Effect of Forces on Gantry Cross-Sections?

[WandrinAndy]

Since this thread started, I've been thinking I got my machine drawings all wrong, and thinking about it day and night.

Blame it on Jazz... lol... It was he who got me questioning that my drawings were all wrong, although I thought I had roughly copied my gantry design from your gantry design.

But... I am extremely pleased that he sold me his simpler green design!

LOL and night night.

[WandrinAndy]

. . . For real meaningful Aluminium and steel work then all of them are not really up to it.!!

The trouble in my case is that my (human-oid) mind, although not (and maybe because of not) having any experience of this field, wants to understand at least the basic concepts of why some things are bad and others good.

Quite sure that I will get a massive buzz with the first proper movement of the cutting tool... maybe just scribing something... but the REAL joy for me is in learning new stuff and putting ideas together, albeit mostly cribbed from others!

My journey started with the intention of only machining wood, and then the idea evolved to...

- maybe it could also be used for at least accurately marking layouts on aluminium parts which would surely be better than marking them manually

- and maybe it could be used to machine aluminium parts like the guys on here have made for the next upgraded version of their machine, albeit at slow speeds and not to the greatest levels of accuracy

Don't think it will evolve further than that... certainly not on the initial machine.

[wilfy]

Depends which world you live in.? The theoretical or the real.!! . . . . . FFS wish folks would stop over complicating things.!!

Here's the real world deal.!! . . . Irving is absolutly correct that unless you can surface the two sides parallel and flat then you can't be 100% sure every things correct.! . . . BUT . . . This is true in one way or another for ALL the surfaces the rails mount onto whether they be 1 rail on top & 1 on front, or both on front etc and unless you can put these surfaces complete and assembled onto a milling machine and accurately machine all surfaces flat and parallel or perpendicular to each other then you are going to have to accept they will need some adjustment or tweaking.!!

How you do this will depend on the design But having the rails on 2 separate sections, no matter if that be profile, boxsection, ali plate will make very little difference and It's FACT that some shimming or filing or grinding will be needed to bring the rails into perfect alignment and parallelism either way.!

Now I'm not going to blow smoke up your arse's saying this is easy and quick because it's not and doing this takes patience and a lot of measuring and masses of time if you want good accuracy.!. . . BUT . . . If your just cutting wood,foam and bit of plastics then even box section will be close and with slight bit of clean up and shimming you'll be there in no time.!

I know it's hard if you haven't hands on experience of the forces cnc impart on frames and accuracy required but really for the application of mainly wood use then any of the designs shown here would be plenty strong enough.!! . . . For real meaningful Aluminium and steel work then all of them are not really up to it.!!

Don't fry your noddles trying to create the perfect flex free gantry for cutting woods etc because your just wasting braincells and time when it's not needed.!

thats a really great post and it goes someway to help people realise what they need. thank you :D