Aluminium Framing Extrusion Kit 40×40 mm 40 Series Cut List for Machine Frames

What is actually in the box

A kit is defined by the list of things that arrive with the profile, and the difference between a good kit and a box of extrusion is how complete that list is. The profile is the easy part. The parts that decide whether the frame goes together on the first attempt are the small ones, and they are the ones that get left out when a kit is quoted on a price per metre.

A worked bill of materials

Take a machine frame 1,500 mm wide, 1,000 mm deep and 2,000 mm tall, with 40 x 40 mm posts and 40 x 80 mm rails on edge at the top. The rails sit between the posts, so the clear span is the frame width minus two post widths: 1,500 minus 80 gives 1,420 mm on the long sides and 1,000 minus 80 gives 920 mm on the short sides.

At about 1.6 kg/m for standard wall 40 x 40 and about 2.9 kg/m for 40 x 80 on edge, that is roughly 25 kg plus 14 kg, so about 38 kg of aluminium in the frame. The hardware is 20 corner brackets, about 64 T-slot fixings counted by joint, four levelling feet, end caps for every exposed profile end, and slot covers for the grooves that will be walked past by a machine operator.

The nesting table is where the price comes from

Profile is bought in 6 m bars and cut down. How well the members nest into a bar is the single biggest variable in a kit price, and it is why two frames of the same weight can quote very differently. A 2,000 mm post nests three to a bar with no offcut at all. A 1,420 mm rail nests four to a bar and leaves 320 mm. A 920 mm rail nests six to a bar and leaves 480 mm.

Look at the fourth row. A member 1,550 mm long nests three to a bar and throws away 1,350 mm every time, which is a quarter of the bar straight into scrap. Changing that member to 1,500 mm does not help much, but changing it to 1,450 mm still nests four to a bar with 200 mm left, and the material cost drops by a quarter for that member. That is the sort of thing we check before quoting, and it is worth knowing before you fix the last few millimetres of a design.

What a design change costs

The instinct is that changing a member from 1,420 mm to 1,450 mm costs 30 mm of profile. It does not. Once the bar has been cut, the 1,420 mm members are scrap and the bar has to be re-cut, so the change costs the whole bar, plus the saw time, plus the re-kitting, plus a second shipment if the first one has already left. On a twenty metre frame that is a change worth several percent of the total.

This is the real argument for freezing the design before the cutting list is issued, and it is also the argument against ordering a kit too early. If the design is still moving, order stock lengths and cut locally, accept the looser tolerance and the extra hardware sourcing, and come back for a kit when the drawing stops changing. A kit ordered at the right moment saves money. A kit ordered while the drawing is still live is the most expensive way to buy profile there is.

1. Freeze the drawing, then release the cutting list. Every dimension on the drawing has to be final before the first cut. Changes after that are charged at the bar, not at the difference.
2. Check the nesting before the final fix. Send the cut list and we will tell you which member lengths are costing you a quarter of a bar. Moving a length by 50 mm is free at the drawing stage and expensive afterwards.
3. Decide flat pack or pre-assembled bay. Flat pack is cheaper to ship and to store, and it lets the frame go through a doorway. A pre-assembled bay arrives square and is faster on site, and costs more in freight because it takes volume.
4. Decide what gets a panel before the kit ships. Panel retainers, gaskets and glazing beads are kitted with the frame. Adding them later means a second shipment for parts that cost very little.

What we need to quote a kit

• A drawing, or a sketch with the overall size, the section sizes and the node positions. DWG, DXF, STEP, IGES and PDF all work.
• What the frame has to carry, and whether any member spans between supports rather than between posts.
• The environment: indoor, wash-down, coolant mist, outdoor. It decides the finish and whether the fasteners need to be stainless.
• Quantity, and whether the frames repeat. A repeat frame is worth setting up once.
• The finish: mill, clear anodised or black anodised, and any colour match.
• Delivery terms, so the freight is quoted with the frame rather than discovered afterwards.

The mistakes that cost a day on site

Flat pack, pre-assembled or somewhere between

Kits are normally supplied flat packed, which means profile, hardware and drawing in bundles with everything labelled. That is the cheapest way to move a frame and the only way to get a large frame through a standard doorway. At the other end, we can supply the frame assembled and squared, which costs more in freight but removes the assembly labour and the risk of an out-of-square frame.

The middle option is usually the right one for a machine frame. Supply the four sides as pre-assembled rectangles, squared on a jig, and let the customer bolt the four rectangles together and drop the top rails in. That gets the squareness controlled at the factory, where the jig is, while keeping the shipment flat.