2024-09-27

Last modified: 2024-09-27 21:47:23

• Sovereign scales
• CNC machine

Sovereign scales

Paul said that he wouldn't mind the device being quite a bit bigger, and having a spot for a quarter sovereign is a new feature not available elsewhere, so let's just make it bigger and add a slot for it, and then today I want to make a first prototype.

I don't have a 1mm end mill just yet, so might have to make do without the slot for now.

I'm going to go with this:

And then see how much of a counterweight it needs, and consider changing the dimensions accordingly. I'm guessing it will need more counterweight than I have provision for, so I'll need to either make the left-hand side of the beam longer, or make the base thicker to accommodate a longer weight.

CNC machine

I discovered that the spindle coolant bucket has basically been drained empty, and the pump has stopped working, presumably due to being run dry. D'oh. And it's not the fuse. I've ordered another pump. I'll just run it without the pump today and try to keep the spindle load down.

First operation: pockets for the coins:

I used a 3mm 2-flute down-cutting tool, 12000 rpm, 500 mm/min.

And I just realised that you won't be able to get the quarter sovereign out without tipping the device upside down, because it is entirely enclosed within the outline. So I'll shrink down the outline just after the half sovereign. Also means less counterweight will be required.

Second operation: chamfer around the outline:

6mm 90 degree V-bit, 12000 rpm, 500 mm/min.

There are 2 outlines because I accidentally did the first one in the wrong place (forgot to tell FreeCAD the tool is a v-bit).

Now I think I want to engrave some text on it, then switch back to the end mill and cut it out, then just need to drill the pivot hole and this part is done.

The main area for text is 27mm by 10mm. The other area is 20mm by 10mm.

I think I want "Sovereign Scales" and "jes 2024". Out of time for now, I've parked the machine at X0Y0.

Well I've made some text in Inkscape and tried to create gcode with "Gcodetools", "Path to gcode", like I always used to. But this is Ubuntu 24.04, and now Inkscape is a Snap, so it doesn't have permission to write to my home directory.

Configuring it to write to /home/jes/snap/inkscape/current has worked.

But now I can't open the Gcode in FreeCAD because FreeCAD can't see the contents of /home/jes/snap/inkscape. So manually copy the file somewhere else. I ought to report this as a bug somewhere. Maybe later.

Kind of blundered the engraving:

Next time I should use the drag engraver instead.

Now it's just the final outline to do. I've spotted the centre of the counterweight hole using the v-bit, will drill and countersink it manually.

Kind of OK:

Next need to put the vice back on the machine table to drill the cross hole.

• counterweight needs to be twice as heavy, or twice as far away, or some linear combination thereof
• needs more clearance between the beam and the foot
• needs more clearance for the counterweight to fall down, so it is more clear if a coin is too light

Paul has suggested that some people would be worried about scratching their coins on metal scales, particularly in sliding them through the slots.

I might actually just try to make my best effort at 3d-printed version of the scales. Maybe now is the time to buy an X1 Carbon.