Sketch is offset by small amount

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dcschooley
Posts: 21
Joined: Sat Nov 21, 2020 10:20 pm

Re: Sketch is offset by small amount

Post by dcschooley »

drmacro wrote: Wed Jan 19, 2022 8:25 pm
As for the Part object, unless you intend to create a quasi-assembly, it is just superfluous for a single solid.
When I started the do-over, I was thinking of doing the clamp part on the end as a different body than the rest of the rest of the drawing. Would I have needed the Part object in that case? I ended up using a linked drawing instead. Given my earlier failures, I wasn't sure if I could put the Part object in later.
drmacro
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Re: Sketch is offset by small amount

Post by drmacro »

dcschooley wrote: Wed Jan 19, 2022 8:54 pm
drmacro wrote: Wed Jan 19, 2022 8:25 pm
As for the Part object, unless you intend to create a quasi-assembly, it is just superfluous for a single solid.
When I started the do-over, I was thinking of doing the clamp part on the end as a different body than the rest of the rest of the drawing. Would I have needed the Part object in that case? I ended up using a linked drawing instead. Given my earlier failures, I wasn't sure if I could put the Part object in later.
The Part object is basically a bucket. You can add it anytime, then the stuff you put in it will move with the bucket.

So a nut and a bolt (each being a Part Design Body) added to a Part object remain in relative position to each other as the Part is moved. Make a washer in Part workbench and add it, then all three move.

Having Part container and the Part workbench and Part Design workbench is a never ending source of confusion. :roll:
Star Trek II: The Wrath of Khan: Spock: "...His pattern indicates two-dimensional thinking."
heda
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Re: Sketch is offset by small amount

Post by heda »

interesting model, here is one version with a slight different take on what one sketches to begin with.
just as alternative from a pure sculpting way (i.e. one solid to a 3d printer), have a feeling though that if you make this one you intend to make different pieces, at least one gets that impression based on how you have made sketches/solids. if so for myself, I would probably have made one body for each "manufactured" part.

have modified a bit constraining - used symmetry in some cases, how to constrain is always what fits your own head, practice can of course broaden how one thinks about constraining - anyhow if it works it works, not much more about it - then there are always ways to make it different (more solver efficient, easier to change, etc).
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servo_mount_remake.FCStd
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dcschooley
Posts: 21
Joined: Sat Nov 21, 2020 10:20 pm

Re: Sketch is offset by small amount

Post by dcschooley »

drmacro wrote: Wed Jan 19, 2022 8:25 pm
dcschooley wrote: Wed Jan 19, 2022 8:13 pm ...

I don't doubt that it is better, it's just a matter of getting my meager mind to work that way. How noticeable a difference does it make in terms of FreeCAD working better?
As for the Part object, unless you intend to create a quasi-assembly, it is just superfluous for a single solid.

As for sketches and constraints.

Sketches should always strive to be as simple as possible.

The solver work increases with each constraint you add, and not linearly. It also increases the likelihood unexpected behaviour by the solver. It solves the equation sequentially, and takes the first valid solution. That solution may not be what you desire, so the constraint scheme is important.

By using the symmetry of the part, it is easier, quicker and less prone error to make a change to the geometry, because you only need to change it in one place. So, something with an 8 hole bolt hole pattern can be changed in 8 places simultaneously if you have sketched just 1/8 of the shape.
Ok, so I went in and cut all of the sketches in half. I can definitely see how it simplifies things. Now I have to train myself to do that from now on. If nothing else, it eliminates most, if not all, of the equality constraints. This is great.
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lower_clamp.FCStd
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servo_mount.FCStd
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dcschooley
Posts: 21
Joined: Sat Nov 21, 2020 10:20 pm

Re: Sketch is offset by small amount

Post by dcschooley »

heda wrote: Wed Jan 19, 2022 10:35 pm interesting model, here is one version with a slight different take on what one sketches to begin with.
just as alternative from a pure sculpting way (i.e. one solid to a 3d printer), have a feeling though that if you make this one you intend to make different pieces, at least one gets that impression based on how you have made sketches/solids. if so for myself, I would probably have made one body for each "manufactured" part.
The part will be used to attach a servo/gearbox to the end of a carbon fiber tube, which is part of the suspension for an open source rover. I use the clamp all over the place, so I split that out first. The "floor" and "wall" will be used as a gear cover for those using the stock suspension. All I will have to do is move the mounting blocks out a bit. All of this exists in OpenSCAD. Reimplementing it in FreeCAD has been useful and I've learned a ton in the last two days.
chrisb
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Re: Sketch is offset by small amount

Post by chrisb »

dcschooley wrote: Wed Jan 19, 2022 7:31 pm I put the Part object in because I thought I might need it in the future.
If you need it later, you can add it later and simply drag the body in. (In softwareengineering using things which may or may not be used in an unknown future are known as a bad smell called "Speculative Generality").
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