The Future 3D Printing & Plant-Based Resin

Raspberry Pi4, UPS and Temperature Sensors

A few months ago I switched over to Eco UV Resin as I wanted to be a good citizen of the planet, and thought that moving to a plant-based product that is water-soluble was the right thing to do. I’m on my third Kg container of this product, and I’m beginning to have my doubts, but perhaps I should back up.

In March of 2020, I purchased an Elegoo Mars 2 Pro 3D resin printer, and have consumed at least 15kg or more of standard resin in at least four colors, so I’m not your typical 3D resin noob. I also picked up an Elegoo Mercury Plus wash station at the same time, and typically wash 20-40 prints per gallon of 97% alcohol. To be clear I’m not printing small figures, but more often than not 3-5″ models of things like custom Raspberry Pi cases, fan mounting brackets, and prototypes of future products. So when using normal resin the alcohol in the washbasin will become discolored after a few washes, but I don’t switch colors much and the prints are always clean, smooth, and free of any residual resin after washing. In fact, often the rapid resin stays in suspension in the alcohol between print jobs, sometimes a week or more without settling. I’ve found that washing with less than 97% leads to stickier prints and the alcohol becomes contaminated faster due to the additional water. Some suggest curing suspended resin in the wash tank by leaving it out in the sun for a bit, then filtering it. Recently, I started using translucent clear plant-based resin, and the experience is considerably different from that of rapid resin.

When I finish printing with translucent clear Eco resin, I put the build plate with all my printed parts into a tank of soapy water in the wash station and run it for twenty minutes. The build plate is then removed, parts are separated from it then scrubbed to remove any trapped resin the wash station missed. Next, the supports are snapped off. One further scrub, some light sanding, and another rinse then on to curing. Seriously, I’m probably consuming a few gallons of water per print, and wash my hands several times thoroughly throughout the process. No, I don’t wear gloves, and this has never been a problem for me as I’m extremely careful, and what resin which has come in contact with my skin has never caused a problem. After I’m done, I then need to wash and scrub out the wash tank and build plate. This is far more labor-intensive than alcohol-soluble rapid-resin where I never clean the model outside of what the wash tank has done. It should be mentioned that I often print hollow models, and very carefully place the drain and vent holes so they are hidden, yet offer the best functionality. Trapped resin is rarely an issue. While Eco resin sounds environmentally friendly, when one takes the volume of water consumed into account it may not be as friendly as it appears. 

Today my $500 setup has a limited print volume of 5” x 3.2” x 6.3” and can produce a full-size single color print in under eight hours, often careful placement means two to three hours. Other products in this 3D printer line are bigger and capable of print volumes nearly triple mine, but they are still single color. Producing a final product that has multiple colors requires multiple prints for the various different colored parts, then you need to assemble them. Between colors, the tank needs to be emptied and cleaned. Designing something from scratch that screws or snaps together requires some serious modeling and slicing skills, along with the professional version of the slicer. A slicer is a program that takes your 3D model and turns it into a file your printer can understand. Even more important though, the slicer helps you layout your model on the build plate, detect and fix print problems with the model, make some adjustments, like creating weep holes and vents so that resin isn’t trapped inside hollow parts, and define supports connecting it to the build plate. How, and where to place supports for a 3D model with a resin printer requires different considerations than a traditional deposition printer. So where is 3D printing headed?

3D Resin printers often utilize a 4K monochrome computer screen that faces up from underneath the build tank. A UV light then shines through the screen and cures resin wherever there isn’t a negative print image. Initially, the slicer produces a raft that is a flat surface on the build plate with a lip around the edge that enables sliding a scraper underneath the raft when the printing is done to separate the print from the build plate. Supports then grow out of the raft and connect it with the model. Models are often suspended five to ten millimeters below the build plate with these supports enabling them to be easily separated from the raft after the build is completed. Once the printed model is rinsed and separated from the build plate then you need to remove all the supports, further clean the model, and often sand the surfaces where supports were attached to remove any pitting. Does this sound user-friendly? It isn’t, right now it’s something that only a devoted hobbyist or employee would leverage to achieve an objective.

Many of us can envision a day when we order a product on Amazon, and while it’s in the cart Amazon checks the supplies in our home “Amazon Replicator” to determine if the proper color resins and cleaning supplies are available to build the product. If so then the order is accepted, and sliced print files for my model replicator are automatically downloaded and queued into the printer. When the parts eventually emerge in the product hopper, along with one-page assembly instructions, the customer is then charged for the print and additional replacement supplies are shipped out when necessary. The customer then assembles their product and they have what they ordered in hours rather than days.

