project overview - an introduction
PROJECT OVERVIEW
- HOW TO START YOUR OWN CNC-PROJECT –
INTRODUCTION
A CNC-machine is a Computer Numerical Controlled machine. Normally a very expensive piece of machinery,well out of reach for the budget of a student or typical DIY builder.
In this project we are trying to build a CNC-milling-machine of our own, cheaply. Luckily this is very possible today, due to DIY controller kits, open source software and with the help from fellow builders on the internet. We estimated that our CNC has the total cost of less than 5000DKR (approx 666EURO) — and could be reproduced even cheaper. see budget and parts for more info.
A CNC-machine consists of different parts. To simplify it you can look at it as hardware parts, electronic parts and software parts. Some of the parts are bought assembled or as kits, some we have found, some have taken from the scrap, and some have been given to us.
PARTS IN OUR PROJECT
Electronic parts:
Control unit: a self assembly kit from www.hobbycnc.com
Power supply: 2 PC-PS to run the motors, the milling-tool runs directly on the outlet.
Software:
EMC2 – Linux-CNC – the program we use to interpret g-code and communicate with the control unit.
Misc. Linux-scripts i.e. truetype tracer (part of linux CNC) for making simple test g-code logos from text strings and true type fonts
We need to involve a CAD/CAM-program, and plan to use PRO/E. We’d like to find a nice open source CAD/CAM program which could replace PRO/E, but haven’t found any good alternative yet. Please contact us if you have suggestions for replacement software.
Hardware:
X/Y/Z-frame: A very critical part in the project. We have bought a homemade frame on eBay, which has turned out to be a bit shaky in the Y/Z-axis overlap. It is the most important component when it comes to precision. You can make it yourself, if you have access to a precision workshop, and you can try and construct it from old printers etc. It is also the single most expensive part in the project.
Stepper-motors: We have bought 4 new steppers from eBay.
Motor-connection: An important part. You have to make the connection a bit flexible for compensating for lack of precision, but still tight so the motors wont spin around inside. We used hard rubber-hose and tight hose-clips.
A computer: Get a cheap used or castaway PC and dedicate it to the project.
Home/limit-switches: Any small push-switches will do.
Wires and parallel ports: We chose standard paralel cables, but this could be any type of cable with enough wires.
Housing for the control-unit and power supply: Find a nice used box – we used a used rack computer-cabinet.
Cutting Tool: We have used a simple Dremel solution. Remember that there are a difference of drilling tools and milling tool! Its important since the drills will brake and fly around if you use them to mill. Use safety glasses!!
Housing for the CNC machine: A lot of thoughts have gone into this, and still we do not have a finished “product”. There is a lot to take into account when building the housing. How are the materials going to be fastened? How big pieces do you want to mill? Do you want your machine to be mobile and flexible? What are the extremes of the machine and how does that affect the dimensions of the housing? How do you take safety issues seriously, and still see the machine in action? We have tried to share our ideas and drawings on the blog, but these are considerations that define the project.
BUILDING THE MACHINE
This is not thought to be a step-by-step guide, since it would be too comprehensive within the scope of the project. We have tried to make an overview of the most important steps and the considerations we have had doing them.
Initial specifications:
As mentioned earlier it is important to have an idea of what you want with the machine. Are you going to mill metal, plastic, foam, wood? Are you going to take the machine with you and mill on the hood of you friend’s car? Is it 3D, 2D or maybe 4-axis 3D? How big pieces do you want to mill? Make the design-specifications and plan the project from them.
The XYZ-frame:
You need to make one or buy one.
Shopping and collecting:
Motors and control-unit – check out the blog.
Tool – try and get one for free to begin with – you can always expand and invest, and a simple dremel solution is good (and safer) for initial testings.
PC-power supplies as mentioned you might need two or more.
A computer – find or buy. Dedicate it. You might consider CNC milling a cool housing for it?
Collect as many different material-scrappy-things you can. They are nice to make test.
For more info: Check the list of materials and suppliers from the blog.
Install linux – EMC2 & ubuntu - linux CNC has made a nice installer pack
Try and make g-code from different resources – start with 2D. You can easy make text in Linux, but you can also make g-code from illustrator (export .dxf files and use software like LazyCam or ACA converter) or just start out with a complete CAD-program.
Assemble the control-board. It should be pretty easy, but pay attention to detail. It’s much easier to make it right the first time, finding bugs sucks.
Wire the motors – make them long-range so you wont get any trouble later on.
Make the motor-connection. This can be a bit tricky, so take your time, and figure out the best way to do it from the beginning. Remember to think which side should be the front and which should be the back of the machine. This might have an influence on where you mount the motors. Also it is nice, if the movement of the machine is logical and is equal to the graphical interface of EMC2. The z-axis is always up/down, but the X and Y can be both ways. The motor-connection can’t be tested before the machine is really up and running, so be prepared that you might have to re-design your setup along the way.
Make the tool mount. Make it so you can shift the tool itself. You might want to start out with a pen, so nothing is spinning at high speed when doing the initial testing. Also consider that a CNC machine can be modified to become a 3D printer quite easily and that this is a much safer tool to work with, as you will have no tools rotating at high speeds.
Make the home-switches. Be sure that nothing gets in the way before hitting the switches, and remember that this sets you (0,0,0) coordinate. The Z-axis home should be when the tool is all the way up! Also consider that your tools might vary in size, and require custom safe switches.
Make an initial test-stand, where you can try out the machine. Remember safety!
Assemble the machine. Connect the motors to the control unit, connect the switches, connect the power supply and connect the PC. The stepper motors should make a humming sound when powered up.
Test the machine. Simple 2D g-code and a pen should be the first test. You can always go all the way later on. There is also a test-run program in EMC2 – use that. The initial testing also involves calibrating the switches, and the machine itself. This can be a complicated procedure with troubleshooting so have patience and progress logically.
Make the housing of the electronics and make the housing for the machine itself. Now that you have an idea of how your machine looks like, it is easier to make a good housing.
Now you are ready to fire up the CNC — remember to also fire up the grill – milling ‘n’ grilling makes good sense.