Author Topic: Next GENERIC sizes up from 2020 Aluminium Extrusion  (Read 1944 times)

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Offline InfravioletTopic starter

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Next GENERIC sizes up from 2020 Aluminium Extrusion
« on: May 27, 2024, 05:23:58 pm »
Extruded aluminium T slot/V slot profiles come in a huge number of varieties, but some varieties in particular are really common, made by lots of different manufacturers and have absolutely loads of different accessory parts (corner joints, specially sized slot nuts wiith the spring loaded ball, end caps, 45 degree connectors, 3d corner joints,...).

I'd like to know what the next common size up from this is, but it seems most of the other sizes become very manufacturer specific, harder to find and with a lot less choice of accessories available (I know I could 3d print any plastic accessories to whatever size I needed, but that won't help for where I'd need the strength of metal ones). Furthermore at larger sizes the actual shape of the profile becomes quite varied and non-standardised, with different shaping and sizings of the slot, even when the outside-most dimensions of the beam are the same.

What are the next generically produced and seemingly standardised sizes up from 20mmx20mm, particularly with a focus on increased strength and rigidity (whether some sort of single slot by single slot or multiples of 20x20 are better for this I'm not sure) for use in the frame of a semi-lightweight CNC machine.

Thanks
 

Offline thm_w

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Re: Next GENERIC sizes up from 2020 Aluminium Extrusion
« Reply #1 on: May 27, 2024, 09:18:54 pm »
For metric sizes: 20x20, 20x40, 20x60, 25x25, 40x40, 45x45, 50x50, 60x60, etc.

I would say 20, 30, 40, 45 are most common and you can easily find accessories.
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Offline Doctorandus_P

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Re: Next GENERIC sizes up from 2020 Aluminium Extrusion
« Reply #2 on: May 28, 2024, 01:15:55 pm »
Lightweight and CNC (routing / milling) do not go well together. Accessories (corner brackets etc) also do not always fit between brands. Instead of attempting to figure out "what sizes do exist", choose a manufacturer or store that can deliver to where you are (or you can pick up yourself) and then just stay with one brand of profiles. Some manufacturers have a limited set of sizes, while others may have thin/medium/heavy variants in the same size (and this varies the wall thickness of the profiles).

But overall, your choice should be guided with what you need to achieve the size of your CNC machine with the required stiffness.

Personally I do not like aluminum profiles all that much. They are much more expensive then steel, and not much "lighter". Do realize that Young's modulus for aluminum is just one third of that of steel. Which means that if you have for example a 40x40mm profile, an aluminum profile would need thrice the wall thickness compared to a steel profile to achieve the same stiffness. and thus it would be even heavier then steel. This makes aluminum a bad choice for a CNC machine, because stiffness is very important for a CNC machine. The reason you see so much aluminium used in consumer market CNC machines, is only because it's easy and quick to make a machine out of it. But in general those are not very good machines.


https://en.wikipedia.org/wiki/Young%27s_modulus
 

Offline DiodeDipShit

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Re: Next GENERIC sizes up from 2020 Aluminium Extrusion
« Reply #3 on: May 28, 2024, 05:04:05 pm »
The next generic size from 20mm is 1" (24mm)  , then 30mm, next is 1-1/4" (31.75mm) .... etc.
You will find all the sizes in Height, Widths and profiles here:
https://www.mcmaster.com/products/t-slotted-framing/
You will also discover all the materials and coatings they are available in and corners, covers, brackets and mounting hardware etc......
Any five fifty five will do ......
 

Offline InfravioletTopic starter

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Re: Next GENERIC sizes up from 2020 Aluminium Extrusion
« Reply #4 on: May 30, 2024, 01:22:29 am »
"Personally I do not like aluminum profiles all that much"
The trouble is, I'm not aware of steel sections being sold with the same sort of profiles with slotting for easy fitting of nuts and such, with steel you're pretty much restricted to square sections, I beams, L cross-sections and round bars aren't you?
 

