Cris Rose, www.crisrose.co.uk
exporting from Solidworks using STL tutorial
Solidworks overview - Why choose this application for Rapid Prototyping?
Solidworks is a 3D modeling application best suited to an engineered style of part (rather than sculptural or organic works), which makes it perfect for complex assemblies of mechanical parts. One of the biggest benefits of using Solidworks for Rapid Prototyping, is the ability to design dimensionally accurate parts and export them directly to STL files (StereoLithography Data Format) for upload to Shapeways!
Solidworks native formats
Natively, Solidworks uses .prt and .asm files for "Parts" and "Assemblies", neither of which can be uploaded directly to Shapeways. Therefore you need to make sure the model is finalised before exporting it to STL format.
STL files are comprised of flat triangular faces in a mesh, rather than surfaces defined by curves and planes, so resolution is very important when converting or you may lose the detail and accuracy of your design.
Step 1: The part
Start by starting Solidworks and opening the part (.prt) - in this case we have a small, 50mm robot torso for the production of a resin mould.
As you can see, the shape is a mixture of flat faces and compound curves with a fare amount of detail. We will need to ensure that these curved surfaces are a smooth as possible after converting the part to STL format, while keeping the number of "Faces/Triangles" to an optimum level. This is something you will need to fiddle with from model to model, but this tutorial will give you a good place to start.
As you can see, the shape is a mixture of flat faces and compound curves with a fare amount of detail. We will need to ensure that these curved surfaces are a smooth as possible after converting the part to STL format, while keeping the number of "Faces/Triangles" to an optimum level. This is something you will need to fiddle with from model to model, but this tutorial will give you a good place to start.
Step 2: Converting to STL and Optimization
Now we need to "Save As" a .STL file. By going to File -> Save As. Once there, use the "Save as type" dropdown to select "STL"
Next we need adjust the level of detail of the STL file. We do this by clicking the "Options" button at the bottom of the "Save As "dialogue box.
Next we need adjust the level of detail of the STL file. We do this by clicking the "Options" button at the bottom of the "Save As "dialogue box.
This brings up the following window, and generates a preview of the part in a wireframe mode (make sure you have the Preview checkbox ticked here!).
Step 3: Triangles and Resolution
For your first export of a new part to STL format, I recommend you select the "Fine" preset under "Resolution". This will give you an idea of the most basic level of acceptable detail, while using the fewest faces. You may find this resolution setting to be perfectly acceptable, thought it can be hard to tell from the wireframe preview.
The number of triangles and filesize is displayed at the bottom of the Resolution area.
If you find your model has a very low resolution (8,000 or less), you will want to choose the "Custom" resolution option and start adjusting the Tollerance and Angle settings (see the screenshot above for practical examples). I suggest an increment of 1 degrees at a time until you get the desired results. It's up to you how much time you spend fiddling, but i can vouch that it's well worth it!
(NOTE REGARDING TRIANGLES) I have found that while the Shapeways servers can technically handle 100,000 - 500,000 Faces/Triangles, if you can keep your parts to around 50,000 Faces/Triangles (or less!) you can achieve a good level of detail, and still have your models analyzed and ready to order shortly after you've uploaded them. I have never been able to get a part over 100,000 faces to become printable, and that took many hours to become available.
If you cannot keep as much detail as you'd like when following these suggestions, i would recommend splitting the part into two or more parts and printing them separately. This robot has arms, legs and a head, but a leg on it's own required at least 53,000 triangles to look ideal, so there was no way of producing this in one piece! The figure is being produced in 6 pieces, which is no more expensive than one large piece.
Once you are happy with the resolution, click "OK" to go back and then save the file.
On saving, the application will show the following dialogue box confirming the number of Triangles.
Step 4: Checking the model in Accutrans
Even though you are now able to upload this STL file directly to Shapeways, i would highly recommend the use of Accutrans 3D to gain a better preview of the STL file's result, and check the mesh is "Watertight".
As you can see, the view is one of a flat-shaded, unsmoothed version of the part. This is the form you need to view the part in, as it's the way the 3D printer will see it. Any artificial smoothing applied to the preview will be misleading.
