3D Printer Standard Operating Procedure Jonathan M. Cabot 10 January 2016 For rapid-prototyping and production of low volume, low cost plastic objects. 1.0 Material Requirements 1.1 Equipment needed for process There are various 3D printers available on the market, including the RepRap Mendelmax series, Makergear units, DeltaWASP, and many other companies. All of these devices contain a plastic extruder that melts and outputs plastic at a controlled rate, and motors that move the extruder and print bed to be able to print in 3D space. 3D Printers typically use Acrylonitrile butadiene styrene (ABS) or Polylactic acid (PLA) plastic, in spools of filament. For a RepRap Mendelmax II, only ABS or PLA in 1.75mm diameter filament should be used. 1.1.1 Hazards associated with equipment The printhead can heat plastic to in excess of 250 C, which presents a burn hazard to the user. The extruder should only be touched after the printer has cooled down thoroughly, after about 30 minutes after being shut off. The print bed can also be heated, so this also requires caution. The traveling print bed and extruder are driven by strong motors, and present a pinch hazard. Hands, loose hair and clothing, and other objects should be kept at a safe distance from from the printer during operation. In the case that the print bed has shattered due to mistakes in printer calibration, and the printhead is driven into the bed, glass fragments can be very sharp. These should be cleaned up with caution using cut-resistant gloves. 1.2 Chemicals needed for process Chemical solvents can be used to clean the glass print bed, typically acetone. Hairspray can be used to increase the adhesiveness of the print bed. 1.2.1 Hazards associated with chemicals Read labeled warnings on any chemicals used to clean the bed, and acknowledge that strong solvents are not necessary for the simple operation.
Hairspray is often kept in high-pressure containers, and should be kept away from direct sunlight, and kept in a standard temperature and pressure environment. Caution should be taken to avoid impact with this material. 1.3 Engineering controls 1.3.1 Hardware Few hardware controls are available on 3D printers, but should be noted. Primarily, it should be noted where the on/off switch is for the printer, and also where the printer is plugged into electricity. This is important for stopping a print in case of an emergency. If any part of the printer is moving when an emergency stop is required, it may be more safe to unplug the printer instead of using an on/off switch on the printer that may be too close to moving parts. 1.3.2 Software Most of the 3D printer operation is done via computer. In a software program such as Pronterface, the print bed can be moved forwards and backwards using software buttons, which can also be used to move the print head up and down, and from left to right. Also, similar controls can be used to move the extruder motors in small increments. Figure 1: Pronterface Controls Also in Pronterface, the temperature of the print bed and extruder head can be set. Allow between five and ten minutes for temperature to increase from room temperature to print temperature. There are also some indirect controls of the printer, such as starting or stopping a print job. During the actual 3D printing process, the computer sends code automatically to the printer to make the desired part, from settings declared in a G-code file by other 3D printing softwares, such as Slic3r.
1.4 Protective equipment needed Protective equipment is only required when touching the extruder or print bed while either component is hot. Touching these components is not necessary during regular use, but may be required for maintenance. In such a scenario, heat protective gloves should be used. Special attention should be paid to keep loose hair, jewelry, or clothing away from the moving parts of a 3D printer. 2.0 Procedure 2.1 Preparing an STL File STL Files, a needed intermediate step to 3D print using Pronterface, can be found in two places. First, STL files for various objects can be downloaded from websites such as Thingiverse, PinShape, or GrabCad. STL files can also be exported from 3D modeling software such as Autocad or Solidworks for custom built parts. To do this, use the Save As button under File and save the part as an STL file. In either case, it is very important that the scale of the object is smaller than the size of the print bed. To ensure this, STL files can be opened and measured in most modeling softwares. Also to be noted is the ability of the object to be printed without support material. This is determined by the shape of the object, as a part with overhanging features can not be printed without support material. For example, if a 3D model of a tree were to be printed without support material, the branches of the tree would be printed in the air, which would not result in a successful print. Only printers with two extruders can print support material simultaneously with the rest of the print. 2.2 Preparing a G-code File G-code is a numerical control file used in various forms of computer-aided manufacturing. In the case of a 3D printer, the G-code file instructs the printer how much to move the motion and extrusion motors, at what time, and in what direction. Other information is also included in the file, such as the temperature of the print head and print bed, and acceleration rates. A software such as Slic3r can be used to control how the STL (object) file is interpreted and how the object will actually be produced, as a G- code file is explicitly defined.
