Scientific molding

[Paolo]

Hi guys,

I'm new here and I'm finishing my master degree on Polymer Engineer. Right now I'm starting my thesis and it's about Engineer otimization more precisely scientific molding. I've read some articles and post's from Mr Suhas about the 6 step study and DOE , APW , DPW and CPW. Right now I have some doubts and I hope someone of you guys can help me.


1. Can the viscosity study (1 step) provide us information about injection speed profile, i.e. in case we need 2 diferents injection speeds to fill the part. If yes, how? If not, how you guys know that you need e.g. 2 profiles speeds?

2. Should we set de max available pessure to all the steps of "pressure study" and only adjust the transfer position? If we conclude for example that the end of fill needs 2000 psi and the max available pressure is 2700 psi , should we use 2000 psi as our pressure on the "process window study" ?

3. how can we find the residence time? There is a trustworthy equation?


Thank you so much for your time guys!

Paolo

[3NGLENN1889]

http://www.ptonline.com/columns/top-10-reasons-why-molders-fail-at-implementing-scientific-molding
Hope this helps G.P.

[Paolo]

Thank you for the link 3NGLENN1889 . I already had read it some weeks later and I understand why you send me this. I forgot to tell you something, I'm doing my thesis on Prettl Adion Portuguesa, an automotive company from Prettl Group. Here I have all the resources ,tools and support . I've made my worksheets to the 6 step study on excel but before to go into the production field and test the 6 step I need to clarify some doubts like I said above.

Regards,

Paolo

[Suhas]

Paolo,

Here are some answers for you:

1. Can the viscosity study (1 step) provide us information about injection speed profile, i.e. in case we need 2 diferents injection speeds to fill the part. If yes, how? If not, how you guys know that you need e.g. 2 profiles speeds?
Yes, you can use two speeds, no problem. The rule is is 'Inject as fast as you NEED and not as fast as you can or what always the Viscosity curve suggests.

2. Should we set de max available pessure to all the steps of "pressure study" and only adjust the transfer position? If we conclude for example that the end of fill needs 2000 psi and the max available pressure is 2700 psi , should we use 2000 psi as our pressure on the "process window study" ?
First you need to do the pressure drop study and set the machine pressure about 10 to 15% more than the required press. This is Injection Pressure.
Then you do the Process Window Study - that will be independent of this pressure since you are now in the holding phase.

3. how can we find the residence time? There is a trustworthy equation?
Not exact but a good estimate is 'Number of Shots in the barrel multiplied by the cycle time'. number of shots in the barrel = Max machine shot weight divided by the weights of all the parts plus the runner. Do not forget to convert the max shot weight of the machine (given in Polystyrene) into the weight of the material you are molding.

Download the Scientific Molding App from the App store and you can see what I am talking about.

Reagards,
Suhas

[Paolo]

Suhas,

thank you so much for your answers.

Best Regards,

Paolo Maradey