Persuading a profile shape to become fully recognised

peter_cuthbert

Hi Folks

Just got back to Onshape after a Summer recess and thought I was doing quite well. The drawing is to be simple, two cylinders joined by a sphere. So clearly a Rotate procedure. Got the shapes set up as construction lines then filled in with the actual shape with firm lines. Everything recognised as properly dimensioned so did a trial rotate to remind myself how to do it. Excellent one piece shape emerged but the join between the cylinders and the sphere really needed to be filleted. So back to the drawing and added in a couple of suitable(sh) three point arcs, deleted the now redundant bits of the globe and the cylinders and job done. Well, NO. The drawing remained determinedly blue. As a possible solution I added a silly number of dimensions but that was no use.

Thus my question is, what simple step have I omitted?

The file is here:

https://cad.onshape.com/documents/42de404025759ac43557ed80/w/116a7930357df23bacd9a0e8/e/afcbf0b47561fe2f810361f0

Your observations would be appreciated.

Regards

Pete

eric_pesty

Use the fillet feature rather than putting in the sketch is the proper solution…

Also in Onshape if you did want to add 3point arcs, you don't need to delete the original corner and blow away your constraints.

peter_cuthbert

Hi Eric

Many thanks for the advice. Unfotunately my 2D habits sometims roll over into 3D.

I have restored the object and am now fighting a losing battle with Fillet. The error message states that the edges must form a single chain per part. As far as I can see they do that. The top of the ball is flat and meeets the flat base of the shaft which is also flat.

I have been looking at the help pages but the examples used there do not seem to be anywhwere near what I am trying to do. I am wonfering if I should go back to drawing in the fillet at the sketch stage.

As ever any suggestion would be appreciated.

Regards

Pete

peter_cuthbert

Hi Eric

I have added a fillet to the original sketch and then left all the lines and measurements before doing the Rotate. Happilly that works (provided one remembers to select the fillets to be revolved too!)

File is Here:

https://cad.onshape.com/documents/42de404025759ac43557ed80/w/116a7930357df23bacd9a0e8/e/afcbf0b47561fe2f810361f0

Reagrds

Pete

rick_randall

@peter_cuthbert - It looks like the problems you're having defining the sketch, comes from missing constraints. Try adding some additional horizontal and vertical constraints, along with two missing endpoint coincident constraints and some tangent constraints. Hint; for troubleshooting under-defined sketches - click and grab (blue/under-defined) lines and points, and manually move them around a little, to check for abnormal behavior. This will give you clues to where problems are located. Hope this helps.

peter_cuthbert

Hi Rick

Many thanks for the advice. That happily confirms what I decided to do and 'scatter' constraints. The idea of dragging lines to look for contraint problems is excellent. I will add that to my 'problem solving' portfolio as it looks as if failure to keep an eye on contraints keeps getting me into trouble.

I am pleased to report that my drawing is now progressing with the biggest problem being the lack of dimensions on the author's 'back of a fag packet' 2D drawing. The other issue for me is that the sketch from which I am working is in Imperial Measure (in the odd places where ther are dimensions) and my default is Millimeters. Anyway, I am struggling along in decimal inches!

Progress so far is here: https://cad.onshape.com/documents/42de404025759ac43557ed80/w/116a7930357df23bacd9a0e8/e/afcbf0b47561fe2f810361f0

Best wishes

Pete

rick_randall

Peter, if you are having trouble with converting dimensions - go to help, and type in "setting default units". This will give you all the information needed to change document units (It's very simple) - but I can't help with what is on that paper sketch, lol.

Also, learning how to go back and edit features and sketches, is a cornerstone skill. Remember, almost anything you have done in Onshape can be changed later (or any mistakes, can be corrected). The whole reason for fully-defining sketches, is so when you make edits later, the sketch will act predictably. I can't stress how important it is to develop this habit (good practice)

Good luck, and stick with it..

MichaelPascoe

Check out the Learning Pathways. They take a few days to complete but are totally worth it and will save you tons of time in the future:

https://learn.onshape.com/catalog?labels=%5B%22Learning%20Format%22%5D&values=%5B%22Learning%20Pathway%22%5D