A portion of my job is the design of aluminum extrusions as framing for small signs, typically 6063-T6. What I learned early on is that the process a diemaker or extruder uses to determine the extrudability of a die isn't at all a matter of FEA or stress calculations or anything like that - someone there with years of experience would review the drawing and give it a thumbs-up or thumbs-down, and if I was lucky, some specific feedback as to what was wrong with it may have followed.
It's been a few short years now that I've been periodically working on these things, but some things have still got me wondering:
- The "tongue ratio", shown here, shown toward the bottom of the page. I've typically been given Area / (opening width)² as the guiding equation, and that it must be 3 or less, otherwise there's a chance that the steel "finger" on the die will snap off due to the forces exerted on it during the extrusion process.
However, I've got an extruded heatsink right here in front of me that has some very deep grooves as part of its extruded profile. The fins are 1.28" tall, and the opening averages about 0.090" wide. (It tapers, from 0.100" at the opening, down to 0.080".)
A/d² = 0.1152in² / (0.100in)²
= 11.52
Any of the extruders I've worked with call for this to be 3 or less, yet this heatsink extrusion here has an array of very deep grooves to form its fins.
- Thin-walled extrusions, either hollow or solid: Extruders like thick walls. Accounting and management would prefer that I extrude foil - more product, less material.
For example, I recently was tasked with making a stylized hollow tube. The outside dimensions are approximately 7x4". It took a few weeks, but I finally found an extruder that would build it with a wall of 0.090" thick. Most others wanted anything from 0.125" to 0.154".
The first run they tried jammed in the die, and produced a single piece that looked like a crumpled wet noodle.
They did some re-carving on the die, and ran it again. It worked rather well. One of the dimensions did end up being slightly out of spec, but the specific dimension and the application were not sensitive to this.
So here's what I'm asking then: Are these more a matter of the extruder not wanting to do these extrusions, or is it genuinely a matter of capability? Is it a matter of maintaining tolerances? Are the heatsink manufacturers using a special type of extruder machine, or die assembly, to get their high tongue ratios?
Thank you,
Jeff
It's been a few short years now that I've been periodically working on these things, but some things have still got me wondering:
- The "tongue ratio", shown here, shown toward the bottom of the page. I've typically been given Area / (opening width)² as the guiding equation, and that it must be 3 or less, otherwise there's a chance that the steel "finger" on the die will snap off due to the forces exerted on it during the extrusion process.
However, I've got an extruded heatsink right here in front of me that has some very deep grooves as part of its extruded profile. The fins are 1.28" tall, and the opening averages about 0.090" wide. (It tapers, from 0.100" at the opening, down to 0.080".)
A/d² = 0.1152in² / (0.100in)²
= 11.52
Any of the extruders I've worked with call for this to be 3 or less, yet this heatsink extrusion here has an array of very deep grooves to form its fins.
- Thin-walled extrusions, either hollow or solid: Extruders like thick walls. Accounting and management would prefer that I extrude foil - more product, less material.
For example, I recently was tasked with making a stylized hollow tube. The outside dimensions are approximately 7x4". It took a few weeks, but I finally found an extruder that would build it with a wall of 0.090" thick. Most others wanted anything from 0.125" to 0.154".
The first run they tried jammed in the die, and produced a single piece that looked like a crumpled wet noodle.
They did some re-carving on the die, and ran it again. It worked rather well. One of the dimensions did end up being slightly out of spec, but the specific dimension and the application were not sensitive to this.
So here's what I'm asking then: Are these more a matter of the extruder not wanting to do these extrusions, or is it genuinely a matter of capability? Is it a matter of maintaining tolerances? Are the heatsink manufacturers using a special type of extruder machine, or die assembly, to get their high tongue ratios?
Thank you,
Jeff
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