Richard Horne

Cheat Sheet / Updated 09-06-2023

Unlike traditional manufacturing, which involves injecting material into a pre-formed mold or removing material from base material objects, 3D printing starts with a virtual 3D model that is transformed into solid form one layer at a time. Each layer is built on top of the layer before, creating a solid form representing the virtual 3D model in all of its complexity and detail without requiring additional forms of machining and treatment necessary in traditional forms of manufacturing. You can buy an off-the-shelf desktop 3D printer or build your own 3D printer using the open-source self-REPlicating RAPid-prototyper (RepRap) family of designs. Check out these helpful articles to guide you toward selecting the right RepRap design for you.

Article / Updated 07-24-2023

When your 3D printer's hot-end gets blocked or your extruder's filament drive fails, the warning signs are usually obvious. The stream of plastic starts to lessen and then stops; the printer keeps trying to print but extrudes layer after layer of nothing. The first things to do are stop the printer and ensure that the heater block on the hot-end is still at the expected temperature. (Ideally, for maximum safety, you should use a noncontact laser temperature sensor.) If the heater temperature is significantly below 160 degrees C, the heater used in the hot-end or temperature sensor may have failed, or the wiring or electronics controlling the heaters may have developed a problem. Unfortunately, wires commonly break — and insulation wears away — on a home 3D printer due to the constant movement of the machine. Wiring should always have plenty of room to move around gently, with enough slack — not tightly bent or yanked back and forth as the machine moves. Using silicon-coated wire can help, especially if it has extra resistance to heat. Increasingly, new machines use gently curved ribbon cable — a ribbon of many parallel wires instead of a single thick wire — which tends to alleviate cable strain and damage. If your heater block is jammed but is at the expected temperature, follow these general steps to clear the jam: Keep the heater block turned on. Make sure that the filament drive isn't blocked and that the filament isn't buckled or wrapped around the extruder drive wheel. If you think you may have a blockage, follow the steps here. If you have buckled filament wrapped around the drive wheel, first remove the buckled filament, and then follow the next steps to check if the cause of the buckle was a blockage. Release the idler bearing, and gently pull out the filament. A filament rarely gets so jammed that it can't be pulled out while the hot-end is at temperature. More commonly, the removed filament shows signs of being overly compressed — a little fatter where it melted inside the hot-end. Usually, pulling out the melted filament removes contaminants from the hot-end nozzle. Cut off the melted filament end, and push it into the hot-end. If you can push down, and material is extruded from the nozzle, you've cleared the blockage. Otherwise, proceed to Step 5. If you can't get the material to extrude, allow the end of the material to melt, and pull it out again. Repeating this step several times should clear most blockages. If not, proceed to Step 6. If you still have a blockage, do either of the following things (extremely carefully): Push a pin or small drill bit into the nozzle end while pulling out the melted filament. Allow the hot-end to cool, and when it's cool, use a chemical solvent (such as acetone) to dissolve any buildup. Before using any chemical cleaner, check with the supplier, and mention the type of material that you were using in the hot-end when the jam occurred. You may be starting to think that having a few extruders is a good idea — and usually, it is. In the event of a blockage, a backup extruder can get you printing again while you repair. Another reason for having a choice of extruders is that your machine becomes much more capable of printing different types of objects, which can widen your selection of available printing materials.

