How to make a rectangle with curved edges

[mraz3d]

I am VERY new to Fusion 360 and CAD in general so forgive me if this is a silly question.  I am trying to create what seems to be a simple part in 360.  At first I thought it was a normal rectangular but after unscrewing the part and measuring the side, I noticed that each side has a very slight rocker or arc and I'm having trouble working that.  Here is what I've tried

1. create a sketch

2. create an arc from a - b, which is the distance of one of the sides of the rectangle.  My first issue was trying to guess as to the radius of the circle the arc tool was asking for.  I wasn't sure how to measure that with my part which resembles an ice skate blade with a slight curve.  

3. I then repeat the process 3 more times, closing the rectangle (each side is arc'd, I believe the same arc/radius.

4. Extrude

5. print and test

What I am noticing is that the model is hard to work with.  I wanted to slight decrease all the sides and the model doesn't work as a unit, maybe this is normal?  Is there a better way to do this?  What are some ways to measure a very slight curve, for example the curve of an ice skate blade?   

[Drewpan]

Hi,

You, my friend, are in desperate need of doing a few of the tutorials to get started with Fusion. These are

very good and you can find them in the Fusion Documentation, Fusion Tutorials, Fusion YouTube and I would

recommend some of @TheCADWhisperer YouTube videos. Trust me, a little time studying these and you will

be where you need to be to get started.

Ok, lets try to answer your question.

One of the secrets to making good models with Fusion is to have a Constrained Sketch. Another secret is to use

the Origin to base your Sketch points on. Use the tools that Fusion gives you and also try not to make it harder

for yourself later - a little planning always comes good when you need it.

A Sketch is the base of your model that you are going to extrude. It will be easier to  create a Constrained

Sketch, extrude it THEN do the moulding of the extrusion to get what you want. If you try to draw a rectangle

then Constrain it then put round corners onto it you will break the Constraints. Try this method.

Create a Centre Point Rectangle on the Origin.

1. Create Sketch

2. Pick a Plane

3. Select Centre Point Rectangle from the Menu

4. Click on the Origin as the centre and make any old rectangle to start with.

5. Notice that you have a rectangle that is blue and the little Icon in Sketch on the Browser at the side has

a little pencil. This means that the figure you have created has a closed boundry that is a pre-requisite for

all extrusions. Any closed boundry will have a blue internal part. The Sketch icon means the figure is not

Constrained. The blue lines are also unconstrained.

6. Constrain the figure by clicking on the Sketch dimension then click one side of the rectangle.

Type the size you want the rectangle size to be in the box and press Enter.

7. Notice the sides have turned black, you have constrained the distance between the two sides.

Now do it again for the other sides.

Now notice that both sides are black and the little Icon in the Sketch menu on the Browser has changed

to a little Lock. This is a fully Constrained Sketch.

You will also notice that there are little grey Icons around your rectangle, these are Constraints that Fusion

has Automagically created for you. Most times these are very useful but sometimes Fusion does get a little

confused and constrains something in a way you don't want it to. These little Icons can be selected and deleted

if necessary but make sure you know WHY you want to delete them before doing so.

8. Finish the Sketch. We are now ready to extrude and model.

9. Select Extrude from the menu or just press "e".

It should now look like this.

10. Extrude the body by pulling the arrow, or entering a value and press Enter. Now you have a Body we can

start to model.

11. Select the Fillet Tool or press "F".

12. Select the edges you want rounded. You might have to use the View Cube to rotate a complex model but

with a simple model you can often hold the cursor over the hidden edge, it will highlight and click to select.

13. Enter the radius you want to make the Fillets and press Enter.

14. Now you are ready to create an .stl file to print. Select Export.

15. Give it a name, choose a file type, pick a place to save it and press Export.

16. Slice and print the model.

This will get you started but do the tutorials. They are quick and easy and will help heaps.

Cheers

Andrew

[TheCADWhisperer]

Can you File>Export your *.f3d file to your local drive and then Attach it here to a Reply?

A picture of actual object would help to.

[mufuo]

I understand you want this type of rectangle. I also left the Fusion 360 file attached. This is one of the drawing methods I made. This square can be created in other ways as well.

[Theoforus]

Good explanation. You said you had to add the constraints before the dimensions. Right? Can you explain, because I need to learn best practices.

[mraz3d]

Thank you all for the detailed responses, very helpful.  I'm definitely going to check out those videos and it might not show yet but I purchased a kindle book that I'm working through.

I can post a pic of the object, but it basically looks like the object that mufuo posted.  I wasn't sure if folks are accurately measuring the arcs or each side or more eyeballing.  In this case, eyeballing is good enough as its just a face place to a light pod on my truck.  I bought some zRoads light pods and the face of ALL of them deteriorated.  I was thinking of creating the same shape, try different colors and 3d print some replacements.  Insteaf zRoads in white, maybe a mental band in red, something like that.

[Drewpan]

Hi,

In a nutshell, if it isn't a fully constrained Sketch it will probably cause headaches later when you least expect.

Pretty deep I know but even us newbies have learned the hard way.

Best practice is pretty much constrain as you go, although there are some who would say constrain at the end.

Me personally, I constrain as I go because it gets a bit tricky for me when I have a Sketch with lots of info. As a

guide, put dimensions on the critical stuff and use constraints for everything else. Remember that Fusion has a

knack of automagically putting constraints on things which work most of the time but not always. You "can" delete

various constraints and re-do them if necessary.

Symetry is your friend, Sketch half, lock it down then mirror it. Sketch simpler and use the tools to model. Eg. Sketch

a rectangle, extrude it, THEN use fillet and chamfer. This way your Sketch stays fully constrained and the Tools

do the work.

If you are having difficulty finding an unconstrained point or you just cannot get something to turn blue, there is

a text command you can type into the Text Command box Sketch.ShowUnconstrained. This will highlight anything

that needs a constraint. Apart from that, don't get caught on not obvious things like when I had a lovely hexagon

with fully constrained everything except the icon on the Browser tree. Then I tried to move it and it rotated around

the origin. Quick vertical constraint on a vertical side - Lock icon comes up and everything black.

The only other advice I would offer is don't try to be fancy, you want it constrained but not in a strange way or

in multiple steps when one will do. While Fusion will throw an over-constrained error sometimes a feature needs

more than one constraint. That is fine if you need it but think about is there an easier straight forward way.

Sometimes you can break other constraints by modifying your Sketch, again this is ok. That is an argument for

constraining at the end. Me personally I do it as I go, I might draw a few things then lock them down, not lock

down each one as I do it. I am currently trying to Sketch simpler and use the tools on the extrude so my Sketches

break less often now.

Hope this helps.

Cheers

Andrew

[Drewpan]

Hi,

Almost forgot.

Dimension critical stuff first, then constrain. Putting a dimension on often automagically constrains what

you want. The constrain the rest.

Cheers

Andrew