Reasonably Rigid Router (RRR) - a cautionary tale (likely) in the making.

[luke peter]

Steve progress:

C Channel parts almost done (weldments). Still waiting on laser cut closure plates for the x rails, then will mock mount the ball screws to get the correct spacing for the bearing support plates and weld it all up.

Its nice to see something that looks a little like what I have been playing with in CAD appearing on the garage floor...

Perspective view:

Top left:

Rear left:


Z axis plates have been beveled appropriately for assembly welding, they are enjoying a nice cool vinegar bath in anticipation of getting together soon.

[luke peter]

Minimal progress this weekend.

I got the z plates beveled for welding, and cleaned up any lasercutting issues so they fit together as they should. 6mm plate holds much better tolerances from my provider than the 12mm plate, 0.1mm clearances for slot and tab construction are fine for the thinner plate, more is required for the thicker, specifically in the corners when dogboning. The plates had a nice 24hr vinegar soak, and have come out mostly clean for welding.


Off topic:

My son (11) needed to make something for his schools art/crafts showcase, and he decided to make a sword. It's tremendously gratifying to have my progeny join me in the garage, and show a genuine interest in making things. He learned many new process and the safe use of lots of tools over the weekend - it did mean almost no CNC work got done, but it was awesome seeing the joy of discovery in his eyes, and the makers thrall he experienced having made his piece.

[luke peter]

Drilled and tapped the z axis back plate.

The plate was too thick for the hole sizes I wanted cut, so the laser cutters mark the hole centers. This means I have to center punch, center drill, drill, then tap. It is time consuming to do if I want it accurate.
Center drilled

Drilled

Tapped


10 points for whoever sees the oops... There are enough holes for the spindle flange that I am going to leave it - lapse in concentration, tapping fatigue builds quickly, its no fun at all.

[luke peter]

All welded up (the Z axis). Some aesthetic grinder work required now, and the machining of the rail slots.

Also shown below, the results of the vinegar cleaning (48 hours in this case)

[luke peter]

cleaned up the Z, and added some fillet stitches on the inside corners.

Looks like a machine component now.

[peteeng]

Hi LP - Painted RED will make it a machine part maybe yellow? Peter

question re: vinegar does it remove millscale? I usually use phosphoric or hydrochloric acid. Vinegar sounds more friendly...

[luke peter]

Hi Peter.

I am partial to machine tool blue

Yes, the vinegar does remove mill scale, completely. It just takes longer to do it than hydrochloric or phosphoric acid (24 hours vs 2).

[peteeng]

Hi LP - Much happier tipping out vinegar somewhere then strong acids. Time passes anyway so 24hrs vs 2 no issue for me. Will give it a go next time needed. Thanks Peter

[luke peter]

Servo drive arrived yesterday, all present and accounted for now.

[ChipsBFlyin]

Steve progress:

C Channel parts almost done (weldments). Still waiting on laser cut closure plates for the x rails, then will mock mount the ball screws to get the correct spacing for the bearing support plates and weld it all up.

Its nice to see something that looks a little like what I have been playing with in CAD appearing on the garage floor...

Perspective view:

Top left:

Rear left:


Z axis plates have been beveled appropriately for assembly welding, they are enjoying a nice cool vinegar bath in anticipation of getting together soon.

Nice build!

Are you heat treating this structure and then sending it out for machining? If not, how do you plan on aligning the planes that the Y axis rails will mount on? Is there a concern for the frame tweaking over time if not heat treated?

[luke peter]

Nice build!

Are you heat treating this structure and then sending it out for machining? If not, how do you plan on aligning the planes that the Y axis rails will mount on? Is there a concern for the frame tweaking over time if not heat treated?

Based on material thickness, TSR is not required. I will nevertheless be sending them for stress relief prior to machining.

The long axis (not the gantry) rails are going to be kept level through batch machining the supports for equal height. And the spacing will be set using the gantry (I will mark the upright to long axis rail mounting holes on the slave side to get rail spacing acceptable). As it is fabricated now, I would probably get away with the slave rail slot being 1mm oversize, but I am not confident enough to just let it be.

