Bobcad + Gerber router

[smurph]

Oh boy... This will spell the end of what you can do in the BobCad post processor. You are going to have to run the G code output of BobCad through another "conversion" program.

If you are going to have to create your own arcs, then it doesn't really matter which post processor you use. Just pick Fanuc 6M and copy it to a different name.

You will need to modify most any Fanuc based post because calculating the arcs will be easiest with absolute midpoint coordinates. Fanuc uses incremental arc midpoints. Change the arc midpoints to be Absolute. For the canned cycles, uncheck all of them. BobCad will generate the long code for the canned cycles if you mark the post as not having any. (Pretty damn cool thing you did there BobCad!!!)

Now, about creating the arcs... What programming languages do you speak? I have some VB code that I wrote to make a back plotter. I scrapped the project because there was a nifty link on this board (in the vb programming section) to a nifty back plotter in VB 2005 that was a little more advanced than my efforts. But my humble code does just what you want it to do. It draws a circle with many little lines. That's because you can't really draw a real arc using GDI on a window! So in effect, it will be perfect. Well... almost. it just needs learn to read G02 and G03 inputs and to spit out X, Y, Z movements instead of screen drawing commands. But the arc segment calculation is there. I spent several weeks perfecting the little devil. It made me wish I had paid more attention in geometry/trig classes!

So in my mind, what you will have to do is make a very vanilla post processor in BobCad that uses absolute coordinates for the arc midpoints. Then create a new "post post" processor/converter program that takes the vanilla G code and spits out your Gerber code.

Let me know if you want to pursue this route.

Steve

[Vigilance]

That is exactly the route I plan to take.

As far as programming languages, though - I'm ashamed to admit that the last thing I programmed was a TI-89 calculator! I think those use at least some form of the Basic programming language though.

The arc segment calculation code you have will probably prove to be most valuable. Also - do you have any code to convert a decimal number to hex? I will need to be able to do that to make everything work nicely. I know that sounds absurd, but I will have to feed some raw hex through the spooler to get the nicer functions to work.

One question I have though - why absolute instead of incremental? I have to check again, but I believe the only thing absolute is used for on the router is for the home position - but again, let me check this (I'm probably wrong). I also have to do some investigating to see how the thing deals with negative numbers (probably not an issue anyway, since the spooler does a fine job with this).

I am hoping to write the converter so that it uses a "standard" G-code file - that way, I don't need to mess up whatever Bobcad (or any other program) is putting out normally. Scott Phillips (I think that was his name) over at Bobcad told me the Fanuc0M was the most basic G-code post.

As far as canned cycles - I don't think the machine really has any - but, since I'm not going to be doing any threading with a router, I don't think I have much to worry about .

When this gets put together, I think I'll post a video - this will certainly be something to see.

[smurph]

I don't think there is any code to convert a decimal number into hex. Where is the decimal in hex? Or do they just represent the decimal number (float) as it is in memory? I need some examples, I guess. Like what would 123.456 look like in the hex format that goes to the router?

Steve

[Vigilance]

2 inches would be sent as 00 03 0D 40 for an individual measurement (all measurements are 8 digits or 4 bytes of hex).

00030D40, converted to decimal, = 200,000 = 2 inches, in this case.

I can send you an email, explaining more, but this is the basic format of it.

Just take your decimal measurement, say 2.00000, and multiply by 100,000, then convert to hex. Took me some frustration and a lot of time to figure this out, but it works perfect.

[smurph]

Ok, I think that is just the binary representation of 200000 in big endian. This is what goes in the serial stream to the router, right?

Like you said to email me. Or give me a call.

Steve

[Vigilance]

Sorry I haven't gotten the chance to email or call, yet. I'll call or email ASAP, but it probably won't be this weekend (I'll explain later).

Thank you for being patient with me.

-John