Split exceeds sketch lines, is this a bug?

[Anonymous]

I made a split in a solid to "carve out" a piece. The carve-out worked but it also sliced off another pieve of the solid, beyond the sketch and lines. I tried all kinds of trisks, closing the lines, putting in constraints, etc. I can't imagine why what is doing is correct, is this a bug in inventor 2016?

See the enclosed model. the "cut out" is the small part at the bottom. The larger flat part should not be split. What am I doing wrong? Any ideas?

[blair]

Welcome to the Forum.

First your Sketch1 is not fully constrained, it can be dragged around the screen both horizontally as well as vertically. Your sloped transition only as a vertical measurement of 6 and not a horizontal measurement or angle. You have a horizontal dimension of 34, since there are no other horizontal dimension's the upper and lower and angled line can be dragged to different lengths.

Not sure what the reason for the Split-Face is for, why not just create a sketch on the end of the extrusion with a closed shape to extrude/cut the material you require. A proper Sketch1 should take care of this.

Not sure why you are trying to build this with three parts as a single part. You might be better served created either a Multi-Body Solid if you wish to have the end items controlled by a single sketch/part. The other would be to create your three individual parts (IPT) files and place them in a assemble file IAM to create your finished part.

I suspect your problem is with the Move Body, not sure why you need this feature in this model.

[JDMather]

As pointed out - your part is poorly modeled.

I recommend that you watch these videos.

If this information had been covered in your first 1.5 hrs of instruction - your design would have been better quality.

Pay particular attention to information on choosing an appropriate location for the Origin Center Point 

and

fully constraining sketches.

Keep in mind that in the real world it is not possible to manufacture perfect parts, and 3D printing is not a particularly precise process.

If you want your parts to slide together - you need to add clearance between the parts (see my Clearance Cut feature).

[JDMather]

also, you can adjust the amount of clearance between parts depending on your printer resolution - but keep in mind that the thickness of your part as designed is only equivalent to 8-10 sheets of paper at this location.

It will actually bend (or break) in this location allowing perhaps a tighter fit between the two parts.

[Anonymous]

Thanks to each of you as I learn this software.

I have 2 "take aways" from this and would like to separate them and understand better. One is comments on the model and the way it is done and the other is the specific (unwanted) behavior of split.

On the behavior of split: With respect to "yoursketch is not fully constrained", is this a requirement for proper behavior or is suggestion for better design? I was not aware that fully constraining was required and this was not mentioned in the introductory lessons. I had thought that outside of the sketch the positions were set such that tools like split would not care.

Same question with regard to the split lines not being closed. Is this a requirement for split? Some of the tutorials used a simple line to split I did not understand it as an issue.

So with the above in mind, i'm still not sure why the split failed (and it is the split, not the move). I will experiment with fully constrining and fully closing to see if the unwanted part of the split goes away. I would like to understand why things don't work.

With regard to a better design approach. What I started with is requirements for the external shape of the bracket. Due to assembly needs I wanted a bit of it to slide out. So the major sketch represented this external requirement. The split is somewhat arbitrary and makes the "cut out". To design these separatly would be a lot more work and introduce possible error.  So the "cut out" seemed reasonable. With this in mind what would be the "best practice" approach?

As for tolerance - I removed later parts of the design to highlight the problem, I used (reverse) thickening to provide .2mm gap in the wedge. I also worked around the split problem. Fortunatly despite my design foibles, it printed and worked well.

Again, thanks for your help.

[JDMather · Accepted solution]

Constraining sketches is not required by inventor - but it is required by me (and most professionals that I know).

If you split with a line (open curve rather than closed curve) treat that as a plane that extends to infinity.

IMO, anyone not fully constraining their sketches after the first hour of instruction should change their career goals.

It actually takes far less time than to not constrain in the long run.

I recommend that your request a refund on whatever you paid for your "introductory lesson".

Go through this thread.

[Anonymous]

JD: I accept your sage advise as to constraints. Also, "extending to infinity" anwers the other questions as to why it behavied as it did, not that such behavior seems reasonable for a bounded line, but at least I understand it.

I will have some follow-on questions with regard to constraints as it tells me adding a constraint will over constrain the model when no visible constraint would be violated. But I will look to some of the other instructions and perhaps that will come out.

As far as over-paying for instruction. Well, I have not paid anything (extra). I was going through the included inventor getting started "path" as well as a few youtube videos.

Thanks again.