Hi Hans,
I change tools as little as possible because it is too easy to break them. Most of the time I use a single drill for the entire board.

One could not use a multi arm setup on a XYZ cnc mill. But by the time you add the arm and electronics I am not sure it would be reasonable. It would take a longer X axis to do the same work. The only software change would be to add a different offset depending on the arm in use. Easy if the software has provision to make such an adjustment during tool changes. Or if on had the source. Maybe a better method would be to generate Gcode and then process it to add the offsets.

On of the problems is lash or play in gears and screws. If one always approaches the target from the same direction it is better. Also if one were to provide a slight load in one direction it would help.

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Hi 3v0,

adding an arm only makes sense using the Tanbo. Since the plate rotates each arm is equidistant from the center of the plate. Adding arms to a "linear" drive makes absolutely no sense.

I need at least 3 different drill diameters making a board. Screw terminals have a pin diameter of 1.2mm. Drilling a hole of 1.2mm for an IC pin there wouldn't be much left to solder with a pad size of 1.6002mm. Box headers and jumpers require 1mm drill size and ideally IC pins require 0.6mm (most DIY-PCB makers use 0.8mm instead).

My most simple PCB drill was made by Isert automation about 1970. It had a strong 12VDC motor with very little vibration and perfect alignment of the drill chuck and had an adjustable power supply. Max speed was 30.000rpm, and using carbide hardened drill bits the holes were smooth and shiny inside, good enough for elelectrolytic through contacting. Using a small magnifier lens directly mounted to the drill stand I could drill holes hitting "bulls eye"

The spindles I was talking about are salvaged parts of industrial CNC machines and they require little adjustment only to move a sledge or a tool carrier without any loss of reference no matter which direction they have to move.

Old lathe machines are fitted with cone shaped heavy stabilizing bars, whereas nowadays linear rollers are used travelling along a precision rod and fixing the moving part so it can only go two directions - forward and backward with absolutely no side movement.

I have already calculated for the X and Y speeds using a precision of 0.005mm. It is still 40mm/second which is fast enough for hobby applications, and much more accurate than any industrial machine. (I am perfectionist, pilots have to be that way to survive 6,000+ flying hours in a combat jet)

Years ago there was an article about a selfmade CNC drilling machine which made me smile mildy. The drives were steppers though, but the spindles were of the kind you can buy at home markets for construction work, max length 1m. The principle was simple: Start at the zero/zero point and move to the destination, drill a hole and return home beyond the zero/zero point. Slowly approach that point again, autozero position using optical sensors and then "hustle" to the next coordinate. (Working off coordinates in sequence would have caused offset errors of 0.5mm in each axis, adding to a total error of 0.7mm)

Looks like you are interested in a cooperation developing an affordable CNC drilling machine for our forum members.
Yes, I go along with that. I'll try to get all the good scrap when I travel to Bangkok.

There should be enough of that stuff to make at least one good prototype. If I can get a contractor there repeated supply with the same kind of spindles should not be a problem. (some of the spindles I saw there were still wrapped in oily paper and I assume they were brandnew.)

I'll have a good look for suitable drill motors too. They must be 100% balanced for vibration free spinning. (Depending on the amplitude of vibration a drill planned to be 0.6mm can quickly become 0.7mm being 0.05mm out of balance)

Hans