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

[JAZZCNC]

Wouldn't have the bottom rail that way around personally due to cutting forces and way it doesn't support the front plate. Personally would have top & bottom.
Also I wouldn't make the Y axis wrap around the gantry like that. It doesn't add hardly any strength makes the whole Y axis heavier than needed lowering accelration and increasing inertia plus it makes building harder because unless the Ends are perfectly 90deg they twist and bind the bearings.

Also rather than having the gantry cross beam central to the bearing try offsetting it back a little to allow for Z axis and spindle balancing the centre of Gravity better.

[EddyCurrent]

The bearing blocks look too close together in the vertical direction to me.

[grain_r]

Hey JazzCNC thanks very much indeed for that it sounds like I'm on the right track now, I did think about top and bottom but thought this might split the forces between up and down and back and forwards although doing it this way I guess the loads are on a single rail more for each movement. So will do I will go top and bottom which will be great to get rid of some of the material around the back. I didn't really want it there but it was the only way I could think off to get the rail around the rear to also try and keep it out of harms way too.

I am really sorry when you say move the rails back do you mean so that the spindle is inline with the upright box section of the gantry ? would it maybe worth going for something like 100x50mm box section for the sides and then put the 50x50 towards the rear to the spindle so it is more inline with the uprights of the gantry, I'm sorry if I've misunderstood.
Also on a side note I would like to thanks you very much for helping so many people on this community I have learned so much from you going through many peoples posts and its great to see people just trying to help each other out.

Also EddyCurrent the same goes for you going through peoples posts you are very helpful I just hope that I can get a machine running to be able to get the knowledge to put something back in.
Don't worry I'm not always a soppy sod.
I thought I might have the blocks a little too close but just picked the figure out of the air really for the distance. Is there an optimum or a way of determining the best gap ?. like most I was trying to maximize the cutting depth but because the bed moves I will add some more distance on it and just move the bed on each time I have a thought to making some fiberglass molds with foam for a dash board and though the more depth the better but I guess it will give a worse cut for other things I will have another go at it and go more in depth on the design now I know where I'm going with it all.

thanks chaps.

Rob

[JAZZCNC]

I am really sorry when you say move the rails back do you mean so that the spindle is inline with the upright box section of the gantry ? would it maybe worth going for something like 100x50mm box section for the sides and then put the 50x50 towards the rear to the spindle so it is more inline with the uprights of the gantry, I'm sorry if I've misunderstood.

No was meaning offset back something like this for better centre of gravity and balanced bearing loads while cutting.

Regards bearing distance then I work on Half the travel required.!

[grain_r]

Oh I see. great thanks I like that. So that I might save a little welding heat is there anything to stop me mounting the screw on the base of the box section although It won't be in the centre or is it best to put some uprights in and then mount to that ?

Thanks
Rob

[grain_r]

I have been working on the updates and getting there now because I intend to make it my build log I thought I would keep updating with work in progress for my designs so people can see for the future . I'm getting pretty happy with the design now it seems to feel much better and thanks to you guys I am learning so much with each design change.

I am having a problem with the X axis I want to use one motor as people have suggested in the past because of Binding and using belts but I cant think of an easy way without using quite a few wheels to send it around the frame if I go directly across It would hinder the work pieces if they hang over the edge.



Any comments would be most welcome. I havn't put the cable trays or the front axis as yet thats being done at the moment.

Thanks

Rob

[njhussey]

I know it's a bit more expense but why don't you make the Y axis rails longer and have the bearings spaced further apart on the top and botom rails? It would give you a stiffer machine and looks like the space isn't needed for cuting as you're rails are shorter than the Y axis already. Eddycurrent hinted at this in a previous post I think.

[EddyCurrent]

For some reason I don't like the look of the box section as brackets for X ball nuts.
You seem to be loosing a fair amount of travel in Y direction by having short rails and ball screw.
Think about how you will access grease nipple on Z ball nut once it's all assembled.
Will you put adjustable feet on the frame legs for uneven floors ?
Can't see how you will adjust belt tension for the stepper motors shown.