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Part 4: plastic & electromechanical parts Phil Prosser’s Phenomenal N ow we are getting to the real ‘meat’ of this project. This article will walk you through the construction of the electromechanical parts and plastic guides. The interplay of light, sound and movement is the essence of a pinball machine. In planning and designing these, we considered what was needed to make a ‘proper’ pinball machine. Asking around, we came up with the following: Launching systems Flippers Reloading systems Kickers and bumpers To make all these parts, we need to combine 3D-printed pieces with solenoids, screws, nuts and other hardware bits. We will explain how these are assembled, keeping the descriptions mostly to exploded diagrams, tips and pointers. Once you have the hang of building, say, the flipper, the kicker is broadly similar in approach. So it gets easier as you go. 📍 📍 📍 📍 Sub-assemblies Pinball Machine Having described and built the electronics and started on the deck layout and cabinet, it’s now time to get to the really fun part: building and testing the flippers, bumpers, kickers, ball return mechanism and related parts. Ladies and gentlemen, fire up your 3D printers! One or two people I spoke to liked the idea of ball traps, where the ball falls into a recess and then the player is given a second ball to use. At some point, the original ball is released, allowing you to play with two balls on the deck at the same time. Still, we had to stop somewhere, so we didn’t include a ball trap in our machine. It probably wouldn’t be hard to make one using the building blocks we supply. There are a couple of unused high-current outputs that could provide that function and the software could be modified to suit. For the various parts (flippers, bumpers, kickers etc), you should be able to build and test them separately without needing a pinball deck. Only the bumper and flipper need to come apart again for final deck assembly. Every part in the Pinball Machine has been sized to work with a 22mm steel pinball. Many professional machines use a larger ball; we wanted to have an authentic pinball experience but really wanted the project to accommodate those with less room. We also didn’t want to make the mechanical aspects of the build too challenging. 22mm ball bearings are readily available. While we’ve done a lot of the hard work and are presenting stuff that we know works, we expect you will have a few ‘go arounds’ on making your first Australia's electronics magazine siliconchip.com.au 70 Silicon Chip Pinball Machine. It’s a big, complex electromechanical device, and no two are likely to be identical. Let’s go over the electromechanical parts in a little more detail than last time before we get to the parts required and assembly instructions. Reload and ball release mechanism The ball reload and release mechanism is automated. This is part of the drama of a pinball machine; when the player loses the game, the system detects this and actuates a solenoid, which propels the ball back into the launch system. This is a simple lever, which allows the solenoid to pull inward, and the lever pushes the ball up the alleyway. Because the table is tilted, once the ball goes over the summit, it rolls down into the release trap. This holds the ball ready for the ‘game start’ signal, which actuates a second solenoid that releases the ball to the launch plunger. The flippers The flippers have a lot of work to do and presented the greatest mechanical challenge. Generating sufficient force to play well is not easy. Good pre-made flipper units are horribly expensive, so we really needed to come up with a more creative solution than throwing money at the problem. Our design was initially very similar to those you will find in an arcade machine. They drive their solenoids with very high voltages and commensurately high currents to get the force required to propel the ball all the way to the top of the table. Our first design followed the oldschool approach, driving 12V solenoids with 48V to get good performance. We could have gone for larger solenoids, but they are very expensive and larger than we wanted. We needed a solution that used cost-effective parts but at lower, safer voltages. One approach we saw on the internet used two solenoids. This is attractive for several reasons. Firstly, we can double the torque on the flippers and get good performance with 24V DC, which is a safe voltage. Secondly, by arranging the solenoids on either side of the flipper axle, we can balance the forces from the solenoids. This increases torque while minimising the overturning moment, which reduces friction in the flipper siliconchip.com.au axle. This is a superior approach to that used in old-school pinball