Newbie- new to CNC - where do I start?

[RebelTaz]

Hi... I am totally new to CNC. After years of drooling over commercial CNC machines, I picked up a book the other day on building your own. Although it expects the reader to figure out a lot of the details as he goes along, all in all it's a pretty good book. I have most of the components I need to start building it, except for the electronics, and I plan to start building it this week or the next.

Here is my problem... Once I get it built, I have no idea how to use it! I have tried searching the net, but all I come up with is classes on running professional commercial CNCs. I know, or at least think I know, that you design the piece in a CAD program, run it through another program that converts it into g-code and then through yet another program that sends the g-code to the machine. For me, though, as a total newbie, that is like drawing a flowchart and expecting the Mona Lisa.

Is there anywhere that I can find like a step-by-step manual or tutorial on how to get started? Any advice or push in the right direction would be greatly appreciated!

[Jack000]

sounds like you got the gist of it.

first you make a cad file

then send it to a cam (computer aided manufacturing) program to convert to gcode (I like cambam, but there are free ones as well)

then the gcode goes to a controller program that outputs the pulses to your stepper drivers (emc2 or mach3), which make the steppers spin around to produce your part.

that's really all you need to know to get started.

[RebelTaz]

Originally Posted by Jack000 sounds like you got the gist of it. first you make a cad file then send it to a cam (computer aided manufacturing) program to convert to gcode (I like cambam, but there are free ones as well) then the gcode goes to a controller program that outputs the pulses to your stepper drivers (emc2 or mach3), which make the steppers spin around to produce your part. that's really all you need to know to get started.

Yeah, that much i do get, but I think my problem is in understanding things like... how do you know (or rather how does the control software know) where you have placed the workpiece, how does the software know where to start the cutting head (ie. router)... Do you just place the piece on the table, manually locate the router to one corner, say, and then design the cutting control codes around that starting location?

I think, more simply, what I have trouble with is the fact that there is no default 'home' position for the cutting tool. Not on the DIY builds - I don't know about commercial units. Do they have a 'home' position? So, without a default 'home' for the router to dock - on all three axis; x, y and z - then how do you tell the software (like cambam) where to start form?

I know this probably isn't coming out right, it's hard for me to put what I am trying to say into words. I guess like this: If the router always started at 0,0 on the x,y plane and .5mm above the workpiece on the z plane, then every time you layout a project, the software could start the cut from those co-ordinates. But since there is no standard 0,0,05mm position, the router could just as easily be at 123,546,12mm when the control software starts the cut.

My head hurts... Is this making sense to anyone other than myself? thanks....

[Crevice Reamer]

Hi Derek. Welcome to the Zone!

Start here:

http://crevicereamer.com/Page_2.html

Electronics:

http://crevicereamer.com/Page__57.html

CR.

[Jack000]

zero is where ever you want it to be. Just manually bring the bit to the corner of the work piece and set that to zero.

if you have homing switches, you can do it automatically.

[RebelTaz]

Originally Posted by Crevice Reamer Hi Derek. Welcome to the Zone! Start here: http://crevicereamer.com/Page_2.html Electronics: http://crevicereamer.com/Page__57.html CR.

Thanks for the welcome The information of your site was very informative. Especially the CNC Information page. I know that you, and everyone else pushes the high-dollar, high-powered steppers/drivers and I do understand the logic. But with money being at a premium for a self-employed sometimes-I'm-jam-packed, sometimes-I'm-twiddling-my-thumbs mechanic/technician, I simply cannot afford to go that route on my first foray into the CNC arena. I may build this thing and in a month ask myself why. Or I may build it and become obsessed with it and have to upgrade. But thank you for the help...

Originally Posted by Jack000 zero is where ever you want it to be. Just manually bring the bit to the corner of the work piece and set that to zero. if you have homing switches, you can do it automatically.

Ok... I get homing switches... one of the boards I am looking at has connections for those. Can you set homing switches on all three axis' or just the X and Y? Thank you as well...

[RebelTaz]

Oh... one more thing I wanted to ask... The cutting bit - does the control software take into account the diameter of the cutting bit? Because if one piece were cut out with an 1/8" diameter bit and then a second piece were cut out with a 1/4" bit, one piece would be slightly larger than the other if the software didn't take that into account, wouldn't it? Or do you have to take that into account yourself when creating the g-code?

All these questions! sorry, guys....

[judleroy]

Yes you home all 3 axis. You can also get software that accounts for the tool size or you can offset your geometry yourself. Pretty much the answer to 99 percent of your can the machine do this questions will be yes. People have long since overcome the obstacles your afraid of running into. The best thing to do before you even consider building anything is to get a cad software and learn to draw your ideas. Then get a cam software to familiarize yourself with the process of setting toolpath info, tool info, part offsets etc...If you get past these obstacles which are really the hard part of cnc(not building the machine) then start your machine build. Good Luck
Judleroy

[analogman]

If you are planning on using Mach3 to control the CNC, check out the videos on their site.

[RebelTaz]

Originally Posted by judleroy Yes you home all 3 axis. You can also get software that accounts for the tool size or you can offset your geometry yourself. Pretty much the answer to 99 percent of your can the machine do this questions will be yes. People have long since overcome the obstacles your afraid of running into. The best thing to do before you even consider building anything is to get a cad software and learn to draw your ideas. Then get a cam software to familiarize yourself with the process of setting toolpath info, tool info, part offsets etc...If you get past these obstacles which are really the hard part of cnc(not building the machine) then start your machine build. Good Luck Judleroy

Ok... maybe I am asking the wrong question here then. For over 25 years I have been able to teach myself everything I ever needed to know about computers - from building them to Photoshop, HTML, C++, PHP, even EagleCAD electronic design... In the CAD arena, though, I am freaking lost.

Is there an online video tutorial (or even a book) that goes through designing simple 2d objects in CAD, running that design through CAM and then on to the CNC after which goes into basic 3d design?

All I need to learn something is to either read books on the subject or see it done a few times. The peoblem I am having with this is that either I can't find any information on what I am trying to do, or the info I find is not making sense to me.

[DIYaholic]

There are several "trial" versions of 3D/CAD software available. Search the CAD Forum for links. I downloaded the trial version of Alibre Expert (with full functionality), after 30 days it converts to a limited function version(all for free). Alibre comes with tutorials. There is also Google Sketch Up, that is also free and full of tutorials. I'm sure there are many more, these are the ones I have tried.
BTW, welcome to the Zone. This is a great place: Talented people with a desire to help (and do I ever need the help).

Randy,

[jsheerin]

To focus on the cam section of the process, generally the way it works is you import your cad file into the cam program. Then you tell the cam program where to position your part relative to the origin (0,0,0). Then things can vary depending on the program, but in mine you tell the program where the material to be cut is and how big it is. This lets you simulate your cutting paths later. Then you might enter some information about the tools you'll be using (typically diameter at a minimum). Then you start creating cutting operations to create the part. In these, you'll typically input information relating to how fast to cut, how deep to cut, how deep to cut per pass, etc. You might create a facing operation to flatten the top of the part, a drilling operation to drill some holes, a pocketing operation to remove some more material, a 3D surfacing operation to cut a 3D surface, etc. Then you specify which post processor you want to use (so the g code generated will work with your machine controller - Mach 3, emc, etc.). Then you generate your g code. The cam program doesn't just magically spit out g code. Hope that clarifies that a little.

The way I got a handle on all of this was to download some trial versions of programs and go through all these steps, following tutorials for the individual piece of software. However if you have never done cad work, I'd get a handle on that first.