SOLVESPACE -- parametric 2d/3d CAD
Examples
Tutorials
Features
Download
Reference
Technology
Library
Forum
Contact
USER FORUM

(you are viewing a thread; or go back to list of threads)

Confused about helix difference (by Kalle)
Hi guys!

I want to create an auger but have some difficulties to get it as I want.
Just creating an auger is easy, bit I want to fill the "bottom" of the auger to be able to fasten it to another part. See attached image.

One way of doing this is to cut out the empty space from a cylinder which will leave an auger like in the image. But I can't get it to work properly. The helix extrusion causes these thick red lines to show up, which I guess mean that Solvespace is angry? And the part doesn't look very good either.
Any pointers on how to would greatly appreciated.

I'm using 7f9117b2bf0 on master.
Mon Sep 16 2019, 15:28:10, download attachment solvespace.zip
(no subject) (by Andrew)
The thick red lines mean that the solver is having problems with the geometry, and the way to work around that that is to tick 'force nurbs surfaces to triangle mesh'.
Mon Sep 16 2019, 16:51:21
(no subject) (by Kalle)
Awesome! That did the trick! :-)

What is the downside of checking this all the time? Less accurate solutions?

And also thank you taking your time to improve Solvespace! I really like it!
Tue Sep 17 2019, 12:57:23
Paul (by Paul)
It has a hard time with twisted surfaces. There is a possible fix in the works (waiting approval actually), but unfortunately it doesn't help your model. On the other hand, it does allow you to make an auger with a single helical extrusion if you draw the cross-section in the plane perpendicular to the axis. See the attached model.

Prior to the fix this amount of twist will create all kinds of red even without doing a difference. Your options for modeling the cutting end of an auger are still very limited, but this at least makes something sharp. You'll still need to force NURBS to triangle mesh until the fix gets in.

Another tip if you do take this approach. When manually twisting an extrusion for 10 times, check the box "suppress this group's solid model". The solid goes away but it's fast and easy to spin the end around. Then uncheck that box.
Tue Sep 17 2019, 19:01:45, download attachment auger4.zip
(no subject) (by Kalle)
Oh, cool! It will give a lot better control when doing threads (method 4 here https://www.freecadweb.org/wiki/Thread_for_Screw_Tutorial).

Speaking of control, would it be possible to add height and pitch of a helix extrusion as text input fields (like step translation has for number of steps)? If you want to make a threaded object that is suppose to match some predefined thread profile it is a bit tedious right now (with the free dragging I mean). Or is it because I haven't been able to grasp the helix extrusion properly?
Thu Sep 19 2019, 15:15:02
(no subject) (by Paul)
Yes, method 4 there. I thought that would be impractical because of difficulty figuring out the shape for a given profile. Like many things, it seems people have already written about that...

>> Speaking of control, would it be possible to add height and pitch of a helix extrusion as text input fields?

The short answer is yes. This came up in discussions about the helix feature. The current implementation is very much in the spirit of solvespace modeling. My own opinion is that the text window just needs a pitch value which would internally constrain the angle and length parameters to have a fixed ratio. Then you could set the length of the helix on the diagram and the turns would come out right (or twist it if you're into that). That seems possible and I think a few people may know how to implement it. I suggest opening an issue on github for that.
Thu Sep 19 2019, 16:45:49
Post a reply to this comment:
Your Name:
Your Email:
Subject:
(no HTML tags; use plain text, and hit Enter for a line break)
Attached file (if you want, 5 MB max):
© 2008-2018 SolveSpace contributors. Most recent update Nov 22 2018.