A body and a part?

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tonyaimer
Posts: 241
Joined: Mon Sep 30, 2019 4:17 pm

A body and a part?

Post by tonyaimer »

I am hoping someone will be good enough to flesh out the following extract from the FreeCAD docs.

I have been able to create two separate bodies in my attached freeCAD file junk1 and the wiki does not enable me to figure out what is going on.

Presumably a model can contain multiple non contiguous bodies as long as they are not created by a partdesign tool like pad or hole.
junk1.FCStd
(15.36 KiB) Downloaded 19 times
"Notes

In informal usage, a "Part" may be any geometrical figure that is visible in the 3D view, and thus its concept may be confused with that of "Body" or "Assembly".

However, when more precision is required, the distinction must be made.

A "Body" is used for single contiguous elements, usually created with the Part or PartDesign Workbenches.
A "Body" has a "Shape".
A "Part" is used to group a single "Body", or several of them to form an "Assembly".
A "Part" has a collection of "Shapes", but doesn't have a "Shape" of its own.
An "Assembly" is a collection of "Parts" arranged in some way, manually, or by using an assembly workbench."

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drmacro
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Re: A body and a part?

Post by drmacro »

A Part Design workbench Body is the accumulation of all operations in the Body. Each successive operation MUST result in a single contiguous solid.

A Part work bench solid (Sphere, cone, Extruded sketch) is a single solitary solid. They have no relation until the user specifies a relationship (using a Boolean between two).

Detailed explanation and example creating identical component use exclusively Part or Part Design:
https://wiki.freecadweb.org/Part_and_PartDesign


A Std_Part container Image is simply a container that can contain Part Design Body objects, Part workbench solids.

Using Std_Part will allow the user to do a simply assembly. More complicated assemblies are typically done with one of the assembly workbenches (A2+, A4, A3).
Last edited by drmacro on Fri Dec 03, 2021 5:48 pm, edited 1 time in total.
Star Trek II: The Wrath of Khan: Spock: "...His pattern indicates two-dimensional thinking."
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Roy_043
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Re: A body and a part?

Post by Roy_043 »

The text is a quote from Part.
TheMarkster
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Re: A body and a part?

Post by TheMarkster »

Each body is a separate contiguous solid. You have 2 bodies, so there is no issue that they are not connected.
tonyaimer
Posts: 241
Joined: Mon Sep 30, 2019 4:17 pm

Re: A body and a part?

Post by tonyaimer »

I am not trying to be clever and use part WB and partdesignWB together - I will leave that to the experts.

Based on the replies so far I have come to the conclusion that "part" belongs to partWB
and body belongs to partdesign WB. OK I get that.

I understand that when using partdesign WB we cannot have non-contiguous bodies when
doing mirrors and other kinds of operations.

But that does not prevent us from building models with multiple bodies as the file attached to my initial post showed.

Lets ignore partWB for a moment as I do not intend to try and mix tools. ( Bit like trying to weld wood with a stick welder! )

Some of the assembly WBenches use the expression "part" when perhaps they mean "body"? Then perhaps they
are using the term not in the strict WB terminology?

Regards


Tony
drmacro
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Re: A body and a part?

Post by drmacro »

tonyaimer wrote: Sun Dec 05, 2021 3:16 pm I am not trying to be clever and use part WB and partdesignWB together - I will leave that to the experts.

Based on the replies so far I have come to the conclusion that "part" belongs to partWB
and body belongs to partdesign WB. OK I get that.
Not quite. Std_Part is an unfortunately named container. It is not particularly Part or Part Design workbench.

It is a generic container. The typical use case is: you've designed multiple components (think a bolt designed in Part workbench and a plate with holes where the bolts go in Part Design) and after you get the bolts aligned with the holes, you now want to move them all as a unit. Put them in a Std_Part, when the Std_Part is moved they all move as one.

I understand that when using partdesign WB we cannot have non-contiguous bodies when
doing mirrors and other kinds of operations.

But that does not prevent us from building models with multiple bodies as the file attached to my initial post showed.
No you just make multiple Part Design workbench Body objects, with one component in each.

Lets ignore partWB for a moment as I do not intend to try and mix tools. ( Bit like trying to weld wood with a stick welder! )

Some of the assembly WBenches use the expression "part" when perhaps they mean "body"? Then perhaps they
are using the term not in the strict WB terminology?
..
I refer to finished "thing" in Part or Part Design as a component to avoid this question. A finished component can be a Part Design Body or a Part workbench, for example, Compound consisting of a cone, a sphere, and an Extruded sketch. (And to make things really confusing a Body can contain a Part workbench object as a BaseFeature. And, a Part workbench component can be made up of, for example, a Boolean union of a Cube primitive and Body. :? )

The assembly workbenches typically are referring to a component (or part) that can be placed in reference to another component.

In general, the context matters and the writer should make it clear in what context the word is used...because the word part has been over used in FreeCAD.
Star Trek II: The Wrath of Khan: Spock: "...His pattern indicates two-dimensional thinking."
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