Choosing the Best CAD File Format
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Choosing the Best CAD File Format

How to choose the best CAD file format for collaboration with external parties? it needs to balance to vary of CAD tools and accuracy of the CAD information that collaborated parties needs...

How do you choose the best CAD file format for any given situation? The CAD Format Ladder can help you optimize data exchange.
在任何给定的情况下,你如何选择最合适的CAD文件格式? CAD格式阶梯可以帮助您优化与发送方或接收方的数据交换。

“When sending out CAD data, or receiving CAD data, go as high up on the CAD format ladder as possible.”

Native CAD Formats 原生CAD格式
Native CAD formats are the default formats written by any given CAD system. For example, CATIA uses CATPart and CATProduct, and SOLIDWORKS uses sldprt and sldasm as their native formats. Here’s a list of native, geometric modeling kernel and neutral CAD formats.


Geometric Modeling Kernel Formats 几何建模内核格式
All CAD systems also have a geometric modeling kernel which underlies the native format, and allows the creation and manipulation of geometry. CATIA uses the Convergence Geometric Modeler (CGM), Creo uses Granite (g) and both Siemens NX and SOLIDWORKS use the Parasolid kernel (x_t).

The geometric modeling kernel is exactly the same as the native format in terms of pure geometry, since the native format for any given CAD system is based on the its geometric modeling kernel. You can’t get any better geometric fidelity than the kernel format as long as you are using the kernel for the source or destination application. For example, if you have a CATIA part and you want to open it in MasterCam, save it to the Parasolid kernel format since that is what the MasterCam software application is based upon.

所有CAD系统还具有一个几何建模内核,该内核是本机格式的基础,并允许创建和操纵几何。 CATIA使用Convergence Geometric Modeler(CGM),Creo使用Granite(g),Siemens NX和SOLIDWORKS都使用Parasolid内核(x_t)。

Neutral CAD Formats 中性CAD格式
STEP, which stands for the Standard for the Exchange of Product Model Data, can work with every major 3D CAD system, but in spite of this versatility, STEP rarely outperforms Native-to-Native or Native-to-Kernel CAD translation strategies. The quality of your STEP translator is the key factor; all STEP translators were not created equal. Importantly, this refers not only to the translator that wrote the STEP file, but the translator that will read the STEP file into your native CAD system. Poorly written STEP translators have two opportunities to mangle your data; on the way out, and on the way in.

Many STEP translators take the shortcut of translating all data to splines, which is the fastest, simplest way to capture geometric data; unfortunately, splines are not as precise as analytic geometry.

STEP作为代表产品模型数据交换的标准的STEP,它可以与每个主要的3D CAD系统配合使用,但是,尽管具有这种多功能性,但STEP很少能胜过本机CAD或本机CAD转换策略。 STEP转换器的质量是关键因素;所有STEP转换器的创建都不相同。重要的是,这不仅指编写STEP文件的翻译器,还指将STEP文件读入本地CAD系统的翻译器。编写较差的STEP转换器有两次机会处理您的数据, 一个输出,一个输入。


IGES, or the Initial Graphics Exchange Specification, is another neutral CAD format that can be read and written by many CAD systems, but is in fact the worst possible alternative. IGES has not seen any development since 1996, over twenty years ago. One of the problems with IGES is files are almost always surfaces; if you do have to work with IGES files, make sure you have a model repair tool that can stitch together surfaces, remove artifacts, and extend and re-intersect surface edges to give you the best chance at producing a watertight solid model. Another problem with IGES is that most IGES translators are not well written, so you’re not only dealing with surface data, but poorly defined surface data at that.

IGES Solids – There is an implementation of IGES which actually supports solid models. This is called Manifold Solid Boundary Representation Object, (MSBO), but it is not widely used; for MSBO to produce reliable and precise translations, it has to be used to both write and read the IGES file.

