Frame Generator Alignment

Jessie_Hulsizer

I'm trying to create a reconfigurable frame. Inside the frame is a drainage system. In some configurations, this system drains to the front, and in some it drains to the rear. Is there any way to fix the rotation of the horizontal frame members to the sketch plane instead of x-degrees about the axis?

I know I could just configure the rotation angle, but these frames are built with different depths and lengths. There is a nearly infinite range of angles that will arise.

Examples below, top is aligned correctly; bottom is... not. Note the channel profile for the most obvious problem.

Thanks in advance!

eric_pesty

Not 100% sure but I think if the reference lines are from a sketch that also tilts, the angle should be relative to the sketch so they should tilt at the same time?
Worst case you do a transform by mate connectors to move them after the fact but that seems annoying. Or maybe you could adjust the angle of the whole thing with a transform/rotate of all the relevant faces.

jnewth

Hi @Jessie_Hulsizer

I'm Josh, one of the Frames devs. 

While I do not have a quick fix for you, I want to explain about how the orientation is picked. Hopefully with this understanding you'll be better able to get the result you want. 

The Frames creation tool has a few different rules you should be aware of:
1. The "first selected" edge sets the profile
2. The profile is aligned to that edge, but gets its initial, 0-degree rotation around that edge from the world's Y or Z axes (a well-defined, stable heuristic).
3. Subsequent frame segments in the same path (so, segments that touch one another) will twist to match the orientation of the first profile.

What the above mean in practice is that you can get two different frames from the same set of inputs, depending on the selection order (the yellow line is showing the first selected):

In your case, picking your first edge "along" the tilt will then constrain the other members to match that rotation. This might be the result you want.  

We do provide that angle adjustment to deal with this case. So for example, in the first photo you could use that angle to "twist" the frame to match the second photo. But as you pointed out, that could become tiresome if you're making a lot of them with different angles.

Your post is motivating me to rethink how we set that initial "0-degree" orientation. Because we provide a lot of flexibility in our frame segment definition (try selecting sketch points!) we have relied on those above rules to set our initial orientation. But for many designs, it might be better to give the user control for that initial orientation in terms of a reference plane rather than just a twist angle.

I'd love to hear your perspective on this! We listen very closely to customer input when determining engineering priorities. Please file an improvement request or bug report.

eric_pesty

Good to be aware of the pick order, at least that's consistent with a lot of things in Onshape.

Having the option to pick a reference direction seems like it would really help resolve this by removing the guess work!

Jessie_Hulsizer

The reference sketch plane does tilt. The frame members within the yellow highlight are all from the same sketch:

eric_pesty

Right, if your frame doesn't have a member going "lengthwise" along the angle then they will align to the "global" plane, I didn't realize that was going to be the case when I suggested ensuring the sketch tilts...

@jnewth, that part is a bit un-intuitive, I think it would make more sense if the angle defaulted to the "feature" creating the edge (so that it would be normal to that sketch plane regardless of which one was picked first...

Overall an option to manually set it would be much better... While we are at it, one thing we could really use is an option to flip the alignment of individual members. Right now if you have a sketch with a bunch of parallel line and you don't use the "centerpoint" you either have to make sure you sketch every line with the same start and end directions (not always easy especially when going back and modifying something), or create 2 separate features just to get the right alignment.

It's the same issue as unequal chamfers pointing in random direction and not being able to adjust them individually...

Jessie_Hulsizer, one possible workaround is to add a "dummy" member to your frame that you pick first to set the direction and remove it right after with a "delete part". A bit clunky but it works...



https://cad.onshape.com/documents/bbc35cf95506dd69cce8bf5b/w/844cf6e7a9e4191272458235/e/413efa9291f61c5014d028c9

jnewth_onshape

@eric_pesty Thank you for the graphic. I think it explains your "dummy" alignment segment idea very well.

@Jessie_Hulsizer The dummy alignment segment workaround is probably the simplest way to get your result for now, if you don't have a "lengthwise" member that you can select first to control the orientation of subsequent segments. I have created a bug to track the improvements discussed here (that is, some sort of "align to sketch" or "align to plane" override control or heuristic). Thank you both for your input. This helps us to continually improve and refine Onshape.

jnewth_onshape

@eric_pesty Thank you for the graphic. I think it explains your "dummy" alignment segment idea very well.

@Jessie_Hulsizer The dummy alignment segment workaround is probably the simplest way to get your result for now, if you don't have a "lengthwise" member that you can select first to control the orientation of subsequent segments. I have created a bug to track the improvements discussed here (that is, some sort of "align to sketch" or "align to plane" override control or heuristic). Thank you both for your input. This helps us to continually improve and refine Onshape.