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(Topic ID: 71086)

How to **safely** flatten warped playfield plastic.

By yonkiman

7 years ago

Topic Stats

  • 31 posts
  • 23 Pinsiders participating
  • Latest reply 40 days ago by dtrimberger
  • Topic is favorited by 26 Pinsiders


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There have been 6 images uploaded to this topic. (View topic image gallery).

DSCF7268 (resized).JPG
3. In Oven.jpg
4. Little After.jpg
2. Big Before.jpg
1. Little Before.jpg
5. Big After.jpg

#1 7 years ago

My Getaway had a lot of seriously warped plastic bits. I looked for the best way to flatten them, and found this thread:
as well as some others. They all basically boiled down to two techniques:
1) Quick but scary: Put them in your oven at 225F and wait for them to just start to flatten then remove heat and press them down (but if you wait a few seconds longer to remove heat they might bubble and be ruined). There were also heater/hair dryer variations of this as well.
2) Slow but safe (but only possible in hot climates): Put them between two sheets of glass in the back of your pickup on a day when it's hotter than 100F outside and wait 2-8 hours. No tricky timing, no chance of harming them...

So the choice was basically either really risky (practice with some pieces you can afford to mess up) or safe but impractical (not everyone has a 100F day whenever they need to flatten plastic).

Well it was obvious to me that you should be able to combine these methods to get the best of both techniques. So I got two sheets of glass cut to fit in my oven. I put the (cleaned) warped plastic between the (clean) sheets of glass and let the oven heat up to 150F. After an hour or so I put a weight on top of the top sheet to press them together. An hour or so after that I turned the oven off. Once they cooled down I had pretty flat plastic (the slingshot plastic had a section that was really bent that I never got perfectly flat - I think some combination of more weight/longer time/higher temp would have fixed that, but I was happy enough with the results that I didn't pursue it).

I started experimenting with an oven temp of 120F - that went OK but I wanted to see how high I could go without any harm. I ended up going to 150F, stopped there because it was working fine and I didn't see any point in going higher. I didn't pay attention to time - put them in the oven, go to the next step about an hour later. I don't think there was any way I could have ruined the plastic at 150F.

Here are some pics:
Big Piece Before:
2. Big Before.jpg

Slingshot Before:
1. Little Before.jpg

In Oven:
3. In Oven.jpg

Big Piece After:
5. Big After.jpg

Slingshot After:
4. Little After.jpg

This could probably be optimized to go faster - you probably don't need an hour between steps, and you might be able to add weight/pressure at the start (I wanted to give the plastic room to breath/expand out as it flattened) - but I wasn't in a big hurry.

Hope this helps some of you guys who have helped me so much in the past!

#2 7 years ago

Awesome post.. Thanks for the info! I'll be using this technique next time I have some plastics that need flattening.

#4 7 years ago

Clean them with Novus 2 or your favorite cleaner before heating them. If they become soft enough to flow flat you do not want any dirt possibly embedding in the plastic. Clean glass surface also.

#5 7 years ago

Awesome...and good point cal, it can be difficult enough to get the dirt out as it is

#6 7 years ago

I've had to faltten a few plastics. I avoid the oven, guess i'm chicken.

Outside on a hot day works great between 2 plates of glass (cooking for a few hours).

Also, using a hair dryer works well. Its not quick, but the risk of screwing up the plastics is very low. Again, once the plastic is soft, sandwich the plastic between 2 plates of glass.

#7 7 years ago

i've always done the heat gun plus 2 pieces of playfield glass.. prep work involves novus to polish them up cause you dont want to imbed the dirt in to the plastics....

Ive done probably half a dozen games this way a the heat gun I use is from Ace hardware, runs about $30

Polish up plastic, lay on one sheet of glass, heat til you see it start changing shape then move the other piece of glass on top of it so it will cool flat

#8 7 years ago

Thanks for that - going to have to be doing this soon for my Getaway plastics as well.

#9 7 years ago

Well beats sending them to Japan and having some sumo wrestlers sit on them!! LOL

#10 7 years ago
Quoted from silverball0:

Well beats sending them to Japan and having some sumo wrestlers sit on them!! LOL

OK, so I guess there originally were THREE distinctly different approaches to flattening...I'll amend my original post.

#11 7 years ago

Wow! I hadn't thought of that. I did the 'normal' oven thing once and ended up with some bubbles in the plastics.

Are there any other oven settings that are important like using hot air/ broil etc.?

#12 7 years ago

Using Bake is fine. Broil (I think) means MAXIMUM HEAT so I'd stay away from that one. Airflow (like in a convection oven) might make the plastic get to 150F a bit sooner, but this is the no-hurry process, so I wouldn't worry about it. I did it in a convection oven but I left the fan off (just like a normal oven).

The thing you're trying to do is replicate the temperature between two sheets of glass left in the sun on a really hot day. Let everything settle to that high temp for a while, the plastic relaxes and the pressure forces it flat.

I think the main thing to look out for is make sure your oven temp goes that low. My toaster oven (for example) doesn't go below 200F.

#13 7 years ago

With no access to a heat gun and too chicken to oven bake them, I also used the hairdryer method (but with books and a bit of pressure)

Took a lifetime gradually heating and pressing at a comfortable pace for me.

Worked and no risk though

#14 7 years ago

Thanks for the instructions! I will be giving this a try, I have 3 machines with very warped plastics.