Article / Updated 10-04-2021

It is possible to capture existing objects into the computer so they can be modified or simply re-created using a 3D printer. This is particularly useful in the case of artwork or other unique formations that could not otherwise be designed easily in a computer model. The Glen Rose dinosaur track, for example, came from a laser scan of the original fossilized impression, which was used to create an electronic copy of the track that can be shared without risk to the original. Optical scanning captures only the outer shape of an object, but it is possible to use ultrasound imaging or CT scan data to create models of internal structures as well. Researchers have recently created a model of the first exposed full skeleton of a living animal, for example, by 3D-printing the bone structure taken from a CT scan of the subject. Similar data is being used to reconstruct the facial features of mummified remains in Egypt and of the newly discovered remains of King Richard III. Using CT scans and a stereolithographic system, researchers at the University of Dundee were able to print King Richard III’s skull into solid form, re-creating what this long-dead former monarch looked like in life. Early 3D capturing systems relied on a probe that contacted the printed object at many different locations, defining a “point cloud” around the object's shape to define its basic geometry, which is then filled in with greater detail as the scanner measures finer points between the original markers. These systems are still used in machinery analysis and other durable environments. More recent scanners use illumination from lasers or structured light — projections that measure the distance from the camera to different parts of an object, so there is no risk of harm to the object under investigation from the contact points of the scanner. A handheld self-contained scanner provided by Creaform was used to scan a human face. Coupled with software on a computer, this structured-light scanner can build a 3D model from repeated measurements of an object's surface structure as the scanner is simply waved above an object of interest. Optical scanners can have difficulty scanning highly reflective surfaces or scanning objects lacking in detailed features. While a mirrored surface would appear as just a longer path to whatever is reflected, a large sphere would appear identical to the scanner from one point to another; the software would have trouble stitching the various different angles together to create a whole model. When scanning large objects with limited features, it is possible to help the scanner by attaching small reflective dots to the object in various locations; the scanner can use the dots to calculate the orientation of various parts of the scan. Commercial 3D scanners provide very high-resolution models of scanned objects; such devices can be as small as a handheld scanner or can involve larger, more complex systems that map multiple angles at the same time. Scanners can image the inside surface of pipes, map out mineshafts and subterranean caverns, or even scan entire build sites for large structures, using laser tools similar to RADAR called LiDAR. Such systems are used to map mining operations to calculate ore removal, or in surveying to create digital terrain maps. Commercial systems such as Creaform, FARO, Artec, XYZ/RGB, and a host of other alternatives provide very high-resolution object models suitable for industrial applications and manufacturing. However, a home user can use inexpensive lower-resolution scanners — like the Kinect video game controller — to model objects for 3D printing. Together with software such as SCENECT, ReconstructMe, or Microsoft Fusion, the Kinect game controller can be used to generate scanned 3D models at home.

Article / Updated 09-26-2017

Here's an important tip for using 3D printing extruders: Use fans. Use a small fan to keep the cold-end insulator of your hot-end below the glass-transition point of your plastic. When you start experimenting with printing ultratiny objects with fine details or printing objects at great speed, you quickly discover an interesting problem in 3D-printing thermoplastic materials: controlling layer temperature. If you print tiny parts that have little layer surface area or turn out objects at such high speeds that each layer is completed in a matter of seconds, the layer of plastic just laid down doesn't have time to cool, so it's still a little molten when the next layer is laid down. With the radiated heat from the nozzle and more hot plastic being extruded, the model can end up being a messy blob instead of the object you intended. You can slow the speed, but you may not resolve the problem; you shouldn't have to wait even longer to print an object anyway. In this situation, a controlled cooling fan can make a massive difference. The cooling fan is usually around 80mm wide and is controlled by the electronics. In your Slic3r-generated G-code, you can specify how fast a cooling fan runs and when the fan turns on and off. When your printer has a cooling fan fitted, Slic3r can run the print at full speed, even when printing fine details of a model. When your printer doesn't have a fan, Slic3r has to instruct the G-code to slow to allow natural cooling of the plastic before adding more. As you can imagine, fine structures can be tricky to print without a cooling fan. A fan permits bridging of extruded material — an essential part of many 3D-printed objects. Bridging occurs when a model has to span a gap, essentially making a bridge in thin air. If you extrude plastic with nothing below it, the extruded material naturally sags and sometimes breaks. Although you can bridge filament without using a fan, you usually have some strings of snapped extruded filament hanging down, as well as a little sagging. When you use a fan to cool the plastic as it's extruded, you can make a tight bridge and get smart-looking results. Mount the fan so that it cools the top layer of the part being printed. If you cool the heated bed, your part will pop off in the middle of the print. If you accidentally cool the hot-end, your extruder may jam. It's quite common for a cooling fan to have a 3D-printed duct that directs a stream of air across the printed object while it prints, to minimize unwanted cooling of the heated bed and hot-end. In almost all cases, it's not advisable to use a cooling fan when printing acrylonitrile butadiene styrene (ABS) material. The fan may cool the edges of the material too fast and cause them to curl; the next layer may be worse. Eventually, the part can be so deformed and warped that the print head may knock it off the build platform. By contrast, PLA likes a fan.