[dazp1976]

Sigh.

Almost a perfect import experience, almost... The seller sent my servo drive and cables in two packages and only gave me the tracking number for one. I will have to find the second number and see if the forwarder has kept the items, I hope so.
Otherwise, all present and accounted for.

No damage on the ship, and the servo motor looks nice and beefy.
These bits and pieces (including the servo drive) landed for $950.

That green spindle head amongst it all.......
When you get it fitted and running, can you let me know how good/bad it is and how it performs plz?.

Been looking at them myself, considering building up a new head box for my mill based on a BT30 one to go up to 6k rpm.
Daz.

Nice haul.

[ChipsBFlyin]

Based on material thickness, TSR is not required. I will nevertheless be sending them for stress relief prior to machining.

The long axis (not the gantry) rails are going to be kept level through batch machining the supports for equal height. And the spacing will be set using the gantry (I will mark the upright to long axis rail mounting holes on the slave side to get rail spacing acceptable). As it is fabricated now, I would probably get away with the slave rail slot being 1mm oversize, but I am not confident enough to just let it be.

Can you please explain the no requirement of TSR based on material thickness. I understand that you are going to do it to your frame, but I was always under the impression that if you welded a steel structure and you need it to not move before machining, you must SR. Is there a ratio? Like thicker materials will distort less if no SR is done before machining?

Can't wait to see more updates on your build.

[peteeng]

Hi CBF - I don't think there is any ratio for the steel to not to move. I've worked on very small welded parts (ultrasonic devices) and very huge mining equipment (trailers that cart 650 tonne trucks around, these are vibration SR) and they all require SR after welding to allow stability before machining. Even just grabbing a piece of metal off the shelf and machining it relieves it in some way. Also been involved in large moulds and they are roughed then released from the machine and let sit for a few days and they change shape when hollowed out. Then they are put back for final machining... SR is ideal to do if possible for any welded structure that requires precision machining afterwards., Peter

[luke peter]

Hi all.

Peter is right, for dimensional stability the TSR is always the way forward. I work with a weld inspector who is a competent person for pressure vessel inspection, he has been adamant I am wasting my time with tsr because most pressure vessel codes have a minimum prescribed thickness below which TSR isn't required. Failure of a pressure vessel and dimensional stability are not the same thing though

I haven't lifted a finger on the cnc build for the last three weeks. My 3d printer decided it had served enough, and one of my stepper drivers somehow fried my ramps board, two other drivers, and a couple of my end stops. I have been systematically fault finding and replacing components.

Happy to report it is extruding again tonight, so free time will return to cnc building.

[luke peter]

That green spindle head amongst it all.......
When you get it fitted and running, can you let me know how good/bad it is and how it performs plz?.

Been looking at them myself, considering building up a new head box for my mill based on a BT30 one to go up to 6k rpm.
Daz.

Nice haul.

Initial impression is very good, runout on the taper doesn't register on my gauge (it's 10um,so not the right bit of kit for this, but there is less than half a division of TIR. Will see how it behaves when mounted once I get there.

[peteeng]

Hi All - I think TSR on pressure vessels is to improve the fatigue resistance of the welds. There must have been some work done on this to establish a thickness threshold. In some of the projects I've been involved with Mechanical dressing or TIG dressing produced the best fatigue improvements. Fatigue is not an issue with CNC structures though. Peter

[ChipsBFlyin]

Thank you for the replies and the info.

[ardenum]

Love the boxy design, although all that grid on the spindle box is actually detrimental unless it's gonna involve some damping material later on. Only make cutouts where its necessary for things like visibility or cables etc.

[Bongodrummer]

Following along, nice build so far. I like that you did a better job than me of resisting the urge to go crazy with the vibration damping until you see how things are performing. In my case, it would have been harder to retrofit concrete in the sides of I beam section on the long axis, but I still think you're doing it the right way round. Did you consider VSR for the welded structure?