X3 mill with rails, ATC, new motor

[Jonathan]

I got the ATC working this weekend - at least in principle:





I've made quite a few parts for the carousel etc, but they're all quite simple so it didn't take long. There's a few issues I've mentioned in the video - the main things are to add sensors, change the coupling between the carousel and gearbox for something stiffer and check the clamping torque upon the toolholder. It's currently just controlled using a few lines of gcode - the air solenoids are currently controlled from LinuxCNC via relays just using the M64/M65 commands and delays. When I've got time I'll do it properly, so sensors are checked at each stage (using M66) to avoid mishaps.

[Clive S]

Looking good, it will be interesting to see it working under real load conditions but it looks like a first on this forum.

Well done. ..Clive

[dazza]

Now that's porn,16 tools..it looks smart..i vaguely remember you mentioning mesa/pico hardware for this mill,did you bother.
will the turret be bidirectional and take the shortest route to the next tool or..not that it matters it seems quick enough.
nice work.

[Jonathan]

Looking good, it will be interesting to see it working under real load conditions

I almost forgot - I did try cutting with the DC motor and it seemed fine, but that's not a good comparison considering how much higher the torque rating of the new motor is.

i vaguely remember you mentioning mesa/pico hardware for this mill,did you bother.

For now I've decided it's too expensive for what it gains - more and faster I/O. If I need more inputs/outputs I can add a 2nd parallel port and until I use servo motors the frequency limit of the parallel port is adequate. One temptation for using a motion controller is it could fit in the back of the column, so I'd be able to get all the electronics inside the column.

will the turret be bidirectional and take the shortest route to the next tool or..not that it matters it seems quick enough

Yes - that shouldn't be a problem. I've currently tuned the carousel motor to run with quite low top speed and very low acceleration as the low stiffness of the coupling means it oscillates too much if I run it faster, so it will certainly be quick enough when that's fixed.

[Jonathan]

Believe it or not, I found some time to work on this project again!
Decided I should do some sort of drawings for the X & Y axes, so here's the rough idea. I say rough as most of these parts are just blocks to show the general arrangement of things - I've not added detail:



The X axis uses a bed from a different machine. I'm adding HSR35-1100mm rails to this and SHS25 rails to Y. These rails sizes are based on what I've got good deals on. For the ballscrews I'll be buying TBI DFU ballscrews, similar to Z, sized to get a reasonable stiffness for each axis.

As a 'first pass' look at it, I've tabulated the stiffnesses of each component, then combined these (as springs in series) to get a value for the stiffness of each axis:



This implies that the stiffness is dominated by that of the ballscrews, as these are by far the smallest numbers in the table, so it is worthwhile to invest more in 'large' ballscrews as improving these should have the biggest effect on the overall stiffness of the axis. For the table above I've calculated the stiffness's based on DFU2005 on X and Y, with angular contact bearings on both ends of the X-ballscrew, to compensate for the lower stiffness of such a long ballscrew.

This analysis is still too basic though, as it assumes the forces are all applied at the respective axis center of stiffness, since moments aren't considered, so I need to re-calculate including the 'pitch' and 'roll' stiffness of each axis. If this shows that the ballscrew stiffness is still significantly lower than the linear bearing stiffness, then I'll consider using even bigger ballscrews.

So far I've started machining the bed and steel spacer strips to mount the rails, that's about it...

[Jonathan]

So today, I got from this:

Via lots of this:

To this (cute little HGH15 bearing is for scale):


Next job is to drill and tap more holes than I care to count in the bed, which I can barely lift as it weighs more than me, so that's going to be fun... then I'll make the aluminium plates which fix on the steel strips that poke out of either end. Finally, I plan to get both sides of the bed surface ground so that the rails have a nice accurate surface to mount upon.

I also started drawing how I plan to mount the X-axis ballscrew drive end:

[mekanik]

Fantastic build Johnathan, thanks for posting, always get very envious looking @ your projects.
Regards
Mike

[Jonathan]

Thanks Mike.

Today, I milled two slots!
4mm wide by 5mm deep slots in the steel strips shown in the previous post. The slots will have simple covers placed into them.


Next I've devised a bit of a mad scheme to drill the array of M6 holes in the bed:


Then checked that it was sufficiently parallel - couple of whacks with the nearest hammer and it's now within 0.05mm over 400mm.


Now to continue the drawing...