Second CNC table build, here we go again....

[Davek0974]

I find the thinner wall box to be pretty straight usually, especially down in the 2-3mm section.

I have belts on my existing table and they cause issues, not solely down to the belts but as 90+% of commercial builds use rack, I am going that way first this time.

[Davek0974]

Reality check time...


How do you decide what table is the right one?


I know the 2'x2' i have now is too small, it works ok for most of my jobs but i can only cut with the plate square on the bed so no quick twisting it to get another cut out etc.


I can physically fit the 4'x4' (1250x1250) into my shop, thats ok.


I cannot lift a sheet of steel that size, have little possibility of lifting gear etc. as its only a double garage. A sheet of 3mm which is my most popular is about 36kg so only just about ok but the other one i use a fair bit of is 4mm and would be 50kg, no way i can lift that.


Would it be better to go 3'x3' instead?


Cost difference in build is minimal, but what makes sense - having the real estate and not using it or saving floor space etc??

[Davek0974]

View from front looking at current gantry design.



This is for the open-bed style table with the longer gantry arms. The linear guides can be easily covered from the top.

The gantry beam will pass through the side support plates and be welded up and gusseted inside with some nicely cut parts, the outer face of the vertical supports can be strengthened with a couple of ribs to resist side-sway.

Mounting the support rails is harder on the open bed style though, I was going to bolt them on but this style really wants a box frame at bed level.

[Robin Hewitt]

Every action has an equal and opposite reaction. If you apply 300N accelerating force to the cutting head, the gantry will push sideways with 300N.

[Davek0974]

Yes I can remember that from school ;)

But those 300N can be countered by applying gusset plates and ribs where needed, most tend to throw a slab of alu at it but that might not be totally needed i think.

[Robin Hewitt]

Or you could move the rails up closer to the gantry they support. The gantry only needs to be 2" above the bed, doesn't it?

[Davek0974]

In theory yes but my Z-axis needs a bit of clearance as its a pretty heavy built unit. I am trunk not to lift the rails - that was design idea one, but it means you do not have a clear open bed - you have rails either side which makes loading harder especially if juggling a bigger sheet on your own.

My high-rail option is sketched out earlier, it had no risers at all on the gantry - the beam was right down on the carriages.

[Davek0974]

Or you could move the rails up closer to the gantry they support. The gantry only needs to be 2" above the bed, doesn't it?

To add scale to my poor sketches, the bottom of the gantry beam is 140mm above the bed surface, not too bad??