gocnc

README

gocnc

A command-line GCode sender and optimizer for CNC routers

This tool is written in golang, and as such requires a configured golang environment (https://golang.org/doc/install).

What does it do?

Well, it sends your gcode. And optimizes it.

It offloads arc approximation, minimizes moves between sections of a job, kills redundant code, and just tries to make Grbl and the router waste less time. Optimizations are thrown in there as I make them up. They can all be disabled or configured where applicable from the command-line.

As for gcode sending, it provides a nice progress bar with estimated time of completion, and ensures that Grbl always has something to chew on by maintaining a full serial buffer. (Normal senders wait for an "OK" on each command, while this tool maintains a full buffer, parsing the responses as they arrive.)

Usage

Installation

  go get github.com/kennylevinsen/gocnc

Update

  go get -u github.com/kennylevinsen/gocnc

Build

In the gocnc directory ($GOPATH/src/github.com/kennylevinsen/gocnc)

  go build

Run

The usage guide can be retrieved with:

  ./gocnc --help

A usage example:

  ./gocnc --device /dev/tty.usbmodem1441 ~/gcode.nc

Or if you don't want any optimizations:

  ./gocnc --device /dev.tty.usbmodem1441 --no-opt ~/gcode.nc

Or, perhaps you only just want to know the work-area and estimated runtime:

  ./gocnc ~/gcode.nc

To stop the job, press Ctrl-C. This will send a Ctrl-X to Grbl, stopping things immediately. For feedhold, press Ctrl-Z. Resume by pressing enter.

Why Go?

Well, because it's awesome. I originally wrote the tool in Python, but performance wasn't quite as good as I had hoped with larger models exported by MeshCAM, which for complex models easily export 4MB+ gcode files - and thats with very efficient gcode.

So, I wrote the new tool in Go. What took up to 2 minutes through PyPy took me 1-2 seconds in Go.

Features

• Optimization (Path grouping, vector optimization, lift speed, .... All configurable with command-line parameters)
• Simple gcode output (Handles arcs and canned cycles internally, outputting only G0 and G1 for moves, and a few other things, such as feedrate mode)
• Manual tool-changes (Moves to a configurable position, turns off spindle of possible and waits for user-entry of new tool-length to compensate for in the rest of the program)
• Manual spindle and coolant control prompts (configurable)
• Spindle and coolant waits (To let the spindle spin up or coolant flow)
• Ability to send to multiple end-points (such as a seperate thing for handling a VFD for spindle control)
• Quick overview of work-area and ETA of file before file it gets executed (Will be way off, but it's helpful for giving you an idea)
• Can output to file if you only want the optimizations or simplifications

Upcoming

• Jogging (High priority, but a tiny bit nasty if I have to do it by sending random G1's)
• Coordinate offsets
• Canned cycles (Peck drill, ...)
• Terminal UI ('Cause it would be awesome!)
• Position status (Slow refresh rate for Grbl at the current rate, but should be fast for TinyG/G2)

Under consideration

• Rotational axes (Shouldn't complicate matters too much, but might require some extra considerations for the optimization passes)
• Web UI (I hate web with a burning passion, but I might consider it if it provides some significant benefit)

Detailed description

This tool has been written to assist me in my use of a Shapeoko 2, where I became horribly frustrated with GCode generators' poor output, as well as GCode senders' poor user experience and speed.

For the GCode sender, this tool implements a "streamer" for GRBL (more to come...?), that ensures that the 127 char serial buffer is always as stuffed as it can be, so that there will always be something for it to chew on. Otherwise, large amounts of very short operations might cause its planning buffer to be depleted, stopping all movement until more input has been processed.

For optimizations, I have gone to quite crazy lengths, implementing a sort of interpreter, or "CNC VM". It "executes" the entire parsed AST, updating its position stack and states along the way. When done, the stack is dumped, which makes optimizing the code much easier, as all states have been kept track of. Working on the AST/file directly, comes with the risk of losing other flags that were on the same line, making modifications an utter headache (Trust me, I speak from experience. That's what my first tool did.)

The optimization passes can be summarized as:

• Remove redundant code (Does not change behaviour)
• Use rapid moves Z-axis lift and drill moves where possible
• Vector optimization (Removes moves which cause a path deviation below the tolerance)
• Group paths, to minimize time spent seeking around

The last is by far the most complicated, and results in the largest gain. The slower the machine, the larger the gain. For my very fast shapeoko, I get ~15-20% speedup on the tests I have made, which will become much more with more sane maximum speeds. It is only really useful for 2D stuff, and automatically bails out with a warning when it might be unsafe to run.

To aid controllers like Grbl, and in general produce higher calculation accuracy and configurability, arcs are calculated by the VM, so that the VM position stack only contains straight lines. This makes optimization and analysis much easier, allows for double/float64 during calculations, and lets a very heavy task off Grbl's shoulders. Many GCode interpreters seem to be unable to handle the more complicated uses of arcs as well, and this ensures that they don't have to worry about that headache.

In the future, more functionality will be soft-implemented, such as peck drilling cycle, etc.

Notes

Path grouping is experimental. If it does not work correctly, please file a bug with the gcode. It can be disabled by using "--no-optpath". I fix the cases as I meet them - Open an issue if one is found.

gocnc currently use a fork of goserial, as goserial handles a lot of things poorly. When my patches reach mainline, it will be reverting to using the standard variant.