A brand new machine build. 2x4 size or something in that region. :)

[AdCNC]

Jazz! Lol will do matey I've been promising you some pics for donkeys now time i pulled me finger out.

[AdCNC]

In wonder if you didn't have anyone to do your machining for you then i could perhaps work something out with you.

[Web Goblin]

If you are worried about any twisting forces you can weld some stiffeners ( viagra as they are called ) inside the "c" section of the beam as Jazz says. This will stiffen it up nicely.

[IN-WondeR]

AdCNC

Got it... Will make the change as soon as I get the program started up again.. :)

[IN-WondeR]

AdCNC

Hmmm, I'm not sure having you doing my machining will be a cheap thing. I live in Denmark, so it's a bit of shipping back and forth... :P

Web Goblin
Yeah, I have thought of adding som braces to the back of the UNP profil. There's enough room for it..

[AdCNC]

Lol lets rule that one out then haha

[Web Goblin]

Dont you deliver Ad?

[AdCNC]

I can do yeh but it would cost a fair bit for a bit that weight, all for it tho.

[Jonathan]

Also Jonathan I know you have FEA software so if you have the time run realistic loads through and see what you get.

Ok, I've done a very quick simulation as I don't think it adds much to the discussion since I'm only comparing the stiffness of sections for which the equations are already well documented. Granted the rails add a bit of stiffness, but it's not that great in the whole scheme of things.



That's run with a 20N force, so nothing serious, at 200mm from the bottom of the gantry. Deflection at this distance (i.e. the tool) is 8.3um for channel and 1.5um for box section.

Before everyone starts pointing out flaws - this model is just a quick simulation to demonstrate the principle, not the exact machine, except for the UNP160 dimensions which I got here, so the exact numbers are not important. What's important is to note that just using the same size RHS made the deflection over 5 times less than with UNP160. This model assumes the ends are perfectly rigidly fixed, so in reality it will be worse.

The rails are already mounted on top of a welded on piece of steel, which will be machined flat to true up the rails.
A Datum edge, is that a straight edge I can mount one rail along, so it will be true to the surface of the machine?

Partly that, but also to help mount the rails straight and parallel.

[JAZZCNC]

What's important is to note that just using the same size RHS made the deflection over 5 times less than with UNP160. This model assumes the ends are perfectly rigidly fixed, so in reality it will be worse.

Ok then now do it agian with 2 Viagra braces has Web goblin calls them equally spaced and see what happens.?