Offline Overspeed

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Re: Next GENERIC sizes up from 2020 Aluminium Extrusion
« Reply #5 on: May 30, 2024, 04:42:45 am »
Hello

to allow to have a wide choice of wall thickness I machine angle ( saw cut ) from square tube so I can make angle ''20x20 mm '' from 2 mm up to 6 mm wall thickness

another parameter to take in consideration is the aluminium alloy as extruded are available in
5083 : soft alloy low tensile
6082 T6 or 6061 T6 : with good mechanic property

Regards
OS

 

Offline Doctorandus_P

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Re: Next GENERIC sizes up from 2020 Aluminium Extrusion
« Reply #6 on: June 01, 2024, 12:11:48 pm »
"Personally I do not like aluminum profiles all that much"
The trouble is, I'm not aware of steel sections being sold with the same sort of profiles with slotting for easy fitting of nuts and such, with steel you're pretty much restricted to square sections, I beams, L cross-sections and round bars aren't you?

Yes. Using steel is more labor intensive, You will have to drill and tap holes. If you have the tools and know how to use them it's not such a big issue. Another issue with steel is cleaning and painting. If you're still interested, have a look at "PrintNC". It's not a "great" machine, but it is designed around ease of making with limited tools, and scalability with locally supplied "mild steel box sections" (Available in many square and rectangular sizes and wall thicknesses) It is not the machine for me, but many have been built, and there is an active community around it (forum, youtube video's etc).

This video from Christoph Lehner is also a good overview of the costs of building a PrintNC CNC machine.

If you go with aluminium profiles, you can stiffen them up a bit by bolting some plates or other profiles to it. Sorotec is a German manufacturer of CNC machines and kits, and they do this to the gantry of the machines they make. You can use them as inspiration for your own design.

An example of the type of machine I am interested in myself is the "CroMachine MF" This has a welded steel frame, and this needs a heat treatment for stress relief. Making such a machine is not a beginners project though. (CroMachine also makes very bad video's, but that is another topic).

Other options is to build a VMC or similar type of machine. Both Epoxy granite or UHPC are good options for those. UHPC is much cheaper, and I don't know any negative sides compared with Epoxy. I never really understood why epoxy is more common / popular.

Upto now you still have not said much about the sort of machine you are interested in and what you want to do with it. Some people are apparently content with "light weight CNC routers", while for others it results in disappointment.

 
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Offline Overspeed

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Re: Next GENERIC sizes up from 2020 Aluminium Extrusion
« Reply #7 on: June 02, 2024, 07:12:44 am »
Hello

If you go with aluminium profiles, you can stiffen them up a bit by bolting some plates

Dont mix ( mistake ) metal with inertia modulus . that possible ( and applied in a a lot of engineering domains ) to built stiff structures by using light alloy beams , no need '' steel '' without the fact there is steel and steel from entry level A3 to high tensile steel and some aluminium alloy provide better performance than entry level steel

Regards
OS
 

Offline Doctorandus_P

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Re: Next GENERIC sizes up from 2020 Aluminium Extrusion
« Reply #8 on: June 02, 2024, 10:07:08 am »
What is an:
inertia modulus

I'm not a native English speaker, but even search engines do not put those words together well.

What is "better performance" in this context?
. that possible ( and applied in a a lot of engineering domains ) to built stiff structures by using light alloy beams , no need '' steel '' without the fact there is steel and steel from entry level A3 to high tensile steel and some aluminium alloy provide better performance than entry level steel

Strength and stiffness are two very different things. A "thing" can be strong without being stiff, and another thing can be stiff without being strong. Steel quality does not matter at all for stiffness. It's part of the reason lots of machines are made from cast iron. Cheap cast iron has (very nearly) the same stiffness (Young's modules) as the "highest grade super strength" steel.
Young's modulus of all steels is around 210GPa, while for aluminum alloys it's around 70GPa.
And apart form material, the form has an enourmous influence on stiffness. But shape is another factor then material. All the zig-zag lines of T-slotted Aluminium profiles are also not good for stiffness, but I'm not sure how much it matters.

