I love the idea of a scaled down pinball. I always thought that a 3/4 home brew would be about the perfect size where it would not only be not too heavy, but could fit in pretty much any vehicle (plus you could easily store it away when you're not working on it instead of taking up the space of a full sized pinball).

Honestly because you're building at 1/2 scale, you're obviously not going to be able to just grab off the shelf parts (or already as I'm seeing, you're having to make them work such as the case with the flipper mechs). You would greatly benefit by 3d printing many of the parts you need. I'd be happy to model something up, but it would greatly benefit you to invest in a 3d printer.

The anycubic mega zero is about the cheapest printer you can buy right now (and simple to build) at $96 (though from China is could take 4-6 weeks to get)
https://www.aliexpress.com/item/4000730911926.html?src=google&albch=shopping&acnt=494-037-6276&isdl=y&slnk=&plac=&mtctp=&albbt=Google_7_shopping&aff_platform=google&aff_short_key=UneMJZVf&&albagn=888888&albcp=9594035441&albag=102695258807&trgt=296904913880&crea=en4000730911926&netw=u&device=c&albpg=296904913880&albpd=en4000730911926&gclid=Cj0KCQiA0MD_BRCTARIsADXoopYjXcNOxwi7M1NKxVp_JbMXqyZqloc8WBp5XH85X2VMnUOHgWiR7ogaAlNVEALw_wcB&gclsrc=aw.ds

The next step up would be buying an ender3 from Walmart for $155
https://www.walmart.com/ip/Creality-3D-Ender-3-High-DIY-3D-Printer-Self-assemble-220-220-250mm-Printing-Size-with-Resume-Printing-Function/664500829?wmlspartner=wlpa&selectedSellerId=101019803

that's the thing, a 3d printer is also for prototyping. I would at least look at some tutorial videos of getting started with a 3d printer:

There's really only like 2 things you have to be aware of
1. Always be sure your bed is level
2. If filament isn't coming out, or is barely coming out, either your nozzle is clogged, your tension pushing the filament isn't tight enough, or your temperature isn't high enough.

Even if it's a long time before you start making your own 3d models, so long as you can send a sketch I can model it up (hell I can even slice it and send you gcode so you literally just copy it to an SD card and start printing). This is a perfect example of that. Jack Danger was at Ed Owens house helping him with his homebrew, and he's like "You're gonna have to make some sort of ramp here", so I message him and ask him to snap a photo of the top view with a coin for size reference. In 20 minutes I had a 3d model and 2 hours later he had a physical ramp to put in the game:

for reference, this is what a typical VUK mech looks like:
https://www.marcospecialties.com/pinball-parts/500-6290-01

This would be everything you need other than the ball guide to keep the ball on track, and then some sort of scoop at the top. If you're stuck on cardboard, this is what I did on the start of my homebrew before I had a 3d printer:
unfolded vuk (resized).png
3d_rendering (resized).png

You may need toothpicks to hold it up from the bottom (so there's room for the ball to fall into the hole), or you need a wall to hot glue it to so it floats.

One other thing (which I'm sure you're aware of), but your lane scale is way off, like by easily a factor of 3x. I know you're probably just doing a simple layout to prove out if a 1/2 scale can be done, but if you're going to start play testing it at the very least you want your outlane sized properly so you aren't constantly draining. Flipper gap looks pretty close.
youtube_screenshot (resized).png

Look at this project for example, even though it's scaled down, most of the layout is to scale (flippers look a little big):

For sure, even in full scale pinball the rule of thumb is usually 125% to 200% of the ball width for entrances to ensure you can make the shot.. but once you get past the entrance, ramps can narrow down to just slightly bigger than the ball width to conserve space and keep the protectory of the ball path inline.

yea it looks like you probably have enough power. That corrugated tube is not smooth enough. Scale the template I posted to the scale of your ball, fold, hot glue together then put it over your hole. If it doesn't quite make it all the way through, shorten it until it does.

I would have used thinner cardboard, especially at your scale (think office folder).. but it sounds like you're going to plunge into 3d printing which is good.

Ender3 is a great, simple, easy to build printer. Are there better printers that are more expensive? Sure, but it's huge diminishing returns. I've owned a prusa, great printer, not sure it's worth 3-4 times the cost. I owned three ender 3's, decided maybe 6 months ago to upgrade them all to the anycubic mega S after I had issues after I upgraded my boards (Chuck from spooky owns five of them).

Ender 3 will need a PEI sheet almost right away. The buildtak sheet they use is crap. The wheels work for the 3-axis is fine, but know as they wear you may have to re-adjust the tension on them because they literally hug the aluminum rails.

