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I'm making a Circuit etching machine (CNC) and I need a good DC motor and drill bit for the spindle.

My machine should be able to etch, drill, and cut:

  • Etching: take copper off the surface like chemicals or a laser would
  • Drilling: drill holes for THT (through-hole) components and possibly 2-sided boards
  • Cutting: cut out a piece of the board (cutting a big piece in half or cut a circle out of a big piece)

I'd like to have 1 drill bit work with all 3 functions if possible. Having to switch out different bits is OK but a single bit is prefered.

What sort of specifications should my spindle DC motor (rpm, voltage/amperage rating, ...) and drill bit (material, size, angle, ...) have?

ChocolateOverflow
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    From [Game plan - What is on-topic?](https://3dprinting.meta.stackexchange.com/questions/276/game-plan-what-is-on-topic), CNC questions are not off-topic. Please be patient and nice to new Stack members. – 0scar Jul 29 '19 at 18:06
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    I've read that CNC questions are acceptable. The machine I'm making is also similar to DIY 3D-printing machines. I believe this should be OK for this forum. – ChocolateOverflow Jul 30 '19 at 01:39

3 Answers3

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There are several sources of PCB "etching" bits. They tend to be single straight flutes and high angle, very pointy bits.

For the motor, high speed is good. Look for 30k+ RPM. The main thing to be concerned about is the amount of runout, or wobble in the tip. With a tiny tip, you can't afford much runout at all. It will broaden the gap you are cutting and put stress on the bit, probably snapping it.

The key to low runout is very careful alignment of the chuck that holds the tip with the shaft of the motor, and a collet chuck to hold the tool.

The power needs aren't high since the speed is high and the cuts are light. I would think that a 250 watt motor should be way more than sufficient.

The question now asks for drilling and routing, which should work better with the high-speed spindle. 30k is better for the tiny drills than a much slower spindle. These are hurt by run out.

Usually the drill bits are made of carbide. For cutting, carbide router or file bits are used. All drill-bits and router bits and copper cutting bits I have seen for sale have 1/8" or 3mm shank.

cmm
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At Hyrel, where I work, we use a 12 VDC, 3.5 A, 40 W spindle tool with 1/4" chuck and 3,000 rpm max (without load) to make prototype circuit boards by machining through the copper layer to make isolation traces.

Greenonline
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Davo
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  • Wow. That is so much slower than I've seen. Tools I've looked at wanted much higher speed. Who makes your tools? – cmm Jul 29 '19 at 13:45
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    We make them, but we purchase some of the components - like the spindles themselves. We also have a three-phase spindle tool, 48VDC, 8.3A, 400W, 12,000 rpm without load, but this is not needed for circuit board work. [Here's the smaller one in action](https://www.youtube.com/watch?v=C88ni0huwhw). – Davo Jul 29 '19 at 16:37
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TL;DR

From Davo's and cmm's answers there seems to be a wide range of drill spindle speeds used (3k-30k rpm). So, just to add to that... 11,000 rpm would appear to be adequate.

I have been looking into converting a Wilson II 3D printer chassis into a CNC PCB etching machine, recently. In particular, what motor I needed to replace the extruder with.

A collegue pointed me to an interesting video, PCB making, PCB prototyping – UV solder mask STEP by STEP, produced by Wegstr (no affiliation whatsoever), and their machine uses a 11,000 rpm drill. From the specification page:

  • Spindle - Brushless AC motor
  • Diameter of spindle - 3.175 mm (0.000737 inch)
  • Spindle speed - 11 000 rpm Electronic overload protection for the spindle motor

Apparently DC motors suffer from carbon brush wear, so a combination of DC circuitry and brushless AC motor is used for "superior performance and durability".

The voltage and current of the spindle motor is unclear/unspecified, but the PSU, that comes with it, outputs 12 V 5 A.

However, the parts page lists the spindle motor separately, spindle 11000rpm, with the following specifications:

  • 26V DC power supply
  • 11000 rpm
  • designed for tools with shank diameter 3.175 mm
  • fastening tool with the setscrew
  • in the rear spindle 4x M4 threaded hole for mounting on a substrate
  • power consumption 25W
  • brushless construction => no carbon brush wear => long life
  • low noise

So, given the voltage and power consumption the current rating would seem to be ~1 A.

Spindle Motor 11000 rpm

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Greenonline
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