[shoot]

Well folks i thought id start a build log for what will be my second machine.

This one hopefully will be up to cutting aluminium and plastics.

It,ll be useing nema 23 420 oz motors

70 volt drivers.

2005 ball screws on the x and y axis,1605 on the z,belts n pulleys.

20mm thk rail on the x and y and 15 mm on the z.

2.2 water cooled spindle.

20mm aluminium plate for z axis,stepper mounts,and x axis bed.

Theres a bit to come off the height of the gantry when i figure it out,the y axis box section will bolt onto flange plates .they,ll also be a bit more box section added to the frame to stiffen things up.

Its all subject to change at the minute ,the 200x100 mm box for the y is in bad shape deformed both sides,,thoughts are to weld a peice of halff inch plate to the face of it and get it surfaced if need be,im also looking into self levelling resins,but the latter seems a mine feild,.. which to go for?

hopefully i,ll get a stat on the welding at the weekend,cheers.

[DonFrambach]

Very interesting. Please keep posting pictures!!

[shoot]

Stick weldings not my strong point but I managed to get started on the frame.
The right hand side of the gantry has moved a little so i,ll be spending some time tommorrow unpicking the welding to put that right
The opening in the face of the y section i had to cut out with a jig saw,needs evening up a little,,i will also be welding some 50mm x 10mm bar around the face of the y section to cater for the profile rail the face of the box section wasnt suitable as is.
when thats done theres a nice chap local to me whos going to skim it all level on a grinding machine for the sum of £20,happy days:cheers:

[RotarySMP]

Good looking design.

[shoot]

Thanks,i cant take credit for the design, theres a few about built this way,and ive pretty much mirrored one machine in particular minus the y-screw arrangement which will be inside the box section, its simple and rigid

[shoot]

i could,nt see an edit button to add these but the y axis is almost finished,managed to weld(in a fashion)the 10 be 50 strips to the face of the y axis then got that all skimmed down ready for the rail..:cheers:.edited other photos didnt upload

[RotarySMP]

Do you have anyone with a furnace who could stress relieve the whole thing before you start milling/ scraping for alignment?

[shoot]

i dont mark,i am wishing though that id just had two slots ground in for the 20mm rail..,it was suggested to me a while back and went in one ear and out the other:/ as everythings here now i should have the thing up and moving in 2 or 3 weeks.

[RotarySMP]

You are making great progress. What controller will power the motors?

[louieatienza]

i could,nt see an edit button to add these but the y axis is almost finished,managed to weld(in a fashion)the 10 be 50 strips to the face of the y axis then got that all skimmed down ready for the rail..:cheers:.edited other photos didnt upload

Those welds look good to me! Looks great!


BTW to add pictures after clicking edit, use go advanced under the text window....

[shoot]

thanks louie,i think the problem was the edit button expires after a time period so you can no longer edit.

rotary im using mach 3 i,ve made a little progress over the weekend and will post updates in the next couple of days

[dmalicky]

Very nice work! If you want more rigidity for cutting aluminum, I'd suggest closing up the slot in the gantry tube. For x loads at the tool, the gantry is put in torsion, and a fully closed section makes a huge difference for torsional stiffness (polar moment of inertia, J). For example, roll a piece of paper into a tube, then twist it -- no resistance. Then tape the seam -- stiff. Yeah, sorry for the late info! Here's a way to "tape that seam" (close the cross-section) while still keeping your slot and y-screw configuration inside the gantry tube: weld a hefty C-channel to the inside of the tube, so the slot is bridged by the channel. If you could find a channel that ~just bridges the slot, the welding could be easily done from the outside. That size may not exist; alternately, weld up a custom sized channel from flat stock. Ideally, the legs of the channel would be short, just enough to squeeze the acme nut in there.

Also for stiffness, and to minimize post-weld distortion over time, I would add a pair of ~45 degree diagonal members from the gantry/uprights down to the main frame. With only the uprights, any relaxation in the weld beads at their base will pull the gantry fore/aft by quite a bit. A pair of diagonal braces would fix most of that, and add a lot of fore/aft stiffness.

