a Steel Box Section Build with SBR20 & Ballscrews Plus a few questions

[irving2008]

You don't need cross bracing at the ends, a single diagonal will suffice, run it in the opposite direction at the far end. One in the middle might be beneficial too.

[grain_r]

Hey Irving2008 great thanks for that. I have made the change I haven't as yet put the middle support in, which I'm guessing that you mean through the centre of the base ?



that will be handy too im so close to being able to use x3 7.5 metre lengths so hopefully if I don't mess up cuts and welds I might get away with it. (So we all know I wont and will need more )

I'm leaning more to the timing belt option because it give me more options on configuration but I'm not sure How I will do that as yet.

Thanks very much for the advice so far it is really appreciated.

Thanks

Rob

[Clive S]

If you put a brace in the centre you lose the ability to have a movable bed. ..Clive

[JAZZCNC]

There's loads you could shave off this structure most those bits at the bottom are not needed. Something along the lines of this but narrowed down will work. You'll use less steel and still be plenty strong.

[grain_r]

Hey Jazz
Thanks for the design, so if the parts missing at the bottom it doesn't get any-more twist of the table when in use ? or is the sheeting around it structural and stops this. I love the slider system I have been thinking that it would be not the easiest to lift the bed and get the bolts in, I imagine its just watch your fingers time as you take the last bolt out. your design is very much more evolved most certainly. and I love that there is space still underneath, Would you mind if I use your example I feel bad not making the design myself although I will change it to suit.

I'm sorry to ask so many questions but on the bracing does this have to be specific dimensions e.g. a true triangle for the strength like 45 degrees or just has to look correct. i'm not sure how easy it would be to make it belt driven the only think I can think of is to put the motor on the bottom of the bed and then use a pretty long belt in a 'v' shaping. I see the gantry uses ali extrusion I imagine I would still be better to use the box section for my design.

Thanks very much for the help.

Thanks

Rob

[grain_r]

Hello Again everyone
I have been designing again and hopefully getting somewhere now thanks to the guidance from you guys. I'm not sure whether to go above the top rail and build up or if it is better to build downwards towards the table my thinking it that the strength of the side will help a little if it is below ? although I will have to shim with something to get a gap from the main frame. or would the gains (If any) really be worth it and just build on top?

[EddyCurrent]

If you are using round rail on the gantry I can't help thinking it's best to have one on the top surface rather than both on the front.
You need to draw the ball screws and motor mounts in place before thinking it's done.

[JAZZCNC]

Sorry to say this but that's a dreadful design. The gantry hanging down like that is acting as a lever and with no support at the ends it will resonate like crazy, this will show in the finish quality.
You need the Gantry supported at the ends connected directly to the sliding carriages.