Playfield stackup ideas

Woke up this morning, checked the blog and wow, lot’s of new hits.  Seems like somebody posted the blog to another website called Dangerous Prototypes.  That kicked the stats up significantly for the day.  The only error I found in the article is that it stated no code is currently available.  If you go to the Google code repository, you can find about 150 different files with the code in them.  These vary from the C files, to project files, to actual S-Record files that can and have been downloaded onto running hardware.  I posted the schematics in 1000.pdf, but I never posted the Gerbers to actually build the board.  The reason for that is I wanted to get more of the board testing done.  Currently the solenoid driver, input driver, and RS232 interface boards are completely tested.  The LED driver has not been tested, but I’ve used the same design on the EEPROM project so I’m pretty sure it is going to work.  (I actually stole the chips that I was going to use to make Disaster to make the original EEPROM burner so that we could get Mark’s Flash up and running.)  The main microcontroller board definitely has some issues which I know what they are, but now I’m thinking about not using that board at all so it doesn’t matter.  (You need some pullups on the debug bus to get the processor to boot without a debugger attached.  Simple fix, but annoying none the less.)  The last board not tested is the bridge rectifier/power board.  It is populated, but I haven’t bothered using the Variac to test it.  I’m not happy about the amount of current I can get using the TL783, so I’m thinking about converting my design to a boost converter.  The added benefit is I could use a standard PC power supply and step it from 12V to 48V DC or whatever the highest “safe” voltage for CE marking.  (I don’t care about a CE mark, I just like to use their safety standards because I dislike being hit by high voltage electric.)  That would allow me to use the same design internationally.  (Why would somebody from Europe want one of my machines?  Who knows?  I’m currently amazed that I’m as far as I am on this design and the number of people from Europe that check out the blog.)

So I’ve been pondering playfield surfaces.  I have clear coated machines and been really happy with the outcome.  Of course, it takes an average of 4 or 5 months to clear coat a playfield, so that process seems unusable.  The second thing is that it costs me about $20 for the Varathane that I used.  I know that if I started using an automotive finish, it would be cheaper, but I don’t have the work area or equipment to do that.  This got me to thinking about using acrylic to cover the playfield.   Acrylic is supposedly more scratch resistant than Lexan (polycarbonate) which is the most important feature.  Acrylic can also be repolished to get rid of scratches if necessary.  So I’m thinking the playfield sandwich would be a layer of acrylic on the top (1/16 inch),  the graphics/art layer sitting on a 2nd layer of acylic, and then a thick layer of plywood.  Insets would be formed by using a CNC machine to get rid of the plywood.  This would allow LEDs to be mounted below, and would make sure that insets would never sink/rise out of the playfield.  Every restoration I’ve done, the first annoying thing is to reset all the insets properly.  This would make the playfield incredibly fast so I might need to tone down the solenoids  a little bit.  Not a problem since I can configure them on a per solenoid basis.  The cost of a piece of acrylic (24″x48″ is $25.00)  Two sheets plus the plywood plus the art hopefully comes in under my $100 target price for that section of stuff.  It also means I don’t need to pay for insets and gets rid of a lot of the assembly headaches.  I might be able to get rid of the second layer of acrylic, but I’m not sure what I would apply the playfield “translite” on.

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4 responses to “Playfield stackup ideas

  1. Bally did this with Plexiglass in Electra ( http://www.ipdb.org/machine.cgi?id=778 ). Their rationale was to solve the lower playfield cutout, but I can see your reasoning.

    I don’t see why you want two sheets though. Can’t you apply the art directly to the wood?

    • I think there are a couple of other examples I can also remember. Basically anything that has a lower playfield. (Haunted house, Black Hole, and even AC/DC LE) The difference as you mention is it is a cutout. I don’t remember how any of those machines played anymore. I don’t remember if the ball went faster across the plexiglass versus the playfield or if it got too scuffed up. I wish I would have been thinking about it at Allentown, because I would have sought out a couple of the machines and played them. Allentown had many good examples of machines that had been played for years and years, so they really showed what a lot of wear did to the different surfaces. I know I played a Flash there, and felt bad talking Mark into buying it. It was so bad I couldn’t play a third game on it because it was so boring. Now, after we fixed his machine up, we just played 10 or 15 games last week, and they were great fun. It really shows why maintenance is so important.

