LinuxCNC angular axis and inverse timing

hello,

Well, I'm having trouble finding a CAM package that will control my 4th axis correctly. Maybe I'm doing something wrong but right now I use a CAM product called DeskProto to do the 4 axis g-code. The code will state something like G1 A360.0 F9.4 Then LinuxCNC moves the A axis one full turn but at 9.4 degrees per minute, not 9.4 inches per minute!

That's very sloooooow, BTW!

Can I tell LinuxCNC to interpret that line differently or is there some sort of converter? I can't seem to find a 4 axis CAM package that supports this "inverse timing." I found all of this in the NIST documents on RS274/NGC and have been very sad ever since. I can't seem to find anybody that can help.

I have a very sweet little CNC and the software is becoming harder to get a handle on than actually building the machine! I though for sure it would have been the reverse.

Thanks for the help!

Can you select different post processors?

Have you read this...
www.linuxcnc.org/docs/2.4/html/gcode_mai...ml#sub:G93,-G94:-Set

Rick G

are you using a specific post processor for linuxcnc or a default one ?
without seeing the full post processor output it may be it just needs the specific G94 or whatever adding either to the gcode output , or the postprocessor amending for use with 4th axis

is the postprocessor editable ?
you just need to dig a bit deeper

Yes, I have read that link. Once I had read the NIST docs I knew finally what to google and found the docs for LinuxCNC. Its been about a month that I have been searching this.

As to the post processors, yes DeskProto has the ability, yes it has one named EMC, no it does not take the angular movements into account.

That said, I started asking all of the CAM companies and they would answer some crazy crap. I haven't found one yet within my price range thus my posting here.

cncbasher wrote:

are you using a specific post processor for linuxcnc or a default one ?
without seeing the full post processor output it may be it just needs the specific G94 or whatever adding either to the gcode output , or the postprocessor amending for use with 4th axis

is the postprocessor editable ?
you just need to dig a bit deeper

For DeskProto, the post-processor is a menu driven system. G94 isn't support via the menus and the guy writing it admits his software does not support this, yet.

As to digging deeper, that is exactly what I'm doing. The other package I looked at, RhinoCAM (Visual Mill as a Rhino plugin) doesn't support LinuxCNC either. They won't come out and say that directly but when you corner them on it they will admit they do not have support for inverse timing.

I really do wish it is as simple as adding G94 some place. I built my system around using LinuxCNC and so far, 3 axis works like a charm. Actually it works far better than I had dreamed it would. Its just when that A axis comes into play everything slows down to a crawl.

all depends on what you use as your drawing package , i'm not a big fan of Rhino , Rhinocam or Bobcad ,
I tend to use either Mastercam or Solidworks & Camworks , but I appreciate they are expensive packages, and not hobby based ,
i'm not sure but if your just woodworking then Aspire might be worth a look , but check on the 4th axis support

it depends on what your needs are of course , HSMWorks is an other , although the free version I believe only supports 3 axis .

you can manualy add g94 etc to the line which has the F9.4 using a txt editor ,
g code files are only a txt file with a .ngc prefix and even that can be changed in your ini file .

cncbasher wrote:

all depends on what you use as your drawing package , i'm not a big fan of Rhino , Rhinocam or Bobcad ,
I tend to use either Mastercam or Solidworks & Camworks , but I appreciate they are expensive packages, and not hobby based ,
i'm not sure but if your just woodworking then Aspire might be worth a look , but check on the 4th axis support

it depends on what your needs are of course , HSMWorks is an other , although the free version I believe only supports 3 axis .

you can manualy add g94 etc to the line which has the F9.4 using a txt editor ,
g code files are only a txt file with a .ngc prefix and even that can be changed in your ini file .

OK, makes sense but I'm tied up by lack of funding. That said, I use Rhino v5 which is a great tool for the price. It gives me access to a good portion of the SolidWorks files other's produce and I can at least express my ideas to other Solidworks owners.

My machine is a Sieg X3 conversion using CNCFusion's deluxe 5mm Thompson ballscrew kit. I use a Sherline 3700 rotary table mounted at 90 degrees with the A2ZCNC tooling plate. Probotix built me a 4 axis electronics package which I am very happy with. All of these companies and people are honorable and very helpful with their products.

So, I am cutting metal. I am specifically building this machine as a two fold project; 1.) to learn CNC and 2.) to use it to build parts for a larger moving gantry CNC machine. My ultimate goal is to design home/amateur built aircraft kits that can be turned out via CNC.

As far as 3 axis milling, I have machine that has exceeded my wildest dreams. The 4th axis is frustrating, not because of the hardware or even LinuxCNC but simply because the CAM software.

So, maybe somebody can send me a really cool g-code file with a neat little thing I can cut in machinable wax and that will prove my 4th axis is usable? Scary running other's code because I don't have a preview tool.

As to manually adding the G94 code, I started that but it scares me doing a search and replace since if I crash my machine, repairing it will be a bigger problem than not driving the A axis to it's full potential.

Yes, I have a fully licensed copy of the 4-axis version of DeskProto. I also have the 6.1 beta version for testing and it is a really nice, easy to use program. It's just not continuous 4 axis milling like say, RhinoCAM (aka VisualMill) but its great for a small time guys like me to learn with.

Here is a sample from the 4-axis version of DeskProto's g-code output;

G1 A360.0000 F15.0
G1 X0.0123 F15.0
G1 A0.0000 F15.0
G1 X0.0368 F15.0
G1 A360.0000 F15.0
G1 X0.0613 F15.0
G1 A0.0000 F15.0
G1 X0.0858 F15.0
G1 A360.0000 F15.0
G1 X0.1103 F15.0
G1 A151.1688 F15.0

The post-processor in DeskProto is very specific and driven with buttons and a few text entry fields. I assume that the other CAM packages have something a bit more advanced like the ability to pull values and reformat things depending on prior variables or whatever to produce this level of alteration of the g-code. DeskProto does not provide that level of ability in the post processor. I would imagine something like a basic or some kind of scripting engine would be needed to do this correctly, right?

That said, the beta version (6.1) says something about JavaScript so I will investigate that. I am not above programming a fix myself and passing it along to everyone else.