Changing dimensions causes a pivot

[kevinrobson]

I'm trying to design a cover for a diesel heater pump.

Basically I'll draw the profile.

Then sweep (possibly not the right tool name) round the axis 180 degrees to create two halves.

I've created the profile (the lower line) then created a 2mm offset (at the left of the diagram)

I've then gone in to try and make the offset slightly bigger at 4mm, to give it more thickness.

But all of the points/dimensions then rotate.

I'm assuming those points/lines need somehow locking, but I'm confused as to how or why.

The dimensions should work out the length and height of each, and I just assumed everything would work off them, remaining at 90 degree angles.

Apologies .. I'm a beginner.

Thanks in advance.

[jhackney1972]

The issue you are seeing is caused by the fact that your original line is not fully constrained so the Offset will distort it.  In the attached video, for speed, I removed the dimensions on the original line segments and Fixed the sketch in place.  You can clearly see that you can then Offset to any value you desire and see no issues.

[davebYYPCU]

Blue lines will keep you awake at night.

From the pics, delete the offset stuff.

Fully define the first outline, until it’s black, you’re not finished.

Now you can offset any size.

Might help….

[Christoph_360]

Hello

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@kevinrobson  wrote:

I'm trying to design a cover for a diesel heater pump.

Basically I'll draw the profile.

Then sweep (possibly not the right tool name) round the axis 180 degrees to create two halves.

I've created the profile (the lower line) then created a 2mm offset (at the left of the diagram)

I've then gone in to try and make the offset slightly bigger at 4mm, to give it more thickness.

But all of the points/dimensions then rotate.

---

Do you mean something like this?

Thanks

Christoph

[kevinrobson]

Thanks all.

@jhackney1972I can see what you mean, and the difference. However, I'm not sure how to 'constrain' those points. Not only that, I may need to move them to fit once I start prototyping.

How do I constrain the points such that they are still using dimensions and are adjustable, but only move in a horizonatl/vertical direction as I require?

@davebYYPCUSorry, I'm not sure what this means "Fully define the first outline, until it’s black, you’re not finished."

@Christoph_360Absolutely yes. I've loaded the sketch, but can't really see what you've done/changed. Are you able to talk me through it? Of course I can see that the sketch lines are black, and not blue.

Incidentally, the pump also has a square connector that I need to take care of. Would you recommend that I add this square connector at this state, and when I revolve I'll end up with a large circle in that part, and cut into it later?

Or would you keep it how it is, then add the square for the connector in just that segment?

Thank You

[jhackney1972]

In the Animated GIF, I show you how to constrain one point and then how it reacts when the locating dimension is changed.  The same would have to be done to all points.

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[Christoph_360 · Accepted solution]

Hello

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@kevinrobson  wrote:

I've loaded the sketch, but can't really see what you've done/changed. Are you able to talk me through it? Of course I can see that the sketch lines are black, and not blue.

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I hope this video helps.

Thanks

Christoph

[kevinrobson]

Thank You. I've maanged to work through that.

Not sure why, but I've ended up using points, dimensioning them, then using those points to draw stuff against them.

So basically we should never do that?

Of can you use points, but for some reason I've not constrained the other stuff I've drawn to them?

Just a bit confused as to the best way to do stuff going forwards?

Thanks

[kevinrobson]

So, two steps forward and one step back.

If I try to do a revolve, it doesn't like that the axis and the shape are touching?
I can get around this by doing a push pull a couple of mm to give it some depth, then pushing in the ends to get them off the axis, but this surely shouldn't be necesery? And of course it means you end up with something that isn't completely round.

What am I missing?

Thanks

[laughingcreek]

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@kevinrobson wrote:...If I try to do a revolve, it doesn't like that the axis and the shape are touching?...

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dollars to donuts the profile is crossing the revolve line.  not just touching it.  attach the new attempt.

[Christoph_360]

Hello

If you attach your file, I might be able to see something.

Thanks

Christoph

[kevinrobson]

Thank You for your ongoing patience 🙂

File attached.

[laughingcreek]

lots of weirdness in that sketch. fully constraining it seemed to help, see attached.

fwiw, it would be much easier to forgo the offset, and revolve it as a solid and then shell it.

[Christoph_360]

Hello

I hope this video helps.

Thanks

Christoph

[kevinrobson]

Well I've followed your video. So thanks for that.

And I can kinda see you are either making stuff forced to be horizontal or vertical, or be constrained to another point.

But if I'm honest I'm a little baffed as to when or why.

Presumably the blue/black lines make a difference.

I seem to have ben caught out by this more than once recently. I've been messing about with Fusion for a couple of years now and muddled though, and had never even heard of constraints until about a month ago on here with another issue I had.

So sounds like I need to have a read up.

Are you or anyone else aware of a good video which explains them?

Thanks again.