could someone explain the use of both side option in surface trim?

[rohit_rajan]

what does the both side option exactly do in surface trim?

[John.Pryal]

Hi Rohit, as i understand it, it simply splits a surface into 2 or more surfaces depending upon the trim item. As regards uses, none immediately spring to mind, but i know i have done this many times in the past, where i split a surface by trimming & kept both sides. Perhaps a surface that straddles a part line of a mould, where both sides need to be kept.

Regards

John

[rohit_rajan]

thanks for your reply John, it no more splits as i have seen..though the arrow surely becomes two sided..but it still trims the opposite side...

try this..make a race track shape from sketcher pallete...extrude it as a surface..sketch a straight or curved line..and try to split it with the sketch line....

[John.Pryal]

Hi Rohit, in this instance the trim object would need to cut across the entire track, not just one side. See the image

Regards

John

[rohit_rajan]

really sorry..the reason i asked you to do particular method..is b'coz i am at home now...and have no excess to proe...you have to extrude a race track sketch....as surface..not a flat surface...

[John.Pryal]

Ok, in that case, a slightly different approach, as long as this race track feature is not solid, then you can still apply a 2 side trim, you just need to use a datum plane or plannar surface as the trimming object. Again, see the image.

John

[rohit_rajan]

if i just need to split one side only?

[John.Pryal]

Then you just toggle the flip arrow to leave left side, right side or both.

[rohit_rajan]

ok may be i am confusing it..split with just one line..is that possible...?like a belt?

[dgschaefer]

I'm thinking we need images of what you are trying to do, but I don't think it's possible, not because of a Creo limitation but because of a geometry limitation.

A single line by itself can trim a surface if it lies on the surface and completely crosses it from one edge to another. To trim a racetrack into two 'U" shapes, however, you'd need to cross it twice, one at each straight segment. A single line cannot do that. Much like a single point cannot cut a circle in two arcs.

[rohit_rajan]

i agree..tomorrow as soon as i get access to proe i would upload what i want...thank you all for being so helpful.

[TomD.inPDX]

This sounds like a similar issue you ran into with the square-round funnel. Creo just doesn't handle this well even if the split is made. You can see in the previews how the division (trim) creates an "orphan". Even if you keep both sides, this is still an orphan. Oddly enough, This orphan can magically switch sides if you force its inclusion.

[TomD.inPDX]

This should illustrate the illusive orphan...

Notice how the orphaned side keeps flipping.

Video Link : 5181

[rohit_rajan]

yes that is exactly what i wanted to tell...

now is that two sided split doing this right or PTC needs to correct this?

[TomD.inPDX]

PTC should certainly investigate this odd behavior. If anyone wrote a specification that required this, they should be drawn and quartered, shot, and hung. Not in any particular order mind you, but we can write that specification also.

However, I suspect this is so deeply rooted in the core that a change will be like asking for complete rewrite of the code. I even tried a sweep along the track where the sketch is divided there. And although the edges recognized the endpoints of the divide, the surface is continuous.

There simply is no way to merge just one end of a surface. If it is connected, it merges... if it find ambiguity (in the opinion of the code) it does a little dance and decides who wins.

If you form a feature to the desired shape, it may maintain that division. Things like spinal bend for instance requires an End to continuous loops. But those features are no longer "native". I suspect sheetmetal does something similar.

[rohit_rajan]

well sheetmetal is able to give a zero thickness cut with a sketch rip..so i thnk may be the surface split option should also do it?

[TomD.inPDX]

Try the racetrack with a spinal bend. I suspect it will work perfectly. The next question is, will it flatten as expected... and here I suspect the spinal bend is not recognized as a surface that can be flattened.

I'll give it a try but there is a very specific case where material can occupy the same space and remain separate, while the same thing in a different definition merges.Unfold sheetmetal, for instance can occupy the same space but remain independent and spinal bends must have an edge and will not join no matter what you do.

[TomD.inPDX]

Nope, I was wrong... yes, a spinal bend maintains the edge in the middle of a surface and yes, it can be flattened without fuss.

[rohit_rajan]

i think the both side option does not make sense in surface trim..as it does not do anything both sided.

however if you select on one of the edges created by the geometry itself..then the surface trim option works to split on both each side i guess?

[TomD.inPDX]

The both sides option is great if you need to segment a surface such as placing text on a quilt but you want to preserve both inner and outer quilts for further processing.

[dgschaefer]

I'd say this is a pretty unique case where "both sides" doesn't make sense.

Typically, a surface trim operation, whether revolved, extruded, by another surface or plane or by a curve on the surface, reduces the size and changes the shape of the quilt. One side of the trimming object is removed, the other remains. When "both sides" is selected, the quilt is trimmed back and the part trimmed away is left as a new quilt.

In this case, the quilt is not really trimmed. It remains the same size and shape but is broken, or at least I think that's what you're after. "Both sides" here doesn't make a lot of sense because each side is the same quilt because it wraps around and meets the other side. Frankly, a "one sided" trim doesn't make sense either here because both "sides" are still the same quilt.

This really calls for a third option, perhaps called "slice" where the entire quilt remains but has a zero thickness cut in it like, as someone said, a sheetmetal rip.

That's why I said Creo really shouldn't do anything here, the traditional idea of a trim doesn't really make sense.

[rohit_rajan]

i guess they can may be use the same code as for sketch rip in sheetmetal to achieve this...

[TomD.inPDX]

I once showed tech support a UI that worked in reverse of the illustration for managing sheetmetal gaps. I was told that this was indeed in error but the effort to fix it would be "significant " and R&D chose not to address it.

Do you really think they will pay any attention to something that is already the status quo?

[rohit_rajan]

Antonius..did you escalate the case?

[TomD.inPDX]

Nope; it went to R&D as an SPR. How far can we push these things?

I look forward to seeing if it was actually fixed in Creo 3.0.

Fortunately it had a simple work around so there wasn't much to escalate.

[dgschaefer]

I'd say that Creo simply shouldn't trim the surface in this case, the trim isn't adequately defined. You've got a continuous loop that you're rtying to split at a single line. That line doens't adequately split the loop in two, it only defines a break point.

It flips because it's ambiguous, there are two equally valid solutions. A more clear definition of the split should solve it.

[dschenken]

I recall a manufacturing engineer trying to be clever and asking about whether CADDS IV could create an unbroken Mobius surface so that there would be no glitch where the cutting tool would start/stop.

[dgschaefer]

Or an extruded sketch.

[nrollins]

Surf trim both sides will trim the quilt at the line (using the racetrack image above as a reference) and will keep both resulting sections of the quilt - what was one extruded quilt is now two. You could accomplish the same thing (in this example) by creating two separate extrudes or on of one half and then mirror... Splitting the surface and keeping both sides is useful (for example) in Master Model building techniques - a master has the overall shape of the design that you want and a split (both side trim) allows you to break out the separate parts - like a housing of a cell phone adn the battery cover and the screen bezel - they all share the same shape and interfaces.

-Nate

[kevinb60041]

Could you just sketch the surfaces that you need and then extrude?