Article / Updated 09-26-2017

For thermoplastic printing on a 3D printer, it's a good idea to have two or more extruders of the same type, but with different nozzle sizes and maybe a choice of 3mm or 1.75mm filament. Some materials — especially experimental materials — tend to come in 3mm and less often in 1.75mm. Depending on the manufacturer, 3mm filament may cost less than 1.75mm filament. Having a choice of nozzle sizes is great if you intend to print parts of varying quality. Although you can always print with a small nozzle, the print job may take a lot longer for certain parts. Using a bigger nozzle can be handy if you want to create rough drafts of your models or intend to finish the resulting object with paints or fillers. A good all-around nozzle size is 0.4mm, which allows for fine detail and a reasonable print time for most parts. You can also select layer heights of 0.3mm or lower. This isn't to say that a big nozzle can't provide high quality. You can select very low layer heights if you're using a big nozzle, which makes the vertical quality of a print almost identical to what you'd get with a small nozzle, though some fine horizontal details may be lost if the model has many sharp corners and features. Think of a 3D-printing nozzle as being similar to a paintbrush. You can use a small brush or nozzle for finer details and sharper edges; a big brush or nozzle "paints" faster but can't resolve intricate details clearly. A typical large nozzle for a home 3D printer is 0.6mm or 0.8mm. A 0.6mm nozzle allows you to print layers of 0.5mm or lower and usually gives you a much faster print time than smaller nozzles. Some large RepRap printers use 1.2mm nozzles to produce models a meter (or more) tall or wide in size. Don't set a layer height that exceeds the size of the nozzle. Keep the layer smaller than the nozzle to ensure good bonding of plastic layer on layer. You can try using as small a nozzle as your machine mechanics allow. Keep in mind, however, that normal minimum layer heights are around 0.1mm (100 microns) — about the thickness of a sheet of office paper. Most RepRap machines allow layers of 0.05mm (50 microns) and even smaller, but printing time increases dramatically, and the extra quality is hard to distinguish. Common layer heights are 0.2mm or 0.25mm, which produce a highly presentable surface. As you become more accustomed to 3D printing and tune your printer to run faster, you'll find pleasing resolution at layer heights around 0.15mm or 0.1mm. If you decide to keep more than one extruder available for your 3D printer, you don't need to fit all the extruders on your machine at the same time. In many situations, having a quick-fit mechanism that allows you to change extruders easily makes sense. Richard struggled with multiple extruders when some of the first RepRap machines were being developed. At the time, all extruders were mounted permanently on the moving X-axis carriage with nuts and bolts. Changing extruders was time-consuming and tricky, and users couldn't even think about having more than one type of extruder. Richard developed a quick-fit carriage and various extruder bases for the most common hot-ends and paste extruders. The idea was to allow experimentation and make extruders easy to change and lock into place on RepRap printers.

