Overview
When we want to get an intricate shape 3D model, the best way is to create and edit it by professional editor such as Blender, 3d MAX, and Maya. The question we discuss today is how to convert STL to STP which we use for mechanical design or manufacturing. It’s also a way of Reverse Engineering.
STL (STereo Lithography or Standard Triangle Language or Standard Tessellation Language) format is the “standard” file type used by the majority of 3D printers. It can communicate shape (without color or texture information) and is universally accepted and very reliable. STLs store the surface of an object as geometric data for a series of points. This generally results in triangular sub-surfaces that describe the outward 3D shape. However, STL files do not give information about color, thickness, or texture. As we can see the definition, STL files cannot be used in engineering and manufacturing by CAD program such as Creo, UG, Catia. The is why we need to convert it.
So, Why we need to convert STL to STP? Let’s take a look of this table. Obviously, if we want to produce the STL format product, we have to convert it to STP so that we can do the next engineering and manufacturing job, which is so call Reverse Engineering.
| Capability | STL | STEP |
|---|---|---|
| Full surface geometry | Yes, with resolution compromises | Yes |
| Full 3D geometry | No, outer surface data only | Yes |
| Accuracy and resolution | Moderate to poor unless resolution and file size are high | Excellent |
| Modification capability | Hard, requires conversion to STEP or another CAD format | Easy |
| Faults that obstruct good printing | Can be common | N/A |
| Interoperability | Universal among 3D printers | Wide |
There are 3 ways to convert STL to STP in product development. Which way is the best for you depends on what the product is, and what are you going to do next.
1.Convert STL Files by Auto surface Tools
This fastest way to covert STL to STP is by FreeCAD, Freeform and Geomagic program, which are universally used in Reverse Engineering to manufacture toy mold. Let’ take FreeCAD for instance.
1. Get a Conversion Tool
The easiest tool to use for STL to STEP file conversion is FreeCAD. Basic converters don’t do such a good job in general. This is because they generally convert as-is and don’t create a smoothed part but instead produce a solid with the flat mesh faces visible. The CAD capabilities of FreeCAD enable the user to progress immediately to make changes or just export as an .STP file.
2. Upload Your STL File
In FreeCAD, the uploading of the STL file is as simple as clicking on it (if it’s assigned as the primary STL tool) or right-clicking the file and “opening with” FreeCAD. This will directly open the file in the FreeCAD viewing window.
3. Repair the Mesh
In the FreeCAD work area, select your STL (mesh) part and click Analyze, then click Evaluate and Repair Mesh. This will highlight and fix the range of basic mesh problems such as coincident but not merged points, missing mesh elements, and more esoteric fails.
4. Transform the Mesh into a Shape
With the repaired mesh selected in the workspace, go to the Part command on the top menu and select “Create shape from mesh.” Set a sewing tolerance, which can be left at the default of 0.1—then click OK. In the combined view, you’ll now have two views—the mesh and the solid part you just created from it.
5. Transform Your Shape into a Solid
If the shape created by converting the STL and repairing any faults is valid, you’ll be able to convert it to a FreeCAD solid body.
6. Export Your Solid Formation into a STEP File
With the solid part selected in the workspace, click File >> Export and choose the STEP format from the options. Once complete, the file is ready for all uses. It is recommended to use Export instead of Save As. The “Save As” option will force the user to use a FreeCAD file format. Let’s learn its Pros and Cons
Pros:
As you can see the way Autosurface software do is quite simply. It can save much of your time for design. After you finish it, you import the part in Creo to assemble with other parts or even do the next step in manufacturing. However, things are not that simple, there are something you need to be mindful, I hope you can read all this page before choosing the right method for you.
Cons:
Very hard to create engineering features like bosses, ribs, and snap fits after you import the STP you got in Creo, because there are so many broken pieces of surfaces form the model, so it is very clunky in Creo or Solidwork.
The picture below shows what it looks like after converting with Autosurface tool. It would be OK, if your component is just a shell without any ribs, bosses any snap fits
2 Convert STL to STP by CAD Program- Creo/Solidwork/UG
Everybody knows Creo for its product design performance, but its ability of reverse engineering is hardly mentioned.
When we import the STL into Creo, in which, as we can see, we can hardly do anything about it. We just can measure the distance from point to point, or just project lines on the STL file. So, how to do next andy why I introduce this method?
If we want to get STP by Creo, the only thing we can do is to design the part by the way as we do in product design, drawing lines, spline curves and bondary blend surfaces. One surface after one surface, merge and turn it into solid, you will finish the part finially, which is the most traditional way.
You may wonder how long it is to model a part with intricate features. Yes, it is the hardest way for reverse engineering. It still makes sense that it is still universally used in industry. Why? let’s see its Pros and Cons.
Pros:
1.You will get a perfect solid/STP that is like you create it in engineering program. The file is very easy to be modified, and to process the further engineering design, such as building snap fits, bosses for crewing and assemble with another parts
2.Easy to be mold manufactured. As we all know, most STP files will be used in mold manufacturing. The STP files created this way would be easier to define parting line, making the mold engineers easier to do their job. Thus, it will shorten the time of mold manufacturing.
Cons:
It takes longer to design than the Geomagic does
3 Combined with The Two Kind of Software.
When we face the product with intricate surface and sophisticated mechanism inside, we choose this way.
First, we will used Geomagic Studio to create the surface, and then export it as IGES or STP.
Secondly. Import the sheet into Creo, thicken the sheet, or solidify the sheet and shell before building engineering features.
This way solve the problem of long time for create intricate surface, and make the component easy for the next engineering design and mold manufacturing.
Conclusions:
So, which way is the best for you? I think it depends what product it is.
1.Obviously, if the products are some small toys with intricate feature, but only have a few parts to assemble, or just one part. This kind of product sometimes doesn’t need to be shelled and have no shrinkage problems. In this case, you can choose the first method
As the picture shows below
2.If the product’s surface isn’t too intricate to create by Creo or other CAD programs, and contain many parts to assemble, such as toy cars, robots. I would recommend you design it in Creo. It’ll take a bit long to time to model the surface, but it make it easy for mechanical design inside.
As the picture shows below
3.If the product’s surface is too intricate and impossible to model in Creo, such as figure face, animations, and it has sophisticated mechanical design, such as some motions. I will recommend you use the combined method, creating the outside surface with Autosurface program, and then import it into Creo to finish the mechanical design.
As the picture show below:
All the recommendations from our company with over 15 years experience in 3D modeling, Reverse Engineering and Product Development. Hope this page can help you.