[louieatienza]

Very nice work! If you want more rigidity for cutting aluminum, I'd suggest closing up the slot in the gantry tube. For x loads at the tool, the gantry is put in torsion, and a fully closed section makes a huge difference for torsional stiffness (polar moment of inertia, J). For example, roll a piece of paper into a tube, then twist it -- no resistance. Then tape the seam -- stiff. Yeah, sorry for the late info! Here's a way to "tape that seam" (close the cross-section) while still keeping your slot and y-screw configuration inside the gantry tube: weld a hefty C-channel to the inside of the tube, so the slot is bridged by the channel. If you could find a channel that ~just bridges the slot, the welding could be easily done from the outside. That size may not exist; alternately, weld up a custom sized channel from flat stock. Ideally, the legs of the channel would be short, just enough to squeeze the acme nut in there.

Also for stiffness, and to minimize post-weld distortion over time, I would add a pair of ~45 degree diagonal members from the gantry/uprights down to the main frame. With only the uprights, any relaxation in the weld beads at their base will pull the gantry fore/aft by quite a bit. A pair of diagonal braces would fix most of that, and add a lot of fore/aft stiffness.

Wouldn't the linear bearings, attached to the carriage, along with the extra thickness at the face, in essence "tape" the seam somewhat?

[JerryBurks]

Wouldn't the linear bearings, attached to the carriage, along with the extra thickness at the face, in essence "tape" the seam somewhat?

I guess it would. While the slot should weaken the structure the whole thing is anyway very massive so I guess it could be "good enough". But why not mesure it? You could clamp another rigid tube to the gantry as to simulate the spindle and then measure the deflection in x and y direction while loading with a spring scale (fish or luggage scale).

From other posts here on the Zone I learned that a rigidity of better than 5 to 10 lbs/mil is (100-200 kgf/millimeter) recommended for efficient aluminum cutting.

[shoot]

Thanks for the comments lads,a pal did voice concerns on the slot idea a week or so back, but i felt it wouldnt come into play, ive pinched the slot idea from this machine in the link.
[ame=http://www.youtube.com/watch?v=ij1_6_hpyd8]InfoTEC CNC Engraver 1111S - YouTube[/ame]
i wasnt concerned because the centre of my/each rail is almost in line with the radius on the box section rather than on the face of it close to the slot and behind those strips are a multi runs/welds.

Im no maths boy so tend not bother with calculations etc but just to be safe i may knock up 3 or 4 more U-plates like ive done in the image attached.
Thers plenty more box section to be welded to the table to strenghen things up,just trying to get the y axis done and put to one side at the minute.
thanks again for the comment

[dmalicky]

Wouldn't the linear bearings, attached to the carriage, along with the extra thickness at the face, in essence "tape" the seam somewhat?

Yes, those would help. Hmm, thinking more about it, the type of torsion the gantry experiences is rather unique, as the torque is applied in the middle, while the tube is ~fixed on each end. So the left side of the front face is trying to shear one direction, while the right side is trying to do the opposite. But they're joined in the middle, which inhibits both. There will be big stress concentrations at the ends of the slot, but the overall deformation is probably not the kind of problem as it would be in, say, a driveshaft.

just to be safe i may knock up 3 or 4 more U-plates like ive done in the image attached.

Nice - those are an excellent idea! My FEA models showed that "collapse of the cross-section" (parallelogram mode) is a very weak link. The bottom and top flanges of the box get pushed/pulled a lot. A total of 4 bulkheads (2 endcaps and 2 internal) raised stiffness by ~3x. I haven't tried cutouts in the bulkheads--I'll look at that.

[louieatienza]

Interesting stuff! I think though, even at this state, that this router build is im terms of stiffness way more than most builds I've seen here; and could almost be classified a gantry mill rather than a router. Great work so far, keep it coming!

[dmalicky]

Yes, it's looking stiff, and great work!

[shoot]

Just an update,i cut out some wedges from the 200x100.box that i didnt bother useing and stuck them to the up rights for a bit of support,not quite 45,s but any more and my z plate would interfear with the supports but they should help stiffen things up.
i still have the plates to weld into the y axis box.and box section for the x rail.
Ive been thinking on how to get the x axis rails level at the minute,should be fun

[twistedfuse]

What thickness 200 x 100 beam did you get?