And really, have a look at the way the gantry of the Sorotec machines are built up. The aluminium T-slot profile is mostly used as a convenient mounting point, and as a spacer in between the steel linear rails on the front, and the stiffening plate on the back. This extra thickness is a mayor contribution to both bending and torsional stiffness.  The Sorotec "Basic Line" has a clear picture of this, just look at the backside of the gantry. https://www.sorotec.de/shop/Portalfraese-Compact-Line-10863.html

But everything put together, I think this is going a bit too deep for a question that started as getting an overview of aluminum profiles.
 

Offline Overspeed

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Re: Next GENERIC sizes up from 2020 Aluminium Extrusion
« Reply #9 on: June 02, 2024, 12:17:14 pm »
Hello

Strength and stiffness are two very different things.

I agree but both are important and linked as that generate concerns with acceleration / inertia to stop / motor size

Carbon fiber / Epoxy beam is also a solution

Designing a machine is a stack of mandatory parameter a router ''cheap '' have the same architecture as a SIP or an Hauser boring machine , but not at all the same design

Regards
OS
 

Offline Doctorandus_P

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Re: Next GENERIC sizes up from 2020 Aluminium Extrusion
« Reply #10 on: June 02, 2024, 12:53:58 pm »
Hello

Strength and stiffness are two very different things.

I agree but both are important and linked as that generate concerns with acceleration / inertia to stop / motor size

Again, not really. Leaf springs can be "quite strong" but not stiff at all. Two gauge blocks held together by an elastic band are very stiff, but not strong at all. In general, adding more material increases both strength and stiffness, but those two are not necessarily linked. Machine tools such as mills and lathes are very heavy to increase their stiffness. The base construction is easly 10x or 100x stronger then it needs to be. Big steel constructions are heavy because they need it to get enough strength. Stiffness is not very important. Flexibility is often a good thing, as it reduces peak loads (thus less strength needed) and spreads impact forces over time.

Carbon fiber is both strong,  stiff and lightweight. It's a good material for machines, but it is still to expensive for most machines. But it is becoming more more common where the combination of it's properties justifies it's extra costs. It's also brittle and this makes it difficult to use. It's not a "beginners" material for a first machine.
 

Offline Overspeed

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Re: Next GENERIC sizes up from 2020 Aluminium Extrusion
« Reply #11 on: June 02, 2024, 04:34:56 pm »
Hello

Machine tools such as mills and lathes are very heavy to increase their stiffness.

Not only , the mass is also used for temperature stability and vibration dampening . modern machine tool ( some ) are built from welded sheet metal poured with composites concrete to be stable , main evolution is feed speed a classic and respectable SIP boring machine is extremely accurate but slow .

Modern machine as the well know brand Mazak are far different in design that conventional '' old school '' machine tool as Deckel ( another very good brand ) or Mikron or Kern ( amazing machine tool ) but the engineering level is high and performances are impressive , after depend of the purpose reach the 1/100 mm in machining of common material is not reach the 1/1000 mm in machining in exotic aerospace materials

Light weight CNC as router and other light gantry architecture are not designed for heavy cutting forces and machining thought material I have a improved router 3020  made from beam and aluminium plate with over sized linear bearing , that OK for small machining up to aluminium but accuracy is limited .

Built home made precision machine tool is fully feasible with knowledge and time

Regards
OS

 
 

Offline Doctorandus_P

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Re: Next GENERIC sizes up from 2020 Aluminium Extrusion
« Reply #12 on: June 02, 2024, 10:18:34 pm »
I have never used a "lightweight CNC Router" myself, but I've seen many designs and youtube video's. And though they can cut aluminium, there are severe limitations in material removal due to lack of stiffness. And that is also directly the resion I never bothered to make such a machine myself. I do have a (beefed up) RongFu RF-30 (a.k.a "round column" drill / mill) And this can chew though mild steel quite satisfactorily, with motor power (1.5kW) being the first limitation.

