Trying to get my machine running fast and smooth

I have been using a combination of cambam and more recently fusion360 CAM which is an offshoot of HSMworks.

2D stuff usually runs at full speed in cambam and pretty well with fusion360.
The one time I tried machining 3D with cambam my machine ran like someone with Tourettes driving a car with square tires.
Fusion 360 comes in and out. It has tolerance and smoothing tolerance settings which do help but it doesn't fix it altogether. The looser the tolerances the looser the accuracy too.

I did some searching and found a little information but not a whole lot. I found something that suggested part of the issue is that linuxcnc only looks at the current line of code or perhaps one ahead. Other responses seemed to think it was more of a CAM issue.

Whatever it may be I am hoping there are some ways I can improve it.

Anyone have any suggestions?

Take a look at G61/ G64 P- <Q- >

www.linuxcnc.org/docs/2.4/html/gcode_mai...#sub:G61,-G61.1,-G64:
and

wiki.linuxcnc.org/cgi-bin/wiki.pl?TrajectoryControl

Also take a look at the new trajectory planner.

www.linuxcnc.org/index.php/english/forum...stersprograms-wanted

Rick G

Awesome info.
Now can you break it down for a total noob?

Can you make some suggestions for a good setup for me or input on how to come to a good solution?
I want to maintain tight tolerances but I am not chasing micrometers here.
Most of what I do I aim for +- .2mm the problem is that I think that's about all I can expect of the machine at the moment so my goal is pretty much to keep everything as tight as I can both in hardware and software.

Is there any way to know what kind of tolerance loss you are looking at with G64?
Or would I be better off going with G64 P- Q- ?
If so could you suggest some starting tolerances?

I have spent years running manual machines, building CNC type machines and all that but CAM, programming and that side is very new to me.
I am totally unfamiliar with Gcode and all that.
Is this something that you can set the machine to do as default?
Or is it the kind of thing you can enter at the beginning of the file to apply for the whole program?
Or is it more complex than that?
As someone pretty new to linuxcnc, and CAM and with a pretty new machine still getting it dialed in would you recommend the new trajectory planner?

I always use G64 P- Q- at the beginning of my G code.

As I work in inches on my mill I might use G64 P.001 Q.001 and on my plasma perhaps G64 P.005 Q.005

G64 P- Q- is a way to fine tune your system for best compromise between speed and accuracy. The P- tolerance means that the actual path will be no more than P- away from the programmed endpoint. The velocity will be reduced if needed to maintain the path. In addition, when you activate G64 P- Q- it turns on the "naive cam detector"; when there are a series of linear XYZ feed moves at the same feed rate that are less than Q- away from being collinear, they are collapsed into a single linear move.

An example of the pre amble to a G code I use would be...

You may be able to set your CAM program to automatically add a G64 P- Q- to the output of the post processor.
In theory if you set either G61 or G64 when you start linuxcnc it will stay in effect until it is changed by another G61 or G64 command.
Take a look at the G code you are running and see if there is a G61 or G64 there, if so edit the G code with the proper G64 P- Q- command and see if it runs better for you. If not just add the command to the beginning of the G code.

The velocity you are running and your acceleration rates can have a dramatic effect on the the output of your machine. The CAM also can have a large effect depending on it's output, an arc may run smoother than a large number of short segment moves.

Rick G

Thanks, I really appreciate it. I will try playing with this when I have some time.

Still curios about the new trajectory planner. Do you think this is something I would be safe and happy diving into or would I be better off giving it a little longer to get dialed in?

I am using the new TP on my plasma table and it runs smoother and faster on complex patterns that are composed of many short segments.
When I get the time I will also switch my router and mill.

Rick G

Thanks again. I couldn't be bothered to read the whole TP thread but I read the first and last few pages.
Would the install instructions in the first post still be my best option?
Or later on I see mention that it's been put into 2.7 master. I assume this is a more risky option?

The simplest way to get it now is to install master from buildbot.

On my new mill 2.7.0~pre runs just fine, but of course there is a risk in running bleeding edge software.
I compiled mine as 'run in place' install. This way it is very easy and quick to switch back to 2.5.4 if required.

I would definitely recommend the new TP. I am running it for a while already and didn't see problems with endmills cutting where they shouldn't.

I would like to try to get 2.7 installed on a second machine so I still have my current computer running the machine with the ability to switch back and forth till it's dialed in. I did some searching to find an iso of 2.7, instructions on how to install it or info related to buildbot but couldn't find anything.

How do I install 2.7?