topic Re: Offset in Fusion Design, Validate & Document Forum

Offset

LMD001 — Mon, 25 Jan 2016 08:27:29 GMT

Hello Everyone,

Offset is now a parameter which is very nice.

Is there a way of making an offset of an offset profile? I seem not to be able to select the offset line to make a new offset based on that, only the original profile is selectable.

For sure I'm missing something.

Screencast: http://autode.sk/1TjIq6l

Best regards,

Ludo

Re: Offset

scottmoyse — Mon, 25 Jan 2016 09:38:58 GMT

I'm seeing the same behaviour.

If you offset again from the original profile and use a different value. Then delete the parameter, and attempt to apply a new dimension between the two offset profiles, f360 warns of an over constrained condition. I managed to get it to crash by trying to reapply the original dimension, between the source profile and the 2nd offset profile.

Re: Offset

LMD001 — Mon, 25 Jan 2016 10:26:24 GMT

Hi Scott,

Selecting a dimension as input does not seem to function either.

In the Parameter table I was allowed to add dimensions by name (like d5 + d9) but from the graphics screen it does not seem to work.

Best regards,

Ludo

Re: Offset

jiang_peng — Mon, 25 Jan 2016 14:40:16 GMT

Currently we are not able to create offset from offset profile. The workaround we have is to delete the offset constraint which will break the offset association. After that we can create new offset from the profile:

Re: Offset

LMD001 — Mon, 25 Jan 2016 15:01:46 GMT

Hello @jiang_peng,

Thanks for your reply.

I tried that same workaround earlier today, I guess it basically sets the Offset command back to the situation before the update.

Anyways, still like the fact that offset is a parameter now.

Will it be possible in the future to select existing (Offset) dimensions as input for a new Offset command ?

Best regards,

Ludo

Re: Offset

scottmoyse — Mon, 25 Jan 2016 19:13:09 GMT

I wouldn't class that as a workaround to be honest. Offsetting again from the original profile and using parameters to drive both offsets would be a workaround

Re: Offset

kenneth.hill — Tue, 26 Jan 2016 20:49:23 GMT

Hi Ludo,

I'm the developer responsible for the implementation of associative offset. Thanks for posting your feedback!

My intention was to allow offsets of offsets, but it turns out that supporting that robustly is a fairly large project. The issue is that modifying the parent profile can cause significant changes to the child, and may even cause the child to break into multiple loops and chains, or cause loops to merge together. If we allow each of those child loops to be in turn offset, possibly with different values and directions (inside/outside), then moving the parent around may cause new loops to be created, destroyed and/or merged. Deciding where to apply the "grand-child" offsets becomes problematic after changes like this.

That is not to say that we can't make it work. We handle this kind of problem quite often. But since it is a bit of a project, and since in most cases one can offset the parent profile multiple times, we felt it was important to get associative offsets into customer hands. This way we can use the feedback to decide where to spend our development resources most effectively.

-Ken

Re: Offset

scottmoyse — Tue, 26 Jan 2016 21:11:44 GMT

kenneth.hill wrote:
That is not to say that we can't make it work. We handle this kind of problem quite often. But since it is a bit of a project, and since in most cases one can offset the parent profile multiple times, we felt it was important to get associative offsets into customer hands. This way we can use the feedback to decide where to spend our development resources most effectively.

Perfect! I agree with this, since it was badly needed, and the current implementation is still pretty cool.

Maybe you could cheat and just take the selection from the offsets' parent and immediately start with the same offset value (internally) as the selected offset profile. Could that cause other problems?

Re: Offset

kenneth.hill — Tue, 26 Jan 2016 21:46:30 GMT

Hi Scott,

If I understand you correctly, you're suggesting that if one attempts to offset a child, the parent gets selected as the source profile. Correct? We've thought about that, but I worry about cases like this:

What is wanted:

What is actually created (Note that the right loop is also offset):

In my opinion, this result may be confusing. Do you agree, or do you feel that the result would be correct often enough to warrant this short-cut? One benefit of this approach is it gives an opportunity to display a warning such as "Offsetting an offset is not allowed, offsetting the parent instead" which helps clarify the issue.

-Ken

Re: Offset

kenneth.hill — Tue, 26 Jan 2016 22:00:24 GMT

Hi Ludo,

Regarding your comment:

Selecting a dimension as input does not seem to function either.
In the Parameter table I was allowed to add dimensions by name (like d5 + d9) but from the graphics screen it does not seem to work.

This is a defect, and we'll fix it. In the meantime, if you finish the offset and click on the offset dimension, you can then replace its value by selecting another dimension.

Sorry for the inconvenience!

-Ken

Re: Offset

scottmoyse — Tue, 26 Jan 2016 22:00:53 GMT

Which one was offset first in your image?

Re: Offset

kenneth.hill — Tue, 26 Jan 2016 22:12:20 GMT

Hi Scott,

@scottmoyse wrote:
Which one was offset first in your image?