IGES或“初始图形交换规范”是另一种中立的CAD格式,可以由许多CAD系统读取和写入,但实际上是最糟糕的选择。自从20多年前的1996年以来,IGES一直未见任何发展。 IGES的问题之一是文件几乎总是表面。如果必须使用IGES文件,请确保您具有模型修复工具,该工具可以将曲面缝合在一起,去除伪影,并延伸和重新相交曲面边缘,从而为您提供了产生水密实体模型的最佳机会。 IGES的另一个问题是,大多数IGES转换器的书写方式都不佳,因此您不仅要处理表面数据,而且要处理的表面数据定义不当。

IGES实体– IGES的一种实现实际上支持实体模型。这称为流形实体边界表示对象(MSBO),但并未得到广泛使用。为了使MSBO能够生成可靠而精确的翻译,必须同时使用它来写入和读取IGES文件。

Polygonal Models 多边形模型
Polygonal models are included at the bottom of the CAD Format Ladder because though they are often confused with CAD models, but are not as accurate or information-rich as CAD models. CAD models are sometimes referred to as ‘precise’ or Boundary Representation (Brep) models, and polygonal models can be referred to as ‘tessellated’ or Visual Representation (Visrep) models, because they are composed of triangles. Typical polygonal formats include Stereolithography (STL), Obj, 3D PDF and Web GL. Polygonal formats are useful for visualizing large assemblies because they are more lightweight than CAD geometry.

多边形模型包含在CAD格式梯形图的底部,因为尽管它们经常与CAD模型相混淆,但不像CAD模型那样准确或信息量丰富。 CAD模型有时称为“精确”或边界表示(Brep)模型,而多边形模型则称为“细分”或视觉表示(Visrep)模型,因为它们由三角形组成。典型的多边形格式包括立体光刻(STL),Obj,3D PDF和Web GL。多边形格式对于可视化很有用

Best format with us 我们的最佳选择格式

As 3D printing services provider for micro part, we want to have good and up level format for technical analytis of printability. also consider vary parties using different native CAD tool, In most typical case, we initially asking the STEP format due to it is a very useful file format for data transfer between CAD tools and from CAD tools to other 3D tools for the purpose of visualization.

Its ability to represent perfect mathematical surfaces means that it meets the needs of engineers who want their designs to be manufactured. But its inability to represent materials, textures, lighting means that a model when transferring to a visualization tool will mean that it will have to be reworked in order to be usable.

作为微型零件的3D打印服务提供商,我们希望可打性技术分析时具有良好的格式, 同时还要考虑使用不同的相关方可能使用不同的CAD工具,在通常情况下,我们会要求STEP格式,因为它是非常有用的文件格式,用于CAD工具之间的数据传输以及从CAD工具到其他3D工具的可视化。

STEP格式有完美数学表面的能力意味着它可以满足的工程师的设计及制造表述的需求, 但由于无法表示材料,纹理,照明,因此当模型转移到可视化工具时,就意味着必须对其进行重新添加后才能使用。

Futher Detail on STEP Format有关STEP格式的更多详细信息

The STEP 3D file format is a data exchange format applied in the computer aided design (CAD) industry. It is primarily used to transfer real-world mechanical and architecture designs between different CAD software tools. Common CAD software tools that support STEP files include AutoCAD, Fusion, SolidWorks, PTC Creo, CATIA and more other popular CAD tools.

A major reason for its popularity as a data exchange format is that it is an official international standard. It was standardized by ISO committee in 1994 under the official name “ISO 10303-21.” Being a standard makes it easier for the various CAD software tools to implement support for it.

