Can't figure out placement

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BenW
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Location: Boston, MA

Can't figure out placement

Postby BenW » Fri Sep 09, 2016 7:48 pm

This is a very dumb question, but I just can't seem to figure out how to do it or find instructions.

How do you manage the placement of a sketch or pad on the base axis in Part Design? I created a circle sketch and then padded it to make a column. I would like to move the column to a specific location on the base axis (ie. X=5,Y=2,Z=1). If I select the pad, it is not possible to open up the placement values because they are greyed out. If I click on the sketch, I can open placement, and I can shift its location in the X,Y,Z directions, but how do I place it exactly at a specific coordinate?
cox
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Re: Can't figure out placement

Postby cox » Fri Sep 09, 2016 8:38 pm

Welcome to the FreeCAD forum :D

You can change the location of the pad through its base sketch placement properties.
Need help? Feel free to ask, but please read the guidelines first
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wandererfan
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Re: Can't figure out placement

Postby wandererfan » Sat Sep 10, 2016 11:51 am

BenW wrote:I can shift its location in the X,Y,Z directions, but how do I place it exactly at a specific coordinate?
A sketch's Placement.Position corresponds to the origin in the original sketch. So if your feature is displaced from the origin, you'll have to translate the sketch Placement.Position to locate the feature exactly where you want it. The arithmetic is easier if the sketch is centred on the origin.
SketchNotAtOrigin.png
sketch not at origin
SketchNotAtOrigin.png (7.18 KiB) Viewed 1315 times
PlacementPosition000.png
Placement.Position = (0.0.0)
PlacementPosition000.png (3.54 KiB) Viewed 1315 times
PlacementPosition-50015.png
Placement.Position = (-50,0,15)
PlacementPosition-50015.png (3.67 KiB) Viewed 1315 times
The sketch is move 50 left and 15 up in the last picture.
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bejant
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Re: Can't figure out placement

Postby bejant » Sun Sep 11, 2016 3:15 am

BenW wrote:I created a circle sketch and then padded it to make a column. I would like to move the column to a specific location on the base axis (ie. X=5,Y=2,Z=1).
Not what you asked, but you also could have created a default Cylinder, then change the Properties for Radius and Height, and change the Placement Properties to move it,
BenW
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Re: Can't figure out placement

Postby BenW » Sun Sep 11, 2016 5:09 pm

wandererfan wrote:Position corresponds to the origin in the original sketch. So if your feature is displaced from the origin, you'll have to translate the sketch Placement.Position to locate the feature exactly where you want it. The arithmetic is easier if the sketch is centred on the origin.
Thanks a lot wandererfan. Two followup questions. How do you center the sketch on the origin from the start? When I draw the sketch, it takes a steady hand to get it perfectly on the origin. And, how did you figure out that the exact X-displacement was 50.0? I can move it by trial-and-error, but I want it to be exact.
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quick61
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Re: Can't figure out placement

Postby quick61 » Sun Sep 11, 2016 5:48 pm

BenW wrote:
wandererfan wrote:Position corresponds to the origin in the original sketch. So if your feature is displaced from the origin, you'll have to translate the sketch Placement.Position to locate the feature exactly where you want it. The arithmetic is easier if the sketch is centred on the origin.
Thanks a lot wandererfan. Two followup questions. How do you center the sketch on the origin from the start? When I draw the sketch, it takes a steady hand to get it perfectly on the origin. And, how did you figure out that the exact X-displacement was 50.0? I can move it by trial-and-error, but I want it to be exact.
To answer your first question, you simply constrain the sketch to the center. In the case of a circle you would just use a coincident constraint between the circles center and the Sketch origin point. If it were a square or rectangle, you would use the symmetry constraint between opposing corners, like bottom left/upper right or other way around.

Second question leaves me to a question of my own, "exact" to what? Placement puts the part, or in this case, Sketch, exactly where it says it is,

Mark
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wandererfan
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Re: Can't figure out placement

Postby wandererfan » Sun Sep 11, 2016 5:57 pm

BenW wrote:[How do you center the sketch on the origin from the start? When I draw the sketch, it takes a steady hand to get it perfectly on the origin.
Use a coincidence constraint to make your circle centre match the origin.
Constraint_PointOnPoint.png
Constraint_PointOnPoint.png (1.06 KiB) Viewed 1248 times
BenW wrote:And, how did you figure out that the exact X-displacement was 50.0? I can move it by trial-and-error, but I want it to be exact.
Horizontal distance constraint:
Constraint_HorizontalDistance.png
Constraint_HorizontalDistance.png (772 Bytes) Viewed 1248 times
Shaky hands aren't really an impediment when using sketcher. Just lay out the design in a more/less correct fashion, then use the constraints to make everything line up correctly.

wf
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NormandC
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Re: Can't figure out placement

Postby NormandC » Sun Sep 11, 2016 6:03 pm

I'd also like to add that the documentation already explains much about sketches.

Sketcher Workbench

There are also a few Youtube tutorials, quite a few by regular users here.
BenW
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Re: Can't figure out placement

Postby BenW » Tue Sep 13, 2016 11:54 pm

Thanks a lot. I seem to be able to position my sketches correctly using constraints now. I feel like I tried this before and it wouldn't let me select the origin, but it is working now easily. Thanks.

Here is a followup related question. How is it possible that the two attached pictures have different constraints? One has X=25 and Y=10. The other has X=-25 and Y=-10. I think I'm looking at the same perspective, and when I merge them together they are perfectly centered on each other. Why is this?
negative values.jpg
negative values.jpg (25.92 KiB) Viewed 1152 times
Positive values.jpg
Positive values.jpg (31.69 KiB) Viewed 1152 times