One of the most common building materials in use today is the two by four. This common lumber size is found in projects ranging from backyard sheds to large construction projects and most people at some point have used them for at least one project. They are so common that a misperception exists with many that a two by four is the same no matter where it comes from and no matter the end use.
Of course those making a living in construction know otherwise and a single trip to Home Depot will educate even the novice weekend shed builder to the many variations in our favorite piece of lumber. There’s surface dry, kiln dry, structural, construction, standard, utility, hardwood, softwood and the maddeningly long list goes on until we either learn what we need for what we are building or just give up and buy a new barbecue grill and call it a day. In the end we need to know at least a few basics about what we are trying to build and the properties of what we are trying to build it with in order to succeed.
As out of place as the above description may seem it describes a common trap for projects in many industries including 3D printing. Nowhere is this more evident than in FFF, or Fused Filament Fabrication. Just as the support stud for a backyard shed in Maine is vastly different than the finish grade structural studs used in a large construction project in Cleveland so too are there important differences in the plastics used in 3D printers. Yet often we seem destined to make the same mistake we do with the two by four, that if we just get the size of the filament right and the vendor for the filament says that it’s made from the “best” materials we can complete our project with little or no trouble.
Controllable Variables in the Printing Process
The problem stems in part from the variables in play before the printer even warms up. Type of material, condition in which the filament was stored, variations in room temperature and airflow around the machine are a few of the variables we can control.
Type of Material: The most common materials such as ABS, PLA, HIPS, Nylon and PVA as well as many others are readily available and each have benefits depending on end use for a project. Once a material has been chosen for the project a brief read of the properties, tendencies and temperature ranges required will help the operator adjust settings appropriately to control output.
Condition of Filament When Stored: Each type of filament has certain unique properties that drive the decision for its inclusion in a project. Some of these materials may be more susceptible to ambient conditions than others. For example, PLA, one of the most common filaments used in FFF is subject to moisture ingress and must be stored properly to reduce risk of poor quality print or print failure. Again, understanding the specifications of the filament material selected will allow for better control at the print stage.
Room Temperature and Air Flow: With large industrial extruders the machine will have a series of temperature zones that allow the material melt to be stabilized and controlled. These large extruders will usually be in a building or room with stable atmospheric conditions. FFF printers generally have one temperature zone and stable ambient conditions are often not available or reliable. This is especially true of desktop printers where home use in the proximity of a fan, an AC unit or a door opening nearby can cause fluctuations in temperature or a shift in airflow that can affect the print. But it can also apply to smaller enterprise shop floors where the same lack of control can cause temperature swings or airflow issues that affect print quality or cause print failure. Analysis of the area of operation and reduction of airflow through simply closing a door, setting a thermostat at a different level, turning off fans or AC or in extreme cases building an enclosure will help narrow the range of temperature variation during print.
Difficult to Control Variables in the Print Process
There are a number of variables that can impact the final print that are largely out of our control or are unknown unless the user has an established history with a vendor. In many cases, and probably most cases when speaking of home desktop printers, cost is the dominant driver in selection of filament material and can result in a lower quality filament due to purchase from a variety of sources based on price alone. These hard to control variables include slight differences in formulation from vendor to vendor for virgin material, homogeneity of virgin/recycle blends and contamination issues both from vendors as well as at the shop floor level during production.
Variation from Vendor to Vendor for Virgin Material: The word “virgin” is used in 3D print plastics to describe an assumed, almost magical, ideal state that in truth has variations in process. It is worth noting that these variations are present even in large scale extrusion facilities where the extruder has a variety of temperature and feed controls that allow adjustment for batch variations. Each batch of plastic arrives at the factory, usually in pellet form, with a series of “process histories”. These process histories can include colors, stabilizers, lubes and other materials and all can contribute to degraded physical, chemical and flow properties of the polymer. Further, with materials such as ABS the addition of color can cause stiffening adding an additional “process history” and possibly affecting performance.
Changing vendors repeatedly whether due to price or other factors can introduce process variations, misprints and print failures as no two vendors will have exactly the same formulation. A printer that has been running a setting that was ideal for a part at a specific temperature previously may need to be adjusted up or down for the same size filament and color obtained from another source. The variations and adjustments may be small but each change in filament may introduce the need to adjust settings.
Homogeneity of Virgin/Recycle Blends: Recycled plastic is a reality in all areas of the plastics industry. In some segments of the industry such as sheet extrusion/thermoforming the scrap rate can reach 60%. And in most applications, except for medical, the scrap can be fed back in in the form of “regrind” to allow reuse of scrap. The problem then becomes twofold:
- One, as the regrind or recycled material is passed repeatedly through the system the polymer chains may weaken. This could cause potential issues at extrusion.
- And two, the addition of “regrind”, or recycled plastic material, during production can result in a lower molecular weight compared to the same material in virgin state and thus could result in potential melt flow problems at the print stage as well. In large industrial extruders controls in pressure in a long chamber and temperature in zones allow for adjustment whereas most desktop and small enterprise printers have a small melt chamber with a feed wheel system where adjustment to increase or decrease feed is limited.
