Printing In Multi-material? Use These Filament Combos

December 7, 2024 by Donald Papp 15 Comments

If one has a multi-material printer there are more options than simply printing in different colors of the same filament. [Thomas Sanladerer] explores combinations of different filaments in a fantastic article that covers not just which materials make good removable support interfaces, but also which ones stick to each other well enough together to make a multi-material print feasible. He tested an array of PLA, PETG, ASA, ABS, and Flex filaments with each in both top (printed object) and bottom (support) roles.

A zero-clearance support where the object prints directly on the support structure can result in a very clean bottom surface. But only if the support can be removed easily.

People had already discovered that PETG and PLA make pretty good support for each other. [Thomas] expands on this to demonstrate that PLA doesn’t really stick very well to anything but itself, and PETG by contrast sticks really well to just about anything other than PLA.

One mild surprise was that flexible filament conforms very well to PLA, but doesn’t truly stick to it. Flex can be peeled away from PLA without too much trouble, leaving a very nice finish. That means using flex filament as a zero-clearance support interface — that is to say, the layer between the support structure and the PLA print — seems like it has potential.

Flex and PETG by contrast pretty much permanently weld themselves together, which means that making something like a box out of PETG with a little living hinge section out of flex would be doable without adhesives or fasteners. Ditto for giving a PETG object a grippy base. [Thomas] notes that flexible filaments all have different formulations, but broadly speaking they behave similarly enough in terms of what they stick to.

[Thomas] leaves us with some tips that are worth keeping in mind when it comes to supported models. One is that supports can leave tiny bits of material on the model, so try to use same or similar colors for both support and model so there’s no visual blemish. Another tip is that PLA softens slightly in hot water, so if PLA supports are clinging stubbornly to a model printed in a higher-temperature material like PETG or ABS/ASA, use some hot water to make the job a little easier. The PLA will soften first, giving you an edge. Give the video below a watch to see for yourself how the combinations act.

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3D Printed Tires, By The Numbers

October 24, 2024 by Dan Maloney 21 Comments

What does it take to make decent tires for your projects? According to this 3D printed tire torture test, it’s actually pretty easy — it’s more a question of how well they work when you’re done.

For the test, [Excessive Overkill] made four different sets of shoes for his RC test vehicle. First up was a plain PLA wheel with a knobby tread, followed by an exact copy printed in ABS which he intended to coat with Flex Seal — yes, that Flex Seal. The idea here was to see how well the spray-on rubber compound would improve the performance of the wheel; ABS was used in the hopes that the Flex Seal solvents would partially dissolve the plastic and form a better bond. The next test subjects were a PLA wheel with a separately printed TPU tire, and a urethane tire molded directly to a PLA rim. That last one required a pretty complicated five-piece mold and some specialized urethane resin, but the results looked fantastic.

Non-destructive tests on the tires included an assessment of static friction by measuring the torque needed to start the tire rolling against a rough surface, plus a dynamic friction test using the same setup but measuring torque against increasing motor speed. [Overkill] threw in a destructive test, too, with the test specimens grinding against a concrete block at a constant speed to see how long the tire lasted. Finally, there was a road test, with a full set of each tire mounted to an RC car and subjected to timed laps along a course with mixed surfaces.

Results were mixed, and we won’t spoil the surprise, but suffice it to say that molding your own tires might not be worth the effort, and that Flex Seal is as disappointing as any other infomercial product. We’ve seen other printed tires before, but hats off to [Excessive Overkill] for diving into the data.

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New Study Looks At The Potential Carcinogenicity Of 3D Printing

October 14, 2024 by Dan Maloney 40 Comments

We’ve all heard stories of the dangers of 3D printing, with fires from runaway hot ends or dodgy heated build plates being the main hazards. But what about the particulates? Can they actually cause health problems in the long run? Maybe, if new research into the carcinogenicity of common 3D printing plastics pans out.

According to authors [CheolHong Lim] and [DongSeok Seo], the research covered in this paper was undertaken because of reports of rare cancers among Korean STEM teachers, particularly those who used 3D printers in their curricula. It was thought that only long-term, continued exposure to the particulates generated by 3D printers could potentially be hazardous and that PLA was less likely to be hazardous than ABS. The study was designed to assess the potential carcinogenicity of both ABS and PLA particulates under conditions similar to what could be expected in an educational setting.

To do this, they generated particulates by heating ABS and PLA to extruder temperatures, collected and characterized them electrostatically, and dissolved them in the solvent DMSO. They used a cell line known as Balb/c, derived from fibroblasts of an albino laboratory mouse, to assess the cytotoxic concentration of each plastic, then conducted a comet assay, which uses cell shape as a proxy for DNA damage; damaged cells often take on a characteristically tailed shape that resembles a comet. This showed no significant DNA damage for either plastic.

