As a custom extrusion equipment manufacturer, we know the importance of good die design in ensuring throughput and productivity.
Expert design balances the melt flow across the die, maintaining continuous uniformity and exit velocity with minimal pressure drop.
Die selection also impacts on product quality, since incorrect die choice can cause extrusion issues and problems with final product shape and density.
When one of our extruder customers began having trouble achieving successful results from their equipment, we immediately began our troubleshooting process. In this case, product was emerging inconsistently from the die and the extruder was stalling out.
The first step is usually to run a trial at our in-house laboratory at Diamond America, using a sample of the customer’s exact extrudate material. This allows our engineers to evaluate the process, monitoring and testing for potential problem sources.
In this case, however, our extruders at the customer’s site had been fitted with dies that had not been made by us, so we asked to review their die design drawings in an attempt to solve the issue.
What we found was very interesting.
We immediately noticed that the die had been fitted into the land area at the end of the barrel, which is actually intended to be a lead in area (Pilot) for a die or spacer. This meant that the feed material was being fed directly into the die from the end of the screw.
This was causing inconsistent feeding into the die, since the root diameter of the screw would not allow enough material to be fed freely into the holes in the center of the die. This would lead to inconsistent product formulation and erratic density, as well as possibly causing the extruder to stall out.
To prevent this from happening in our own designs, we use a spacer plate of about ½” to ¾” thickness to allow the correct volume of material to accumulate before feeding uniformly into the die at the appropriate pressure.
Once this issue was identified in the customer’s die, a quick modification recessed the die plate facing the screw to allow space for the feed material to collect before entry into the die. Lead chamfers into the holes also helped to channel the material more smoothly into the die over the short distance involved – see image 1.
Ideally, the addition of a spacer ring would have resolved the flow issue completely, allowing space for the material to accumulate, correcting the erratic feed and promoting uniform fill across the die.
In the secondary part of the die, the sharp corners at the funnel area were also rounded off to ease the pressure in this area and generally assist with exit flow – see image 2.
Implementing the suggested changes to die design achieved the successful outcome shown in the video below, where it can be seen that uniform product is produced to a consistently high-quality standard.
Call Diamond America at 330-535-3330 for expert die design to help you achieve perfect results today.