Extrusion gives you a length, not a part
An extruder produces continuous profile. Almost nothing seals against a continuous length - frames, doors and housings need discrete pieces cut and often joined. What happens after extrusion is usually where the tolerance is won or lost.
Cutting to length
Square cut for butt joints, mitred for corners. On a mitred frame the angle accuracy matters more than the length accuracy - a half-degree error per corner opens a visible gap across four joints.
Corner bonding
Mitred corners are bonded so the joint closes and stays closed. Done well there is no visible step and no misalignment at the join. Done badly the corner is where the seal starts to leak, and it is the first thing an inspector looks at.
Adhesive backing
Tape applied to the back of a profile, with a release liner so it stays clean in transit. Useful where mechanical fixing is awkward or where the end user replaces the part. Specify the substrate - tape that holds on painted steel does not necessarily hold on powder coat or plastic.
Slotting, punching and die-cutting
Vent slots, fixing holes and shaped cuts can be added in-house. Doing them in the same factory as the extrusion means a dimension that has drifted is caught before the parts are boxed rather than after they reach your line.
Why in-house matters
Every secondary operation is a place for tolerance to disappear, and every subcontracted operation is a place for a schedule to slip. Keeping cutting and bonding under the same roof as the extruders removes both risks from your quote.
Profiles for this application
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Working on something like this?
Send the drawing, cross-section, operating temperature and what the seal has to resist. We will tell you whether a stock profile fits or the part needs extruding, and quote both.