machines, if more complex. We specify 12V, 1.5A solenoids which we overdrive at 24V relative to their 12V specification. Be sure to order the right ones, as there are outwardly similar units that are rated at 12V but operate at a much lower current. These do not generate sufficient force for this application. Our software drives the solenoids at 100% duty cycle for 200ms to generate maximum force for the ball hit, then if the button is held, pulls the duty cycle back to 20%, which reduces dissipation in the flipper significantly while the player holds the flipper ‘open’. This is essential, as the solenoids get very hot when driven at 24V continuously. Bumpers Bumpers sense the ball hitting them and then ‘bump’ the ball away through the action of a circular plunger being pulled down by a solenoid. This is quite a violent action; it is a noisy and interesting aspect of a pinball game. Photo 13 shows how they look on the deck. The forces involved led us to using threaded rod to connect the solenoid to the plunger. this is a strong connection, but somewhat fiddly to set up. We initially tried to 3D-print the whole thing, but it would never have survived long term. Old-school machines used a rather complicated approach to sensing the ball hitting them, which involved the ball rolling onto a disc and tilting it. A finger protrudes through the deck, and this finger actuates a microswitch as its Photo 13: bumpers are one of the most exciting parts of a pinball game. It’s important to include plenty of LEDs to enhance that. Australia's electronics magazine angle changes. We replicated this in an early prototype, but the complexity of this and the fine adjustment required precluded us from proceeding down that path. We have instead taken the approach of integrating a small tactile switch under a similar sense disc and adjusting this to be a ‘hair trigger’ with a jacking screw. This screw serves two purposes. Firstly, it holds the disc above the deck, which the play ball will depress when it rolls onto it. Secondly, it ‘primes’ the tactile switch so that it is on the edge of actuation, making it quite sensitive to the ball rolling onto it. Apart from this, the overall bumper design draws many parallels to those used in conventional pinball machines. One challenge with the bumpers is that there are parts both above and below the play deck, so while you can assemble and adjust the bumper away from the board, you need to separate the upper and lower parts to install it. Old-school mechanisms used a steel plunger. To avoid the complexity of fabricating this, we used 3D-printed parts. When you print the plungers, make sure to set the wall thickness to a minimum of 2.4mm to achieve very thick walls that will better weather the impacts on the ball. We have also used two threaded rods to attach the plunger to the solenoid and made the attachment point of these to the plunger quite thick. This gives us a largely printable bumper that is reliable. To get lights in the top of the plunger, there are holes that run through all parts of the plunger, including the sense disc, allowing the LEDs in the top to connect via flying leads. We have specified two high-brightness LEDs at the top of the bumper and operate them at 30mA to generate bright light effects. Once the holes through the parts are clear (a 2mm drill is your friend), assembly is not that hard. Of all the parts in the machine, the bumpers are definitely the most challenging to assemble, but once you have built one, they are not too bad. Also, they are really important in making the game ‘authentic’! Kickers The kickers operate by sensing the ball hitting a microswitch and then September 2026  71 actuating a solenoid that pushes or ‘kicks’ the ball away. They are not complex, being essentially a curved lever actuated by the solenoid. We have mounted the sensing microswitches via separate brackets, as this allows you to install and adjust these independently. The most important tip we found setting these up is that adjusting the microswitch lever is very important. It needs to be sensitive but not get stuck on. We ended up bending ours with needle-nose pliers to get the sensitivity just right. Because of the way the kicker works, the sensitivity, speed and direction in which the ball is kicked vary a lot. This is all part of the random fun of these in the game. Parts List – Reload Mechanism 1 TAU-0826 12V 1.5A solenoid 1 2-way vertical pluggable terminal block 2 2-way polarised header plugs with matching pins 2 LJ12A3-2 2mm inductive sensors 1 assembled Switch Input PCB (code 08107268) 3D-printed parts (all PLA) 1 Lower Deck Layout L (10% fill, 1.2mm wall, print on raft) 1 Lower Deck Outer Runway L (10% fill, 1.2mm wall) 1 Reload Load Coupling Bushing (30% fill, 2.4mm wall) 1 Reload Load Coupling (30% fill, 2.4mm wall) 1 Reload Load Flipper (30% fill, 2.4mm wall) 1 Reload Load Retaining Washer (solid) Hardware & wire 1 6mm-long self-tapping box screw (4G self-tapper) (to attach the coupling to flipper) 7 6G × 16mm wood screws (to attach the reload mechanism to the deck) 2 M3 × 25mm panhead machine screws (connecting the reload coupling to the solenoid armature and the coupling to the flipper) 2 M3 Nyloc hex nuts 1 M3 × 6mm panhead machine screw (to attach the solenoid to the base) 1 1m length of medium-duty figure-8 speaker wire M3 nut & bolt Self-tapping box screw Fig.22: this shows how the 3D-printed parts of the reload mechanism in the lower-left deck area go together. Parts List – Lower Deck Middle 1 3D-printed Lower Deck Layout M (PLA, 10% fill, 1.2mm wall, print on raft) 4 6G × 16mm wood screws Fig.23: the lower centre deck section is simply this 3D-printed plastic part with guide rails for the ball. 72 Silicon Chip Australia's electronics magazine Rollover sensors There are several rollover sensors, which in our case are inductive sensors. We chose 12mm diameter, 2mm detection range sensors. These mount through the play deck and sense the ball either rolling over them or stationed above them. We use one on the reload mechanism. Most of these are specified to operate from 6-32V DC, so we have designed the controller and breakout board to provide 24V DC to these. Their output is open-collector style, so they pull the relevant input to ground, as do all other inputs (like microswitches). If you choose to use old-school microswitch rollover sensors, they are a direct substitute. We have 3D-printed parts to form under-deck brackets holding the inductive sensors in place; you can use a 3mm screw to hold the sensor tight. We found that drilling a 12mm hole for the 12mm sensors worked well; we kind of ran the drill in and out a ‘few extra times’ to clear the hole, which is terrible form but made the mounting hole that little bit larger so things fit easily. Now that we’ve gotten that all out of the way, let’s build some parts! Reload (lower deck left) construction ■ The reload mechanism is in two parts. The left side of the deck needs the ball sensor installed through the deck, as shown in the deck drawing last month, so the controller ‘sees’ when the game is lost and the ball is ready to reload. This is essential. While part of the deck, it is good to get the marking and drilling for the hole done along with the reload mechanism. We find that marking the exact locations of holes like this using the printed parts reduces errors in the final alignment. Fig.22 gives a sense of what goes where in this part of the deck. Mount the 12V, 1.5A solenoid to the deck section using 6mm M3 screws, with either superglue or Loctite to ensure the solenoid never shakes loose. Then install the bushing onto the axle, which is printed into the base section. It will slip right on and should rotate freely. Install the flipper on top of this. Connect the solenoid armature to the coupling with the 25mm machine screw, but do not over-tighten the nut, siliconchip.com.au as this needs to articulate over the throw of the solenoid. Install the reload flipper on top of the bushing and push the armature into the solenoid, then the coupling onto the flipper. Using the printed washer and self-tapping box screw to secure the coupling to the flipper. We have printed a hole into the flipper axle so the self-tapping box screw will tighten easily. Do not over-tighten this, as you need the coupling to move freely. This screw is just there to stop it from falling off. Make sure to keep that spring with the solenoid, as it returns the flipper to a neutral state when the solenoid is not operating. Take care, because if you drop them, they tend to disappear into another dimension. Lower deck middle construction ■ The lower middle deck section is simply one 3D-printed piece, shown in Fig.23. This fits to the right section with two locating lugs and butts to the left section once installed along the base. Parts List – Ball Release & Launcher 1 TAU-0826 12V 1.5A solenoid 1 2-way vertical pluggable terminal block 3D-printed parts (all PLA) 1 Lower Deck Layout R (10% fill, 1.2mm wall, print on raft) 1 Ball Reload Positioner (30% fill, 2.4mm wall thickness) 1 Launcher 6.6 degree Shim (solid) 1 Lower Deck Outer Runway Right (10% fill, 1.2mm wall) 1 Reload Ball Release Drive (30% fill, 2.4mm wall) 1 Reload Ball Release Lower Washer (30% fill, 2.4mm wall [solid]) 1 Reload Ball Release Slide Coupling (30% fill, 2.4mm wall) 1 Reload Ball Release Slide (30% fill, 2.4mm wall) 1 Reload Ball Release Solenoid Coupling (30% fill, 2.4mm wall) Hardware & wire 5 6mm-long self-tapping box screws (4G self-tappers) (ball positioner fixing, attaching