Imported Files - Sketches and Offsets

geoff_josey

Hi,
I wonder if someone could give me some guidance on the best strategy for this task.
 I have dxf and igis files of a number of boat hull sections at various stations.
I have downloaded these into Onshape and want to create a sketch for each section. They are all overlaid in one view in the imported file.
The first problem i have is selecting the profile I want to work on. The second problem is offsetting the profile by 3.8mm which is the planking thickness.
I have looked at the guide which suggests that if I offset one part of the profile the rest of the profile will follow. It does not seem to work for me.
I am on a steep learning curve so any help is appreciated.
Thanks  Geoff

john_mcclary

When using offset and you want the whole profile to follow, you just click and drag the edge. But it will only work if the lines are tangent connected. It also doesn't seem to work when selecting geometry outside of your current sketch.

In your case, I would consider making a surface first, then thicken the surface. Try to keep from editing or adding onto the existing sketch if you don't need to.

Although I can't see the shape you are making. But usually a boat hull is pretty curvy. Which my mind goes straight to lofts and surfaces.

geoff_josey

Thanks for your comment. I am not sure if i have understood edge correctly. I select the line and then offset it but just get a small section.
If I can come from a different direction. I have imported a test dxf file into Onshape. I then want to copy the imported polyline  drawing to a sketch. I am able to select it for "copy" OK in the imported drawing but then cannot paste this into the sketch.
I am assuming that if i can get the profile into a sketch I may then be able to progress to the offset.

john_mcclary

You can't copy entities directly from the DXF's tab. You will need to insert your DXF into a part studio before you  can reference it. 

Start by creating a new sketch, then find the insert DXF option


What that does is take all of the compatible entities from the DXF and dumps it into a new sketch. You will need to constrain it yourself. After that you should be able to copy / paste individual lines or the whole sketch.

geoff_josey

Many thanks for your help. "I am getting there ! If i may ask a further question. Excuse me if my use of the terminology is not correct. I have a polyline - chain - which is made up of multiple straight lines. I can offset this by laboriously offsetting each individual  line. How do I select the complete chain and then offset it ?

NeilCooke

Click the offset button first, then click and drag one of the entities in the chain in one smooth movement. Alternatively, box select the entities first then click the offset button. 

geoff_josey

I tried the first option and just get one section of chain. With the second option I get a message "can only select a single chain at once " Is this problem related to the restraints mentioned in an earlier post ?

NeilCooke

No, that’s just how it works. 

geoff_josey

Hi Neil Do I understand you correctly then ? i.e. I have to offset each segment individually ?

NeilCooke

Each chain of edges, yes. That's because it has to create a set of constraints between each segment of a chain and cannot relate multiple chains together.

geoff_josey

OK Thanks for your help.