Optimising aluminium stock lengths for fewer offcuts

Most workshops order the same stock length for every profile because that is what they have always ordered. The right length for a head track is not necessarily the right length for a bead, and the difference shows up in the scrap bin. This article walks through choosing stock lengths from your own cutting history, nesting jobs into one order, and reading the result.

Look at your own cut lengths first

Before changing anything, gather the cutting lists from your recent jobs and sort the cuts for one profile from longest to shortest. You are looking for a pattern: are most cuts clustered around a couple of lengths, or spread evenly? A profile used for sills and heads on residential windows will cluster around common opening widths. A jamb profile clusters around common heights. A bead profile is all over the place.

That pattern is the whole basis for the decision. A bar length that divides well into your common cuts leaves short remainders. A bar length that does not leaves a long one on every bar.

Matching bar length to the work

Suppliers usually offer more than one stock length for a profile. The questions to ask about each option are practical:

• How many of my common cuts fit in it, and what is left after they do?
• Does the longer bar cost more per metre, or attract a different freight charge? A cheaper bar that leaves a longer remainder is not cheaper.
• Can I store and handle it? A bar that does not fit the rack or the saw bed will be cut down before it is even on the list.

A worked example makes the method clear. Say a profile is sold in two lengths and most of your cuts for it are a little under half the shorter bar. Two cuts fit in the shorter bar with a small remainder; the longer bar takes four cuts and leaves a remainder about the same size. Per cut the longer bar is more efficient, provided you can handle it. Do that sum with your own cuts and your own supplier's lengths, profile by profile.

Nesting several jobs into one order

Cutting one job at a time means the end of every bar is decided by that job alone. Nesting the cuts from two or three jobs into one cutting plan lets a short piece from one job fill the end of a bar from another. The rules that keep it safe:

• Only nest the same profile in the same finish; a black jamb cannot become a white one.
• Only nest jobs whose fabrication dates overlap, so nothing waits on another job's schedule.
• Label every piece with its job and item number as it comes off the saw.

For a small workshop this is a weekly habit: gather the jobs going to the saw that week, group the cuts by profile and colour, and run the cutting plan on the group rather than the job.

Running the offcut rack

Nesting reduces remainders but does not remove them, so the rack still matters. Three rules cover it:

• Label every remnant with profile, length and colour before it goes on the rack.
• Set a minimum length per profile. Anything shorter is scrap. The rack should hold stock you will use, not everything you could not bring yourself to throw out.
• Use the oldest first, and check the rack when each new cutting list is prepared so a remnant is consumed before a new bar is opened.

Reading the result

An optimised cutting sheet shows two numbers that matter: the bars the job uses, and the bars it would need if every cut packed perfectly with no waste at all. The second number is a floor you cannot go below. The gap between the two is where your stock-length choice and your nesting are either working or not.

Keep those two numbers per profile for a few months. When the gap stops shrinking, you have found the right bar length for that profile and can stop fiddling with it. In Alumetric, the special cutting sheet can be optimised into stock lengths for the profiles you select, and the aluminium sheet lists the profile quantities the job consumed, so both numbers come from the same job data.

Start with one profile

Do not try to re-plan the whole catalogue. Take the profile you buy the most of, work through its cut lengths, pick the bar length that fits them, nest the next few jobs, and keep the two figures. One profile is enough to learn the method and to see whether it is worth applying to the rest.