Article / Updated 09-26-2017

Here are some tips to keep your extruder and 3D printer happy. Keeping your extruder in tip-top condition is important, because the extruder is the device that takes the most wear and tear in your 3D printer. Follow this advice to make your 3D printing go smoothly, prevent failed prints, and keep your new 3D printer in action: Check the accuracy of your software and firmware. Always make sure that the temperatures reported by your firmware and software are accurate. This check can resolve a lot of common problems and extend the life of your 3D printer. You can check the temperature in several ways. One of the best methods is to insert a thermocouple probe into the hot-end nozzle. Or invest in a noncontact digital laser temperature sensor, which sells for around $30. To use it, point the laser at the place you want to measure. This device is good for checking the temperature of the heated print bed, motors, and drive electronics. Verify the temperature of your cold-end. It's a great idea to check how hot the cold-end (thermal barrier) is getting on your hot-end. The cold-end's temperature needs to stay below the glass-transition temperature of the material you're printing. This limit is most critical for printing polylactic acid (PLA) materials, so check your extruder when it has been turned on and printing for 20 minutes or so. If the extruder heats up more than 50 degrees C, consider adding a cooling fan. Make sure that this fan points across the cold-end part of the extruder, not toward the hot-end or the object being printed. Some 3D-printer kits come with a fan to cool the cold-end of the extruder — usually, a very good idea. A fan isn't always necessary, but having your incoming filament go quickly from cool to melting temperature is much better than trying to push a plug of heated, semisoft, rubberlike material into your extruder nozzle. Keep your filament free of fluff. Add a fluff-capturing device to your 3D printer, because dust and fluff on the filament going into your hot-end can clog it and eventually jam the nozzle. Such gunk is very hard to clear out. A piece of sponge, secured around the filament with a zip tie, catches fluff and stops it from entering your extruder.

Step by Step / Updated 09-26-2017

A RepRap development goal for home 3D printing is to print objects in many colors and even mix, on demand, the color of your choice from a set five or six master materials. Full-color home 3D printing is still a little way into the future, but you can use several current methods to brighten your 3D-printed objects.

Article / Updated 09-26-2017

Any standard 3D printer's single-grip extruder also needs an idler wheel to push the filament into the teeth of the drive wheel. An idler wheel usually is a round bearing pushed by a spring or a rubber bushing. The following figure shows an idler bearing/wheel fitted to a printed lever; the spring on the left causes the bearing on the right of the image to be pushed into the drive wheel (middle), gripping the filament tightly. With a design using a bearing idler wheel, it must not be overtightened or it will squash rather than grip the filament. If your extruder uses the dual-drive system, in which teeth grip both sides of the filament, the bearing idler wheel is no longer required and the filament is unlikely to be squashed. Don't overtighten the idler bearing. If the grip on the filament starts to squash it out of shape, the hot-end's thermal gets harder to force down, and it may jam. Check how much the drive wheel is biting into the filament. You should see small, regular marks where the teeth bite in, and the filament shouldn't be crushed. The hot-end normally is attached to the extruder body with bolts to allow it to be removed if the extruder jams or gets blocked. A finished extruder also requires a heating element on the hot-end, as well as a temperature sensor (see the following figure). This wiring, along with the four motor connections, must go back to the RepRap electronics wiring. Never try to drive the motor or rotate the gears driving the filament if the hot-end isn't at the correct temperature. Doing so can cause the extruder to strip and chew up the filament, and you have to clean the teeth on your drive wheel before you can print again. A thermoplastic extruder needs to be carefully calibrated to operate well. Extruders are highly active subjects of development for RepRap. Many designs exist, some more specialized than others, offering higher temperature, faster extrusion, or finer detail. Most extruders usually meet the requirements of home 3D printing with thermoplastics.