      The two sheets is because I’m thinking the plastic sheet with graphics needs to be sandwiched to protect it. I think I mention in the post that it might not be necessary, but I feel without better knowledge of what the graphic print is made out of, I should account for two sheets in the cost roll up. If it is sticky on the back of the graphics, I might need a second sheet to adhere it too, otherwise there would be no backing over the insets. I currently know nothing about printing large scale graphics. That is going to be a whole week or two of research to try and learn about that stuff.

  2. I mentioned Elektra because it DIDN’T use a cutout, but instead one giant sheet for the lower PF. it was a neat approach.

    As for durability, it’s hard to say as there aren’t a lot of good examples. PF cutouts like gottlieb used are always placed a reasonable distance from any high speed direction change/friction points such as slingshots and pop bumpers. Elektra had a fairly low speed PF as well, though it’s still probably the best example. Though it’s a fairly uncommon machine.

    You might also look at Orbiter-2, they had some kind of composite PF. I don’t know what it was made of but it might be interesting to see if the material can be fabricated at a reasonable cost as most of the Orbiter’s I’ve seen look pretty good despite their age.

    A lot of the art will come down to your local printer, but you can generally find places that can print on thick durable vinyl, which should hold up well enough, assuming your PF wood isn’t abrasive. You can also usually find this same material in sticker form, I believe Ben Heck went this route; though I don’t know what he used to protect it.

    Honestly a sticker + automotive clearcoat would probably be the best solution. Try asking around local body shops and see if they’re willing to quote you a price on it. I’m not sure what the curing time is but I’d guess around 1.5 months, which seems long but remember you still have to build and test all of the boards, program the game logic, etc.

    I’ve been looking at wood printing services. I’m not yet convinced it’s the best route as you need to throw down a base coat of white first, meaning getting graphics alignment down is now twice as hard. But I’ll have to call them up and see if they’re able to high the level of alignment I need.

    • Elektra is a machine that I have never seen. I will see if there is one around or look for it at the next show. Looking at IPDB, I missed that it didn’t just have an insert.

      My current guess is a vinyl for the graphics, and if it is thick enough, I shouldn’t need the second sheet of acrylic. That would be nice. I also like the advantage of not needing/having inserts. Just letting the LED shine through the vinyl beneath the acrylic seems like a simple solution. Inserts are probably around $ .25 in quantity, so that could save quite a bit of money.

      All the printing on wood that I’ve seen has been less than stellar. Of course that was a couple of years ago, and it is probably highly dependent on how the wood was prepped/type of primer on the wood, but I’m not thinking about going in that direction because of the results that I’ve seen.

      Sticker/clear coat would probably be the cheapest if I had a large volume, but I fear that the volume for a run will be too low to make it economical. 10 playfields at, say, $25/board (same price as acrylic), is only $250 total. Most of the boards list it costing $250 to clear coat a single playfield, so that would be out of the price range for what I’m trying to do. I know that after clear coating one of my machines using Varathane, it is not something that I could do even for a production run of 10 machines. While the result was great, it is just too labor intensive.

      A curing time of 1.5 months doesn’t bother me at all. I still am so far from getting this together. The firmware is programmed, but that is the easy stuff. Finishing the layout, trying to get somebody to do graphics so they look good, video editing, finishing a prototype cabinet, testing, … the list is endless, but as I’ve said before, I’m further along than I was expecting for less than a year.

      Thanks for the comments. I started the blog to elicit feedback to make the design better. Every comment I get, every person I talk to, I try to soak up the information and find a way to do it better than has been done before. If somebody else finds any of this useful, that makes me that much happier.
      -H

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