couplings to drive and drive to deck) 5 M3 flat washers (under self-tapping box screws to secure the couplings to the release drive) 7 6G × 16mm wood screws (to attach the reload mechanism to the deck) 1 M3 × 25mm panhead machine screw (to connect the reload coupling to the solenoid armature) 1 M3 Nyloc hex nut 1 1m length of medium-duty figure-8 speaker wire Ball release & launcher (lower deck right) construction ■ The lower right deck section includes the ball release, the launcher and reload adjustment. Take a look at the exploded diagram, Fig.24, to get a sense of what goes where in this part of the deck. Install the solenoid using the M3 × 6mm screws and make sure to glue or Loctite them into place. Then install the large washer and the circular drive mechanism. Take the drive, coupling and slide, and work out which is which. Next, secure the solenoid coupling to the solenoid armature using the 25mm screw and Nyloc nut, then get these assembled to the deck section. Finally, use three 6mm self-tapping box screws to secure the couplings to the drive and the drive to the deck. The ball positioner can be loosely installed now; final adjustment is required once the deck is assembled, to get the ball in the best location for the launcher to propel it up the table. We include a 6.6° launcher shim, as this will be required to get your launcher to fit neatly against a vertical front panel. Make sure to keep that spring with the solenoid, as it returns the release siliconchip.com.au M3 nut & bolt self-tapping box screw & washer Fig.24: this shows how the parts for the ball release, launcher and reloader go together in the lower-right section of the deck. to a neutral state when the solenoid is not operating. If you apply 12V to the solenoid now, it should operate freely. Flipper construction ■ The flipper assembly has quite a few parts, shown in Figs.25 & 26. You need a 23mm or larger hole in the deck. For our prototypes, we simply used a 25mm spade bit to make that hole. The flipper assembly goes through the deck, with the solenoids and drive below and the flipper above. Australia's electronics magazine You should do an initial build off the deck, then pull the flipper off for final installation. We apologise right now that this mechanical part will be fiddly to set up with the multiple solenoids and couplings. The assembly process follows these steps: 01 There are normal and mirrored parts for the flipper base and drive. Make sure you have the right set of parts. If you try fitting the wrong bits together, it will be really confusing. September 2026  73 Parts List – One pair of Flipper Assemblies 4 TAU-0826 12V 1.5A solenoids 4 2-way vertical pluggable terminal blocks 3D-printed parts (all PLA unless noted) 1 Double Drive – Driver (solid) 1 Double Drive – Driver Mirrored (solid) 2 Double Drive – Limiter (40% fill, 2.4mm wall) 1 Double Drive 12mm Deck (30% fill, 2.4mm wall, PLA or ABS [preferred], print on raft) 1 Double Drive 12mm Deck Mirrored (30% fill, 2.4mm wall, PLA or ABS [preferred], print on raft) 2 Drive Arm Washer (solid) 2 Flipper 90 plus 4 (40% fill, 5mm wall, ABS) ■ 4 Solenoid Coupling 38mm (solid) ▲ 2 Washer Lower (solid) 2 Washer Upper (solid) ■ “plus 4” is the shaft length, which is 1mm more than a 12mm deck needs. Other lengths are available if you need them. ▲ other lengths are available if you need them. Hardware & wire 4 6mm-long self-tapping box screws (4G self-tappers) (to retain the flipper drive to the flipper axle) 4 M3 flat washers (under self-tapping box screws) 6 6G × 16mm wood screws (to attach the flipper base to the deck) 4 M3 × 25mm panhead machine screws (to connect the couplings to the solenoid armatures) 8 M3 × 20mm panhead machine screws (to connect the drive limiter to the base and the solenoid couplings to the plungers) 4 M3 × 16mm panhead machine screws (through the drive mechanism to secure the couplings) 8 M3 × 6mm panhead machine screws (to attach the solenoids to the base) 9 M3 Nyloc hex nuts (for the 16mm & 25mm machine screws) 1 1m length of medium-duty figure-8 speaker wire 1 50cm length of 10 × 5mm neoprene rubber band Fig.25: the flipper mechanism is somewhat complex, using two solenoids in a balanced arrangement for more power and stability. Assemble them as shown here. M3 nut & bolt from underneath drive & deck 20mm M3 nut & bolt underneath Fig.26: an exploded view of the flipper assembly. This is ‘upside down’; the solenoids are underneath the deck and the flipper above. The two M3 × 16mm machine screws with nuts connect the drive to the couplings (red and green), with self-tapping screws and washers holding the couplings to the flipper axle. 74 Silicon Chip Australia's electronics magazine 02 Fit the drive limiter to your base section using four M3 × 20mm machine screws and Nyloc nuts. Fit each solenoid to the base using two M3 × 6mm machine screws, with Loctite or superglue on the threads. Our design assumes the TAU0826 20N 12V solenoid, which you really need to use for the flippers to get the torque required. These need to go on before installing the base to the pinball deck. 03 Fit the base and bushing from the underside of the deck. The bushing fits through the hole in the deck and ensures that the flipper operates smoothly. You need to use the 12mm drive part for a 12mm deck. Screw the base section to the underside of the deck with the hole lined up. Fix the base section to the underside of the deck using 6G × 16mm wood screws. 