Generally solid models can be more easily translated to correct STL-models than surface models. This is due to the fact that solid models resemble real physical objects more than surface models.
In surface modeling software the user must create the surface models so that surfaces form objects without leaving any face of the object as a hole and without any overlapping surfaces. In case of overlapping surfaces or holes in the shell of the object will most likely create errors in STL-files and errors when the STL- file is sliced in to printable layers in Rapid Prototyping software.
Minimum shell thickness in final Rapid Prototype that is hard enough to handle is 1 mm (one millimeter). The material of the Rapid Prototype is ABS plastic.
Following instructions apply only to Insight rapid prototyping software, that is in our computer classes.
- Open Insight software [Start - Programs - Stratasys - Insight 4.2 - Insight]
- Check that in [File - Preferences] window there is [Millimeters] selected to both [Display Units] and [Default STL units].
- Open your STL-file [File - Open > (Select Your STL-file)].
- Open the slicing accuracy settings window from the right hand side window called [Modeler Setup] using the lowest lonely button that has very fuzzy text [Plus] in it.
Set the slicing accuracy from this [Configure Modeler] window using the lowest selection box. Select the slicing accuracy to be [0.17] , [0.25] or [0.33] mm. Notice that it takes more time and is therefore more expensive to make create objects using very small slicing value. It takes double amount of time to create an object using [0.17] slicing thickness than [0.33].
- Rotate the model to the position which is most reasonable considering the objects form and most important visible surfaces.
Generally all open forms like cups and plates are usually made open part up, so that support material is not used in vain.
Open from the upper menu [STL - Rotate] and select suitable rotation direction from the right hand side green [x-] and [y-] buttons. [Rotate increment] can be used to define another angle than 90 degrees.
- Slice the model by first pressing double arrow button on the upper right corner to get back to the previous menu. Then press in [Modeler setup] window the button that is on right side of the green flag button. Then the software slices the model into slices which thickness was selected earlier. All red lines are succesfully sliced layers and yellow lines are problem layers that contain errors.
- If there are yellow lines in the sliced model you must correct them using following tools. Before doing any operations save the whole work [File - Save As - Job], just in case something goes wrong.
You can try to combine all open curves using upper menu command [Edit - Merge - Open Curves > Adding segments]. Selecting all lines with this tool by holding the left mouse button down while dragging a window that encloses all the curves. If all curves turn white they are correctly selected. Then you can try to press button on the right hand side that has some red line figure in it.
If some lines are still yellow after the previous attempt and there is a dubious message "Due to self intersection after merging, some curves are left open at ...", you can try to filter the points to fix the problem.
Select from the upper menu [Edit - Filter points > Point reduce tolerance] and start testing different values from smallest possible value. After selecting the filtering value select all curves with a window and press blue [OK] button. Notice that filtering changes the form of of the object, and therefore using the smallest value changes the form only slightly.
After filtering you can try to combine all open curves again using upper menu command [Edit - Merge - Open Curves > Adding segments]. Selecting all lines with this tool by holding the left mouse button down while dragging a window that encloses all the curves. If all curves turn white they are correctly selected. Then you can try to press button on the right hand side that has some red line figure in it.
- If none of the previous instructions helps try one of the following techniques:
Open the STL-file again and rotate the model as mentioned earlier, but rotate the model slightly, like 5 degrees around z-axis. This may in some cases prevent the yellow error line formation. You can also try to rotate the STL-model around two different axis, that might help sometimes too.
Go back to the program, where the model was originally made and change settings that define what kind of STL-model is to be created.
Do the STL-file creation using some other software. In some cases when the model is transferred as surfaces or solids to another software that does the STL-file creation better, all problems are solved instantly.
- Still if there is no help from any of the instructions mentioned above, you must try to fix the problems manually, slice by slice.
Rotate the view of the model using [F5] key from the keyboard. After that click once with left mouse button on the black area of the view and press [End] key from the keyboard. This will show the most bottom slice of the model.
Start to check all slices (in program the slices are called layers) by going upwards layer by layer by pressing [PageUp] from the keyboard and constantly checking that the next layer connects correctly to the previous one. [PageDown] goes back to previous layer.
