🍏 ⛹🏿 🐄 3D Printing: Quick Tips for Moving from a CAD Model to a Printed Object 👩🏿‍🤝‍👩🏼 ⬆️ 🐅

Message from the moderator: the article was republished, because was removed from publication due to a technical error. Please treat with understanding. Thank!

The basis of the process of three-dimensional printing - whether it's just a hobby or a source of income - is always the design of the product. Those who are accustomed to traditional technologies will have to restructure their entire approach to product design and manufacturing.

When the project is ready, a number of additional operations are performed: setting the orientation of the model and other parameters that ensure the proper execution of the printing process. In addition, it is necessary to take into account the fact that most 3D printers allow you to choose the degree of filling the model with mesh structures. The correct choice of this parameter provides protection of the object from deformation and destruction during the printing process, as well as significant material savings and reduced manufacturing time.

Finally, the last factor affecting the success or failure of the 3D printing process is the strength of the connection between the model and the table. If during printing the workpiece is separated from the table, then all the work will go down the drain.

Here we will talk about 3D printing processes and provide some simple recommendations on using the capabilities of additive manufacturing at the design stage. In addition, we dwell on the methods of preparing the finished project for printing, and also consider ways to securely fasten the workpiece to the table.

These recommendations are mainly for printers that use fused deposition technology (FDM), but may be useful when working with other types of printers. The process of obtaining the finished part by 3D printing is basically the same regardless of the method used.

We design an object

Any 3D printing begins with design. If you are developing a product yourself, then you need to build its 3D model in a computer-aided design (CAD) system to make the designer's vision a reality. Moreover, an object can be either very simple or very complex. However, models that are too thin and too small should be avoided.

3D CAD from Siemens from this article for 49900r (90% discount), the offer is valid until March 20, 2020. More details >>

Save the file in a special format for printing

To print an object, its model must be saved in a file of a special format - for example, STL, which has become the de facto standard in the world of three-dimensional printing. In this format, the surfaces of the model are represented as a grid of triangles. Simple surfaces break into a small number of triangles. The more complex the surface, the more triangles will be needed. Today, other formats are also used in 3D printing, in particular, the 3MF format developed by Microsoft. But the most common is still STL.

CAD systems make it very easy to save the model in the desired format: just run the Save As command. To improve print quality, it is advisable to set a number of save settings in the STL format — for example, conversion tolerance and plane angle. The lower the conversion coefficient and the better the angle, the smoother the printed part will be.

Open the file in the slicer

Most, if not all, 3D printers come with their own slicer software. The slicer loads the STL file created in the CAD system and cuts it into layers, and then creates a control program for the printer to work.

Correctly place the model in the print space

After entering the printing parameters, the model (or several models) must be placed on the printer table. You can print many objects on one table at once. At the same time, compared with printing one object, the time is slightly increased, but in general it is still less. Below we give tips on choosing the right model orientation.

Set parameters

In the slicer program, the user sets such parameters as print speed, material consumption, nozzle and desktop temperature. Most slicers have simple settings for beginners. Moreover, most often there are advanced settings so that experienced professionals can achieve optimal results. Advanced settings include percent fill, amount of support material and type of support substrate or raft (this is a small thin base that maintains the stability of the printed part. At the end of its manufacture, the substrate is removed). The number of options is truly endless. The specific setting values depend on the brand of printer. Setting them up is quite simple.

Send the control program to the printer

After setting the print parameters, the locations of future objects on the table, their orientation and quality, it is time to finally start the printer. Just click the Print button and find yourself something to do while production is in progress. Depending on the complexity of the design, the process takes from several minutes to several hours.

We carry out final processing

Final processing includes removing the printed part from the table, as well as removing the supporting material by smelting, mechanical separation or dissolution (depending on the design of the printer). A part may require light grinding or polishing, but on the whole a correctly printed object looks good from the very beginning. Other types of final processing are placing plastic parts in a container with acetone to smooth out surface roughness, bonding (if the dimensions of the structure exceed the dimensions of the 3D printer or individual elements of the object must have different orientations), drilling holes and painting.

3D printing process

Design-based 3D printer capabilities

Eliminate sharp corners

If the direction of the surfaces changes dramatically (for example, a vertical wall intersects with a horizontal overlap), then such a model is difficult to print. The printer will build internal surfaces of excess thickness, consuming too much material. There are two simple ways to prevent this: add chamfers to smooth the joints of surfaces, or round corners so that the printer gradually begins to build a vertical surface. In addition, fillets will increase strength, as fracture most often occurs at sharp angles.

Elimination of thin walls and small geometry elements

The technology of layer-by-layer deposition consists in feeding hot plastic through a nozzle with the formation of a printable object layer by layer. The thickness of the extruded plastic layer cannot be made smaller than a certain limit, depending on the diameter of the nozzle and the speed of movement of the print head. Excessively thin-walled parts are printed with difficulty - often the result is a chaotic interweaving of fibers. If the part can be printed, it turns out to be very fragile and breaks easily.

