+x

 

Hanaldo - 11/11/2020 4:25:01 AM

Yeh I'm gonna say it's a combination of both as Lester suggested. Really I feel the actual issue is the ramp rate was too fast and you don't have a fine enough control over the oven temperature (I've experienced warping when the actual temperature varies from the target temperature as little as 2 degrees C), which leads to stresses that cause the warping. Then you've got the resin build up in the corners which creates a big differential in temperature throughout the part, exasperating the stresses from the cure cycle.

It makes sense that you haven't experienced warping in more complex tools, as the geometry can overcome the stresses that are trying to distort it. This is why the flatter your components are, the more important it is to balance the layup and have good control of the cure cycle. It can actually be quite difficult to make thin pre-preg sheets without getting distortion because of that lack of balance in the layup, while if there was even a slight bend in the panel then it becomes significantly more rigid.

+x

 

K.C.C - 11/11/2020 1:58:06 PM

+x

 

Hanaldo - 11/11/2020 4:25:01 AM

Yeh I'm gonna say it's a combination of both as Lester suggested. Really I feel the actual issue is the ramp rate was too fast and you don't have a fine enough control over the oven temperature (I've experienced warping when the actual temperature varies from the target temperature as little as 2 degrees C), which leads to stresses that cause the warping. Then you've got the resin build up in the corners which creates a big differential in temperature throughout the part, exasperating the stresses from the cure cycle.

It makes sense that you haven't experienced warping in more complex tools, as the geometry can overcome the stresses that are trying to distort it. This is why the flatter your components are, the more important it is to balance the layup and have good control of the cure cycle. It can actually be quite difficult to make thin pre-preg sheets without getting distortion because of that lack of balance in the layup, while if there was even a slight bend in the panel then it becomes significantly more rigid.

The resin build up is the least problem because the part actually warped the most on the high spots
 
ordered new oven cotroller and added more heater elements in the oven to get better controle.

Third time good time I hope.

+x

 

Lester Populaire - 11/11/2020 7:01:51 PM

+x

 

K.C.C - 11/11/2020 1:58:06 PM

+x

 

Hanaldo - 11/11/2020 4:25:01 AM

Yeh I'm gonna say it's a combination of both as Lester suggested. Really I feel the actual issue is the ramp rate was too fast and you don't have a fine enough control over the oven temperature (I've experienced warping when the actual temperature varies from the target temperature as little as 2 degrees C), which leads to stresses that cause the warping. Then you've got the resin build up in the corners which creates a big differential in temperature throughout the part, exasperating the stresses from the cure cycle.

It makes sense that you haven't experienced warping in more complex tools, as the geometry can overcome the stresses that are trying to distort it. This is why the flatter your components are, the more important it is to balance the layup and have good control of the cure cycle. It can actually be quite difficult to make thin pre-preg sheets without getting distortion because of that lack of balance in the layup, while if there was even a slight bend in the panel then it becomes significantly more rigid.

The resin build up is the least problem because the part actually warped the most on the high spots
 
ordered new oven cotroller and added more heater elements in the oven to get better controle.

Third time good time I hope.

I feel like you should mostly improve air circulation. more heater elements doesn't necessarily decrease the temperature gradient?

+x

 

K.C.C - 11/12/2020 6:56:55 AM

+x

 

Lester Populaire - 11/11/2020 7:01:51 PM

+x

 

K.C.C - 11/11/2020 1:58:06 PM

+x

 

Hanaldo - 11/11/2020 4:25:01 AM

Yeh I'm gonna say it's a combination of both as Lester suggested. Really I feel the actual issue is the ramp rate was too fast and you don't have a fine enough control over the oven temperature (I've experienced warping when the actual temperature varies from the target temperature as little as 2 degrees C), which leads to stresses that cause the warping. Then you've got the resin build up in the corners which creates a big differential in temperature throughout the part, exasperating the stresses from the cure cycle.

It makes sense that you haven't experienced warping in more complex tools, as the geometry can overcome the stresses that are trying to distort it. This is why the flatter your components are, the more important it is to balance the layup and have good control of the cure cycle. It can actually be quite difficult to make thin pre-preg sheets without getting distortion because of that lack of balance in the layup, while if there was even a slight bend in the panel then it becomes significantly more rigid.

The resin build up is the least problem because the part actually warped the most on the high spots
 
ordered new oven cotroller and added more heater elements in the oven to get better controle.

Third time good time I hope.

I feel like you should mostly improve air circulation. more heater elements doesn't necessarily decrease the temperature gradient?

Proble is that at higher temp with not enough heater elements it takes to long to get the temp rising but when it does it rises to much and then cools down again.
So you got a temp that isn't stable .
So I hope when got stronger heaters it wil be more correct.
Its a big oven