Today we pour 200 ml or so of a single color resin into the tank then print a single color until the job is complete. What if the printer sprayed an appropriately thick layer of a specifically colored resin onto the tank bottom, for the layers needing to be printed next in that color. Then between layers requiring a color change, the tank bottom could be cleaned, drained, dried, and the new color sprayed thick enough for the next layers requiring that color. When the print is completed the tank would be drained, cleaned, and dried for the next job. The build plate and the print would then be fully washed. At this point, simple robotics would be needed to separate the print from the supports coming up from the raft using one of several types of tools to clip, melt or vaporize support resin where it meets the model. At this stage in the process, the model is dropped into the curing bin for a few minutes then released into the output bin. Meanwhile, the raft and supports are recycled, perhaps back into supplies or for return to Amazon for reprocessing. With advances in modeling, slicing, and printing we may eventually reach this point for some simple products, but given my experience, this is still a number of years away. 

Regardless, it’s awesome to think that even today we can take an idea, create from it a 3D model, then slice and print it all in the same day! I really love technology.

3D Printing, an Art Versus a Science

Creality Ender3D Printer

One of our cherished holiday traditions is to craft homemade gifts for family members. My now 22-year-old son, when he was ten used his Erector Set to make a fishing pole for my dad, complete with working reel, fishline, and lure. Dad was big into sports fishing, and although he passed back in 2012 that rod is still on display in my mom’s FL Keys home. This year my son returned from college bringing his Creality Ender3D printer, an entry-level product he purchased this fall in kit form for about $250USD. He wanted to print several gifts he’d been designing, but hadn’t had time to while in school. 3D Design and printing is something he’s been into for the past six years on various projects and thought it was about time to have one of his own. If you’re not familiar with the Ender3D it’s a fundamental design where the print surface moves in one dimension (forward and backward) and the single printer head moves in the other two directions (left or right and up or down). Both the print bed and the print head have controllable temperatures, as well as cooling fans designed to cure a print rapidly. This enables the printer to utilize the most common plastic, PLA, but also many other more exciting materials like TPU, a sort-of plastic/silicone blend which is both flexible and resilient. On the surface this sounds awesome, we can printer whatever we like from things we’ve designed to those designed by others and posted to sites like Thingverse. Who wouldn’t want this remarkable capability at home, right?

Phone Case with Un-removable Raft

It’s not so amazing though, as 3D printing is still very much an art more than it is a science. For those not familiar with this subtle distinction, when something is a science it must ALWAYS be reproducible, while when something is an Art there remain significant variables under control of the artist, and sometimes nature, which makes the process nondeterministic. Everything we print, of any size above an inch or two, often takes several attempts to produce a final product. Sometimes even that final product results in a print that is unfortunately unusable as a result of the process settings (not the design). For example last Monday morning, after two failed attempts we finally succeeded in printing a mobile phone case using TPU. The two prior attempts failed due to a break down in the adhesion of the print job to the build plate, the most common class of failure. Since this is an entry-level printer, it isn’t aware of a failure, so it continues printing until it jams or the job completes.

Epic Print Error – Ball of PLA Behind Print Head

This lack of intelligence or feedback into the system results in some epic messes. The previous Friday night we returned home to find a PLA print job had broken loose from the build plate, and the print head had shoved it off onto my desk. It was only 1/4 complete and a blob of PLA the size of a jawbreaker was riding the back side of the print head like a tic on a dog. Did I mention it was still printing, perhaps an hour or more after the failure? The phone case discussed above, which we’d been printing using TPU, finally finished successfully on the third attempt. It removed cleanly from the build surface. To increase our chance of success for the third attempt, we added a “raft.” A “raft” is several extra layers of print material which are laid down as a foundation prior to printing the actual job. The “raft” has a slightly larger footprint than the print itself, and that footprint has 100% coverage using a tightly weaved pattern to ensures that plenty of material is applied to the build surface to secure the print until the job is completed. We’ve never had a problem with PLA prints separating from their “rafts” but as mentioned TPU is far more flexible and resilient which made it impossible to cleanly separate the “raft” from the case, rendering the case unusable.

One of Four Puzzle Pieces Making Up
5×7 Photo Frame Gift
Note Extra Tape to Avert Curling

As mentioned previously build plate adhesion is the single biggest problem making 3D printing today an art. Various build plate materials are available from aluminum to tempered glass, and PVC, all with their unique bonding characteristics with different build materials. Tempered glass works reasonably well with TPU, provided the build plate temperature is set correctly and consistent within two degrees Celsius. With the third print, we opted to lay down a thin layer of diluted Elmer’s white glue to provide adequate binding of the print to the build plate. Something we do now as a regular process when printing with PLA.

The second problem, which impacts print adhesion to the build plate, is temperature control. Here there are three variables, the temperature of the head, the build plate, and air flow from fans designed to cool a print in process. PLA shrinks as it cools, so often prints larger than an inch tend to curl if they cool too quickly. This is where the bed temperature needs to be just right at the start then cool slowly as successive layers are applied. Peeling with PLA has been a problem for some time, so “rafts” and a little extra glue on the raft early on often solves this.