But just because a substance doesn’t cause DNA damage doesn’t mean it can’t mess with the cell’s working in other ways. To assess this, they performed a series of cell transformation assays, which look for morphological changes as a result of treatment with a potential carcinogen. Neither ABS nor PLA were found to be carcinogenic in this assay. They also looked at the RNA of the treated cells, to assess the expression of genes related to carcinogenic pathways. They found that of 147 cancer-related genes, 113 were either turned up or turned down relative to controls. Finally, they looked at glucose metabolism as a proxy for the metabolic changes a malignant cell generally experiences, finding that both plastics increased metabolism in vitro.

Does this mean that 3D printing causes cancer? No, not by a long shot. But, it’s clear that under lab conditions, exposure to either PLA or ABS particulates seems to be related to some of the cell changes associated with carcinogenesis. What exactly this means in the real world remains to be seen, but the work described here at least sets the stage for further examination.

What does this all mean to the home gamer? For now, maybe you should at least crack a window while you’re printing.

Better 3D Printing Via Chemistry?

August 21, 2022 by Al Williams 8 Comments

If you have problems getting a 3D print to stick to the bed, you might consider using glue to — hopefully temporarily — attach the print to the bed. In addition, some plastics glue together well if you use a solvent. [Stefan] asks the question: What if you use solvent to glue each layer of a 3D print to the previous layer? The answer is in the video below.

If you know [Stefan], he is always meticulous, so the first test was with normal ABS parts. Then he used a solvent to glue two broken parts together to show how a single layer does with bonding. Then he moved toward trying the solvent for each layer.

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Keycap Shine? No, Shiny Keycaps

August 19, 2022 by Kristina Panos 34 Comments

No matter how often you wash your hands, ABS keycaps will eventually exhibit shine wherever you strike them the most. And that’s the problem right there: the shine might be okay if it were somehow uniform across the surface of the keycaps, but instead it just tends to make one feel seen. And since there’s really nothing you can do except to replace your keycaps (or start with PBT), you might as well embrace the shine, right?

Well, that’s how [mmalluck] feels, anyway. He recently experimented with using acetone vapors to refinish a set of keycaps from Drop, making them super-duper shiny in the process. Now, the operative word here is vapors, because straight acetone would acid-wash those ‘caps faster than you can say ‘bad idea jeans’.

So to that end, [mmalluck] poured acetone in a glass cake pan, used a piece of cardboard to separate the keycaps from the acetone, and covered it all with a glass cutting board. It doesn’t take very long to achieve a good result, and [mmalluck] says it’s better to err on the side of too-short instead of risking reaching the point of too-melted.

We wouldn’t have thought we’d react this way, but we think they’re pretty cool looking. That particular set seems just right for this process, which makes them look like new old-stock typewriter keys or something. Looks way better than the ultra-personalized shine of usage. What do you think? Let us know in the comments.

Via KBD #90

Simple Sensor Makes Filament Measurements A Snap

February 7, 2021 by Dan Maloney 29 Comments

Just how tight are the manufacturing tolerances of modern FDM printer filament. Inquiring minds want to know, and when such minds are attached to handy fellows like [Thomas Sanladerer], you end up with something like this home-brew filament measurement rig to gather the data you seek.

The heart of this build is not, as one might assume, some exotic laser device to measure the diameter of filament optically. Those exist, but they are expensive bits of kit that are best left to the manufacturers, who use them on their production lines to make sure filament meets their specs. Rather, [Thomas] used a very clever homemade device, which relies on a Hall effect sensor and a magnet on a lever to do the job. The lever is attached to a roller bearing that rides on the filament as it spools through the sensor; variations in diameter are amplified by the lever arm, which wiggles a magnet over the Hall sensor, resulting in a signal proportional to filament diameter.

The full test rig has a motor-driven feed and takeup spools, and three sensors measuring across the filament in three different spots around the radius; the measurements are averaged together to account for any small-scale irregularities. [Thomas] ran several different spools representing different manufacturers and materials through the machine; we won’t spoil the results in the video below, but suffice it to say you probably have little to worry about if you buy from a reputable vendor.

When we see a filament sensor, it’s generally more of the “there/not there” variety to prevent a printer from blindly carrying on once the reel is spent. We’ve seen a few of those before, but this is a neat twist on that concept.

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PLA-F Blends PLA And ABS

September 12, 2020 by Al Williams 31 Comments

In the early days of 3D printing, most people used ABS plastic. It is durable and sticks well to simple surfaces. However, it smells and emits fumes that may be dangerous. It also tends to warp as it cools which causes problems when printing. PLA smells nicer and since it is made from corn is supposed to be less noxious. However, PLA isn’t as temperature resistant and while it will stick better to beds without heat, it also requires more airflow to set the plastic as it prints. [Kerry Stevenson] recently reviewed PLA-F which is a blend of the two plastics. Is it the best of both worlds? Or the worst?

[Kerry] did several tests with interesting results. He did a temperature test tower and found the material printed well between 190 and 240 °C. He did note some stringing problems, though.

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