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Matt's Projects

Sometimes I make things

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PCB Mill CNC

Project: Analogue Tape Delay – Etching PCB

Another opportunity to test out my CNC!

Sadly, through no fault of the CNC, what should have taken about a 45 minutes ended up taking about 2.5 hours!

The PC I use to drive the CNC is a 15+ year old laptop running Windows XP. This makes it very prone to blue screening and it crashed TWICE during the whole process. Given that it takes about 20 minutes to boot and become stable this results in a massive waste of time. It also meant that each time I restarted the software I had to realign the board which resulted in a loss of accuracy. Nonetheless the board is now fully etched.

I took a slightly different approach to what I have done before. Usually I do all of the drilling by hand after I etch, however I thought it would be neater if the CNC drilled the holes before it etched them.

Not wanting to risk drilling through the PCB and into the CNC, I compromised and decided to have the CNC drill 0.7mm into the PCB, making it really easy for me to drill the rest of the way later on.

The final board! Pretty pleased.
The final board! Pretty pleased.
The board with only the holes drilled. Looks pretty cool.
The board with only the holes drilled. Looks pretty cool.

Obviously in future I want to avoid situations like this. Therefore I have decided to try and get Grbl working.

Grbl is a system that allows any computer with a USB port to control a CNC parallel port interface using an Arudino Uno in the middle. This will save me lugging around a massive old laptop and will hopefully be more reliable 🙂

Project: PCB Mill CNC – In Use!

Here is a video of the CNC etching the circuit board for my next project (details to come hopefully). Enjoy!

Skip about 30 seconds to avoid the blurry bit!

Project: PCB Mill CNC – Built

It’s been a long time since I last posted. The last couple of months have consisted mainly of work, holidays and back-to-uni chaos. Nonetheless, I have found time to work on the CNC. In fact the majority of the mechanics AND electronics have been done.

The current design has not strayed far from the original plan. There have been a few minor changes including adding extra spacers and changing the shape of brackets but nothing too interesting.

The largely finished mill!
The largely finished mill!

All of the electronics are tucked away inside a standard project enclosure into which I drilled a hole for the parallel port and a hole for the power and motor connections.

The electronics are hidden away showing only a parallel port and a tangle of wires for the motors and power. Shame about the tape!
The electronics are hidden away showing only a parallel port and a tangle of wires for the motors and power. Shame about the tape!

Remaining tasks:

-Add a support bracket connecting the horizontal aluminium to the vertical aluminium to minimise wobbling of the drill.

-Properly attach the electronics to the body with bolts rather than tape.

-Insert proper power supply plug and buy power supply

-Test

Unfortunately, with the exception of the last one, none of these tasks can easily be done while I am at university due to lack of tools (although as an engineering student I probably could if I tried hard enough).

Fortunately, none of them seem particularly important as current results look promising and these will merely be icing on the cake.

Yesterday, for initial testing I put a pencil lead into the drill and set it drawing Road Runner on a piece of paper. After a little while the lead fell out (drills aren’t made for this 😦 ), but what it managed to do looked promising.

You can make out Road Runner's wing!
You can make out Road Runner’s wing!

Today I put a 1mm end mill into the drill and set it spinning at 8000rpm. Rather than let the CNC loose, I controlled it myself using the arrow keys to direct the drill over some copper clad board.

Copper clad board with some random copper etched away!
Copper clad board with some random copper etched away!

As you can see, the copper removed nicely, if not a little deep, and left sharp edges. In fact the drill cut through the copper with no stutter at all so I am confident it will be up to the job. I am looking to order some finer end mills, maybe 0.1mm so that I can etch useful circuits!

Hopefully the next post will be sooner.

Project: PCB Mill CNC – 3D Model

It’s been a little while since I last posted. I’ve been pretty busy with work-work and uni-work. But I’ve also been working pretty hard on the design for the Mill as well as gathering parts.

I decided to base the design off 3×1″ aluminium U-channel and will be using Nema 17 stepper motors.

