the vent, use tape or silicone to seal it.
If you have mounted the fans on the inside, ensure the wires are accessible before you seal the container, in the next steps.
Step 3: Creating the Playing Surface
MDF is used because it is already very smooth. If you prefer, you can use acrylic, though beware that with the amount of holes, it is likely to crack in a few places.
Turn the box upside down, and draw around the perimeter carefully, onto the MDF. Cut out this section and check the fit; filing where needed.
Step 4: Drilling a Few Holes...
This is the most time consuming part, be prepared to drill 300-600 holes.
Start by creating a square grid with a pencil, where each square is 20mmx20mm. Before this though, account for the border material at the sides. Remember to drill through the top, so that the damage is minimal on the 'good' side.
Begin drilling (with a 2mm bit). Try to drill straight down, both to prevent snapping the bit, but also to make sure the air flow is optimum. If the holes are not angled perpendicular, the puck may move towards one side. Occasionally stop and remove the dust. If the holes close up, use a vacuum cleaner to reopen them.
I found that with the size of puck I used, this was not a high enough hole density. Save yourself the trouble of having to drill more holes later and add another hole in the center of each square - it makes a dramatic improvement.
Now that you have done this (and probably broken a few drill bits), you can clean up the underside with a sander. Note: it may close up the holes. I again used a vacuum cleaner to remove the dust clogs. I would however try this on a small section first, because if they are becoming permanently clogged, you probably don't want to have to drill every hole again.
You can now use very fine sandpaper/a rubber to remove the pencil grid from the top.
Step 5: Seal the Box
Inspect your MDF. Hold it up to the light to check the holes are all open. Roughen the surface of the plastic box so that glue will adhere to it better. At this point ensure, as mentioned earlier, that all wires are accessible on the outside and that the box is otherwise airtight. Run a relatively thick bead of silicone along the perimeter of the box. Carefully place the MDF sheet on top, correcting the alignment. Make sure the smooth side is face up.
Now carefully flip the box upside down, so that the MDF is facing down. Run another bead of silicon along the join from the outside to ensure it is sealed. Finally, add some weight onto the box, and let it cure.
Step 6: Wiring
As you wait, you can begin the wiring. Extend the wires from the fans so that they can meet at a central point on one of the sides. I created a small box (3D printed) to encase the switch and the socket.
Complete the circuit, as shown in the diagram above. You can use a strip of tape to secure the wires running from the fans to the power supply. When soldering the connections on the socket, make sure they will not short: use tape.
Step 7: Test It Out!
Turn on the fans, and confirm that that there is air flow from the holes. If there is, find a light, plastic lid and see if it slides around freely, without much friction. If this works, move on; otherwise, perform the checks below:
Are the holes obstructed?
Are the fans receiving enough current?
Are the fans mounted correctly, so that they blow air into the box?
Is the box airtight?
Is the lid you are using too heavy?
Is the table and/or lid smooth?
Step 8: Finishing Touches
Using the border wood, measure out each side. Account for the 45 degree cuts at each section.
Check that these angles are the correct way round if you are using a 1/4 cylinder dowel. Cut with a tenon box & saw or a mitre saw.
Finally, make goals by removing an appropriate length of wood from the middle of the two shorter sections.
Use wood glue (and clamps) to affix them to the MDF. Avoid getting glue on the playing surface.
Use a marker to create a halfway line. You can draw around tape reels to create a centre/goals. Avoid using paint because it will block the holes and roughen the surface.
Puck and Mallets:
I 3d printed these mallets, scaled down. (There is also a puck on the same page). Just remember to use a low infill so that it remains light.
To prevent scratching, you can put felt on the bottom of the mallets. I found that paint tube lids work well as pucks - they are very smooth and light.
If you want to develop this further, you can create a wooden box, using the same dimensions, providing they work. The silicone should come off easily, and you simply create new vents and mount the fans again.