Polyline precision for smooth cutting? No faceting?

  • Advertise with us

« back to CNC Woodworking forum

Forum topic by 007lab posted 12-21-2014 12:26 AM 1410 views 0 times favorited 2 replies Add to Favorites Watch
View 007lab's profile


22 posts in 2958 days

12-21-2014 12:26 AM

How many line segments in a wavy polyline are too many before one blows up their cnc machine?

I’m trying to draw a wavy line about 15” long. It can’t be faceted at all. Very organic looking.

So, I have two questions:
1-It’s easiest for me to draw the shape I want with the spline tool. Do I need to convert this line to a polyline when I send the dwg file to the cnc? (The CNC runs on Millwright 6.)
2-When drawing a 15” wavy spline I can convert it to a polyline and then specify the precision from 0-99. Roughly what number along that range would remove faceting, but not bog down the program?

It would be a lot easier to test this out on my own if the shop wasn’t 30 minutes away. So unfortunately I can’t walk over to the machine and run a test cut.

I’m running autocad for mac 2015.

2 replies so far

View changeoffocus's profile


467 posts in 2628 days

#1 posted 12-21-2014 12:40 AM

I don’t know about your CNC but ACAD has a join command that turns segments into polylines.
I view the output to the CNC like sending a drawing to a plotter which provides a far more smooth line that the screen zoomed in. If you regen those lines will smooth out on the display as well. I always to curves and such as half of the drawing then mirror the image so they match perfectly.
Overlapping arcs and trimming is preferable to spline lines as spines tend to make the drawing size go up very fast.
Hope this helps.

View DS's profile


3683 posts in 3431 days

#2 posted 01-02-2015 01:59 AM

Most CNC controllers can interpolate an arc line just fine (no facets at all)

I have yet to encounter a CNC machine that could manage ACAD splines. I’ve always had to convert them to arcs. (No g-code equivelent for splines)

Polylines allow you to make a continuous cut without the tool lifting out of the workpiece after each segment.

Also, as far as limits to the number of facets, I’ve found CNC machines to be very patient with the minutiae and diligently execute each and every line of code, usually without blowing up.

Happy new year

-- "Hard work is not defined by the difficulty of the task as much as a person's desire to perform it.", DS251

Have your say...

You must be signed in to reply.

DISCLAIMER: Any posts on LJ are posted by individuals acting in their own right and do not necessarily reflect the views of LJ. LJ will not be held liable for the actions of any user.

Latest Projects | Latest Blog Entries | Latest Forum Topics