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ACIS solids and parts
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* November 21, 2017, 11:14:12 AM
I am confused with "ACIS Solids" and "Parts". If I create two extrusions and join them together they become a part. If a part is exploded it becomes an ACIS solid.
I noticed that the computer slowed down to a ridiculous level while working on a fairly complex drawing and, loading the file on start up took some minutes. I eventually found that exploding all of the "Parts" making them "ACIS Solids" solved the problem. I still think I am missing something though as I am forever exploding "parts". Any comments please?
Dave Steward


November 21, 2017, 01:12:14 PM
Hi Dave
If you explode a 3d box or cylinder once it becomes an ACIS solid object, a part is formed when you have turned on Options - Acis - Part Tree ( when checked ). The Part Tree is very powerful when you want to create an object and perform subsequent modifications to establish an accurate model.

You can turn off the Part Tree ( uncheck ), if you do this then any all objects that are reported as parts need to be exploded or broken apart one time to remove as a part from the part tree.

I presume that turbocad had the part tree option turned on when you 1st started the drawing.

TCW V21, 2015-2020 PP, Animation Lab V5.2 & Redsdk enabled, LightWorks rendering mostly. Ender 3 3D printer.

* November 21, 2017, 03:03:38 PM
Parts are objects with associations, which means that the solid rebuilds itself to a modified state when its generating objects are modified, ie the shape of a profile or path is altered, and actions that have been performed on it, like filleting and shelling, keep the parameters that they've been given, radii and shell thickness.    TC activates history associations when the "compound profile" option is checked.   ACIS solids are what are commonly called "dumb solids" because their associations are lost, they can only be modified by boolean operations.  Dumb solids are more flexible than they used to be because feature recognition means that programs like TC detect what are called "analytic" surfaces, plane, cylindrical and conical sections, and they can be modified through "direct editing" on those faces with tools like facet editor and quick pull, but that breaks the associations too, so better to use those tools on dumb solids rather than using them to make dumb solids!    A part can be a composite object, too, it can be modified by editing the generating processes of another object that's been added, subtracted or intersected to it, and the sequence in which operations have been performed can be re-ordered to some extent, because sometimes features depend on other features to be possible.  Associations give you a way to redo an operation that's impossibly removed from the undo stack or which was produced at some earlier session, without a complete rebuild.  It's a really big subject area, but what it comes down to here is that exploding things in TC dumbs them down, deprecates them a level.  That can be useful, if you understand why you're doing it, but I disagree strongly with it being any sort of quick fix for problems, or acceptable common practice.    I'm able to model and edit files >100Mb with many complex composite parts in 64-bit TC on a vanilla (slow! 1.44GHz)  Atom CPU tablet with 4Mb RAM, and I don't know what the top end file size is.   


* November 21, 2017, 10:41:19 PM
like Murray I leave the editing history on - I find it useful.
 I also work on relatively big drawings with a Vanilla laptop.

TC20 platinum
TC 2015 platinum
TC 2017 with lightworks

November 22, 2017, 03:58:18 AM
    Whilst Murray's thorough reply is 'on the money' (correct), my simple brain has found it much simpler to deal with ACIS solids only.
    This working practice evolved from earlier versions of TC, failing too many times when using the Part Tree.
    Time moves on and things hopefully improve.
    It's good that choices in TC are still there for it's myriad users.

Regards Tim
« Last Edit: November 22, 2017, 04:00:01 AM by Tim Stewart »

Regards Tim

You can design without engineering, but you cannot engineer without design.
Using Win 10 with Designer 2017-2020 and TurboCAD Pro. Plat. 2018-2020 + Lightworks (64-bit versions) + AnimationLab 5.2.
Windows 10 Pro (1909) 64-bit

* November 22, 2017, 01:47:57 PM
The most enjoyable CAD jobs that I've done have had scanned, parametric designed-freeform or semi-freeform surfaces, at least the visible dress surfaces, for consumer product design and/or reverse engineering.  Without part tree history, it's somewhere between impractical and impossible to keep surfaces like that consistently attached to engineered features like ribs, stiffeners, mounting posts, internal volumes that house mechanics and/or electronics, maintaining relationships and skin thickness, all while remaining editable.  Without it, development is effectively stonewalled when the CAD file's committed, and updates require complete remodelling and redrawing.    I haven't found that TC is less reliable than other systems I've used in the past ten years, so blaming the part tree for unreliability is questionable IMO.  Much of my CAD work relies on it, I use it by default, so I can't say that it's slowed me down compared to not using it.  I suppose that it must have had some impact, but the time loss is more than offset by the added-value things that it makes possible.
If you've got professional CAD aspirations with TC or beyond, you need to be proficient with it, because almost all of the CAD modelling systems used in enterprise at any level are history-based.           
« Last Edit: November 22, 2017, 01:51:42 PM by murray dickinson »