Anycubic: little pricier (maybe $100 more), but it adds a textured glass bed that lasts forever, filament runout sensor, touch screen, and more importantly linear rails spread apart (so you don't get teetering).

Of any chinese printer, I highly suggest upgrading the cooling fan. If you don't care if it prints a little slower, it's fine. I like printing at 5,000mm/min.

As far as an enclosure, don't let that dictate your printing choice. If you have no skills I got you covered:
https://www.instructables.com/3d-Printer-Enclosure-from-Upcycled-Furniture/

Don't let that scare you, you do NOT have to be that fancy. At the very least buy the 2 cheap Ikea tables, go to your home depot and have THEM cut some 1/2 plywood to size (I can help with dimensions). You can literally screw that wood to 3 sides, and then the front side just tape a piece of cardboard that you can lift. I would suggest some sort of lamp inside. you do not need an enclosure (especially with PLA), but it's always a good idea to keep it enclosed (especially if you have cats).

Ugh, don't buy that. It's a flashforge clone which is only supported on one side of the bed (design flaw). When I owned one it printed ok for a year then started to give horrible fish scale and I got rid of it. You could buy an ender3 and a separate enclosure for less.
https://www.amazon.com/Comgrow-Creality-Ender-Aluminum-220x220x250mm/dp/B07BR3F9N6/ref=sr_1_2_sspa

https://www.amazon.com/Creality-Enclosure-Constant-Temperature-Soundproof/dp/B082VS6XDL/ref=asc_df_B082VS6XDL/

assembly of the ender3 really isn't that bad (took me 20-30 minutes). If that's intimidating, buy the anycubic mega s:
https://www.amazon.com/ANYCUBIC-Printer-Updated-Extruder-Filament/dp/B08CDB8KWQ/ref=sr_1_3

It's literally 8 screws, 3 plugs.. level the bed, start printing

The biggest thing you should always check is how well is a printer supported:
Are there aftermarket mods?
Are there spare parts?
Aftermarket build sheets?
Are there printer profiles for the slicer or are you going to have to hunt for one that's similar?
Are there facebook groups and youtube channels to help you in case you run into problems? If not, you're on your own.

good choice. if you have questions ask away. dont use the horrible manual to assemble, you are better off following along with a youtube build video.

also if you need 3d models i can help, just need a sketch with some dimensions.

consider freecad

I tried that out a few years ago just to see how it compares. Where are you seeing free?
https://www.onshape.com/en/pricing

tinkercad also tends to facet round edges horribly. I'm considering freeCAD not to model (I use solidworks) but to start tinkering around with CNC gcode. I don't want to invest in a CNC machine until I'm confident I can make toolpaths. Unfortunately I bought SW in 2017 just a year before they started offering CNC plug-in for free.

As for your groove, I don't know how similar freecad is but if I were in solidworks I could create a plane perpendicular to a side surface, sketch my profile (round), then make a cut using the outside shape as my guide. Another way to do it would be to sketch on top, copy the outside edge, then offset that perimeter line, do a cut but also offset the cut (so it's in the middle). This will give you a square cut, but then you can just fillet the corners. If you truly get stuck with something and just need a model let me know. You can export to IGES, and I can export it back out.

Ah, didn't think to scroll to the bottom. Onshape is very similar to solidworks / fusion360 which is pretty amazing for a browser based parametric modeler. They have some odd EULA rules that basically say anything you model they own the rights to (at least the free versions). Not an issue if you're just tinkering making pinball models, but I could see someone modeling something significant and not owning it.

"free" programs with subscription based versions always worry me because at some point they start yanking features (or the software completely like solidworks did to draftsight last year). If you don't care about that and just want the experience of learning parametric modeling in general it doesn't matter, but don't expect it to be free forever. Nice thing about freecad is it's open source so it should technically stay free forever.

Haven't tried this (I paid for the full version of solidworks 4 years ago), but I got this tip from a 3d printing facebook group. If you become a member of experimental aircraft association for $45 a year, you get a student version of solidworks for free:
http://eaa.org/eaa/eaa-membership/eaa-member-benefits/solidworks-resource-center

Yea fusion360 used to let you import solidworks like a year ago, then they killed that off (assuming a lot of people paying for solidworks were just downloading fusion for free and pulling in their library). Besides not being able to switch between programs (unless like you say you export as solid shapes, or as we like to call them "dummy models"), every single time you upgrade to the latest solidworks (and you re-save your model), you can't load that model from an earlier version.

Solidworks tends to be the standard however. Just look at the 3d models on pinballmakers:
https://pinballmakers.com/wiki/index.php?title=Files_Section

For sure Stern has moved over to solidworks for a while now.

