Aluminium profile CNC

**routercnc** · 08-11-2017

Whether you can use the plate you already have for the gantry sides really depends on how flat and straight it is. If it is not flat enough you will put some kind of loading in the X axis carriages and they may bind or at least have a shorter life.

If you have the plate already then try lightly clamping it in place and see if the carriages move freely. Maybe you can get away with a bit of shimming.

Ideally I would go for the tooling plate myself as it is not much more than the regular plate and is much, much flatter.

One of the earlier questions was 'is tooling plate a type of T6?'. My understanding of the types aluminium goes as follows-

Aluminium 1000 grade (1xxx)
This is good for bending into shapes and is usually what the thin stuff if made from. But it is a fairly pure aluminium (99.5%) and likes to weld itself to the cutter, so flood or heavy spray coolant is required. Plus I have been recommended by experienced machinists to use carbide cutters.

Aluminium 6000 grade (6xxx)
This good for machining, and is what the general purpose thicker stuff is made from. It is only 97.9% aluminium with the rest coming from various beneficial ingredients.
Of the 6000 series you will often see 6061, which is a specific and popular product from that range.
Of the 6000 series (and maybe others as well?), -T6 (e.g. 6061-T6) refers to the product being heat treated and aged, which improves the material properties. Again this is a popular choice.

There are other grades, 2000, 3000, 4000, 5000 (good for corrosion e.g. marine use), 7000 (stronger), 8000. I've not knowingly used these other grades and have certainly not ordered them for workshop use.

Eco-cast / tooling plate / mic-6
Happy to be corrected but tooling plate / ecocast / mic-6 are the same basic thing to my mind - machined fairly flat and good to use as-is for DIY CNC machine.

So in short, for main construction go for 6061-T6 to get the machinability and other properties you need, and where flatness is important go for the ecocast/tooling plate/mic-6 versions of this grade which have been machined flat for you.

Hope this helps, and if anyone can add to this or correct me etc. please do.

p.s. Having a peak at Wikipedia to see what they say about it all gives a whole lot more info and here is the link if you are brave enough:
https://en.wikipedia.org/wiki/Aluminium_alloy

**BriceO** · 16-11-2017

Hi,

It's clearer now, really nice! I finally found locally a plate 20mm, but this is grade 5083. (500x500mm is 182.- with the cut.)
Here is the specs: height tolerance: +/-0,1 mm, flatness tolerance max. 0,15 mm/m

I have made several changes on my design according to your advice. I'm trying to find the best way to mount the rails.

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In this configuration, the block is on top of the extrusion. Will it be stiffer?

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In this arrangement, it will be easier to mount as the space between the block and the plate is the same size as my aluminium height (20mm).

Which one do you think is the best? (The first image has the y axis a little bit lower)

Thanks again for your help :)

**Nr1madman** · 17-11-2017

In both scenarios you need a way to adjust the width of the gantry as you will be "trapping" either the ballnut or both ballnut and linear bearings.

If you have the rail on top it can be adjusted sideways in the screwdown moment.

For the ballnut you can mount it like that if you shim it..

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**routercnc** · 19-11-2017

Top one will most likely be stiffer as you are not bending the gantry sides. Limiting factor is the gauge of the extrusions on the bed sides. If space and access to the bed at each end allows you can plate over the ends to join them to each other.

**BriceO** · 20-11-2017

I'll go for the top one so, I wasn't thinking that it could have any bending problem, thanks.

Limiting factor is the gauge of the extrusions on the bed sides.

I'm not sure to understand it. Do you mean the extrusion is it too high?

Good idea for the end plat, do you think 5mm aluminium is enough to do it?

I found this documentation about hiwin rails : http://www.hiwin.com/pdf/linear_guideways.pdf
It can be interesting for someone. Is it a good choice to have a HGW (wide flange carriage) could be a good choice for the Y axis for example? And HGH for X and Z axis.

Any advice higly appreciated.

**routercnc** · 20-11-2017

Originally Posted by BriceO

I'll go for the top one so, I wasn't thinking that it could have any bending problem, thanks.

I'm not sure to understand it. Do you mean the extrusion is it too high?

Good idea for the end plat, do you think 5mm aluminium is enough to do it?

I found this documentation about hiwin rails : http://www.hiwin.com/pdf/linear_guideways.pdf
It can be interesting for someone. Is it a good choice to have a HGW (wide flange carriage) could be a good choice for the Y axis for example? And HGH for X and Z axis.

Any advice higly appreciated.

The extrusion is not too high all I wanted to point out was that using extrusion, especially thin wall (gauge) extrusion, will be the limiting factor for the stiffness. The wall is thin, and it essentially has lots of deep slots cut in it. Imagine pressing sideways where the gantry rail is situated, and imagine how it will want to bend and vibrate.

Lost of people use steel box section instead as it is much stiffer, with a continuous outer section, usually with a high wall thickness (to allow thread tapping), and it is cheaper.

End plates of 5mm will be fine as shear panels don't need to be massively thick to be effective, but it will limit feed in / out access if that is a consideration.

Hiwin carriages - either wide or narrow are both fine. Use wide if that gives a better footprint and mounting for your design.

**BriceO** · 20-11-2017

Thanks, is it the same problem for the Y axis?

Should I place the rails on top and bottom or is it fine?

To be honest, I can't really imagine how it will bend and vibrate. I was thinking that the weight/force is supported by all the length of the extrusion.