Sixth Time’s the Charm

I finally made a good flipper! After yesterday’s mistakes, I had three bits of raw material left to make the flippers I need. Today I examined my CNC programming, learned what mistakes I made and how to fix them (and hopefully avoid them in the future), and reprogrammed the mill to make my flipper. So I run through the whole process, three different tools, and it looks great. Then I put it next to yesterday’s failures and see that the 0.376″ hole looks way bigger than in should. Sure enough, the auto toolpath algorithm cut to the outside of the hole instead of the inside! So I get back to the CAM station (it’s connected to the milling machine), fix the toolpath, and go back and happily start getting my second flipper. Except when it gets to the hole, it’s cut too big again. Arg! Then I realize that although I fixed the toolpath, I never sent the revised instruction set to the milling machine and I just reran the bad program. *Sigh*

So I resend the file, cross my fingers, put my last bit of material in the vise, and start machining. Sure enough, I get my first viable part! Aside from my time, manufacturing this single flipper has cost me about $24 in materials. My next one, as long as I don’t make some other silly mistake, will cost me about $3. Way more reasonable.

I ended the night on a success, which is nice. Soon I’ll mill the other armature piece I need, and I’ll assemble the full flipper mechanism and be ready to test it!


Aluminum Flippers

Tonight I milled the flipper program I finished last Saturday. I made several mistakes, both stemming from my inexperience with the milling coordinate system. The parts still look nice, so I’ll keep developing my technique and finish them despite not being able to use them on my table.

Milling Prep

I had only a short time today, but I used it to get a refresher on the use of the software that runs the milling machine and to get the two new parts I’m milling ready to go. After some great suggestions from my mentor Marty, I decided to change the way I’m making the flipper and mill it upside down. It will take longer, but will allow me to accurately mill the 0.376″ hole in the bottom. It does mean using a key cutter to cut part of the outside profile though, since there is a 0.100″ overhang when cutting this way. The part will then be removed with a band saw and faced on the mill.

The second part, the arm that turns the flipper shaft, will be quicker to make but generally be done in the same fashion. I will be making these parts Monday evening after work.

Still Working

I was in Portland last Wednesday night through the weekend, so I didn’t make any progress during that time, but Monday (May 8th) evening I worked on a couple of flipper parts. First, I turned down the heads of two M6 bolts to fit the solenoid hole. The bolt heads are just a little bit too big to fit, but the lathe made quick work of that. Both bolts now are perfect fits, and both support and align the coil on one side as well as provide a stop for the armature to hit.


I needed new armatures to fit the new, bigger coils. I cut up some of the bars I previously milled (see 30 Apr 2016 heading here) and ground them down to the length I needed, which is to allow the mouth of the armature to protrude completely even when the coil is fully engaged, so the linkage doesn’t jam.


This week I have also drawn (in CAD) my flipper design to mill out of aluminum. I also have been working on the shaft that supports the flipper as well as the link that connects to the solenoid armature and allows the whole thing to turn. That link will also be milled from aluminum, and I designed it to look kind of like a miniature flipper. One side will fit over the shaft of the flipper and an M3 bolt will screw down into the shaft, holding it in position. The other side is designed to fit over the “bone” linkage I’ve already milled, though I’ll have to either design a shorter version or cut it down. Overall, these are the last few parts I need to finalize my flipper assembly and move on to the next part!

Flipper assembly

Last Wednesday (the 26th of April, 2017) I worked on some flipper assembly parts. After getting things together, I started working on how to a) get the right rotation out of my assembly; and b) make the whole thing as small as possible.

To do this, I put my new coil on a 12v power supply and gave it what it could, almost 3A! the armature got sucked in good, and the whole coil started heating real quick. So I connected a small inline scale and found that for about the first 1.25″, the pull was pretty even at 1.5 pounds. Once I pulled the armature out further, it dropped off drastically and popped out of the coil. So giving room for the armature stop in one side of the coil, I can use one inch of movement to rotate my flippers. Since I want to get 90° of rotation in one inch of pull, that means the arc can be scribed using a right triangle with a hypotenuse of 1″. Each leg would be 0.707″, and the distance from the center point of the hypotenuse to the endpoints of the other two legs would be 0.676″ away. That second point is the center of the shaft that rotates the flipper, and together with its bushing it’s 19mm in diameter (or 0.374″ radius). So there’s about .300″ from the outer edge of the bushing to the line where the solenoid is pulling. I should easily be able to make that work. This means, however, that the linkages I made way back when aren’t going to work, they’re all too long. Oh well.

So on to some pictures to look at. The first one is some parts laid out (and some old parts on the left there too). I’ll probably ditch the tapped aluminum bushing for a straight 3/4″ square bar now. The second picture is a side-by-side of my first coil vs my new coil (both resting on the same level surface). Bigger, stronger, faster. Oh yeah.

Flipper assembly

I worked on a new design for a compact flipper assembly using my new solenoids. I’m still working things out, but have a prototype ready to try tomorrow. I’m thinking about a torsion spring for returning the armature/linkage back to it’s normal position. I may have to redesign my linkage piece to save space, too.

NW Pinball Expo

I just purchased tickets and booked a hotel for the Northwest Pinball Expo in Tacoma, June 9-11. I will be bringing my coiling machine and my work-in-progress pinball machine. I have a lot of work to do, but will do my level best to have the lower third ready for the June show!