Thread: sliding gantry or sliding Base ?
Thanks for your answer Jonathan,
i'd rather spend a little more money for a sturdy machine, than being dissapointed afterwards, so that wont be a problem for me to justify a little more money.
I am not sure about the steel box section, i could only bolt them together, because I dont think I can weld good enough so that it wont distort and warp in every direction :)
Whats your opinion on that ?
If you look in my gallery you will see i am using box section in my latest build, Like you i was worried about warp, a friend of mine who has been welding for years (surgical instruments) helped me, i made up a Jig with angle iron and used a single tack on all joint faces and from there i built up the joints gradually on each side untill i was finished, there was no measurable warpage. as long as the two pieces to be welded are held clamped in the Jig and you are in no hurry i dont see it as a problem.. and it taught me how to get some great mig welds as well...
RickAlways bear in mind that your own resolution to succeed is more important than any other - Abe Lincoln
Have you considered epoxy?
I can weld decently enough, I studied it at college and my cousin is a crazily skilled welder with 25 years experience but I'm still going to use a mix of bolts and epoxy when I build my machine because I think it is a better fit for the task. 3M's DP range of epoxies are used to hold airplane wings on and by BMW/Lotus for car chassis and a well done epoxy join will outperform a poorly done weld.
DP-420 3M EPOXY overlap shear test by Doctorbass PART 1 - YouTube
I am still not sure about the steel box section yet, because when making a rectangular frame out of box section, the areas of the 4 sections touching each other, are rather small, i am not sure if the epoxy would be strong enough when the contact area is so small.
Nevertheless, i got round making a first design of the gantry it self, the Z Axis is just thrown together as of now, i dont like it either :)
I used 40x40 Aluminum Profiles, the "Spindle Base" is a 20mm Aluminum Plate.
The other plate is also 20mm Aluminum.
All Components used are from zapp, Y and Z are SFU16 Ballscrews with 5mm pitch, the rails are TBR20.
The big Profiles are 120x40 both.
I had the design in mind, that was chosen as the most rigid one in the "heavy duty design" paper, regarding the orientation of profiles,
as well as the orientation of the Y axis Rails.
The Assembly, as pictured, weighs in at 38kg right now, without stepper motors, only the parts you see.
For the profiles i would use ITEM profiles, as I know them well, because we design dust covers for our products using them at work.
I would use the heaviest option of profiles, ITEM has to offer.
Further plan would be to space the gantry up, as far as necessary to reach the workpiece height i desire, by using another two 120x40 each side, reinforce it by 45 degree pieces inwards, little bit restricting the workspace, but obviously useful.
And then creating a base, either chunky 60x180 Alu Profiles, or as mentioned, steel box section,
just rectangular , reinforced by 45 degree pieces and cross beams, with two TBR20 Rails and one Ballscrew for the X Table.
What do you think ?
Back to the fixed/moving gantry question for a mo'...
If you have something solid to bolt the machine down to I would suggest fix the gantry.
If the machine simply rests on something solid I don't think there is much advantage either way.
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