hi i was wondering if someone could clarify what types of material count as “extrusions…” 
For instance, is aluminum tubing (listed on small parts pg. 114) an extrusion? Or would bars be extrusions? thanks in advance. 
Hi there,
Aluminum extrusions can include but are not limited to tubing and bar stock. It most often refers to aluminum shapes that are available through several outlets, i.e. Home Depot, McMaster -Carr, and Small Parts or any local industrial suppliers. These shapes come in square and octaganal (sp.) tubing, structural extrusions, etc. The caveat here is that many shapes come in very thick cross sections that add unnecessaary weight because they are capable of supporting much heavier loads than the robot will encounter. Many teams use these strctural shapes for the base because they are easy to fabricate and assemble. If you have access to MIG welding at school you can also weld these shapes for whatever design you need. Check with your shop teachers, they proably know where to get the parts and how to weld the aluminum. Good Luck!
Al
In industry, an “extrusion” is anything that is created by squirting the material out through a die. This process creates a long, solid material whose cross sectional profile/shape is dependent on the die.
Imagine a speghetti/pasta making machine, or the Play-Doh Fun Factory you may have played with as a kid. Those are both examples of extrusion making machines.
This technology is primarily used to make long solid shapes of constant cross section, most often out of metal or plastic. Examples are: bar stock, hollow round or square (box) tubing, L (angle iron), C & U channels, metal trim, and the like.
Companies like 8020, Bosch, or IPS take extrusions much further, making “Fractal X” patterns know as “structural shapes” for scaffoldings. These are often used in FIRST contests as a primary structural construction material because it bolts together easily (no welding required), it only takes a hacksaw and a screwdriver to make something very strong, and you can change things rapidly. The down sides can be cost and weight, because with a complex shape you often end up buying and carrying around more material per linear foot than you may really need. You may go overweight in a bigger machine, and it takes more power to haul it around. See the threads here on structural materials for more info.
For FIRST purposes, extrusions are simply limited as to the maximum X and Y cross section dimensions, and allowable materials.
BTW… FRCtech2002 has recently ruled the dimensions are NOT combinable. For example, although you’re allowed to use ‘Extruded Aluminum, Any length, Up to 2"x3"’, you may NOT use 6" x 1" extrusion just because it HAPPENS to also be “six square inches” in cross sectional area.
Be warned: Most people associate the term extrusion with “HOLLOW extrusion”, so if you are thinking of for instance using a piece of 2"x3" SOLID aluminum stock, you’d better check with FRCtech2002 first about it. They may not consider that an extrusion. That is because although “bar stock” CAN be made as an extrusion, solid shapes are most often formed instead by rolling or squeezing it.
- Keith
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Keith McClary, Advisor, Huron High “Rat Pack” Team 830
*Originally posted by kmcclary *
**Be warned: Most people associate the term extrusion with “HOLLOW extrusion”, so if you are thinking of for instance using a piece of 2"x3" SOLID aluminum stock, you’d better check with FRCtech2002 first about it. They may not consider that an extrusion. That is because although “bar stock” CAN be made as an extrusion, solid shapes are most often formed instead by rolling or squeezing it.
**
In past years, FIRST had defined “extrusion” as any part that was manufactured by extruding through a die. Therefore, solid bars counted as extrusions.
When someone would ask “does xyz count as an extrusion?”, FIRST would respond: “find out from the manufacturer if it was made by extruding the material; if so, it counts as an extrusion; if not, it is not an extrusion.”
Of course, just like this year, virtually every known part on earth was asked if it counted as an extrusion. It’s very simple: if the material was extruded, it’s an extrusion. If you’re not sure how it was made, contact the manufacturer and ask.
-Chris
We were able to meet the requirements of “extrusion” one year by producing a document from our local extrusion shop. It was a drawing on company letterhead of a 2"x3" extrusion die.
“Fish at your own risk”