Wasn't a pretty sight...and I've got big hands
SN Certified Technician
- Mar 2, 2015
All clean....soon as I pick up the little pile of trash. Finally !!!
Yup. There was a small wave the first heat cycle. There's a flat bar underneath, too. I heat cycled it two more times and it was straight, but I'm leaving the clamps on till I get off tomorrow. A little extra time clamped up can't hurt it.Still straight when you pull the clamps off then?
Here's what I see, the bumper almost returned to the exact same shape it had before you heated it.Just for the the record....the heat on bumper thing has worked for me many times in the past. I think the problem here is that its been out of shape for so long that the plastic has memory to that shape. Usually, a plastic will automatically want to return to its original shape.
Who knows how long this bumper has been f'd up. I've got an idea for it. Just has to wait.....for now. Unless @Davedacarpainter has any ideas.
Good thing I have a shrinking hammer. [emoji106]Here's what I see, the bumper almost returned to the exact same shape it had before you heated it.
What would cause this? It's the plastic memory of the piece. At some point when the original warping took place, either some heat helped to shape it in the stretched position, and/or the bumper sat for a long, long time in that stretched position. I'm betting the second. The plastic has had enough time, over the years to have the molecular state to relax into that position.
You have tried to cause the plastic to reshape through heat into what was the factory position. As you have found, it returned to the stretched shape.
What you need to do to change this is similar to stretched metal. You need to shrink it. Just like metal, the molecules need to be reshrunk (you need to beat on it while you have your bar underneath it and are using heat.).
You'll actually be beating the plastic molecules into an original tighter formation by doing this. Once you have done the shrinking routine, let it set for a week with the clamps still on it. This should take care of it.
You understand what I'm saying though, right? Just like taffy, it has been stretched beyond it's original formed shape. So much so that it has formed into a new shape. Once the plastic molecules have had time to relax into that new position, they'll try to return there unless they have been beat into a new shape forcing their molecules closer together again.
So, it's takes more than just heat and supports on old plastic. It takes a type of forging, so to speak.