CNC software... some questions (Uber-Newb)

[TroyO]

I have been contemplating using some expected "extra funds" to CNC my X2.

If I understand the posts in the CNC forum I will need some software that will also impact the budget. I *think* I have a handle on what I need but I could use some advice.

1) CAD software.... Alibre looks like a decent bet.... $100

2) CAM.... not really sure what this does. I get that it's "Computer Aided Machining" but I'm not sure why it's not already part of the CAD software? It's kind of like peanut butter and jelly? Anyway... not sure what I need here. It takes the 3D drawing and turns that drawing into text based G-code, right? Is Mach3's built in "LazyCam" sufficient for most hobby uses?

3) "NC" Machine controller... Mach3 seems the popular choice. Is the 500 lines of G-code allowed usually enough for simple parts without buying the full version? Can I run 500 line "chunks" in sucession for more complex stuff? .......$175

So, that's $275 just for software. Makes a $750 budget mighty slim.... any respectable freeware options out there?

 

[kvom]

CAD - Alibre is a 3D drawing program with, apparently, a somewhat steep learning curve. Since most model engine parts are 2D or 2.5D, the drawing portion is overkill for CAM. That said, being able to build visual models can be useful.

CAM - this program takes the output of the CAD program (e.g., a drawing file such as DXF) and generates the g-code for machining the part. The program I use is CamBam, which is a quite good 2.5D CAM program and also does 3D CAM as well. It's a good value, and you can try it free for 40 executions. I know Steve Huck on this forum has just started using it as well. CamBam has a basic, useable CAD facility as well, so you could draw and machine some parts before investing any software dollars.

Controller- EMC on Linux is shareware if you are comfortable with Linux. With CamBam you can generate separate machine operations from the same drawing, allowing several short programs. In any case, most 2.5D g-code programs are less than 500 lines. OTOH, 3D programs can be many thousands.

 

[TroyO]

I'm fine with Linux... been a few years since I played with it, but I once used it regularly on a desktop.

Hmmm, OK... so what's 2.5D? Not sure I follow? (EDIT.. never mind, looked it up. 3D profiling from one side/no undercuts.)

As I read and learn more (I'm all over reading everything I can get to, LOL) I think maybe I understand why CAM is different than say using an image editor and choosing to save it as a GIF instead of a JPG, which IMHO should be built in. It was bugging me... I was equating it to buying a copy of "SuperImagePaint" and paying good money for something that couldn't even export to "GIF".

If I have it right, G-Code isn't just a different file *format*.... it's actually the result of a series of calulations resulting in a set of toolpaths which *result* in an object that matches the CAD file. What you are paying for is software to calculate out what the toolpath is, not just something that converts file formats. I can feel better about that, LOL.

Is EMC pretty complete, or is it one of those open source apps that you can only make work if you are really desperate? (And I may be... LOL...)

 

[kvom]

g-code is a language interpreted by the machine controller. A code is a letter (G or M typically followed by parameter code).

Some examples:

G0 X0 Y0 - move rapidly to the part origin coordinates

G1 F5 X1 Y2 - move the spindle at a feed rate of 5IPM from its current position to (1,2) in a straight line

G2 X1 Y2 R2 - move the spindle in a clockwise circular path with radius 2 from the current position to (1,2)

G81 X1 Y2 Z-.5 F3 R.1 - move rapidly to (1,2), then down to .1 above the Z origin, then drill to a depth of .5 below the Z-origin at 3IPM, and then retract rapidly to Z.1. This is called a drilling cycle.

T1 M6 - change the spindle to tool #6

M3 S2000 - turn on the spindle clockwise at 2000 RPM

M8 - turn on the coolant

The files containing the g-code are text files, which in windows typically have a suffix of .nc or .cnc. They can be hand-edited to correct problems once you understand g-code reasonably well.

 

[TroyO]

Hmmm, CamBam does look like it would give me a decent start. Even if I get Alibre later, it would still cover the CAM portion of the CAD/CAM/Control triangle if I decide I need something better later.

So, my proposed path at the moment is Mach3 Demo on a Win Partition and EMC on Linux set up as a Dual boot, with CamBam on another PC to draw out the parts.

That way the option to upgrade by adding Alibre and/or getting the full version of Mach3 won't be "wasting" anything.

So, I'm going to budget $150 for the software (It doesn't need to be down to the penny.. just seeing if it's even feasible for $750 total) so I have $600 left... this just might be doable. (Counting on having a decent chunk of stock on hand and using a stock-leadscrew modified version of Hoss's plan)

Thanks Kvom! +1

 

[shred]

In a nutshell:

CAD converts what you're thinking of into a dimensioned drawing or model inside the PC-- Generally this output is in a standard format like say "DXF" for 2D parts

CAM converts that drawing into commands for the machine controller "Go to X1 Y.2 then go to Y3 at a speed of 3 IPM" That's G-code and also mostly standardized (it varies some by controller)

The controller then converts those into "Motor X, on" ...wait a bit... "Motor X off" to drive the machine around. In the PC / homebrew CNC world that's mostly MACH, but on bigger machines, the machine itself takes in G-code and drives the tool around.

Some programs do both and are called "CAD/CAM". The integration can be nice... if it does what you want. Generally CAM gets a lot more expensive when you go from 2.5D to 3D, and more so to go to 4th-axis. Most of the time, unless you're doing sculpture or something, you'll be doing 2.5D parts.

You can also write G-code yourself. I've seen some amazingly complex parts done completely by hand on a machine control panel. It's worth having some experience reading and writing G-code for those times when you want to check what's coming out of your CAM program.

 

[TroyO]

Heh... well, I used to write my webpages with notepad.exe so I will probably become a G-code fiddler in short order. ;D

Now to figure out if I can manage the rest of it for $600... it will be tight. Not that I intend/expect it to go forever more without upgrades (Better software/Ballscrews/Whatever) but I'd like to get up and running and started for around the $750 mark.

 

[Tin Falcon]

troy
If you have not already done so read and reread my post on what is needed for cnc . There is a lot of info on that post and a whole lot more on the web in general.
http://www.homemodelenginemachinist.com/index.php?topic=9787.0
there is also my x-2 conversion thread
http://www.homemodelenginemachinist.com/index.php?topic=4054.0

Tin

 

[TroyO]

Thanks Tin!

I have indeed read (And re-read) your post on what's needed for CNC several times. As I learn more and more of the terminology it's starting to "click" better. Thank you for the post, it's been helpfull!

Right now the plan is:

Hardware from Hoss's plans existing stock, Fastener kit, Pulley($100)
TB6550 Driver/Steppers/Power Supply/Etc (http://www.hossmachine.info/Shop_Info.html#x2 electronics) ($250)
Software ($150)
Misc cabling and connectors ($100)
Screws/Nuts for Z (Using stock X and Y) ($40)
Bearings ($40)

Total of $680

Leaving $70 for "Gee I didn't think of that."

 

[TroyO]

As it ends up... LOL, scratch all the above.

I just got back from visiting "Club Workshop" in Denver. It's a work center where they have all kinds of tools you can use, including as it turns out 2 big old CNC milling machines.

So... I think I'll not CNC my mill after all.. but I will get Alibre so I can draw up my parts.

So... thanks for all the help, everyone. I still learned a lot by fact of doing the legwork!