Vacuum forming windshield using PETG

[Len Woodruff]

Anyone of some experiance doing this. Like what temp sould you heat the PETG to etc.

[Rick L]

120 to 160 degrees. How will you perform the shaping? Are you vacuum forming or drape forming?

[MrObsessive]

1 hour ago, Len Woodruff said:

Anyone of some experiance doing this. Like what temp sould you heat the PETG to etc.

Len, take a look at my vid here..........there's no heat control on the unit, you have to look at the sheet as it starts to "sag". It may take a bunch of tries as I explain.

 

[Dave Van]

Agree......'SAG' is the best way to tell if sheet is ready. Even my commercial vac former says to use the sag to see if ready!!! 

[Len Woodruff]

I am pullng the PETG over a puck that I created for the windshield & the back light.

It says Petg should be vacuum formed when it hits around 280 degress. I used my IR gun to check. But the heat source is under the Petg so the gun may be reading wrong.

The problem is that it didn't pull around the sides with good definition so I could cu it.

I tried the sag 1st but let it get to soft and it wrinked but did comform to the puck better.

 

 

[Rick L]

Sorry about the temps. They are in centigrade but still accurate.

[Ace-Garageguy]

2 hours ago, MrObsessive said:

Len, take a look at my vid here..........there's no heat control on the unit, you have to look at the sheet as it starts to "sag". It may take a bunch of tries as I explain.

SO nice to see somebody who actually knows what he's doing actually doing it.   

[Rick L]

On 8/27/2022 at 3:26 PM, Len Woodruff said:

I am pullng the PETG over a puck that I created for the windshield & the back light.

It says Petg should be vacuum formed when it hits around 280 degress. I used my IR gun to check. But the heat source is under the Petg so the gun may be reading wrong.

The problem is that it didn't pull around the sides with good definition so I could cu it.

I tried the sag 1st but let it get to soft and it wrinked but did comform to the puck better.

 

Try putting your heat source on both sides if possible for uniform stretch. If your heat source is on one side only, the cooler side will fight the hotter side from draping.

[robdebie]

On 8/27/2022 at 9:26 PM, Len Woodruff said:

I am pullng the PETG over a puck that I created for the windshield & the back light.

It says Petg should be vacuum formed when it hits around 280 degress. I used my IR gun to check. But the heat source is under the Petg so the gun may be reading wrong.

The problem is that it didn't pull around the sides with good definition so I could cu it.

I tried the sag 1st but let it get to soft and it wrinked but did comform to the puck better.

There's another limitation to take into account. At a certain temperature, the moisture in the plastic will boil and form bubbles. PET-G is quite difficult to use because of this. Drying the plastic sheets before use should help, but I haven't found an easy method for that. Here are examples with and without steam bubbles:

Rob

[Len Woodruff]

Thanks for all of the above posts and Bill for his You Tube video.

Here are some picks of my vacuum forming machine & the puck I was using for the back window.

1. Is the puck high enough off the plate?

2. Should the higher side be pointed toward or away from PETG?

 

 

[Curt]

Len, from your description it sounds like you are not getting enough vacuum.  Your former should be able to suck the PETG tightly around the buck.  I would want the buck to be lower in relation to the plate.  This will make it easier to achieve a seal, and also keep the plastic from being sucked under the buck, which makes it hard to free the buck from the part.

As to temperature, I don't measure it.  When I was starting out doing this I read that the PETG will get wavy as it hits a certain temperature.  Watch carefully as it will rapidly smooth out after that.  That is when you should swing the frame down over the buck and should give you a good part.  This works very well for me.

One more thing - dust is your enemy!  Before you commence the forming take a used dryer sheet and run it lightly over both the buck and your PETG sheet.  This will greatly reduce any "inclusions" in your part.  Good luck!

Edited September 1, 2022 by Curt
Spellin correction

[Rick L]

I would lower the puck and also block all excess holes with duct tape. You only need the holes directly under the the perimeter of the window. This will give it better suction. 

Edited September 1, 2022 by Rick L

[Chariots of Fire]

I have a vacuu-form machine as well.  I would sit the buck for the windshield right down on the grill so that when the softened sheet drops over it the rest of it gets pulled down evenly all around.   Having the buck raised off the grill may be your problem.

[Len Woodruff]

Guys I am back at this and I have one of Bill G's acuum forming machines that is much superior to the one I had before.

I am trying to use the "sag" method. I notice in the You Tube Bill's sheet sagged below the metal rim.

Haven't let the sag go that far but that will be my next step.

The only issue I am seeing now is some cloudiness on the part after it is formed. I tried heating the buck in my dehydrator at 95 dgrees but still got some cloudy spots.

Any feedback will be greatly appreciated.

[Chariots of Fire]

I'm going to try the swipes next time to see if that improves the quality of the plastic.  I have the same machine as Bill Geary and have had the same trouble with bubbles.  I was not aware it was moisture that was causing it.  I found if the plastic sheet gets too hot too quickly that is when the bubbles start.  I try and put the sheet a little lower than the top setting that is next to the heat source so the plastic melts a bit more slowly.  Still not an easy process to get nice clean results.

[Len Woodruff]

4 hours ago, Chariots of Fire said:

I'm going to try the swipes next time to see if that improves the quality of the plastic.  I have the same machine as Bill Geary and have had the same trouble with bubbles.  I was not aware it was moisture that was causing it.  I found if the plastic sheet gets too hot too quickly that is when the bubbles start.  I try and put the sheet a little lower than the top setting that is next to the heat source so the plastic melts a bit more slowly.  Still not an easy process to get nice clean results.

Keep us updated Charles. I have been using the anti-static dusters before I load the plastic to get rid of dust.

I tried some yesterday and got 1 windshield without the cloudiness but the other 3 still have it. Not sure where the sweet spot is yet.

Edited April 15, 2023 by Len Woodruff

[Chariots of Fire]

One of the most frustrating things about it, for sure.  I wasted more pieces of PETG that I wish to count!