3D Waterline slow/jerky movement

Here's the place for discussion related to CAM/CNC and the development of the Path module.
Forum rules
Be nice to others! Respect the FreeCAD code of conduct!
Post Reply
AD47
Posts: 7
Joined: Sun Jan 22, 2023 11:42 pm
Contact:

3D Waterline slow/jerky movement

Post by AD47 »

Hi all,

I am attempting to utilize the Waterline operation to put a roundover on the part in the first image below. Using a 0.5 inch ball nose endmill. The path produced causes my machine to move in a slow, jerky fashion. I am running mach3, ESS, my Freecad details are below the images.

I have played around with both the Waterline "sample interval", and the Mach3 Constant Velocity settings to try and smooth things out. I haven't found an acceptable configuration yet. The machine runs very well on more typical paths for pockets or profiles.

The second image shows a view from the top of how the path is generated. The path seems fairly jagged, which lines up with the machine's behavior. Have others experienced this? I know the Mach3 controller isn't the best - curious if others have similar experiences. Freecad file is attached. Thanks for your thoughts!

Screen Shot 2023-01-30 at 6.20.13 PM.png
Screen Shot 2023-01-30 at 6.20.13 PM.png (292.03 KiB) Viewed 491 times
Screen Shot 2023-01-30 at 6.22.25 PM.png
Screen Shot 2023-01-30 at 6.22.25 PM.png (47.22 KiB) Viewed 491 times

Code: Select all

OS: macOS 10.15
Word size of FreeCAD: 64-bit
Version: 0.21.0.31641 (Git)
Build type: Release
Branch: master
Hash: d28d63b87b60161419c6c0c532fbbfaed96926b8
Python 3.10.8, Qt 5.15.6, Coin 4.0.0, Vtk 9.1.0, OCC 7.6.3
Locale: C/Default (C)
Attachments
Tincture Holder 2.FCStd
(130.71 KiB) Downloaded 20 times
GeneFC
Veteran
Posts: 5373
Joined: Sat Mar 19, 2016 3:36 pm
Location: Punta Gorda, FL

Re: 3D Waterline slow/jerky movement

Post by GeneFC »

AD47 wrote: Tue Jan 31, 2023 3:34 am
Yes, I have seen exactly this behavior.

The jerky movement comes from the code that consists of a great many short G1 segments. Many adjacent segments have rather different trajectories. The controller typically slows or stops between code steps so that machining precision can be mainained without cutting corners, etc. When there are a fair number of long segments the slowdowns are not really noticed. However, when there are many steps that take only milliseconds the start-stop feature of the controller will cause jerky motion.

One probably does not want to detune the controller because pattern inaccuracy could result. A change in feed rate might help in some cases, especially if the rought motion causes some sort of resonance.

The waterline operation finds the "tool touch points" at every location selected by the parameters (stepdown, sample interval, stepover). The FreeCAD code creates the g-code path. It could probably use a bit more smoothing.

Gene
Post Reply