04 Take the 10×5mm neoprene rubber and cut one end at 45°. Wrap the rubber around the flipper and work out where to cut the other end so the rubber fits tightly onto the flipper. Use superglue to glue the two ends together. 05 Select your flipper (right or left) and put the 27mm diameter printed washer on the flipper axle. Put this through the deck from the top. 06 Once this is secure, install the flipper and upper 27mm washer from the top of the deck side. 07 Connect the two solenoid drive arms to the flipper drive using M3 × 16mm machine screws. The screw comes through the drive from the rear, and the coupling is secured to the small axle with it, which adds significant mechanical integrity to this coupling. We used the 38mm arms; you should dry-fit yours and choose the right length. 08 Now put the lower 27mm washer on the flipper shaft from the rear and then add the flipper drive coupling. 09 Referring to Fig.25, connect the flipper drive to one of the solenoids using a 25mm-long M3 machine screw and Nyloc nut, then assemble the flipper drive to the flipper and insert the solenoid armature into the solenoid. You should now be able to insert the second solenoid armature into its solenoid and then insert the connecting 25mm M3 machine screw and Nyloc nut to get the assembly together. 10 Secure the flipper drive to the rear of the flipper axle with two 4G × 6mm screws and 3mm ID flat washers. This will hold the flipper drive to the siliconchip.com.au Photos 14 & 15: a completed flipper assembly, viewed from underneath and side-on. flipper axle, and if you ever need to get things apart, you can. 11 At this point the flipper ought to be able to rotate quite freely. If not, is your deck too thick? We have included flipper STL files with extended axle lengths that would allow thicker decks to be accommodated. 12 Connect the solenoid couplings to the solenoid plungers using M3 × 20mm machine screws and Nyloc nuts. You should now have functional flippers. Photos 14 & 15 show the finished flipper assembly. You can test this section by applying 12V to the solenoids. If you choose to do this, make sure there is a reverse diode across the solenoids to stop the back-EMF from damaging your power supply. The flipper action is pretty rapid and will give you a sense of what to expect with the other parts. Bumper construction ■ You’ll probably want to make several bumpers (our machine has three). The assembly process is: 01 Check that the 3D printed pieces fit together and run smoothly. We have designed everything with a good gap to ensure things don’t stick. Check the prints don’t have bumps or dags; if things don’t run well, you can sand parts if needed, though we didn’t with these tolerances. The exploded drawings are in Figs.27 & 28. 02 We put two high-brightness white LEDs in the top of the bumper as shown overleaf. We used parts from the Cree C513A series, which worked a treat. Bend the legs as shown and solder them anode-to-cathode so they are in series. We ran the anode and cathode wires right through the assembly, as shown in Photo 16. 03 Now we need to get the lower base assembly piece and install the ball detection microswitch. The part has been made to accommodate an siliconchip.com.au Parts List – Bumper Assembly 1 TAU-0826 12V 1.5A solenoid 1 2-way vertical pluggable terminal block 2 2-way polarised header plugs with matching pins 1 four-pin SMD tactile switch with short actuator [Altronics S1112A, Jaycar SP0610] 2 Cree C513A series 30mA LEDs (any colour) 3D-printed parts (all PLA) 1 Bumper Ball Detect Larger (solid) 1 Bumper Base Lower (30% fill, 2.4mm wall) 1 Bumper Base (30% fill, 2.4mm wall) 1 Bumper Plunger Coupling (solid) 1 Bumper Plunger (solid) 1 Bumper Top (solid – make this colourful, maybe transparent or translucent; the LEDs light through it) 1 Bumper Under Deck Bracket (30% fill, 2.4mm wall; should not need supports but remove them if used) 1 Bumper Shim for Base to Clear LED Holders (2.4mm wall) Hardware & wire 9 9mm-long self-tapping box screws (4G self-tappers) (attach upper to lower base, attach lower base to deck bracket, secure top of bumper) 2 80mm lengths of M3 threaded rod (cut from a longer piece) 1 M3 × 20mm panhead machine screw (to secure the solenoid armature to the coupling) 1 M3 × 10mm panhead machine screw (as a jack screw for the microswitch) 2 M3 × 6mm panhead machine screws (to secure the solenoid to the under-deck bracket) 9 M3 Nyloc hex nut (for the 20mm machine screw and threaded rods) 1 1m length of medium-duty figure-8 speaker wire 4 1m lengths of light-duty hookup wire (green, green, red & black/white) Fig.27 (above): an exploded diagram of the bumper assembly, with the threaded rods not shown. 