3D model of the Mill made in Creo Parametric
3D model of the Mill made in Creo Parametric

3d_view2
Here is the back view

I’m pretty pleased with the design.The grey stuff is metal, the brown stuff is wood and the green things are sliders.

You can see the three stepper motors – one for each dimension; the vertical assembly which will have the drill strapped to it; and the horizontal piece of wood which is the actual platform on which the material will rest. The drill I chose was pretty cheap on eBay: 10000-30000RPM and 135 Watts should be perfect, and it doesn’t wobble much at all.

Hopefully the U-channel will come by the weekend and I will be able to get going with building it.

Project: PCB Mill CNC – Testing the Motor Driver

The bad news, I managed to blow two of the three motor drivers by connecting 9v into a 5v pin. Oops.

The good news, the remaining driver works fine!

Here is a video of it in action:

Here you can see me reversing the direction of the motor by connecting the DIRECTION pin to 5v or 0v.

The step pin is actually disconnected and is therefore floating. However, because the voltage on it is therefore fluctuating, it more or less simulates a quick step pulse train.

I have ordered some replacement drivers and some opto-couplers as I reckon the next step is to connect the stepper motor to the pc and see it in action. The opto-couplers ensure that, should anything go wrong with the motors, no electrical signal can be fed back into the pc, potentially damaging it.

Project: PCB Mill CNC – First Steps

Last time I tried to build a CNC, I didn’t realise how CAM software interacted with the hardware. From research I have found that packages like Mach3 generally communicate with a CNC tool via a parallel/printer port. The protocol is pretty simple: each motor has two direct pin connections – step and direction.

So first things first I need a parallel port. You don’t find these kind of things on modern laptops, so I took a dive back in time to my dad’s old laptop from about 10 years ago. We are talking a 256MB of RAM, 20GB HDD, 1GHz pentium processor, 3.37kg beast.

This is what a parallel port looks like.
This is what a parallel port looks like.

The first step I decided was to check that the parallel port is spouting out the right kind of data. So with the help of a parallel port break-out device (thanks again, dad) I hooked up the PC to my oscilloscope.

What I would expect is a series of pulses on the “step” pins and a constant voltage (until I change direction) on the “direction” pins. Luckily, this is exactly what I got.

The Mach3 interface. Retro but functional.
The Mach3 interface. Retro but functional.
The parallel port breakout device with probes.
The parallel port breakout device with probes.
Oscilloscope reading. Can you make out the tiny pulses?
Oscilloscope reading. Can you make out the tiny pulses?

What this means is that the PC can be connected directly to stepper motor controllers which coincidentally also have a “step” and a “direction” pin and therefore I do not need any kind of intelligence in the form of a microprocessor.

In the end the stepper motor drivers I went for are these albeit from a significantly cheaper distributor:

My choice of stepper motor driver.
My choice of stepper motor driver.

So, next thing I reckon is to wire up one of these drivers and motors and test it out.

Project: PCB Mill CNC – Introduction

With the Smart Watch project drawing to a close (all that’s left is software refinements and a final video), it’s time to begin a new project.

Having just completed an entirely electronic/software project, I think it would be nice to move onto a hardware based project. It is for that reason that I will be attempting to make a Printed Circuit Board Milling CNC based of these plans by Tom McGuire. This isn’t actually my first attempt at a CNC machine. Back in 2012 I had a first attempt, using only parts from a scrap printer. This didn’t go to plan for a number of reasons – lack of planning, cheap parts, lack of research and impatience to name a few. But this was before I started my Engineering course at uni.

This was my first attempt at a PCB Mill.
This was my first attempt at a PCB Mill.
P1020507
This was an “improvement”.

 

 

 

 

 

 

To cut a long story short, it didn’t go well. I didn’t think properly about how to interface it to a PC and I didn’t get appropriate motors. It is now gathering dust in my room.

Here is a video of it at it’s peak:

Hopefully, by taking time to do appropriate research and buying high(ish) quality parts, I should be able to make something useful.

Let’s hope for better luck this time.

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