I'm wondering if Infravioleet (OP) is still present   ;D
 

Offline SmallCog

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Re: Next GENERIC sizes up from 2020 Aluminium Extrusion
« Reply #13 on: June 02, 2024, 10:29:59 pm »
"Personally I do not like aluminum profiles all that much"
The trouble is, I'm not aware of steel sections being sold with the same sort of profiles with slotting for easy fitting of nuts and such, with steel you're pretty much restricted to square sections, I beams, L cross-sections and round bars aren't you?

It may or may not be suitable for your project, but there are steel bolt together profiles available with sliding nuts.

Various brands make this sort of product, 2 that I frequently use are Unistrut and Ezystrut

Commonly used for mounting pipework, cabling, equipment etc for industrial purposes. Even has little trolleys available if you want to make a roller coster or something.

https://www.ezystrut.com.au/assets/catalogues-and-downloads/Ordering-Code-Quick-Reference-Chart-Channel-PUBLIC.pdf
 

Offline InfravioletTopic starter

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Re: Next GENERIC sizes up from 2020 Aluminium Extrusion
« Reply #14 on: June 03, 2024, 04:17:28 pm »
Regarding size and weight, my thoughts were I could use aluminium extrusions and keep it light (enough to move as easily as a chair or small table, though still a bit heavier than either), but pretty rigid, so long as I was willing to go for a small working area for it. So I'd be using aluminium extrusions to build up a fairly big frame to surround a relatively small working area. I don't have a need for big cutting areas like that printNC has, just a say 10cmx10cmx10cm volume in which to machine things out of aluminium, so I'd be able to double up on a lot of the structural members. The attraction of the aluminium profiles is particularly the ease of mounting things to it and adjusting the design, useful when designing one's first CNC. Also, it's a lot easier to drill, tap and cut aluminium extrusions than steel beams. Also, I'm only after an accuracy on the parts I produce of something comparable to 3d printed parts, I'm not trying to get serious precision, just precision as good as or a bit better than the 3d printing I'm already used to, so I need enough rigidity to stop seriously damaging chatter occuring, and enough to ensure the machine can mill its way through aluminium, but not as much rigidity as needed in a lathe or a proper milling machine.

All the replies have given me quite a bit more to think through, I was away for a few days and didn't notice them until now, but the idea of bolting on reinforcing plates of steel sounds particularly interesting... Would that typically give you rigidity as good as a much bigger aluminium profile evn if you went for 2020 size? Also, the other thing about going to bigger profile sizes is you can get bigger slot nuts which accomodate bigger sizes of screw, does this usually count for much, or is the situation usually one where  the aluminium itself, however big the profile, is "un-rigid" enough that increasing the size of screw by going to large profiles is insignificant by comparison?
Thanks
« Last Edit: June 03, 2024, 04:21:07 pm by Infraviolet »
 

Offline Overspeed

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Re: Next GENERIC sizes up from 2020 Aluminium Extrusion
« Reply #15 on: June 04, 2024, 06:22:25 am »
Hello

In industry the most common Bosch profile is the 40x40 , use for multiple purpose in a lot of industries

If you want to built an easy 100x100x100 ( millimeter ) for aluminium machining in 2.5 Axis ( so not complex shape )

Best is to purchase a good quality a 3040 ( full aluminium frame )  and make the frame stiffer by adding extruded profiles and plates + bigger diameter linear bearing for the table with ball screw and use a quite bigger spindle but also with higher quality as the original one .