Article / Updated 09-26-2017

The extruder is one of the most important parts of a 3D printer, so the quality and reliability of parts are critical. The filament drive mechanism almost always takes the form of a round bolt or rod with concave teeth that grip around the plastic. Filament drive mechanisms can be machined in a variety of ways. Look for even, well-cut drive teeth that grip but don't strip or grind through your filament. Too-sharp teeth can be as bad as too-blunt teeth. Filament drives used in thermoplastic extruders perform the same job but are manufactured in various ways. At the top of the figure is a traditional hobbed-bolt filament drive, which is the most common type of filament drive; it performs adequately. In the middle is a professionally machined drive wheel, which usually provides the most grip around the filament as it's pushed into the extruder. This wheel is usually mounted directly on the shaft of the extruder motor or on a gearbox attached to the motor. At the bottom is another machined bar with shallow, blunt grooves; this design won't grip as firmly as either of the top or middle drives shown. You can assemble an extruder in several ways. In the simplest assembly, the filament drive wheel fits directly on the shaft of the extruder's stepper motor and drives the filament directly via rotation of the motor shaft. This method provides the lowest torque but requires the fewest other components. The most basic filament extruder can perform adequately if you have a powerful drive motor and well-machined hot-end to reduce the forces required to push the filament. On the left side of the following figure is the same professionally machined drive wheel shown earlier. On the right side is another direct-drive motor, but with only a basic drive cog with a groove for the filament; it won't have as much grip as the one shown on the left. This cog costs little to manufacture but also has the lowest drive performance. A direct-drive motor has no gearing to improve torque, so you should avoid this type if at all possible. Direct-drive extruders do have one advantage: Two of them can be placed close together to provide dual extrusion. A compact gearbox can be attached to the output of a stepper motor to greatly improve the torque and rotational resolution compared with the direct-drive extruders (see the following figure). The gearbox can be compact to allow for dual extrusion. Many enhancements in extruder drive mechanisms have been developed in recent years. One of the most successful is the dual-grip system, shown in the following figure. The advantage of a dual-grip system is that the round filament is gripped and pushed from both sides instead of being pressed flat on the idler side (which usually squashes it onto a metal rotating bearing). More manufacturers are switching to a dual-drive gear system, which increases grip on softer filaments such as ThermoPlastic Urethane (TPU) rubber and helps drive harder or slippery materials faster. In RepRap 3D printers, it's still common for the motor to be connected to a series of 3D-printed gears (see the following figure). The gearing allows the motor to turn quickly while the drive mechanism turns slowly, thereby increasing the torque and allowing the filament to be driven with increased force and precision into the hot-end. This arrangement provides fast printing and retraction with less chance of material becoming jammed due to lack of torque. Another common type of extruder is the Bowden, which works on the same principle as the brake-lever cable of a bicycle. A slippery Teflon (PTFE) tube separates the extruder drive motor from the hot-end. This tube allows the driven filament to be constrained and pushed into the hot-end section. The Bowden extruder is often used in small or lightweight machines because it offers several advantages: The design removes the bulk, mass, and weight of the motor from the moving carriage, leaving only the hot-end. More hot-ends can be mounted on one 3D printer. The design can be ideal for machines with a lightweight head that moves quickly. A Bowden extruder does have a few disadvantages: The design has more parts and complexity compared to a non-Bowden design. The printer must perform a longer filament retraction after every print move to minimize oozing due to the pressure and spring that occur when the filament is pushed down the tube. The design can be hard to control and tune. The Bowden extruder shown here uses a 1-meter PFTE tube and would be used in a large 3D printer that produces models wider than 500mm.

Article / Updated 09-26-2017

As a general rule, slowing print speed on your 3D printer improves print quality. Fast travel speed can affect print quality because the print head gets to a new point quickly, and the high acceleration and deceleration sometimes cause unwanted shadows and artifacts on the print. Experiment with machine travel speed before changing other settings. Temperature also plays an important role in print quality and is especially linked to print speed and layer height. As a general rule, if you start to slow your printing speed below 20mm per second, you should also reduce your printing temperature. You may decide to print more slowly for a variety of reasons, such as printing a single small object or a part that's been tricky to print in the past. Most thermoplastic materials print perfectly well at temperatures lower than you'd normally use. Reducing the temperature also helps stop hot plastic from oozing out of the extruder nozzle, which can make a big difference in the quality of fine parts being printed slowly. You have more control of the plastic being extruded with such an approach. Also, you lower pressure in the extruder nozzle, which further improves print quality. If you're getting lots of print failures when you print plates of multiple parts, you may have a small mechanical-alignment problem. Check your belts to see whether they're tight enough. Also check carriage speed. If you're moving the carriage too fast for the frame design of your 3D printer, try slowing it. If that change doesn't help, consider tweaking another Expert-mode setting in Slic3r: Avoid Crossing Perimeters. This option tries to move the print head around the outside of a printed layer instead of across the part to reach the other side of the build bed or other object. The setting extends the time required to print an object, but it also improves the quality and reliability of the print. PLA prints at temperatures as low as 160 degrees C when you're printing parts slowly, which can produce less oozing and finer detail for smaller parts. You can still use a fan to force-cool the plastic layers, even at such low temperatures.