While the curved surfaces may not be quite as smooth as the original part, the increase in Triangles required to achieve this would make the resulting file much bigger and less likely to become printable in my experience. Past the optimum detail point, a very small change in Angle results in increasingly larger numbers of faces, while little real visual improvement.
A certain amount of cleanup will always be required on a Rapid Prototyped part, especially ones with many curved faces, so if you are new to the process, please don't expect a surface like a snooker ball!
As you can see, the view is one of a flat-shaded, unsmoothed version of the part. This is the form you need to view the part in, as it's the way the 3D printer will see it. Any artificial smoothing applied to the preview will be misleading.
While the curved surfaces may not be quite as smooth as the original part, the increase in Triangles required to achieve this would make the resulting file much bigger and less likely to become printable in my experience. Past the optimum detail point, a very small change in Angle results in increasingly larger numbers of faces, while little real visual improvement.
A certain amount of cleanup will always be required on a Rapid Prototyped part, especially ones with many curved faces, so if you are new to the process, please don't expect a surface like a snooker ball!
Step 6: Checking if your mesh is watertight
As an extra precaution, you can let AccuTrans check if your mesh is 'watertight'. 3D Printers require manifold meshes that don't have any holes in them. Imagine filling up your model with water - would it somewhere leak out?
From the Tools menu, select 'Check for Water-tight Meshes':
If you get an 'ok', you're good to go to the next step. If not, return to your 3D app and check for holes in your mesh.
From the Tools menu, select 'Check for Water-tight Meshes':
If you get an 'ok', you're good to go to the next step. If not, return to your 3D app and check for holes in your mesh.
Step 7: Uploading the STL
This part is pretty simple, but there is one VERY important point to note - Scale.
Once you have selected your file to upload, YOU MUST SELECT MILLIMETERS AS THE SCALE! This is vital, as the Shapeways server interprets 1 "STL Unit" to be equal to 1 METER as default, and without this adjustment, your model will be massively oversized and not upload correctly.
On clicking the Upload button, an uploading screen will appear until the file is done, and then you will be informed that you will soon be receiving an email regarding the outcome of your part's printability analysis.
If your part is close to 50,000 Triangles, as this one is, you will most likely receive an email informing you that the analysis may take a while, as the model is complex. You should receive a second email informing you that your part has become printable within the hour, two at most. Then you can go to your "My Designs" page to view the part and order it.
If you do not recieve an email within a few hours, your STL mesh most likely has errors that have upset the printer, and now it's not talking to you!
You may want to check the mesh for flipped normals, non-manifold areas or very thin walls. I found that filleting some sharp corners in problem areas also helped a lot. A quick email to service@shapeworks.com with your STL file attached will also help if you cannot diagnose the errors. Errors are common, so please don't be disheartened by them!
Once you have selected your file to upload, YOU MUST SELECT MILLIMETERS AS THE SCALE! This is vital, as the Shapeways server interprets 1 "STL Unit" to be equal to 1 METER as default, and without this adjustment, your model will be massively oversized and not upload correctly.
On clicking the Upload button, an uploading screen will appear until the file is done, and then you will be informed that you will soon be receiving an email regarding the outcome of your part's printability analysis.
If your part is close to 50,000 Triangles, as this one is, you will most likely receive an email informing you that the analysis may take a while, as the model is complex. You should receive a second email informing you that your part has become printable within the hour, two at most. Then you can go to your "My Designs" page to view the part and order it.
If you do not recieve an email within a few hours, your STL mesh most likely has errors that have upset the printer, and now it's not talking to you!
You may want to check the mesh for flipped normals, non-manifold areas or very thin walls. I found that filleting some sharp corners in problem areas also helped a lot. A quick email to service@shapeworks.com with your STL file attached will also help if you cannot diagnose the errors. Errors are common, so please don't be disheartened by them!
Step 8: Viewing and ordering
Now that your part has become printable, and you have found it in your "My Designs" page, you will see a preview of the part. However, you need to disregard this preview, as it is not an accurate representation of the 3D Printer's output. If it looks very messed up, you may wish to contact Shapeways before ordering, but if it just looks like the screenshot below, it should be fine.