First, find and open the Slic3r software. Drag the STL file into the window, so the Slic3r window now looks like this: (Figure 2) (The square object in Pink will take the shape of the object imported into Slic3r, in a top-down view.) Figure 2: Slic3r Window Next, use the tabs Print Settings, Filament Settings and Printer Settings to adjust the options for the print. Some variables can be left the same, but others are important to note. Under Print Settings, the Infill density and pattern are important details that affect the print duration, material used, and strength of the part. For most uses, the interior of the part can be honeycomb, a strong but open pattern. A density of around 40% is also effective for most parts. For Filament settings, it is important that a diameter of 1.75mm is set, as this is the only filament diameter the Mendelmax II supports. The temperature of the print in degrees celsius, is also important. For PLA prints, the extruder should be set at 180 C for all layers, and the print bed should be set at 60 C for all layers. Under Printer Settings, note the bed size, print center, g-code flavor, and nozzle diameter, all constants that should be stated in manuals for the printer and extruder head. Once all settings are determined and set properly with regard to the printer and print job, the Export C-code button can be used to obtain the G-code file necessary for Pronterface to print the part. 2.3 Orientating the 3D Printer With the computer connected to the 3D printer, find the Home button in the Pronterface software. This will be used to make the printhead and print bed go to an origin coordinate. Unless the previous use of the printer resulted in damage to the machine, click the Home button to make the printer return to this position. What is most important in this orientation is the z-axis. The printhead will be at an appropriate height from the bed if there is significant friction when sliding a thin object (business card) between the printhead and bed. If when sent to the origin there is too much space between the bed and the printhead, turning the set screw will adjust vertical orientation. The hand screw is underneath the print bed to the back right. Turning the screw clockwise increases the height, and turning the screw counterclockwise decreases this height. Making sure to not turn the screw more than 90 at once, an optimal height can be found by repeatedly
checking the height, rotating the screw, clicking the Home button in Pronterface and waiting for the printer to adjust, and checking the height again. 2.4 Printing With the printer orientated and a G-code file loaded into Pronterface software, all that is required before printing is ensuring the temperatures are correct (indicated under the directional controls in Pronterface). With this correct, the Print button can be clicked, and the print will begin. After this, there are two main scenarios: the filament sticks to the bed as intended, or the initial layers go astray from what was intended. In the first case, let the print continue until it completes or a problem arises. It is important to keep watch over the printer during a print job unless it is determined very unlikely that something will go wrong. In any case that the print job does not go properly, refer to section 2.6, Troubleshooting Steps. 2.5 Removing a Printed Part from Print Bed Parts created with the 3D printing process often are strongly attached to the print bed. Removing a part should be taken with patience and caution. A razor blade can be used to separate edges of the part from the glass. After this, a thin strong object like a metal ruler can be used with leverage to slowly remove the part from the bed. Rushing the process of removing the part can result in damage to the part or 3D printer. 2.6 Troubleshooting Steps In the case that a print does not go ideally, it is often best to stop the print early. An indicator of later print quality is how well the first layer replicates the computer model, or what the printer is intending to print. If test loops are used, they should ideally be composed of straight lines connected by uniform arcs. If the first layer of the print job is not ideal, it is likely that the filament is not properly sticking to the print bed. 2.6.1 Slowing the Print Speed The first step to take when this happens is to slow the speed of the print. In a software such as Slic3r, the speed of the first layer can be set separately from the rest of the print. For this, try setting the print speed of the first layer to half of what it is currently, and then running the test again. 2.6.2 Increasing Adhesiveness of Print Bed If further problems with the first layer sticking occur, there are chemical solutions that can be used to increase the adhesion of the bed. Consumer hairspray, available in spray cans, is one of these solutions. The print bed can be moved away from the printhead using the software controls in Pronterface, which allows for more of the bed to be treated. With this, use one hand to hold a piece of paper between the print head and the hairspray, and use your other hand to spray a light layer of hairspray onto the print bed. This light layer will increase the adhesiveness of the print bed, and further prints should be more successful. If there are residual pools of hairspray on the print bed, make sure to wipe them off before attempting another print.
2.7 Cleaning the Print Bed The print bed can be cleaned with a wipe slightly damp with a weak solvent. For easy access to the print bed, make sure to use the software controls in Pronterface to move the print bed away from the extruder. These solvents, such as acetone, should be used in small amounts. If done properly, the cleaning process consumes solvent, and the wipe used is not left damp with the solvent. In this case, the wipe can be disposed of in the trash. In the case that the solvent is not consumed, the damp wipe can be brought to a satellite accumulation area to be wrung out and the solvent collected, and then the wipe can be disposed. 3.0 Storage The materials required for a standard 3D print job (filament, hairspray) are not strongly hazardous, and do not require special treatment. Note that hairspray is likely to be in a highpressure container, so keep this in an environment with standard temperature and pressure, and away from impact. Weak solvents that can be used to clean the print bed, such as acetone, should be kept in labeled containers alongside other stored chemicals in a designated place. A fume hood is not a chemical storage area. 4.0 Waste Products If solvent used on a wipe for cleaning the print bed is not consumed, the damp wipe can be brought to a satellite accumulation area to be wrung out and the solvent collected, and then the wipe can be disposed. Residual hairspray on the print bed can be wiped up and then disposed of. 5.0 Accident Procedure 5.1 Contained Accidents In a few circumstances, it is required that the Printer halt operation quickly. These include: A mis-oriented printer sending the printhead down through the print bed, potentially damaging the printhead or shattering the glass print bed. Clothing, hands, or loose hair being caught in the motors of print bed or print head.
To Stop a Print, the Stop button in Pronterface can be used. In more extreme scenarios or if the Stop button is unresponsive, switching off the printer or unplugging it will quickly stop motion. Ensure that there is no risk of anything being caught in the moving parts of the printer when reaching for the switch or plug. 5.2 Unconfined Accidents As the 3D printer is an electrical device, especially one with a heating element, there is a potential for a fire hazard. In the case of a fire, refer to the Emergency Procedures chapter, Fire Response section of the UMass Lowell Chemical Hygiene Plan. For convenience, a segment of this is provided below: Visible Smoke or Fire 1. Activate the fire alarm pull station and evacuate the building. 2. Do not use the elevators. Exit through a stairway that leads directly outside. Be familiar with at least two means of egress from your area. 3. Call the University Police at 44911 from a SAFE phone near an exit. Provide information. 6.0 References Scalfani, Vincent F., Josh Sahib, and John H. Sandy. 3D Printing at the University of Alabama Libraries. Tuscaloosa, Alabama: University of Alabama Libraries Narative, Jan. 2013. PDF. Chemical Hygiene Plan. Lowell, Massachusetts: University of Massachusetts Lowell Environmental and Emergency Management and Environmental Health and Safety, n.d. PDF.