Blow Molding Help

powernxs

Member
Join Date
Oct 2006
Location
nebraska
Posts
9
I have been doing control design for 12+ years but have recently been asked to redesign control system for a blow mold machine from china. I can design the system without issue but is anyone familiar with the timing of the molds from low blow to high blow? The processor currently in the machine is something I can't get into for it's logic as it will destroy itself. Anyone familiar with blow mold processing?
Thanks
 
Volume (speed) and pressure is all based on the shape & wall thickness of the end product, it's 80% art and 20% science.
 
Temperature is important too or the parison will flow at inconsistent speeds making getting the length and the thickness right. There is no consistency without good temperature control. I agree that there is some trial and error involved in setting a machine up right for each part but it is easy to see where the plastic is too thin or thick and make adjustments. You need to know your machine. Making adjustments in one place may change the points where the thickness changed near the bottom.

What kind of control do you have now? I am familiar with the old Moog controllers that had 32 zones with a slider for the wall thick for each zone. This is pretty simple and hard to screw up but limited.

Basically a timer would start when the parison blocked the first photo cell at the top. The timer would index through the 32 zones and thicknesses until the parison blocked a bottom photocell when the mold closed and was injected with air and the parison at the top cut then the mold opened at the part fell out.

I was involved with starting up a new two head design from scratch. It took about a week with wiring and temperature tuning problems being the biggest head ache.
 
The process of blow molding machine is as follow:
The plastic is heated in extruder and pushed through a screw to the heads.
The heads have movable parts (die and mandrel) that adjust the thikness of paraison using servovalves controled by paraison controller.
The mold caught the paraison then the air is injected in the mold to get the shape.
There are 2 important parameters to watch, the cooling time and exhaust time.
Hope this help.
 
Blow Molding

Tarek,

I think you are talking about the injection molding not the blow molding.

The guy is asking about the blow molding.

Hagos
 

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