Too thick walls are bad too

On the other hand, if the walls are too thick, then they become brittle and easily crack. This is especially important when printing from materials other than polymers, since in the manufacturing process excessive thickness leads to the appearance of internal stresses in the part. Even when printing from plastics, material that is too wasteless is wasted on too thick walls at a high expense.

We eliminate large overhanging elements

3D printers allow you to create stunning shapes and surfaces, but they are not able to print right in the air. If the part contains a void with material above it, it is necessary to use additional supporting material. Most slicers add material automatically, but require the orientation and volume of the supporting structure. Printers with a single nozzle create an array of thin columns, which then have to break off. The result is not a smooth surface. Therefore, it is recommended that large overhanging elements be avoided as much as possible in order to reduce the need for support material.

If such an element is inevitable, you can try to flip the object. Most printers are capable of printing overhanging elements with an angle of about 45 degrees. At a certain height, the edge of such an element may slightly sag. The actual capabilities of a particular printer are determined by trial and error.

Holes shrink

Remember that the part is made of heated plastic. When cooling, it inevitably shrinks. Therefore, holes and other critical structural elements have to be made larger so that after shrinkage their size is as close as possible to the required.

However, if you need to make a hole with a tight tolerance, it is better to print it with a smaller diameter, and then deploy it with a suitable tool. This is especially true for holes whose axis is parallel to the printer table.

We increase the area of the support

If the area of contact between the object and the base is small, the part may detach from the table directly during printing. To prevent this from happening, wide bases are added to the model supports, which are installed on the printer table. In general, the closer to the table, the more material needs to be added to the support. There are other ways to securely mount parts on a table, which we will discuss a little later.

Special tricks

The right design approach makes printing easy. In addition, there are special post-processing techniques that are important to be aware of.

Arrange round surfaces vertically

The model should be oriented in such a way as to use the minimum amount of reference material. Ideally, it should rest on a table with a large flat face. In addition, circular geometric objects should be placed so that the circular faces are located vertically. If you look at the printer table from above, we should see a round silhouette of the object. In this case, the part comes out as symmetrical as possible with the formation of a strong round structure.

Vertically place voids and holes

If there are voids in the model (for example, it is a pipe of rectangular cross section), it is advisable to place such voids vertically to reduce the volume of the supporting material. If you print the pipe in a horizontal position, you will have to provide support for the entire interior. If you put the pipe on the end, then no support will be required at all.

This is also true for holes: to get a hole with a straight axis, it is best to print it vertically - in the form of a stack of rings, which avoids warping or deformation of a round hole into an oval one.

Set print quality settings

Correct selection of printing parameters - such as the tolerance of conversion in STL format and settings of the slicer program - allows you to produce parts with a surface quality that matches the quality when cutting. However, this entails an increase in print time. When choosing quality parameters, one should proceed from the purpose of the object: is it a finished product or a prototype? Will the part be visible or hidden?
Quality parameters also affect the shape of the holes in the part. In CAD files, holes are represented by a set of straight lines, angled to each other. The higher the quality of the model in the saved STL file, the less the circle looks like a polygon.

Reduce layer thickness

To obtain the best quality, especially when using the technology of deposition, it is necessary to reduce the thickness of the layers. It really increases printing time, but the end result is worth it!

We optimize the filling with mesh structures

In terms of strength, objects do not have to be solid. Like bee honeycombs, printers can create a honeycomb filling that allows you to achieve a balance between strength characteristics and the saving of expensive polymer material. However, if the printed part serves as a prototype for strength tests, and the serial product will be manufactured by traditional methods, as well as in the case of exposure to the part of certain types of mechanical stress and pressure, a solid design will be preferable.

Choose material

The success of printing largely depends on the right choice of material. Materials have different properties. For example, the melting point of thermoplastic polyurethane (TPU) and polylactide acid (PLA) is lower than that of acrylonitrile butadiene styrene (ABS). In addition, the material is taken into account when choosing the type of supporting structures. For an object made of polylactide acid, support elements can be made from the same polylactide acid, since it will be quite easy to separate them from the finished part. If the part is printed from ABS plastic, then the supporting elements need to be made of another material, and it is better not to use such elements in thermoplastic polyurethane parts.

Mesh filling

A solid body is not always the best choice for 3D printing. Printing solid parts has its advantages, but the internal mesh structure saves both expensive material and time.

Creating objects with a given degree of filling with mesh structures is a unique opportunity for three-dimensional printing. Moreover, it is not required to design such a structure: this is done by the slicer program. As a rule, it is enough to set only the percentage of filling (the closer it is to 100, the more solid the object will turn out) and choose the type of cells, if the printer has such an option.

In addition to saving time and material, the internal cellular structure has many other advantages.