#15 7 years ago

We do the glass in the oven (or sun) trick for dewarping vinyl records all the time in the DJ world. Works pretty good but you have to be careful.

#16 7 years ago
Quoted from Jam_Burglar:

We do the glass in the oven (or sun) trick for dewarping vinyl records all the time in the DJ world. Works pretty good but you have to be careful.

what's the best way to get smaller pieces of glass for this?

#17 7 years ago

I sure as hell wouldn't do 225 degrees. I do this at 150 and it affords me a higher degree of safety.

#18 7 years ago
Quoted from mof:

what's the best way to get smaller pieces of glass for this?

I just went to my local hardware store, gave them the dimensions (I think I went with 12" x 18") and they cut two pieces. It's not the rounded edge, tempered glass we're used to in pinball so I was more careful with it, but it worked fine...

#19 7 years ago

I live near an Ikea and got 2 small glass shelves. They have rounded edges and were cheaper for me than buying glass from a 'glass store'.

#20 7 years ago

Of course! IKEA to the rescue once again!

#21 7 years ago
Quoted from mof:

what's the best way to get smaller pieces of glass for this?

Remember, that some of the affect comes from the weight of the glass. If you go too small you won't get enough pressure. Recently they've actually come out with a vinyl flattener product (as opposed to the DIY way we used back in the day). Something like this may even work better.

#22 7 years ago

I read this thread last week and had a warped piece of plastic that I wanted to flatten. Looked around for pieces of glass and found my wifes pyrex cooking collection. Put the piece of plastic on top of the bottom of a pyrex pie dish and put another pyrex pie dish on top of it. Took about 40 minutes at 170. I turned the plastic piece over about half way through. It's now almost perfect. Thanks OP!

10 months later
#23 6 years ago

Thanks for the help, I have a few pieces for a Stern Lightning that need flattening (and if you know the game you know to which ones I refer).

Thanks for the Pyrex idea, that's something we have around here! Cheers.

2 years later
#24 3 years ago

So there's no concern about glass touching the ink side while at 175°f ?

1 week later
#25 3 years ago

Good question. No problem at all the one time I did it. Glass plates were perfectly clear after, plastics looked good as new (or at least as good as before the flattening).

1 month later
#26 3 years ago

Nice, using this method soon.....

6 months later
#28 3 years ago

Sometimes you do not have to reheat wrap plastics back into shape based on severity.
Various pinball designs of the past with long plastics did not use proper reinforcement which caused the bending in the first place.

If you add a post and spacer in a key point (I am not advocating drilling a new hole in the plastic itself) UNDERNEATH the plastic you can "shim" the plastic upwards into its correct flat height, and make fine tune adjustments with the outer screws in tension.
This way the plastic is permanently supported correctly, and not sag again over time.
After attaching the metal screw with the spacer and T-nut under the playfield, add a *tiny* piece of rubber technicians tape on top of the screw (not the plastic itself) or small PETG washer to prevent scratching the plastic, but still allow it to be removed, as required.
If you do it right, it will be nearly invisible, and not affect lighting.

1 year later
#29 1 year ago

I just did this with some seriously warped plastics. My oven only goes down to 170F. I put them between glass and heated them for 45 minutes. Pulled them out, put a hot pad on top, placed a heavy object for 10 minutes. Then removed the weight and let cool to room temp. Perfectly flat.

1 year later
#30 9 months ago

Wake up old thread!!

So usually when I shop out a game, I buy new plastics if they are available. I am shopping out my recently acquired Grand Lizard right now. Even though Marco has plastics, The ones in the game were just a little warped, not broken for a change. So I decided to resurrect this thread and try the method described. First I got 2 pieces of glass cut. 18" x 16" x 1/4" seemed to be a good way to go for my oven. 10 bucks a sheet with sanded edges! I thought was real fair.

Hentges Glass
Address: 1631 Voll Dr NW, Byron, MN 55920
Closed ⋅ Opens 8AM Mon
Phone: (507) 282-1769

So in a nutshell, I sandwiched most of the set between the glass sheets, ran 170 degrees in the oven because like the last poster, that is all the lower the oven will go. Left them in there for an hour, let cool down on the stove before removing top sheet of glass. Presto. Flat as a pancake plastics ready to install. Really happy with the results!
DSCF7268 (resized).JPG

8 months later
#31 40 days ago

Reviving this thread because it was helpful and I just wanted to add my technique to the multitude of techniques on here.

I didn't see the reason that glass needed to be used for the oven technique, other than needing to see the plastic. From what I gathered nobody had any shrinkage (insert jokes) problems or other issues with their plastics that required constantly visualizing there plastic in the oven. My Stars manta ray plastics were too big for the pyrex techinique (that worked well btw for the small bits) so I just used 2 cookie sheets and parchment paper (not wax paper as noted in another thread). I set the temp at 170, sandwiched the plastics (upside down cookie, parchment, plastics, parchment, right side up cookie, Le Creuset dutch oven pot for weight) and set the timer for 45 minutes. The dutch oven (again insert joke) is basically the same weight as a engine block so that helped a bit I suspect. One small curve still remaining on the end of one of the manta ray plastics but otherwise success without loss of paint or other problems.

Interestingly as I was cleaning the plastics before the process one of the plastics sat in a pool of water for just a few seconds and paint flaked off. Water was the last cleaning product that I would have thought would wreck the print on the plastics so don't let your plastics soak even in a small amount of water.

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