STEP 3D文件格式是在计算机辅助设计(CAD)行业中应用的数据交换格式。 它主要用于在不同的CAD软件工具之间传输实际的机械和建筑设计。 支持STEP文件的常见CAD软件工具包括AutoCAD,Fusion,SolidWorks,PTC Creo,CATIA等几乎所有的主流CAD工具。

其作为数据交换格式之所以受欢迎,其主要原因是它是官方的国际标准。 它由ISO委员会在1994年标准化,正式名称为“ ISO 10303-21”。 作为标准,使各种CAD软件工具更容易实现对此的支持。

Pros of STEP Format 优势

Wide Support by CAD Tools 广泛的CAD工具支持
There is no other CAD format that has such wide adoption among professional CAD tools. There is no CAD tool that we know of that has significant usage that does not support the STEP file format. Thus if your goal to achieve wide interoperability with a large variety of CAD systems, this is by far the best format to use.

在专业的CAD工具中,没有其他任何一种CAD格式被如此广泛地采用。 我们没有已知的CAD工具具有大量不支持STEP文件格式的用法。 因此,如果您的目标是与各种CAD系统实现广泛的互操作性,那么这是迄今为止最好的格式。

Mathematically Perfect Surface Definition 数学上完美的表面定义
The STEP 3D file format stores its data using a mathematical representation of curves referred to as NURBS. The NURBs curve specification is capable of storing data with exact precision. This level of precision can not be achieved using the polygon and triangle representations utilized by visualization-oriented OBJ, FBX, glTF and USDZ. The NURBS representation is used by CAD files because it allows for the final manufactured creations to have perfectly smooth curves, like nicely rounded iPhone cases or beautiful sweeps on car bodies.

STEP 3D文件格式使用称为NURBS的曲线的数学表示形式存储其数据。 NURBs曲线规范能够精确存储数据。 使用面向可视化的OBJ,FBX,glTF和USDZ使用的多边形和三角形表示无法达到这种精度水平。 NURBS表示法由CAD文件使用,因为它允许最终制造的作品具有完美平滑的曲线,例如圆润的iPhone外壳或车身上漂亮的横扫

Cons of STEP format 劣势

No Materials or Textures 没有材质或纹理
The STEP file format is focused on the transfer of shape and form and not on visual appearance. This is partly because of its historical roots back in the mid-1990s when CAD systems were simpler. In the last decade CAD software tools have invested a significant amount of effort to support material on the CAD designed objects. For example, in an architectural design, the CAD tool may allow you to specify different surfaces to be concrete, or painted or stonework. In a mechanical CAD design, the CAD tool may allow you to specify surfaces as rubber, brass, steel or even a colored plastic. This material data is unfortunately not supported by the STEP format. Thus when using STEP to transfer data between CAD tools these rich material and texture assignments are lost.


No Lighting or Cameras 没有灯光或相机
Similar to the reason that STEP does not contain material and texture data, it also doesn’t contain lighting nor camera information. Again it is because when the STEP file format was designed in the mid-1990s, CAD software tools were just focused on representing and transferring the shape of the objects being designed. This means that you can not represent camera or lighting setups in CAD files, where as you can in FBX and USDZ files.


Can’t be Directly Rendered 无法直接渲染
NURBS, the mathematical surface representation used by STEP 3D files, can not be directly rendered using a GPU nor can it be loaded by most renderers. Rather it needs to be processed by a software algorithm that converts the mathematical surface representation into a series of triangles. These surface “tessellation” algorithms are very complex, especially if you want efficient and fast results. Often people license these algorithms rather than writing it from scratch.

NURBS是STEP 3D文件使用的数学表面表示,不能直接使用GPU进行渲染,也不能由大多数渲染器加载。而是需要通过将数学曲面表示形式转换为一系列三角形的软件算法进行处理。这些表面“镶嵌”算法非常复杂,特别是如果您想要高效,快速的结果。人们通常会许可这些算法,而不是从头开始编写它。

Complex Format Requirements 复杂格式要求
The STEP file format is relatively complex. Its data representation is very similar to a software programming language with an order set of procedural calls that can reference other procedural calls specified earlier. The specification, while complex, is open and well documented. This means that while it is a lot of work to implement, it is possible to implement it perfectly given sufficient time and attention.


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