- Even if the assumption is made that a mix of virgin and recycled material can be dependably achieved and is processed well in a given printer there is no guarantee that the virgin to recycle ratio from one vendor is the same as another nor can it be assumed that the ratio is stable from batch to batch with the same vendor on the next run. If the ratio of virgin to recycle is consistent settings can be stabilized. However, the higher the percentage of recycle the higher the scrap rate on the end product. This is true of larger extrusion operations and will carry over to 3D printing in filament form as well.
- Contamination: There are two avenues for contamination that can affect print quality. The avenue that can be controlled directly by the operator is the machine and its surrounding conditions. Keeping the machine clean, free of dust and debris, limiting sudden changes in airflow, consistent cleaning of all parts to remove dirt and plastic buildup around the nozzle and keeping the feed wheel assembly free from obstruction will allow for a higher print quality related to the machine itself. However, contamination from the vendor is also possible and more difficult to control. If you are using a virgin/recycle blend it is possible that contaminants, called fines, from the regrind recycling process, may have been included in the filament extrusion. Even if the material is virgin there is still possibility for contamination as the virgin material may have additional compounding steps for coloration, lubes and other additives as mentioned in the “process history” discussion above. If these additional compounding steps are subcontracted by the original vendor the opportunity for introduction of contamination even in virgin material is increased. Because of the small size of the extrusion nozzle on FFF printers the hot end can become clogged due to contamination in the filament even if the machine itself is well maintained.
- Answering Questions Addressing the issues of process variation with virgin filament from vendor to vendor, virgin/recycle homogeneity ratios and contamination are concerns among users of FFF 3D printers both within the desktop and maker world as well as small enterprise users. These concerns are usually voiced in the form of questions such as:
- “How can I guarantee that the “virgin” filament supply I am purchasing is the same formulation as my previous vendor”?
- “How can I assure that a filament using recycled material will be homogenous from lot to lot”?
- “What can I do to reduce risk of contamination within my purchased filament”?
The short answer to these questions is…you can’t. The questions are actually a reflection of unrealistic expectations placed upon additive manufacturing in recent years. The hype in the press as well as from many within the industry has created a series of myths and impossible-to-meet expectations that lead many to assume that 3D printers and the materials introduced to create projects have become as simple as a microwave. We just plug it in, put in our food, set the timer, press the button and voila, our product comes out within minutes.
- That this doesn’t happen doesn’t mean that the evolution and advancement of 3D printing technology has hit a dead end or has failed and it doesn’t mean that there are no steps that can be taken to improve and control performance and output. It means the answer to successful production will rely on better understanding of the processes and materials involved, minus the myth, and it will also require a reset of expectations.
- New Expectations
- The FFF method of 3D printing is simply plastic extrusion on a micro scale. To put this method in perspective and begin to address the common questions and misconceptions as well as unlock the capabilities to fulfill a user’s needs some expectations will need to be reset to separate the myth from the possible:
- Realize that FFF, as part of the larger field of plastics extrusion, is linked to the same technological constraints and inherent characteristics of the entire extrusion industry. If large format extrusion is constantly dealing with scrap, recycle ratios, vendor formulation variances and process histories then the filament form of materials for 3D printing will likely have the same inherent characteristics. The user will need to educate themselves on the characteristics of the materials they wish to use and adjust settings accordingly.
- Accept that if low cost filament alone is the driver of material purchase choice for a 3D printer then the variables mentioned above will be more likely to have much larger variance ranges for the reasons listed and will more often than not require more adjustment, result in a larger scrap rate, affect the lifespan of wearable parts and possibly affect overall finish quality.
- Identify and address the controllable variables for each printer’s environment and maintain controls on those variables throughout the project. The prospect of a new project, new printer or an “aha” moment is exciting but losing a print near the end due to shop floor contamination, improper storage of materials or a blast from an oscillating fan that affects a print at a critical moment can be disheartening.
- Setting realistic expectations that match reality for operation and material utilization will allow each project a greater chance of success. These expectations can also yield increased knowledge, and therefore proficiency, for the user on both equipment operation and the understanding of the properties of the materials used as well as possible variations based on supplier. The result will be higher quality prints with less frustration and perhaps even savings on time. You may even have time left to pick out a few nice two by fours at Home Depot for that backyard project you’ve been planning on. Just make sure you read up a bit first. Not all two by fours are the same.
- IC3D produces its own line of 3D filament in both ABS, PLA and Nylon. We don’t use recycled material thus eliminating possible variances that could be caused by recycled scrap during print. To further reduce filament variation our 100% virgin material is extruded in house in Ohio in the USA using strict production standards and achieving tolerances of +/- 0.10mm and within 4% ovality. Our filament is backed by a 100% satisfaction guarantee. Check out our line of materials online, or, if you’re looking for consulting, enterprise solutions or design needs, contact us and our staff will be happy to help guide you to the solutions you need.