Keep going up until you reach a yellow layer. When you reach yellow layer you can manually try to connect the curves together using [Edit - Merge - Open Curves > Adding segments]tool. Select the curves with a window and ad use the button that has a red line formation in it to connect the curves. If the curves connect crossed, you can undo the connection by pressing the blue curved arrow button. After that you can change the single curve direction using the tool button that looks like a large % character. The direction of the curve should be same for all curves and it is indicated with a white tiny arrow. Curves that are separated to multiple parts must all be selected at once when joined together.
If one of the curves does not join to some other curve, there might be somewhere in the curve itself a self intersecting form, like a small loop. If you find that spot, that is usually some place where the curve changes radically, and removing that spot the curve usually becomes joinable again. Self intersections are most easily corrected by deleting single vertices [Edit - Vertex > Delete selected vertex] one by one. You may have to zoom in using [F10] key from the keyboard and dragging in a zooming window. [F5] key takes you back to zoom all position.
[Edit - Delete > Segments] deletes extra lines, that are usually caused by self intersecting surfaces. Select the line by clicking it so that it changes to white colour and press then [OK] button from the right hand side. Holding down a [Ctrl] key on the keyboard you can pick multiple lines. You can also deselect the lines holding Ctrl-key and selecting already selected line again. If you must select almost all lines except one, you can first select all with a window and then deselect the ones that you do not want to select by holding Ctrl-key while clicking the ones that are not going to be selected. This is very handy if you have a lot of small crap in the layer that must be selected and only a couple of lines that should be left there.
If one of the layers misses half of the form you can mirror the existing half using [Mirror - Selected Curves] command. Before doing this it is good to check the mirror line location as well as possible. [Edit - Vertex] tool can be used to do this. Point some line end close to the mirror line and check from [Selected point] x- and y- coordinate. Write down the values on paper and write the value to [Mirror - Selected Curves] tools mirror line location [Move mirror line end points] x- and y- coordinate entering boxes. When mirror line has been determined select command [Select curves to mirror] and select the curves to be mirrored. Mirroring should be done to all missing halfs on different layers all at the same time, one layer at one time. Otherwise you must define the mirror line over and over again, which is extremely slow. Just use [PageUp] and [PageDown] to move from layer to layer.
After mirroring all possible extra lines should be removed and curves must be connected using [Edit - Merge - Open Curves > Adding segments] tool, so that all curves are displayed with red colour.
If one of the layers misses completely inner or outer side of the shell, which can be found from layer above or below you can copy the curve that resembles most the missing curve from another layer. Select command [Edit - Copy curves thru Z] tool and [Copy mode > Up one / Down One] depending on which way you want to copy the curve. Select the curve and click [OK] button.
- When all layers have been checked and they are all red, you must save the model with [File - Save As - Job] . After saving you can start to calculate the support materials. Click first the blue double arrow button on top right corner of the view. Then click from [Modeler Setup] window the [Support] button right hand side of the slicing button that has blue and brown lines in it.
- Calculating the toolpaths. You must now decide whether your object is going to made hollow or solid. Creating it solid will increase the price of the object a lot. That is why it is strongly recommended to create it hollow every time it is possible.
Select the [Part interior style > Sparse] to make the object hollow. If you for some specific reason want to make it expensive and solid select [Part interior style > Solid - normal] . After this click [Toolpath] button that has green round figure in it.
- When the calculation finishes check the slicing layer by layer using [PageUp] and [PageDown] . If all layers are ok then save the job again [File - Save As - Job] , and pay attention to where it is going to be saved.
You only need [yourfilename.cmb.gz] file for creating the physical 3D object.
All the rest of the files are necessary for slice manipulation afterwards and all files are saved to folder named [ssys_yourfilename] . There is also a text file named [log.txt] that contains all technical details concerning the time and material consumption:
Est. build time: XX hr XX min = Estimated building time that is inaccurate, so it can not be trusted completely.
Model material: XXX.XX cm³, T12, ABS P400} = Estimated ABS plastic consumption in cubic centimeters
Support material: XXX.XX cm³, T12, ABS P400SR} = Estimated support material consumption in cubic centimeters.
Slice height: 0.3302 = Selected slicing (layer thickness) height in millimeters.
- Take your file to room 875 or save it to the [Colorprints folder] . Rapid Prototyping machine is operated by our caretaker Osse Federley and he will print out your 3-Dimensional STL-files.
Reserve enough time for modeling process. It may take many hours depending on the size of the object and used slice height.
Reserve at least two days for printing, because there might be lots of other people who want to print, too. Office hours are Mon - Fri 8:30 - 11.00 and 13.00 - 15:00