Mastercam spline-spline extend

[SlaveCam]

When I try to extend two splines to each other, I get the message they do not intersect. However, when I extend the splines using a specified length so that they overlap each other and then trim them to each other, they trim just fine. Why is that?

[Thad]

Not sure why, but splines must overlap before they can be trimmed. You cannot use trim to extend and trim them like you can lines and arcs.

 

I guess that doesn't answer your question, but that's just how it works.

[AMCNitro]

2D/3D

[Thad]

2D/3D

 

Makes no difference.

[Zoober]

A spline is a mathematical calculation. To trim to another spline would require knowledge of the next node and control points. Since they don't exist, they can't be calculated.

[Colin Gilchrist]

The "extend" function, when performed on a spline, also takes into account the "direction" and "end-point" condition of the spline itself. Sometimes when you "extend" a spline, you'll notice that the extension is not smooth and tangent, but goes off in a "kinked" direction.

 

Zoober hit the nail on the head about a Spline being a mathematically calculation for fitting a smooth curve between control points. It is not a discrete piece of geometry like a Point, Line, or Arc.

 

Also, to add a further wrinkle, the spline may be a "trimmed" spline. That sounds well and good, but what happens is that in the background of the database, the "original" spline is still stored, and the trimmed spline is just "what's left over" after the trimming operation. This can quickly get messy when driving the geometry for a tool path, or trimming.

 

Best bet, if you have a Trimmed Spline, is to use the "Create > Point > Segment" function and create a bunch of points along the spline. I like to use fairly short spacing interval, just to maintain the original shape as close as possible. I also do a "Create > Point > Endpoints" on the spline, to make sure I have the exact start and end point of the Trimmed Spline. (Then do a "delete duplicates" so that you don't have overlapping points)

 

After creating all the points, use Create > Spline > Automatic, and pick the First, Next, and End of the spline. Mastercam will generate a new spline from those points, and you now have a "clean, untrimmed" spline in place of the trimmed one.

 

Last step I usually perform is Settings > Run user application > RMNodes.DLL. The "Remove Nodes" Chook will look to "filter" the spline, within a given tolerance, to reduce the memory needed to store the spline and perform calculations on it.

[Mjölnir]

A spline is a mathematical calculation. To trim to another spline would require knowledge of the next node and control points. Since they don't exist, they can't be calculated.

 

i used Cadkey (with Robert White's Fastsurf and Fastsolid add ons) for ages throughout the 1990's and well into the 2000's, and it would trim splines by extending them naturally based on curvature then trimming at intersections. 90% of the time for my work that was suffice. when i needed curvature different than the given result, or the trims were unsuccessful because they didn't intersect, i had to sculpt my own extensions. 

 

on the contrary, working with splines in Mastercam is like working in the stone ages. 

 

however, it is MasterCAM, not MasterCAD, so we should not be to critical of it i guess.

[K2csq7]

create

spline

blended spline

 

click the first spline and drag the arrow to the end you want to "extend"

click the 2nd spline and drag the arrow to the end you want to "extend"

 

Play with it a bit and note that you don't need to "drop" the arrows at the end, you can drop them a bit before the end and possibly get more desirable results. 

[David Colin]

As Colin explained, after trimming, you still can see (and even alter) original nodes clicking a button in 'Analyse entity' window.

Note that in 2017, there is a new information field in 'analyse entity' window which indicates trimming factor of splines.

[Teh Bear without Brains kinda idiot]

As Mr Lister from Red Dwarf would say extension and sometimes even  trimming of splines in MC is

smeggy.

 

Even convert to arcs and lines not always the best 

That`s why the best way for me is to   run command

edit>break many peaces>with tolerance 0.02 mm  and  with lines and arcs

I proceed  as in good old days

BR

[SlaveCam]

i used Cadkey (with Robert White's Fastsurf and Fastsolid add ons) for ages throughout the 1990's and well into the 2000's, and it would trim splines by extending them naturally based on curvature then trimming at intersections. 

 

This is how I wish it worked. Got to add to 2017 wishlist..