Nice, you're already way ahead of the curve. When you do get your printer I would think about downloading some of the files from pinballmakers.com, solidworks should import into onshape. While in there you can export out to STL (you can do the scaling in your slicer).

The 3d printer REALLY has advanced this project a lot. As for the layers, I wonder if you got some bad filament. Some filament is just crap, some filament absorbs too much moisture (sometimes you can save it if you dry it out). I know you probably don't have a lot of spools yet, but I have a lot to store so I have a rubber sealed plastic storage bin (pick it up at almost any store like walmart), and then buy one of these to absorb the moisture:
https://www.amazon.com/gp/product/B000H0XFCS/ref=ppx_yo_dt_b_search_asin_title

It's simply a container of silica gel that changes color when it gets too moist. When it does, you plug it in the wall for 6-8 hours (has built in heater), and it's good to go again.

it's not layer thickness, I print .25mm when I need something quick.

I've put blue tape on my playfield in that area, THEN hot glued. It tends to peel off easier, and if it does rip up the tape that's easier to replace than the whole playfield.

Because of the gearing inside servos, they're pretty decent at holding position. As for controlling them, it's not going to be simple. They are based on data defining the rotation. Normally you would use an arduino to set positions (using a potentiometer to figure out what the values need to be), but I did find this handy simplistic device normally used for cosplay where you can dial in the position of each switch position:

That one is only 2 position, but he sells a 3 position (use the dropdown menu)
https://www.freewebstore.org/heyok-performance/Servo_Positioner/p1742582_18227999.aspx

AMH used a servo to control a swinging door that took a beating

I don't know what your other hobbies or skills are, but you'd be amazed at the non-pinball things you can design. I don't know how many drill fixtures I've printed over the years. If you can 3d model, a 3d printer is a priceless tool to have.

If you get your shot geometry to where you want it, I would order some thin stainless strip:
https://www.mcmaster.com/1421T41

I remember growing up, if we were making a little electronic box (or a custom joystick like a track and field control panel) you were at the mercy of whatever project boxes they had at the electronics store (radio shack was ok, but there was this bigger local store called Tri-state electronic). If I had a 3d printer growing up I would have been making my own boxes the exact size I needed.

well that's something.. you might even get away with printing that without support.

That's ideal, though I've used some thin card stock as a ramp flap in a pinch. You just need something flexible and thin.

have you considered simply filling in material underneath (especially if a ball is never going underneath)? Or you could print it flat, add a boss or two on the back to raise it up (so you have the slant). A lot of real pinball ramps (one I can think of is the giant ramp on back to the future) are actually flat.. the upper half is mounted high, and the entrances droop down and then get attached to the playfield.

No, there's no reason you shouldn't be able to print what you have there.
Spongy walls: underextrusion (either nozzle is blocked, or there isn't enough tension on your gear extruder)
Separation: same as above, possibly not enough heat during extrusion, or layers too high (but I don't think you mess with those settings)

https://www.simplify3d.com/support/print-quality-troubleshooting/layer-separation-and-splitting/

Maybe just tighten them up so that they have to be perfectly lined up to get through? Also assuming you've tried reducing the playfield angle to reduce speed?

holy crap, that's a long shooter lane. You're a 3d printing madman.

Far as shooting the ball, you always want a groove to get the ball going in the right direction. I mean maybe it'll work because it's sitting in that pocket at the bottom. I would consider making the angle of the ball drain not as steep so the ball ends up a little higher. That'll give you more options for adding a spring to create a real plunger.

I'm guessing you've tried only using one flipper at a time. If it's still low powered, I wonder if you pushed too much voltage through the coil? I would find the spec sheet then check the resistance and make sure the coil doesn't have any short.

I don't know which program you're using, but I think what you want is a spline. If there's no spline option, you may have to do a bunch of individual arcs but make them tangent to each other.
https://en.wikipedia.org/wiki/Flat_spline

Again I don't know what software you're using, but in solidworks if I had an existing prototype or a sketch, I would scan what I have and texture map a playfield block that matches the same size, then you can just trace over the existing data.

That's what I did when Jay was trying to turn his rough prototype into CAD:
https://pinside.com/pinball/forum/topic/lionman-custom-game#post-2799249
https://pinside.com/pinball/forum/topic/lionman-custom-game/page/2#post-2982308

For something rough like a whitewood, you could probably get by just taking a single photo, but since it won't be perfectly perpendicular you will likely need to bring it into photoshop to skew it until it's straight, then scale the X/Y until it matches the correct proportions. If you don't have photoshop I believe you can still install CS2 (they stopped supporting server authentication). If you need help, send me a photo with dimensions and happy to clean it up.