The offset of dimension 13.527 was offset first, but it created two loops (as it should). Now a second offset was desired on just the right loop as shown in the first image. But following your suggestion, we re-offset the original profile, resulting in the second image. Instead of one new loop as was desired, we got two.

-Ken

Re: Offset

LMD001 — Tue, 26 Jan 2016 22:31:06 GMT

Hello Ken,

Thank you for explaining the associative Offset.

Actually, after playing around with the command, it works pretty well for me, and as you wrote, you can edit (select other dimension, formula) the Offset dimension after creating it.

Again, thanks for 'parametrizing' the offset.

Best regards,

Ludo

Re: Offset

scottmoyse — Tue, 26 Jan 2016 22:38:46 GMT

@kenneth.hill wrote:

Hi Scott,

@scottmoyse wrote:

Which one was offset first in your image?

The offset of dimension 13.527 was offset first, but it created two loops (as it should). Now a second offset was desired on just the right loop as shown in the first image. But following your suggestion, we re-offset the original profile, resulting in the second image. Instead of one new loop as was desired, we got two.

-Ken

Yes in this scenario my suggestion falls over. How often do you think this would come up? Because the excess geometry could be converted to construction geometry in those situations. How complicated/clever does this offset command need to be?

Re: Offset

kenneth.hill — Tue, 26 Jan 2016 23:25:21 GMT

@scottmoyse wrote:
Yes in this scenario my suggestion falls over. How often do you think this would come up? Because the excess geometry could be converted to construction geometry in those situations. How complicated/clever does this offset command need to be?

That is a good question, and I don't know the answer. We'll give it more thought and will gather feedback.

Thanks!
-Ken

Re: Offset

pbreed — Tue, 02 Feb 2016 05:59:35 GMT

Can you just detect the deviant loop case and say no?

Re: Offset

mfeathers — Tue, 02 Feb 2016 23:19:16 GMT

Would it be possible to maybe have a checkbox (like loop select) to enable/disable associative offset? Having to go in and delete constraints is a major hickup in my personal workflow. Going back to early days of AutoCAD, most of my drawings are 2 lines and a bunch of editing

Re: Offset

kenneth.hill — Wed, 03 Feb 2016 03:03:23 GMT

@pbreed wrote:
Can you just detect the deviant loop case and say no?

We've been giving this topic some thought. The biggest problem seems to be one of discoverability: you've got a chain that you want to offset and for some reason you can't select that chain. It turns out it's disallowed, but there's no error message that lets you know.

To address the discoverability issue, the current plan is to allow the selection, then fail with a error indicating that offsetting offsets is not allowed, and suggest offsetting the parent instead. This seems like the cleanest and most transparent way to handle the situation.

Longer term, if there are use-cases that can benefit from proper handling of nested associative offsets then I think we should invest in dealing with them properly. I'd like to have some real-world workflows that show the value of nested AOs so that we can justify the cost. If anyone has such a workflow please share!

-Ken

Re: Offset

kenneth.hill — Wed, 03 Feb 2016 03:07:03 GMT

@mfeathers wrote:

Would it be possible to maybe have a checkbox (like loop select) to enable/disable associative offset? Having to go in and delete constraints is a major hickup in my personal workflow. Going back to early days of AutoCAD, most of my drawings are 2 lines and a bunch of editing

I'll circulate your idea around the team and get back to you.

-Ken

Re: Offset

pbreed — Wed, 03 Feb 2016 04:09:03 GMT

You asked about workflows needing offset of offset...

here are a few:

Any place you are building mateing assemblies with clearance one would likely do an offset for thickness then another offset for clearance

on the mating part....

This would also apply do things like electrical PCB outlines, ie I have a spot in my machine to put the electronics...

I'll offset the area to make wall thickness for the cavity, then I'll offset the inner wall to allow tolerance build up and then

export this inner twice offset outline as the potential PCB outline to give the Electronics/PCB guy.

Any structure that will have internal flow channels such as cooling for molds etc...

would benifit from having offsets of offsets....

You can see the internals of a part I built that has offset of offset of offset...

(Done in Rhino, tryign to recreate in fusion but its takign a bit...)

http://unreasonablerocket.blogspot.com/2015/11/motor-design.html

Another use case is where you have clearance issues, ie I'm making a turned surface with clearance and oring seals...

There will be the outline, the offset for thickness, the offset for clearnace, then the offset for oring depth...

One might choose to dimension each of these seperately, but I can also see using multiple offsets for at least some of these....

Another multiple offset use might be a recesed bolt hole...

I have the thread diameter, the bolt clearance diameter, the bolt head clearance diameter and the tool (socket) clearance diameter.

One might do these as individually dimensioned circles, but I could easily see this as offsets wherr one ended up with a complex recess geometry as the rsult of multiple nearby bolts.

In general one can work around this by having multiple offsets from one core line, but asking the designer to do math to calculate offsets if fraught with peril.

IE the prototype is built, there is not enough clearance so the designer goes back in a ads 0.5mm to the clearance. If the clerance is defined as the differnce between multiple individual offsets, its not going to be obvious to the designer which dimensions to modify, and if he has to modify more than one....