[peteeng]

Hi Mactec - I agree that VSR can crack structures. Tabs and small cantilevered areas can freely vibrate and over deflect and crack in my experience too, even with thick structures. That's one reason a modal analysis is first done to establish if there are areas of concern. With the mining equipment VSR small pieces are tacked or clamped onto ram mounts and areas of concern or experience to stop them from getting over excited at resonance.

All processes require a good understanding of how it works & its pitfalls. Horses for courses... As a note - we are not really concerned about the internal stress of a structure this is in equilibrium and will not affect the performance of a machine,. We are really concerned about making a correctly dimensioned machine. So the TSR or VSR or peening or whatever is used is a step along the way that allows the maker to get to a satisfactory dimensional result. As you have said you can fabricate stuff and hit the required dimensional spec. This can be done in a repeat environment as the people learn along the way how to get a result., The hobby maker has one shot at it so they only learn about this stuff once and correct it once... Hopefully the forum stores & transmits some useful knowledge to short circuit some grief... Peter

[mactec54]

Hi Mactec - I agree that VSR can crack structures. Tabs and small cantilevered areas can freely vibrate and over deflect and crack in my experience too, even with thick structures. That's one reason a modal analysis is first done to establish if there are areas of concern. With the mining equipment VSR small pieces are tacked or clamped onto ram mounts and areas of concern or experience to stop them from getting over excited at resonance.

All processes require a good understanding of how it works & its pitfalls. Horses for courses... As a note - we are not really concerned about the internal stress of a structure this is in equilibrium and will not affect the performance of a machine,. We are really concerned about making a correctly dimensioned machine. So the TSR or VSR or peening or whatever is used is a step along the way that allows the maker to get to a satisfactory dimensional result. As you have said you can fabricate stuff and hit the required dimensional spec. This can be done in a repeat environment as the people learn along the way how to get a result., The hobby maker has one shot at it so they only learn about this stuff once and correct it once... Hopefully the forum stores & transmits some useful knowledge to short circuit some grief... Peter

The only problem with these stress relieving processes, is if there is any machining needed then Heat Treating is the best as every part of the structure is stress free before machining

The machine frame I was talking about was a one off that I fabricated it in my home shop, so would be comparable to what any Hobby builder could do, I will be doing another one soon so may do a thread on it, threads take time and I usually don't have much of that, anything is possible if the builder thinks about the process before they attack, one misplaced or incorrect weld procedure can mess up the whole build

[Matthew_H]

Thanks everyone!

I've made a whole lot of progress, and spent a lot more money.

A small change: I beefed up the ends of the gantry with a big slab of 6" x 2" C-channel.

That's the only change to the design that I've made.

Got a buddy who's a welder to do the frame for me.

Then another buddy and I did the gantry ourselves. (Forgot to get pictures of the gantry.)

Then I got both pieces (frame and gantry) stress-relieved at a heat treatment facility. I didn't know what to expect for the cost of that, but was pleasantly surprised.

Then I got the base frame machined at a machine shop...they were able to hook the whole thing into a big mill and mill it all at once, so the X-axis rail beds are straight, parallel, and flat. And they drilled and tapped the holes. (The machining cost was horrifying; that's why it took a while to get it done.) They did say, however, that having the thermal stress-relief done was a huge help.

There is a weird feature to my X-axis rails...they are counterbored for socket head cap screws, but the counterbores aren't actually wide enough to accept a standard SHCS screwhead. I had to turn all 36 screwheads down on a lathe to get them to fit.

Then I took the gantry to our local makerspace and machined it myself on a Bridgeport. I doubt it's perfect, but I haven't drilled/tapped the rail holes yet, and I can't exactly tell how well I did until the rails are bolted on.

Next up: finish the gantry, build the Z, start wiring. Seems easy enough.

[peteeng]

Hi Matt - The holes and counterbore are correct size. They are for the screw size down so there is adjustment in the rail. Looks good. Peter

[Matthew_H]

The Z axis went together really well. Again I have access to a manual mill through my local makerspace, so I was able to drill all the necessary holes in both plates and both spacers quite precisely. No alignment issues at all.

[Matthew_H]

Here are a few photos of the X-axis motor mounts. There is a little spacer between the frame and the motor mount, due to the imprecision of the welding. A bit of aluminum to use as a shim is all it needed. Ball screws are installed. (The bearings on the opposite end of the ball screws are mounted similarly to the motor mounts.)

[Matthew_H]

The y-axis was the part of this design that had me the most nervous. Alignment issues in the X or Z, whether with the screws or the rails or both, could be fixed with shims. The screw on the y-axis had to be right the first time.

I used the manual mill to drill the holes for the y-axis (gantry) rails. It was really tricky because I had to clamp the gantry to the table, drill the holes, then unclamp and flip it over, reclamp it down, and drill the new holes...and they had to align perfectly. I got lucky with all that though, and it worked out. The screw was going to be a lot harder.

I used some aluminum blocks to mount the screw bearings; this was so that, if I messed up the alignment, I only had to make new aluminum blocks, and not a whole new gantry.

I installed the screw but left the bearings unattached, so it was just connected by the Z axis. Then I rolled the Z axis all the way to one side, and used some clamps to temporarily fasten the block to the gantry on that end. Then I rolled it to the other end and clamped the other bearing. I adjusted everything a few times to make sure the bearings were located right, then I drilled through the blocks and the gantry and bolted it up.

It actually worked, so I'm pretty excited about that.

So:
- the frame and the gantry are welded, leveled, and drilled for rails
- the z axis is built and assembled
- the rails and screws are attached to both the frame and the gantry
- the z axis is installed on the gantry

Next:
- get the motors attached and the shaft couplings in
- wire it up
- turn it on