Mesh filling prevents warpage

Printing large objects in a single piece leads to the risk of warping. With a decrease in the percentage of filling, air passes through the part during printing, providing more uniform cooling and eliminating warping.

Cellular filling does not lead to loss of strength.

Printing cells instead of solid material does not reduce the strength of the part. In many cases, a part with a cellular structure is strong enough for the chosen field of application, but at the same time it is lighter and less material-intensive.

Functionality determines the choice of cell geometry

Most slicers support a wide selection of cell geometry. The best option is determined by the functional purpose of the object. Standard rectangular cell filling simplifies printing, while hexagonal and triangular cells add strength. Wave filling allows the object to bend or twist.

How to choose a suitable percentage of completion?

In general, the strength of the object increases as the percentage of filling increases. Most printers have a default fill percentage of 20, which in some cases is optimal, but in others it turns out to be too large or too small. Consider the mechanical stresses in the printable and increase the percentage of fill in areas where greater strength is required. If high strength is not required, select the lowest possible filling. This will save material and increase print speed. Most often, the selection of the optimal percent filling is done by trial and error.

Methods of fastening the workpiece to the table

“Rafts”, “brims”, “skirts” - these terms sound funny, but they only indicate the three main ways of attaching a printed 3D-part to the printer table. Consider each of these methods and their applications.

Skirt

The skirt provides for the creation of several rings around the object at the beginning of printing to ensure the normal extrusion of plastic. The skirt does not touch the object at all. It surrounds the print area and helps start the process of fusing. When creating a skirt, a large volume of hot thermoplastic polymer passes through the nozzle. Thus, the printer is prepared to print the actual part. This ensures good adhesion to the table and smooth surfaces of the object.

Brim

A brim is a wide, flat area connected to the main object as a support base (imagine hat fields). It is very similar to a skirt, but connected to a model. In addition to all the advantages of a skirt, the brim holds the edges of the manufactured object on the table.

When printing, the outer part of the object often cools faster than the middle, which is why the edges are wrapped. Brim prevents this phenomenon by holding the edges.

Raft

A raft is a detachable base made in the form of a thin mesh platform located under the entire object (which lies on the raft). To create a raft, the printer first prints a flat plate in two or three layers, and then begins to make an object.

Rafts provide excellent adhesion to the surface of the table, and also serve as a solid base for printing. This is especially convenient in the manufacture of small parts and parts of an unusual shape, poorly fixed on the table, as well as thin-walled objects.

After printing, in most cases, the raft is easily separated from the part.

If the printer does not have a desktop warm-up function

Rafts are used if the printer does not have a desktop heater. In this case, excessive adhesion becomes a problem.

An alternative method is to stick an adhesive paper tape onto the printer platform, possibly wrapping its edges down (this also protects the platform itself). You can use packaging tape, but it is usually more expensive.

If warping does occur or the object is detached from the table, soluble glue stick should be applied to the adhesive tape. This will enhance adhesion.

Learn the features of a particular 3D printer and consider them when preparing your model.

Three-dimensional printing is not only a science, but also an art. Effective design for subsequent 3D printing requires an understanding of the process, taking into account its features and the purpose of the future object. This will significantly improve print performance.

Using Solid Edge in 3D Printing

Not all CAD systems are suitable for 3D printing.

The capabilities of the system used should not limit the designers. Our Solid Edge system is equipped with design tools tailored to the latest 3D printing technology. Various 3D printers and 3D printing services are supported.

Get to the next level using special techniques for designing parts for 3D printing

Generative modeling in Solid Edge opens up new possibilities: the designer selects a specific material, sets the space for design decisions, permissible loads, restrictions and the target mass of the part, and the system automatically calculates the desired geometry. As a result, the most complex forms can be obtained using 3D printing methods.

In addition, when constructing models, the use of the results of three-dimensional scanning is provided. Solid Edge successfully combines the traditional boundary representation of solid models (B-Rep) and the representation of surfaces in the form of a grid of triangles, which avoids lengthy transformations fraught with the appearance of errors.

If you have already downloaded the STL file for printing, our unique synchronous technology will provide quick and convenient editing of imported models in Solid Edge to prepare them for this process.

Printing on your own printer or transferring an order to a 3D printing service provider

Printing in Solid Edge on a local 3D printer is done with the 3D print command. Models can be saved in STL and 3MF formats or sent directly to the Microsoft 3D Builder application. If you don’t have your own 3D printer or if you need to try different materials and surface finishes, Solid Edge allows you to directly send models to cloud-based 3D printing services (such as 3YOURMIND). You will immediately receive price offers for the manufacture of parts from various materials with its subsequent delivery directly to your door.

3D CAD from Siemens from this article for 49900r (90% discount), the offer is valid until March 20, 2020. More details >>

3D Printing: Quick Tips for Moving from a CAD Model to a Printed Object