Most times you buy an older pinball machine you'll have some plastics cracked or missing or so yellowed you just want to replace them. Here's what I did although there are other options including buying them.
My method is a bit less complicated than others I've seen but produces a nice finished product quickly. Let me begin by saying the best way to produce a plastic is with silk screen but this is typically very involved requiring multiple screens and is best left to those who wish to go into pinball plastic production rather than repairing or making a one off for their own machine.
For the < $25 crowd
1/16 Lexan ( polycarbonate )
Router or Scroll Saw or something to cut the Lexan. I used a Dremmel router.
Razor / Box Knife to score/cut the Lexan into rough sizes.
Sandpaper course/fine or Belt sander or similar.
Clear 2" Packing ( The kind you use on shipping boxes ).
For the over $50,000 crowd
Laser cutter ( $3000-$25k ) and UV Solvent printer ( $40k and up ) - please note I'll not be posting these instructions here. If you own these products you should already know how to use them :)
The process is simple. Use 1/16 Lexan ( polycarbonate ) which is far superior to plexi. You can get enough for 2-3 machines in one sheet on ebay for maybe $15-$20.
Start by scanning your old plastics and repairing / cleaning / re-coloring the images using photoshop or similar. If the plastics are warped flatten them with a heat gun or oven or whatever your preferred technique is. If your plastics are missing areas you'll need to fudge the graphic. I'm not about the get into a 'how to use photoshop' tutorial here but if you don't know how yourself I'm certain there's 1000 folks in your neighborhood who do. Make sure the scan at high resolution. 300 dpi or higher is good. The original plastics aren't nearly this detailed.
Most plastics have a black border. To make trimming easier extend this outer border an additional 1/2 inch or so. This allows you to trim with scissors a bit easier then trying for follow a close tolerance black line. I've taken the creative liberty of increasing the saturation after cleaning. In this example there are actually 5 distinct colors - black, 2 skin tones, purple, and red. It's difficult to see in the original scan but does add texturing. You can make the to skin tones out easily in her hat. I did not bother copying the original part number. Also, I did not mark the holes - I'll do this when I drill them.
Once you've got the images scanned and cleaned you'll need to print them. I use plain off the shelf photo or matte finish paper. Glossy always produces the best, brightest colors. The paper doesn't have to be transparent at all as most techniques require you put a white backing on the plastic. With photo paper it's already there. Another tip - using thinner paper allows more light through the plastic.
In some cases the plastics will be larger than the 8.5x11 standard printer size. You can always go to Kinko's and have them print in large format. I've also seen some drug stores like CVS or Sam's Clubs that offer poster size prints. There's a ton on line. I'm not getting involved due to copyright issues. I've printed them onto a single sheet here. You'll want an extra copy in case you flub with the tape later.
Ok, now you've got the plastics printed. Trim them to about a 1/16" black border with scissors. Cut into the black a bit - this creates a nice solid black edge.
Tip: don't remove the paper backing on the Lexan plastic until it's time to apply the image. Hopefully you've still got the original plastics. If not you're most likely out of luck unless a friend can send you scans. Cutting the Lexan is straight forward. Just mark the outlines and holes. If you start by marking the holes you can re-position the plastic should it move while copying.
Once traced I used a straight edge ruler and razor knife to cut the lexan into 3 easy to handle pieces. Just score the plastic a few time with the razor blade and snap. Make sure to cut through the paper.
And then rough cut these on the Dremmel router ( or whatever you choose ). These things run about $40 for the Dremmel, $40 for the table, and $20 for the bits but I'm certain you could ebay a used one or borrow a router from someone with a table mount.
Here's the rough cut plastics.
Run your finger on the edges - they're rough and lumpy. You need to sand them. I used a belt sander upside down on a table. You can also do it the hard way by rubbing them back and forth on sand paper.
For the finer areas you can't really get into I used a file on the plastic between two pieces of cardboard in a vice.
Sanding / Filing takes the longest. Cutting the plastics with the router takes about 5 minutes per piece. Sanding / Filing about 10-15 minutes per piece.
This is the easiest part. I found some sites where they suggested glues and such. I cheaped out here and just used clear packing tape. After several tests with glues I was really unhappy with the haze on the graphics. Here's one I did with clear spray adhesive. I tried a few other things but none were as clear as I'd like.
It's now time to remove the paper from the Lexan. Surprisingly this works well. I had a roll of clear packing tape w/dispenser and went to town. Here's the graphic being taped to the Lexan. I laid the plastic down and positioned the graphic with an even border. I then cut a strip of tape a bit longer than the plastic and applied it to one half of the plastic. I put a second piece on the other half making sure the edges were pressed down well. I then trimmed with a really sharp new razor. Perfect. And the graphic was bright with no adhesive obstruction or bubbles. You can barely see the tape on the edges. And using clear tape has one BIG ADVANTAGE - you can remove it and apply a new graphic without damaging the Lexan as I had to do 3 times with the first plastic - I didn't like the artwork and re did it. The tape has a good tension which holds the graphic firmly to the back of the plastic.
I can't even see the tape at all in the photo of the back side of the plastic.
Just about done - just need to drill the holes. Lay the old plastic on top of the new one, center, mark the holes, drill. Simple. I used a drill press but it's not necessary. Also just be careful to use a nice sharp bit to avoid damaging the artwork.
Here's a shot of the old vs new. The purple in the new one matches the purple on the playfield. As the old plastics were very yellowed it's hard to determine the exact color. Since I did all plastics it really doesn't matter.
Here's all six plastics in place. It's a shame the playfield is so shot.
And that's all I have to say about that.. I think I'll go scan all my other machine's plastics for future use.
There are several great resources on the web for making plastics. Here's a few: