Aluminum router build - Could use some input

[Washout]

If you are using ali extrusion for your frame then you may be able to get some ideas from my build here: http://www.mycncuk.com/threads/5139-It-s-begun
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Some caveats though - my machine is compromised by using the round supported rails. Its not useless by any means, but not as good as using profiled guides/rails and bearings (especially on the Z and Y axis). I think your rails should also be mounted differently (especially X axis).
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Most guys on here also go for a welded steel frame, as it is cheaper, generally stronger, but of course you may not have someone who can weld it for you (I also did not at the time).
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Oh also consider using twin X axis ballscrews (one on each side).
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I'm sure you get tons of advice and best of luck with the build.

[Tumblebeer]

Thanks for the feedback, much appreciated!

I'd like to be able to mill aluminum, otherwise I'd feel like I failed. The building materials I'm using can handle alu at the precision I'm happy with, as Washout clearly shows in his build videos. It's up to me to make sure it does.

As for the FEA, I'm not really looking at the numbers at this point. I know I've made too many simplifications and false assumtions for that. It was mostly there to get a visual feel of where the weaknesses were.

I've redone large parts of the construction, trying to listen to the advice routercnc gave me. I've also taken some inspiration from Washouts machine.
What kind of precision are you getting with yours when milling alu?
Also, what kind of problems are the round rails giving you? Chatter, instability, binding?

It's out of my league working with steel I think, even alu is stretching it.

I've uploaded another album with some pics of my revised build.
http://imgur.com/a/pM3GU

It was done in a bit of a hurry, I have to admit.
What do you think? Did I improve it? Have I missed anything, apart from the obvious mounting of the ballscrew supports on the y-axis?

[Washout]

Here's the last issue I sorted out on my machine: http://www.mycncuk.com/threads/7420-...ith-my-machine
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Some profile rails rather than round rails sorted that on the Y axis. I will likely upgrade the z axis as well at some point and Jazz pointed on my thread, profile rails are a lot better than round due to better resistance to play.
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I didn't have many issues with alignment/binding once I had taken the time to do it properly. I did have a job drilling the ballscrew holes off centre on the left hand corner posts, through the extrusions, but luckily the holes were not critical in diameter and I oversized them so I had some adjustment room when aligning the ballscrews.
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Repeatability is good on my machine and on a part I am milling, which has 56 identical pockets on it, each pocket was within 0.02-0.04mm of each other dimensionally.
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At the risk of "I told you so" from Robin and a debate about capabilities ;) , I am happy with the machine for wood, plastics and ali work. However, there are limitations in using >8mm cutters due to general rigidity and although I have cut 1mm slots accidentally through some holding steel washers, I am planning to buy a commercial milling machine (Warco GH) to convert to CNC and do steel and other harder materials. So I would think carefully about how much ali and metals you want to cut generally as a milling machine conversion maybe better (although you will need custom brackets etc made up, which needs CNC to start with).
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Best of luck with your design and I'm sure others more in the know will give finer advice on your design, which looks much better to my layman's eyes than your first.
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Cheers
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Chris

[routercnc]

To help you get more feedback I've dropped a screengrab from your site into this post - hope this is OK.

Here is your version 1:


Here is your version 2:


If you are keen to stay with supported rails and aluminium extrusion then this is a pretty good layout, and much better than the first one. My view is that you will be able to cut wood easily and accurately, and the occasional bit of aluminium.

But if you end up doing a lot of aluminium then you will find that this machine is not enough. An upgrade to profile linear rails on at least Y and Z is recommended, the gantry sections are too small and not joined to each other (e.g at least a plate over the back), and the X axis stepper motors are mounted off long brackets.

With the layout you have now I would look at moving the X ballscrews outwards and down, level with the supported rails. Then extend the small horizontal plate which the gantry sits outwards and screw the ballnut to the underside of it. There are other variations but you get the idea. This will enable you to mount the motors nearer to the frame, effectively stiffening the X direction when cutting. If this is too big a change then at least make the small plates on the outside much bigger and triangulate up to the motor position.

[Tumblebeer]

I'm pretty much convinced that I should switch to profile rails instead. I guess 15mm should be enough?
Something along the lines of: http://www.aliexpress.com/item/China...489001007.html or http://www.aliexpress.com/item/6-x-H...934543282.html

What should I consider when switching to square rail? Can I mount the rail straight to the extrusion t-slot? Any special considerations?

[JAZZCNC]

What should I consider when switching to square rail? Can I mount the rail straight to the extrusion t-slot? Any special considerations?

If mounting directly on profile then you'll need 20mm because 15mm won't span the slot properly. To be honest 20mm are not much more money and they also give other advantages due to there bearings being slightly higher and giving more support. This esp true when you come to build the Z axis.!

[routercnc]

For info a number of us have bought profile linear rails from 'fa-system' on ebay. They are used but the ones I bought still had plenty of life in them and have been running for a few years without problems. You'll have to cost it all up and make a choice.

Here's an example . . .

http://www.ebay.co.uk/itm/THK-SSR20-...ht_1899wt_1006

[Tumblebeer]

http://imgur.com/a/kszzz

There we go, third iteration. I've switched to square rails, 20mm. The frame is now a mix of 60x60mm and 80x80mm alu profiles. The alu plates are 20mm, except for the backpiece spanning the gantry, that one is 10mm.

The steppers should be more securely mounted, the gantry should be stiffer and hopefully I think it might be slightly easier to assemble.

What do you think? For some reason it just looks "wrong" to me, can't really put my finger on it.

[Tumblebeer]

Made some smaller adjustments, mostly cosmetic, but should have made it slightly more stable as well. Especially the table.

http://imgur.com/a/zyBVw

Any input is most welcome, I'm about to start ordering parts unless someone has any objections and/or improvements...