Nothing difficult just a question of available time , start from a white page need much more work and tools

Regards
OS
 

Offline Doctorandus_P

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Re: Next GENERIC sizes up from 2020 Aluminium Extrusion
« Reply #16 on: June 04, 2024, 11:17:38 am »
100x100x100mm working area, that gives already a much better reference for the direction you want to be going.

A machine like PrintNC can be built in any size, but it does waste a lot of size because of the ways the axis are built (Carriages don't go fully to the side, motors are in line with the ball spindles) Both of those can be fixed with relative small changes, but for such a small machine PrintNC does not scale very well.

Bolt size does not matter at all for rigidity. Zero, nada, Njet. With a bolt you create a clamping force and friction. As long as forces are lower then the maximum friction, the parts stay in place, and thus zero movement "infinite" stiffness in the joint, as soon as the forces become higher then what the friction can handle, something moves (or a bolt breaks, etc) and it don't work properly no more. Bigger bolts do give more strength, but that is a different topic. This is also an excellent example of the difference between strength and stiffness.

For a small machine you can think about building something similar to the rat rig mini mill:
https://ratrig.com/catalog/product/view/id/1827/s/mini-mill-configurable/category/166/

The Proxxon MF70 is also relatively popular for conversion to CNC. But it's popularity is probably not based on it's quality, but because it is (probably?) the only option in that size and budget.

I would avoid anything with those unsupported round rails. The pictures of those machines look attractive, but those rails are never stiff, and there is also no way to improve upon it.

If you search Aliexpress for "square rail 3020" you find a small machine that is built out of PVC plates and aluminum box sections. This may be a good beginners machine. It surely is not a "great" machine, but in that price range you always have to make severe compromises. It's also relatively easy to upgrade this machine by replacing the PVC plates with something stiffer. Sometimes I think about buying one just for fun and to see how usable it actually is. But overall, I already have a machine of approximately that size, and the biggest problem is that it's too small for me.

One of the best DIY machines on the internet is:
https://www.instructables.com/LOW-COST-DIY-500-CNC-MILL/

It's not the stiffest, nor has it the best accuracy, but it is a decent build for a small budget. It can of course be scaled to your own prefered size. The way it is built also has a big working area compared to its size (For example because the rails of the X-axis extends to beyond the vertical legs of the gantry. It also uses Aluminum box sections where they are advantageous, and simple plywood for the rest. It is a good machine for starters. If you want more stiffness, strengthening the gantry is probably one of the first modifications. Just screwing some aluminum or steel box or angle sections to it already helps. Gluing more wood to it also helps, especially if you make it a hollow box section. (with some internal plates). Another important upgrade are the locations the Y-ball spindle (under the table) connects to the front and rear plates. These plates can bend easily when the ball spindle pushes agaist it, and that needs some improvement. There are more upgrades you can do on that machine, but the important thing here is that all your hardware (rails, bearing blocks ball spindles, motors) are reusable. The things you upgrade are the easy to replace cheap parts. Also note that this machine is very similar to the "Sorotec Compact-line"
You probably can do light (and thus slow) milling of aluminum on this machine. And this enables you to make improved parts for this machine on itself. You could replace the wood parts with aluminium where needed (But there are smarter options, just bolting in some metal is an easy and affordable upgrade already).

With a small machine, clamping and tooling become a huge issue. You often have to clamp your work piece on the right location to be able to reach all parts of your work piece, and you also need room around your work piece to mount the clamping hardware. With a very small machine such as the Ali 3020 I mentioned earlier it's also difficult to impossible to make parts for the machine itself. With the 500EUR machine as shown on instructables, you can make improved parts for the machine on the machine itself, and clamping is a lot easier, You can for example place a decent sized vice on it.

The spindle motor you want to put on your CNC machine is another topic, which deserves a thread on it's own.

Yet another topic is the dust and noise machines like these create...
« Last Edit: June 04, 2024, 11:24:49 am by Doctorandus_P »
 


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