9mm jiffy screw Fig.28 (right): joining the upper and lower 3D-printed sections of the bumper. M3 10mm screw Australia's electronics magazine September 2026  75 Photo 16: LEDs installed in the top of the bumper. The recess in the upper base section has been sized to fit a 5mm LED. We chose high-brightness white LEDs, but you could use coloured types. Photo 18: the upper and lower bumper sections with the switch and LEDs installed and secured. Altronics S1112A SMD tactile switch (it has standard dimensions so if you can’t get that one, you’ll be able to find an equivalent). The connections for the wires are as shown in Photo 17. Use a multimeter to check that you have connected to the right terminals, as it is bothersome pulling this apart to fix a silly error. 04 Feed the green wire through the inner holes in the upper and lower base pieces. We ran a 1.5-2mm drill bit through all the holes to clear the printing dags from inside these holes. After that, the light-duty wire fit well (it didn’t at first!). 05 Solder the tactile switch to the 500mm lengths of light-duty hookup wire and get the switch snug in the cavity. This is deep enough that you need to use the M3 adjusting screw to raise the switch when adjusting it later on. Make sure the tactile switch is central to the recess. Adjust the hookup wire if necessary – this is required to get the jacking screw central to the switch. 06 Using two 500mm lengths of light-duty hookup wire, run red and black wires through the lower and upper bumper base pieces. Solder the red wire to the anode (more positive) LED terminal, making sure not to leave a blob of solder, as this needs to fit into a 1.2mm hole. Repeat with the black wire for the cathode. 07 Now fit the ball detection disc to the lower base section as shown in the figures, then feed the LED wires through the holes in both the ball detection disc and the lower base section. 76 Silicon Chip Photo 17: the bumper LED and sensor wiring. We soldered lightduty hookup directly to the LED leads and tactile switch. Take care with soldering to the LED leads to ensure it fits into the 1.2mm hole in the bumper. Make the flying leads at least 500mm long to reach the breakout board. 08 Push 4G 9mm panhead screws into the holes in the lower base section and affix the lower and upper parts (see Fig.28). Once together, this should be as shown in Photo 18. 09 Push a 10mm M3 machine screw into the centre hole. We can screw this in to adjust the sensitivity of the ball detection. This needs to be screwed forward enough to jack up the tactile switch to the point that it lifts the ball detect disc to the upper base assembly. When adjusted properly, the switch is not depressed, but pushing down on any edge of the ball detect mechanism will actuate the switch. This is noticeable when you push the disc with your finger, so adjusting it is not hard. Do not over-tighten this as you will simply force the switch to always be on. 10 For a 12mm deck, cut 80mm lengths of M3 threaded rod and thread them onto the plunger. Remember that the top is the flat side. Use a Nyloc nut at the top so you can get this off later if needed. Run a normal M3 nut up from the bottom of the thread and lock it to the bottom of the plunger bracket. Put a drop of superglue or threadlocker on the bottom nut to ensure it does not come loose. 11 Now present this assembly to the below-deck section. Push the lower base section in until the top of this is about 0.5mm above the deck height, which will need to include the mounting shim, as shown in Photo 19. This prototype used machine screws that were about 6mm too short. This resulted in the top two assembly holes aligning between the under-deck bracket and the lower base piece. These accept 4G × 6mm screws but use the holes which align for you. We have included a whole Australia's electronics magazine range of staggered holes, allowing the bumper to be used with a range of deck thicknesses. 