Vacuum formed windows help

[Len Woodruff]

I have some bucks that I used to vacuum formed windows. They formed pretty well using .020 Pet-G.

But there appearto be some bumps in the clear.

Any idea where I need to look to fix this issue?

Thanks in advance for your help.

 

[Rick L]

Your bucks look good by the photo’s but more info is needed. 
Is that primer on the buck? Is there spot putty below the primer? 
If so, the heat from the plastic could be gassing out the solvent in the putty or primer. I’m assuming the buck is freshly made.  Even a slight piece of dust can create a bump. I’ve seen some of your work before Len and it appears that you know what your doing. I’m just throwing this out for discussion.

 

[Len Woodruff]

5 minutes ago, Rick L said:

Your bucks look good by the photo’s but more info is needed. 
Is that primer on the buck? Is there spot putty below the primer? 
If so, the heat from the plastic could be gassing out the solvent in the putty or primer. I’m assuming the buck is freshly made.  Even a slight piece of dust can create a bump. I’ve seen some of your work before Len and it appears that you know what your doing. I’m just throwing this out for discussion.

 

Those were cast in Gray resin.

I was think maybe some dust on them or the Pet-G but i used canned air to blow them off before heating the Pet-G.

The masters had primer one them.

The buck feel very smooth to me.

I might try to polish them using my micro sanding pads going 4000 thru 12000.

[Mark]

I have done some vacuform bucks in the past, using the same industrial resin used to make molds for packaging.  I then had someone who does industrial packaging stick my molds on the perimeter of one of his jobs.  I polished the molds, occasionally got some good parts but often had problems with dust and cloudiness.  I'm now thinking the molds may have been too polished.  After the holidays, I'm going to contact that guy and pick his brain regarding the finish on his molds.  I've got my own small machine now, but still have some of that old mold resin (but stand ready to buy new if needed)...

[Len Woodruff]

2 hours ago, Mark said:

I have done some vacuform bucks in the past, using the same industrial resin used to make molds for packaging.  I then had someone who does industrial packaging stick my molds on the perimeter of one of his jobs.  I polished the molds, occasionally got some good parts but often had problems with dust and cloudiness.  I'm now thinking the molds may have been too polished.  After the holidays, I'm going to contact that guy and pick his brain regarding the finish on his molds.  I've got my own small machine now, but still have some of that old mold resin (but stand ready to buy new if needed)...

I am think it might be some static electricity that is attracting me dust on the Pet-G.

I am going to try to polish the mold some to see what happens.

Thanks for your heads up.

[Len Woodruff]

I am getting some god Vacuum Formed Pieces now.

Since I am heating the plastic a lttle more I am getting splotchy clouadiness on them.

Here are some pics.

You can see it in the upper right (your left) corner of the windshield.

Edited January 16, 2023 by Len Woodruff

[Len Woodruff]

On 12/18/2022 at 12:27 PM, Mark said:

I have done some vacuform bucks in the past, using the same industrial resin used to make molds for packaging.  I then had someone who does industrial packaging stick my molds on the perimeter of one of his jobs.  I polished the molds, occasionally got some good parts but often had problems with dust and cloudiness.  I'm now thinking the molds may have been too polished.  After the holidays, I'm going to contact that guy and pick his brain regarding the finish on his molds.  I've got my own small machine now, but still have some of that old mold resin (but stand ready to buy new if needed)...

Mark did you ever get sme feed back about the cloudiness from vacuum forming the Pet-G Clear?

[Mark]

Nope, too much other stuff going on! I've still got a couple of those old window molds (stupidly threw a few others away).  I'll probably just do some tests, starting with them highly polished and progressively going to slightly less polished with each additional test.  

 

 

 

 

 

[Len Woodruff]

6 minutes ago, Mark said:

Nope, too much other stuff going on! I've still got a couple of those old window molds (stupidly threw a few others away).  I'll probably just do some tests, starting with them highly polished and progressively going to slightly less polished with each additional test.  

 

 

 

 

 

Thanks Mark. I read today that it might help heating the mold (mine are resin). I might put one of the pucks in my dehydrator for awhile then try to form it while it is still warm.

[Len Woodruff]

Mark I tried heating the buck in the dehydrator but I still get some clouding. 

[stitchdup]

Quote

50 minutes ago, Len Woodruff said:

Mark I tried heating the buck in the dehydrator but I still get some clouding. 

 

could the cloudiness be caused by not enough heat in those specific areas? if it maybe warming the glass a little with a heat gun/hairdryer would cure the cloudiness. I am just guessing here, i dont have any vac forming experience with clear and only did some little things at school using non transparent  plastic about 35 years ago but i seem to remember using more heat in some areas

[Len Woodruff]

20 minutes ago, stitchdup said:

could the cloudiness be caused by not enough heat in those specific areas? if it maybe warming the glass a little with a heat gun/hairdryer would cure the cloudiness. I am just guessing here, i dont have any vac forming experience with clear and only did some little things at school using non transparent  plastic about 35 years ago but i seem to remember using more heat in some areas

Could be Les. I did heat it for an hour in my Dehydrator at 95 degrees.

[Rick L]

Hi Len 

PETG is fairly hygroscopic. Meaning it will absorb moisture if not properly stored. If your plastic is old, My guess is that steam is forming between the plastic and buck. Again I will say this is only a guess. I’ve never experienced this problem  because I’ve always been supplied with fresh plastic.

Good luck my friend and please keep me posted on your results if you find the culprit.

[Len Woodruff]

53 minutes ago, Rick L said:

Hi Len 

PETG is fairly hygroscopic. Meaning it will absorb moisture if not properly stored. If your plastic is old, My guess is that steam is forming between the plastic and buck. Again I will say this is only a guess. I’ve never experienced this problem  because I’ve always been supplied with fresh plastic.

Good luck my friend and please keep me posted on your results if you find the culprit.

Thanks for the encouragement Rick. I bought the plastic July 22. So it should be fresh. It has been stored in the house since I bought it.

Mine has white protective film on 1 side and clear on the other. 

Any thoughts if one side should be toward the heat and the other toward the buck?

 

[89AKurt]

Only because I've done vacuum-forming, am going to watch this thread.  For what it's worth, some of my bucks are Corian®, and I get this too.  Any speck of dust ruins a perfect job.  I've found that having sharp edges, turn down, tends to be a liability, need to have the edge of the part curve down, but I haven't experimented with this idea yet.