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.
In response to a specific customer requirement, Diamond America engineers had to challenge convention and rethink the design of a monolith die.
Commonly used for extruding catalysts and some food products, a monolith die produces an outer profile that contains many channels, separated by thin walls. The final product is reminiscent of a honeycomb in the way that it has multiple, parallel holes when viewed from the end.
The customer currently produced a profile containing 25 holes in each one-inch solid block of product. A request had come in for them to form a product with only 20 holes.
Could they adjust the internal configuration of the honeycomb shape from 25 to 20 internal channels?
Or would the whole die set need to be re-made?
Our design engineers set to work and created an adjustable mandrel tray – see image. This new design meant that it was not necessary to order a completely new die to accommodate the reduced number of holes. Only the tray and the pins of the existing mandrel die set needed to change.
For Diamond America this new, modular invention made the monolith die much easier and quicker to manufacture. Traditional monolith die designs leave the mandrels as an integral part of the second die plate, whereas the new insertable mandrel tray incorporates only the exact number of pins required as an interchangeable part, allowing the mandrels to remain separate from the die plate and thus reducing its complexity.
For our customer, as well as avoiding the need to purchase a complete new die set, the process benefits were threefold:
- Dramatically reduced product manufacturing lead times
- Faster changeover between different product runs
- increased scheduling flexibility for different product configurations
They were able to deliver to their customer, exactly to required specification, faster and without significant additional investment in a completely new die set – now that’s service!
Call Diamond America now at 330-535-3330 for your partner in productivity improvement.
Image 1. Diamond America’s modified Monolith Die for rapid changeovers