×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Delamination caused by shear heat

Delamination caused by shear heat

Delamination caused by shear heat

(OP)
Here is another problem I would like to get feed back from all the experts here. It does really help to bounce ideas off other people even if you are sure you know the answer because it allows you to sit back and think from different angles.

Customer called me in complaining of bubbles/blisters around the gate area. My first though was moisture of course since this is a nylon 6 25% glass/mineral filled material. In this case though I thought it was an over dry due to the fact we sent it in at 0.05% and they dried it after that. They do not utilize a moisture analyzer by the way.

The investigation led me to do a audit on there hot runner system. The first thing I noticed was this customer is running barrel temps at 500F across and manifold and the drop temperature at 440F. I have never seen that much disparity in temperatures, especially on the low side. I have seen them to high due to undersizing of the hot runner system. I looked at the gate (which I have attached a picture of) and almost laughed out of disbelief of what I was seeing. My conclusion is that the gate is producing so much shear heat that it is causing the degradation of the nylon. The only area affected is a 4" diameter around the gate. This is a big part and they have gated it in a corner where it must flow around 25" to fill. That is an issue in it self but it is automotive and the automaker insisted on doing this.

Please give me your thoughts on this..thanks   

Technical Service Manager

RE: Delamination caused by shear heat

Hi,

The exploded area in the picture (the one facing towards us), is that the gate? Did anyone do something to it, cause it look exploded.

At 440F coming out, and with 4inch diameter gate, i don't think the material would shear that easily.

Hotrunner tip may be overflowing but i'm thinkign how the hell did you remove the part if it did overflow.
 

RE: Delamination caused by shear heat

(OP)
That is the gate but what you see is from a shot where the gate area was not cooled and pulled off. This caused molten material to adhere together. The 4" is not the gate size it is the area around the gate that is showing layer separation. It is a 4" "diameter" area.  

Technical Service Manager

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources