CNC 2.5D milling machine, working area: 35 x 35 x 5 cm

photo of cnc milling machine

Hardware

Construction: 20 and 30 mm plywood, glued, screwed and bolted
Linear guides: X axis runs between 4 drawer guides
Y axis runs on 4 drawer guides
Z axis runs between 2 drawer guides
Lead screws: M12 ISO threaded rod with nuts cut from Polyamid
Motors: 400 step, NEMA 23, 1.7A stepping motors
Motor drivers: Driver kits from Pollin Electronic, 2 amps.
Spindle: Proxxon IB/E, max. speed: 20,000 RPM
Tools: Proxxon 1 mm and 2 mm mills with 3 mm shafts

Software

CAD: QCad V.2.0.5.0 (RibbonSoft)
DXF to G-Code: Ace V4.0 beta (DAK Engineering)
G-Code to plot: Code editor and backplotter V.1.2 (NC Plot)
CNC: TurboCNC for DOS V.4.01 (DAK Engineering)

photo of keys cut by CNC machine
This machine was intended for cutting, drilling and routing plywood - no more than that and it has turned out to be strong and accurate enough for this purpose.

some CNC projects

Home made digital touch probe
A touch probe is a sensor which is mounted on a CNC machine, usually in place of the cutting tool and is used to detect and record the shapes of objects placed underneath it. The machine lowers the probe until its stylus just touches the object and then the X, Y and Z coordinates are recorded by the computer. It can be used to find a specific edge or dimension, to find the exact centre of a circular hole, or to measure several hundred points on a grid and so record the shape of a surface.
photo of probe
Touch probe details

Based on a Renishaw probe. Briefly: each of the 3 brass prongs of the probe (two are visible) is pressed against a gap in a brass wire, by a spring - just visible in the centre. This completes a series circuit:
-__o____o____o__+
Operation: The probe is moved toward the object. When the probe touches, one of the contacts is opened, the circuit is broken and the current position of the probe is recorded. The probe is then backed away from the object and the circuit closes again.

NB. The preferred material for the electrical contacts is hardened steel - not brass.
spare part for the Thinking Machine
a 2D scan with the touch probe

I used TurboCNC to scan a crudely-made, but finely-adjusted prototype part. It found the centres of the two holes and the positions of the two arms (marked red) and these dimensions formed the basis for a CAD drawing. The milling machine then cut out the finished part.

A screenshot of a 3D scan of an Italian 1 Euro coin



a 3D scan with the touch probe

The Vitruvian Man on an Italian €1 coin rendered in 9 colours, like a relief map, using a short BASIC program. The measurements were made on a 0.1 mm grid.
Another screenshot of a 3D scan of an Italian 1 Euro coin
another way of looking at it

Here, the same 150 x 150 "point cloud" was rendered in a different way: comparing each height measurement with its north-westerly neighbour, noting the difference in their height and then shading its pixel, lighter or darker accordingly.

A noisy image, but perhaps the best that can be expected from a touch probe with brass contacts. Some tweaking needed there.

At this point I removed the touch probe from the tool holder and replaced it with a brush to try some computer assisted calligraphy:
my brush
CAD screenshot with kanji caligraphy
Brush plot



New Year's Greetings in Japanese. On the left is my original CAD drawing. I then spent some of the time between Christmas and New Year adjusting the program until it was able to produce something resembling my model (the small picture above.)

drilled printed circuit board
Drilling printed circuit boards (PCB's)

After I had etched some printed circuit boards, the machine drilled the holes.
  • Two holes were drilled by hand in each PCB through register marks - arrow.
  • The machine first drilled two corresponding register holes in the base board and then halted.
  • A PCB was pinned down in register through the holes and clamped.
  • The machine was then restarted. (It takes 20 minutes to drill the 224 holes in one board - but faster than I could do it by hand.)
  • The two register marks were sawn off.
Next time, I will try milling the pads and traces instead of etching them ...

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