topic Re: Problem with a simple assembly in Fusion Design, Validate & Document Forum

Problem with a simple assembly

lemelman — Tue, 24 May 2022 11:28:28 GMT

I have a rectangular tray with rounded corners and need to place moulded edging on each of the four corners.

I created two sketches; one for the profile of the moulding and one for the plan, then swept the profile along the plan and created a component from the result. Then copied it 3 times.

One at a time I assembled each moulding to each corner by using the joint origin of the arc centre of the top flat of the moulding and the arc centre of the bottom surface of the tray. That all seemed to work OK, BUT...

Looking straight down on the tray the mouldings don't line up. They each seem to be rotated slightly around the start of the plan line of the plan sketch. Why? The plan sketch clearly shows that the 2 legs are perpendicular.

Here are some screenshots to illustrate the problem.

Re: Problem with a simple assembly

TrippyLighting — Tue, 24 May 2022 11:41:47 GMT

You've been on this forum long enough to know what the next question is we ask , so ...

Re: Problem with a simple assembly

davebYYPCU — Tue, 24 May 2022 12:31:43 GMT

Path sketch is perpendicular, but the last picture shows the edging is out of square.

why was this not one Sweep, around the table, and then cut into sections?

No data, just guesses.

Re: Problem with a simple assembly

TrippyLighting — Tue, 24 May 2022 12:43:59 GMT

@davebYYPCU wrote:

why was this not one Sweep,

I possibly would not even use a sweep.

Re: Problem with a simple assembly

lemelman — Tue, 24 May 2022 12:58:20 GMT

I couldn't use a single sweep because the moulding was to be 3D printed and it would have been too big for the printer.

I should have included the.f3d, but was interrupted before I'd finished, and then forgot. Sorry. Here it is

Re: Problem with a simple assembly

TrippyLighting — Tue, 24 May 2022 13:41:10 GMT

@lemelman wrote:

I couldn't use a single sweep because the moulding was to be 3D printed and it would have been too big for the printer.

LOL.

Re: Problem with a simple assembly

TrippyLighting — Tue, 24 May 2022 14:10:23 GMT

Your design has 8 warnings and 1 error in the timeline.

You've been using Fusion 360 for quite a while now, so its time to step up your game and fix that stuff!

Re: Problem with a simple assembly

TheCADWhisperer — Tue, 24 May 2022 14:16:47 GMT

Are your sketches fully defined?

Re: Problem with a simple assembly

g-andresen — Tue, 24 May 2022 14:39:52 GMT

Hi,

Your canvases don't give me any clues as to what is to be created in the end, which is partly due to the fact that there are no recognizable top or side profiles.
Please show with pictures of a real object what it is all about.

günther

Re: Problem with a simple assembly

lemelman — Tue, 24 May 2022 16:30:43 GMT

This model is for a collapsible tray on a special wheeled zimmer-frame for a bariatric patient, the manufacturers of which are unable to supply. The frame is foldable and the strange angles of the various parts make a straightforward design impossible.

The tray is just a flat piece of plywood which needs a raised edge to minimise the possibility of plates sliding off when the client moves the frame. The raised edging is 3D printed but, because of it's size, has to be printed in parts - that's why I created one part that is printed 4 times.

Here are some photos of the actual zimmer-frame and a couple of screenshots of the actual model.

Re: Problem with a simple assembly

TrippyLighting — Tue, 24 May 2022 17:02:48 GMT

@lemelman attached is a file with a modeling approach for the tray edging that does not use a single sketch.

You should be able to apply that directly to your design.

Re: Problem with a simple assembly

jeff_strater — Wed, 25 May 2022 04:30:38 GMT

There are no doubt other ways to model this, and I encourage you to look at those other approaches. However, to start to answer your original question, first we need to look at the joint failures. Those are the ones that are specific to your problems. The other errors in your design might be related, but because you asked a joint question, let's start with the joints. If you do "Review Warning" on the first of those failures, you will get:

and, if you edit that joint you can see that a reference is missing for Component1:

So, my first recommendation is to try to fix those errors. With those errors, it is no wonder that the parts do not align. I would try to fix them, but I don't know exactly what you had picked for those joints. If you are able to fix those, then we can look at the design again, if the parts are still mis-aligned.

Re: Problem with a simple assembly

lemelman — Wed, 25 May 2022 11:06:18 GMT

Thanks Peter, that's really neat - I've rather avoided surface modelling 'till now, and have sort-of regarded it as a black art. It's clearly time to spend some effort in getting to grips with it.

Re: Problem with a simple assembly

lemelman — Wed, 25 May 2022 12:09:33 GMT

Thanks for your response Jeff. Actually, I think I've now found the problem.

I think that the joint honours the flat horizontal surfaces of the components (top surface of the edging and bottom surface of the tray), then matches one end of the edging vertical surface against the tray and the inner tangential point of the fillet radius, at the centre of the curve, against the edge of the tray, thus causing the far end of the edging to be misaligned.

So, it appears that the internal fillet of the edging is confusing the joint origin of the edging. When I removed it the parts fitted with no distortion.