[RNation0001]

went and picked up some flat head bolts today and got the uprights partially put together heres some pics


got some more of my rod supports made

[dodger889]

On your up rights you might want to move them to end of your carriage (way from the side you are planning for the spindle to be) and add an end plate to give the a little more strength. Because you are trusting on the one piece of angle to keep it straight and not to flex.

A flat plate of 3/16 or 1/4 with 3 holes to lineup with the center holes(you have to tap them) in the bottom piece of 82/20 and at least two or more holes for bolts going up the up right piece should take care of any flex that you might see. I understand you are trying to build this as cheap as you can but it's going to cost you in the long run and having to do something twice cost more down the road. We all are trying to help you be happy when you are completed.

Here is a general rule of the thumb in design work "think triangle and arches for strength".

[RNation0001]

Its not just thesingle piece holding it. Ive also tapped the bottom of the vertical piece and drilled holes in the horizontal piece so there's three bolts going down as well as the 90 degree angle bracket. Then I'm also going to use a single 90 degree bracket on the studs that come up from the bearing truck to the vertical piece. I may also try to fab up a 1/2" bracket for each side but I cant slide it to the end due to the bolts going up thru the horizontal piece into the vertical piece.

Do u think that will b ok? It seems pretty sturdy

[PaulRowntree]

I'm with dodger889 on this one. The weight of the gantry is trying to twist the support off the rail, for no really good reason. Try to move the vertical section to over the rails, then support the vertical post down to the side of the horizontal block for strength. You may gain some cutting area for free. If you need an extra plate to carry the drive nut, that is ok ... for most accelerations and cutting conditions the weight of the gantry is greater than the force on the nut.

[dodger889]

Hope this makes better since of what I.m talking about. The Green is the plate the red is to show where the holes are. the blue are the holes.

[RNation0001]

ok guys how bout this , i dont wanna move the uprights to the edge because then the bolts i have going thru the horizontal into the vertical wouldnt line up, so how bout a comprimise what do you think about this?? half in aluminum brackets

[RNation0001]

heres the reason i cant move it to the edge

[PaulRowntree]

I like the fully bracketed support, no matter where you end up doing the upright attachment. Three vertical bolts in a line don't do much for the side-to-side forces; without the angles you are counting on the square edge to keep it all plumb.

Two ways I can see to move it to the edge.
1) Make the horizontal piece longer, move the two bearing blocks farther apart, and put the vertical bolts in between. Wider stance is more stable, you win all around, if you have the space.
2) Put a footing plate under the upright with 3 sides of angle support, another plate over the blocks, and tie them together with a round of bolts and a tall vertical joint plate on the side of the extrusion nearest the edge. If the joint plate was as wide as the horizontal piece at the bottom and tapered in at the top you would have some very seriously strong triangulation to fight forward/backwards tipping forces, much stronger than just 1" angle at the bottom. More pieces to make, but it would be solid as a brick outhouse.

Cheers!

[dodger889]

If you are following your original plans. Then those would help. Here is what I'm looking at that you will be beyond the bearing surface with your spindle. That will add to the flex of the gantry over all. Take a look at the way professional tables are built. There is a reason that they build them that way. Even better yet look at guys on here building their second or third machine at what they are doing.


Here is something we all have been trying to get you to understand. Every point of flex no matter how small it is adds up to a poor quality of machine. You are thinking that oh that is a thousandth here or hundredth there but they multiply by twice or there time has much in the end. Then you go to cut a project out and you get shadowing in that project or the surface is not flat and smooth. And then you spend days chasing a problem. That was built into the machine. Which could have been avoided just by simple little changes.

[RNation0001]

I'm confused Lol. Yay or nay on the 1/2" brackets?

[RNation0001]

If you are following your original plans. Then those would help. Here is what I'm looking at that you will be beyond the bearing surface with your spindle. That will add to the flex of the gantry over all. Take a look at the way professional tables are built. There is a reason that they build them that way. Even better yet look at guys on here building their second or third machine at what they are doing.


Here is something we all have been trying to get you to understand. Every point of flex no matter how small it is adds up to a poor quality of machine. You are thinking that oh that is a thousandth here or hundredth there but they multiply by twice or there time has much in the end. Then you go to cut a project out and you get shadowing in that project or the surface is not flat and smooth. And then you spend days chasing a problem. That was built into the machine. Which could have been avoided just by simple little changes.

lol excuse my ignorance but what u mean by that you will be beyond the bearing surface with your spindle?

[RNation0001]

heres a quick render of the changes so far

[dodger889]

lol excuse my ignorance but what u mean by that you will be beyond the bearing surface with your spindle?

By the time you mount a spindle to your x axis . You will beyond the bearing that supports the gantry. Now this is sorta using the norm for mount the z axis. But you have a trick or two up your sleeve that I do not see.

Here is an example of what I mean. Your spindle is going to be outside of the bearings as it is set up in the Y axis. Where it should fall inline with or in between the bearings on Y axis. Now if you wish I could draw you a picture.

[RNation0001]

I think I see what ur saying. Basically that the spindle will b in front of where the bearings will b? ? I didn't realize that was a big problem. But now that u mention it I could c how it would b.

[louieatienza]

I think I see what ur saying. Basically that the spindle will b in front of where the bearings will b? ? I didn't realize that was a big problem. But now that u mention it I could c how it would b.

It might be OK of the CG of your gantry falls between the two bearing blocks (with the spindle attached.) But the closer the spindle to the gantry and the wider the spacing between the bearing blocks, the less the 'levering' effect would be...

[RNation0001]

well got some progress today, went to my fathers work and played with there multicam 3000 cnc, cut out my table, and drilled all the holes for the rail supports, and acme supports. was a neat experience as ive never messed with a cnc in person before. however all my tool paths worked out good. now just gotta build a base, the base pic is just reference i plan on making it much more sturdy than the pic

[RNation0001]

heres some renderings of some of the gantry brackets ill b using

[RNation0001]

got a little progress done, working on the gantry uprights trying to make sure there as stiff as possible.


ignore the off center holes i was using a scrap piece of aluminum. then right before i drilled the holes in the bottom i realized it was around .68 inches thick instead of .5 like i thought so i offset the drilled holes to one side since there will b about .20 hanging off the edge, cut it out milled it flat and drilled it to .315 and ready for some carriage bolts and the gantry uprights should be pretty darn stiff. now just gotta figrue out what to do to make the gantry span as stiff as possible. any ideas there?

[dodger889]

Use the support like your rendering. 1/4 inch should be find. I would try to get down as close to the bottom that you just made and go out has far as you can without causing interference of the z axis or about 6 inches.

[RNation0001]

so.....gets points for that...

Huh???? Lol