Stag Coral Bud Vase with Scaffolding
Looking Like Something a Spider Wove

Another problem is the supports created by the program that compiles your 3D model into your print file that you can then send to the printer. These supports often called “scaffolding,” are required if a print needs to expand much beyond the printed surface below it. 3D printers are akin to hot-glue guns with excellent control over print material placement. With that in mind, you can’t have the printer squeeze out a bead of plastic with nothing below it for very long before gravity takes over and introduces chaos into your print. The print programs are aware of this, and they have tricks to prevent this from happening. Imagine you are printing a capital “T” as you see it on this page. Normally you’d print this T laying flat on its’ back or even upside down to limit wasted material and ensure a successful print. For this to print properly standing up, the print program inserts temporary scaffolding under both arms of the “T” as it starts building the base of the “T.” This provides a structure onto which the printer can then print the more solid arms of the “T.” This holds especially true if you’re a grandson whose custom designed a “stag coral bud vase” with many outstretched branches as shown below, or a phone case where the protective lip touches the front glass. With PLA the scaffolding often removes pretty easily once the print is complete, and if not a Dremel can be used to clean up any remaining mess. With TPU some scaffolding can never be removed.

Same Stag Coral Bud Vase
After Removing Scaffolding

More expensive dual head printers, often starting around $800USD, can utilize a water-soluble plastic to print the scaffolding in parallel with the primary print material. Once a job has finished printing you just remove it from the printer and drop it in a tank of water overnight. On returning in the morning you find a clean print with no supports. Single head printers don’t have this technique available to them.

Other materials like wood, metal, and ceramics can also be printed on these printers, but these exotic materials require even more of a craft approach to printing. We’ve attempted a wood product several times, but have had no success to date as it’s jammed up multiple print heads. This product is VERY finicky when it comes to temperature, too low it jams up, too high and you end up burning the wood. As for metals, you can even print simple circuit boards; we’ve not yet experimented with those.

Exercise #5 of 20 in In Learning 3D Design

Another craft aspect of 3D printing which I’ve not discussed yet is the area of designing something to be printed. Design programs like SolidWorks or Fusion360 by Autodesk, the leader in this market, enable you to create practically anything you can dream up, sometimes even more. That doesn’t mean though that what you design is always in-fact printable. Shown to the right is one of the twenty exercises my son assigned me to design in Fusion360, a little role-reversal. With a single head printer if you want to create something that requires different materials or colors you have to design it for assembly post printing. Most single head printers don’t allow you to stop mid-job to change out a spool of black PLA for white PLA. Designing something for assembly, post-printing, requires considerations be made during the design process which would not be necessary if you were using a dual-head printer. Most dual-head printers today pause the job and notify you a spool needs replacing, like back in the day when your plotter needed another pen to draw with green.

Final Stag Coral Bud Vase

If you live on the bleeding edge sometimes you get cut, or in my case lately a little scorched, by the technology you’re looking to wrangle. Perhaps you might like to learn a bit more, please consider listening to this recent podcast we did on this subject. If you’re one of those out there who thinks 3D printers are something that will soon be gracing the shelves of Target, then I’d love to hear your perspective.

Below, you can see two print jobs, both from the same file, one in white PLA and the other in black, both material spools were from the same company. Note that the white printed fine, while the black has a series of raised sections that make it unusable as one-quarter of a decorative picture frame. In fact, all four puzzle pieces that were printed out in white PLA all came out fine. We’ve reached out to the Reddit community to see if anyone has any idea why this would happen with the black PLA.

Two 5×7″ Picture Frame Puzzle Pieces, Both From the Same Print File,
Using PLA Plastic From the Same Company

02/17/19 then 5/6/19 UPDATE: Extensive work with Fusion360, Cura (slicing/print utility) and the Creality Ender3D printer has resulted in an understanding that tightly controlling six variables is the most important thing one can do to create great repeatable results when using PLA:

  1. Print head temperature: 200C, but initial layer 215C
  2. Use a tempered glass print bed.
  3. Print bed temperature: 70C and enable retraction, this is key to preventing stringy prints.
  4. Print bed height in relation to the print head at the lowest point: 1/2 the thickness of an average business card, enough so that the first bead of printed material is slightly squished.
  5. LEVEL print bed, this can be done by moving the head over all four adjustment zones and checking the spacing as mentioned in step four. With all the above steps nailed down we no longer use any glue or adhesives for the PLA to stick to the build plate.
  6. ONLY print with a “raft” if the print is small or has a small footprint. It wastes a bit of material, but I’ve yet to have an issue once the above five variables were all resolved.

Once all these issues were addressed, printing was almost as repeatable and flawless as printing on an ink-jet printer. So good luck, and happy printing.

A print for a friend. Note this was without a raft, so the feet on the bottom curled a bit. An earlier print had a raft and even so shrinkage of the material while cooling resulted in curling in both cases. Also, you can see some odd gaps between letters, this I think is also due to shrinkage. It should be noted that this is how it came out of the printer, no stringy fibers.
While printing you can see the shrinkage under the front right corner. This should be a perfect 90% angle, but instead, it is shaped more like the leading edge of a snow ski. This capture is low-res because it’s live coming off a Raspberry Pi using Octoprint.

*Note to see any of the above pictures in more detail just click on them.