Eyeballs and comments sought for noob build

[Tom J]

Thanks for that. I'm a little concerned that a belt that long will introduce other issues, so will see what to do about that. Will attempt to alter the z axis for a belt drive. I don't suppose it should be too difficult.

use good quality gates HDT 15mm braided one - there will be flex which shouldn't give you error bigger than 0.02mm (I referring here to my steel machine which was 115kg)

[danilius]

Food for thought. Thanks! Time to get back to drawing :-)

use good quality gates HDT 15mm braided one - there will be flex which shouldn't give you error bigger than 0.02mm (I referring here to my steel machine which was 115kg)

[paulus.v]

Hi,

Connecting the gantry at the bottom will give little benefits but, by moving the legs far apart, the base will be a lot weaker.

Why would you put the X rails "hanging"? Only for dust/swarf protection? The side plates extension for guide blocks will deflect a lot and put pressure on the rails/blocks trying to twist them. I don't think it's worth it.

The gantry side plates are beefy but only when looking from one direction. If you cut out one third longitudinally and bolt it perpendicular you will have more rigidity in the Y direction without any loss or weight gain. And you can connect to your t-slot profile overhang.

[danilius]

OK, I think I have understood all this correctly. So, I'll move the rails up top, and stiffen up the gantry walls.

[danilius]

So, I have made some changes. I wasn't convinced that the extrusion on the gantry was going to be rigid, so that has been dropped in favour of some solid lumps of metal. It is also much shorter, and the rails have been moved up to the top.





What I'm wondering is if there is an optimum distance between carriages for the gantry.



I dont have any worksop equipment beyond the basic tools, so don't want to drill into the extrusions or anything, but I'm getting a bit lathered about the hseer size of the machine, given that it's only going to have a work area of 600 x 900. Currently the overall dimensions are roughly 1400mm x 940mm. I can trim a small amount off the length, but is there any way of getting this more compact?

[paulus.v]

Whydon't you put the horizontal plate of the X axis carriages under the gantry side plates. You will have a lot of unnecessary weight removed and by putting the ball nut support under the same plate you can shorten the ballscrew and the main frame (to the length of the rails). The gantry will slide above the ballscrew end blocks. It is also a good point to put the ballscrews closer to the working surface/plane.

I think you need a plate at the back of the gantry to crate a box. Even a thinner plate will increase rigidity.

What I'm wondering is if there is an optimum distance between carriages for the gantry.

I don't think there is an optimum distance... The 20cm that you have in your project looks good to me. But I'm not an expert.

[Boyan Silyavski]

If you are using Hiwin 20 long blocks/ or even short/ , 200mm between both ends from outside measured is good for your machine. 260mm is desirable for serious build and i would say ideal, and 300mm for OTT and heavy gantry and really strong and large machine. So basically with Hiwin long blocks they will be almost touching each other .

The idea is the bit to be in that distance , looked from side. In other words the spindle overhang. But on a machine like yours even if not, its not a big deal, as bearings are much more rated than forces involved.

[danilius]

Took me a minute to figure out what you meant, but that's going to be the next change! Thanks.

Whydon't you put the horizontal plate of the X axis carriages under the gantry side plates. You will have a lot of unnecessary weight removed and by putting the ball nut support under the same plate you can shorten the ballscrew and the main frame (to the length of the rails). The gantry will slide above the ballscrew end blocks. It is also a good point to put the ballscrews closer to the working surface/plane.

I think you need a plate at the back of the gantry to crate a box. Even a thinner plate will increase rigidity.


I don't think there is an optimum distance... The 20cm that you have in your project looks good to me. But I'm not an expert.