12 Now we need to install the plunger coupling to the solenoid using an M3 × 20 machine screw and Nyloc nut. 13 With the plunger and base assembled to the under-deck section at the right height, we now need to assemble the plunger coupling to the plunger’s M3 threaded rod. With the plunger aligned with the top of the bumper (as high as it will go), put two normal M3 machine screws onto the threaded rod about 15mm from the bottom, then push the plunger coupling on and add two Nyloc nuts from the bottom. You will need to have the solenoid in the base assembly to do this, loosely affixed using two M3 × 6mm screws and lock washers. With the plunger at maximum height, tighten the M3 nuts on the threaded rod. Now push the plunger down and check that it does not hit the ball detect disc. Adjust these until it works, and fix the normal M3 machine screws with superglue, then tighten the solenoid. 14 Make the connections to the solenoid using heavy-duty wire. Solder 500mm lengths to it and insulate the connections. 15 Photo 20 shows the finished bumper. To test this, use a 24V DC supply. On connection, the bumper should compress downward quite Photos 19 & 20: the initial construction of the bumper (left). A completed bumper, ready for installation (right). siliconchip.com.au rapidly, and if you have everything connected to the bumper/kicker board, the LEDs will light. If anything is not running smoothly, address the problem before proceeding. Our prototypes all worked fresh off the printer, so if your printer is adjusted well, you should not need to fiddle too much. Kicker construction ■ You’ll probably want to make several kickers (our machine has two). The overall kicker design is shown in Fig.29. We have made the parts different colours to make them easier to distinguish. Assembling of the kicker is pretty simple, especially compared to the bumper. We have included holes to suit the two main solenoid types that we expect you will find. The assembly process is: 01 Check that all the parts printed OK. 02 Screw the kicker coupling to the solenoid using a 20mm M3 machine screw and Nyloc nut. 03 Connect the kicker coupling to the kicker arm using another 20mm machine screw and Nyloc nut. 04 With all of these connected, push the solenoid into the kicker base and jiggle the kicker arm to align the mounting hole. Use another 20mm machine screw and Nyloc nut to secure these. The complete assembly is shown in Photos 20 & 21. 05 Solder a diode across the solenoid leads if you are testing this, as the back-EMF from these solenoids is extremely powerful. 06 Use a 24V DC supply to test this. Apply voltage and the kicker should kick quite violently, then return to its rest position when disconnected. To assemble the microswitches used to trigger the kicker: 01 Take a kicker microswitch bracket and assemble a 25mm lever microswitch to it. The aim of these is to get the lever end of the microswitch up to the height of the rubber band around the kicker. 02 Use 20mm-long M2.5 machine screws and Nyloc nuts to secure these, as shown in Photo 22. 03 Mount the kicker microswitch assembly next to the kicker, under the play deck. Use the adjustment to set the depth so that the kicker rubber band ‘rope’ is close against the microswitch, to ensure this switch is sensitive to the ball hitting the rope. Next month Wow, that is a lot of parts, and in most cases, you need several of each. That is all for this month. Next month, we will finally get to the end of this series. We will show the final assembly steps and how to get your whole Pinball Machine up and running. You will see that we have a custom theme for our machine. We really expect you will have your own theme and approach to decorating your own creation. This is where you get to go wild. Loud colours, light layouts and your artistic creativity can come to SC the fore. Parts List – Kicker Assembly Photos 20 & 21: the assembled kicker when printed using white filament. The final kicker has a narrower ‘paddle’ at the top and you should use Nyloc nuts on all machine screws. 1 TAU-0826 12V 1.5A solenoid 1 2-way vertical pluggable terminal block 2 2-way polarised header plugs with matching pins 2 KW12 25mm roller (straight) lever arm microswitches 1 50cm length of 5 × 5mm neoprene rubber band 3D-printed parts (all PLA) 1 Kicker Arm 12mm deck (solid) 1 Kicker Base (solid) 1 Kicker Coupling (solid) 2 Kicker Microswitch Bracket (solid) Hardware & wire 3 M3 × 20mm panhead machine screws (to secure the solenoid armature to the coupling and then to the kicker) 2 M3 × 6mm panhead machine screws (to secure the solenoid to the under-deck bracket) 3 M3 Nyloc hex nuts 4 M2.5 × 20mm panhead machine screws 4 M2.5 Nyloc hex nuts 1 1m length of medium-duty figure-8 speaker wire 2 1m lengths of green light-duty hookup wire Photo 22: the kicker trigger microswitches attached to their 3D-printed brackets. Fig.29: this shows how the 3D-printed sections of the kicker go together. siliconchip.com.au Australia's electronics magazine September 2026  77