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100 things you (probably) didn’t know about #extrusions (but definitely should) 💯in no particular order.

Dear Reader,

If you have landed here you probably have too much time on your hands or you are short of things that will make you sound smart at parties 🤣

Seriously, this list of 100 things that you probably should know about extrusions can make your life so much easier when wading into the world of aluminium and plastic extrusions.

Keep checking back for new episodes! Let us know at hello@bwcprofiles.co.uk or in the comments if you need any assistance or want anything explained in any more detail.



Episode 1. Quantity tolerances. ⚖️

Episode 1. Quantity tolerances. ⚖️

Fancy 10% more or 10% less than you asked for. Well buckle up. Did you know it’s standard practise in the extrusion market to operate a shipping tolerance like this? But why you ask?

The amount of billet that is selected to be pressed cannot be precisely calculated and is an educated guess. It’s based on the theoretical weight per metre of the profile, the predicted startup waste and the size of the customers order. Resulting in a final quantity somewhere near the order size.

Usually any material that passes quality checks will be aged, packed and shipped. Likewise if the order is a little short because of some scrap or poor quality pieces the order will not be pressed again to meet the ordered amount.

This is something to keep in mind if you need a specific amount to make a kit or assembly that requires an even number of pieces. Or if it’s a one off project you need to make sure you get what you need on the first shot.

Working with a stockholder can help you to keep overrun bespoke material until the next time you need it, keeping your warehouse free of odds and ends and your cash flow free from goods you can’t use or sell.

Stay tuned for episode 2. Gripping stuff right? 😉

Episode 2. Die scrapping 🪦

Episode 2. Die scrapping 🪦

Most #extrusion #tooling has a very long life… it’s a lump of steel right? Well in theory that’s true.

Over the longer term, unused dies need maintenance and servicing to prevent corrosion which could ultimately lead to poor surface finish and a host of other issues. But the biggest issue about keeping dies for a long time is the space they take up.

Most extruders will scrap a die if it’s not used, often without notice, usually if a period of between 2-5 years passes, depending on the extruder.

Some, offer long-term die storage and maintenance as a service. Some have a no scrappage without notification policy. But it’s always a good idea to check the terms of your quote especially if you know there will be a long interval between your need to use a tool.

Working with an Independent stockholder can give you some protection. For example, none of our extruders will scrap a die without notice and we have policies in place to make sure you are made aware of the costs of die storage and the risk of die scrappage upfront.

Stay tuned for episode 3. Riveting stuff 😅

Episode 3. 30-Second Sense Check 🕛

Episode 3. 30-Second Sense Check 🕛

New profile projects can often benefit from a little sense check upfront. For example, knowing how many metres an extrusion run will yield?

You need to work out your profile's theoretical weight per metre to even get started.

Simply multiply the cross-sectional area of the profile by 0.0027g/mm3 (approx density of most extrusion grade aluminium alloys).

For example, a 25x25x2mm angle has an area of 96mm2, so multiply by 0.0027 and 0.259 kg/m is the theoretical weight per metre. (Excuse the crappy sketch 😜)

So if the press states a 500kg minimum order, divide 500kg by 0.259kg/m and you yield 1930m of extrusion.

Now it’s easy to work out the cross-sectional area of an angle, but what if your profile is an irregular shape? If you're working offline try to break it into smaller shapes, work out the areas and sum them up. Most CAD packages even the free ones, have an option to tell you the surface area of a face in a model.

If you can’t be bothered with all that, just send in your sketches, drawings, CAD models, etc to hello@bwcprofiles.co.uk and we can help you get these sorts of questions answered fast.

Sorry for the unsolicited maths lesson 😳 whether you like it or not the next episode is coming soon.


30 second sense check 130 second sense check 230 second sense check 3


Episode 4. Only solids pushed through the hole 😉

Episode 4. Only solids pushed through the hole 😉

So now we have your attention here’s the scoop.

Aluminium is never in a liquid or molten form during the extrusion process.

The boiling point of aluminium is 660 degrees Celsius and most extrusion processes run at about 375-500 degrees Celsius. So whilst the material is softened by the heating process it’s never a liquid and it doesn’t glow red like the hot molten metal you might be picturing running through the die.

We’re not sure what use this information is to you, but you can use it to surprise and delight your friends at parties 🤓🥳

In all seriousness, when you think about the high pressure involved it helps to understand essential design principles such as tongue ratio - the topic of our next episode ✅



Episode 5. Check your tongue ratios 👅

Episode 5. Check your tongue ratios 👅

When designing profiles it's really important to avoid creating any very deep channels or recesses that have a narrow opening.

If you think about the extrusion die as the "inverse" of the profile the area of the tool that holds the channel or recess open is called the "tongue".

If your tongue ends up very large, but it is only joined to the rest of the die by a small amount of material it becomes very fragile and under the immense pressures of the extrusion process, can break!

The image below shows the design of a hopeful client looking for an 80x15x2 Channel.

The channel depth is 78, the width is 11 so the depth is a little over 7x the width or a 7:1 tongue ratio. Without some redesign. it's not going to be possible.

A ratio of 3:1 is usually considered acceptable, 4:1-5:1 difficult, but can be done in some limited simpler scenarios by introducing large radii transitions and other techniques. Beyond 5:1 is extremely difficult and will often require a redesign or using a tear-out strip to extrude the design as a hollow.

If you are ever unsure you can fire some ideas at us via WhatsApp here and we’ll give you some guidance. https://buff.ly/3B4G7A1

Now, put your tongue away and get ready for the next instalment.

80mm (1)


More episodes. Coming Soon

More episodes. Coming Soon

Watch this space... 😉👌