The Wanhao Duplicator CNC Heat Sealer

February 2, 2022 by Dave Rowntree 19 Comments

One custom, compliant heat exchanger, coming right up!

[Thane Hunt] needed to find a way to make a variety of different heat-seal patterns on a fluid heat exchanger made from polyolefin film, and didn’t want all the lead time and expense of a traditional sealing press machined from a steel plate. Pattern prototyping meant that the usual approach would not allow sufficient iteration speed and decided to take a CNC approach. Now, who can think of a common tool, capable of positioning in the X-Y plane, with a drivable Z axis and a controlled heat source? Of course, nowadays the answer is the common-or-garden FDM 3D printer. As luck would have it, [Thane] had an older machine to experiment with, so with a little bit of nozzle sanding, and a sheet of rubber on the bed, it was good to go!

Now, heat sealing is usually done in a heated press, with a former tool, which holds the material in place and gives a flat, even seal. Obviously this CNC approach isn’t going to achieve perfect results, but for proof-of-concept, it is just fine. A sacrificial nozzle was located (but as [Thane] admits, a length of M6 would do, in a pinch) and sanded flat, and parallel to the bed, to give a 3mm diameter contact patch. A silicone rubber sheet was placed on the bed, and the polyolefin film on top. The silicone helped to hold the bottom sheet in place, and gives some Z-axis compliancy to prevent overloading the motor driver. Ideally, the printer would have been modified further to move this compliancy into the Z axis or the effector end, but that was more work. With some clever 3D modelling, Cura was manipulated to generate the desired g-code (a series of Z axis plunges along a path) and a custom heated indenter was born!

This isn’t the first such use of a 3D printer we’ve seen, here’s an earlier failure, and like everything, there’s more than one way to do it – here’s a method of making inflatable bladders with a defocused CO₂ laser.

(warning! Two minutes of a 3D printer head-banging into the bed!)

Continue reading “The Wanhao Duplicator CNC Heat Sealer“ →

Defective 3D Printing For Great Strength

February 2, 2022 by Al Williams 6 Comments

Most of us want our 3D prints to be perfect. But at Cornell University, they’ve been experimenting with deliberately introducing defects into printed titanium. Why? Because using a post-print treatment of heat and pressure they can turn those defects into assets, leading to a stronger and more ductile printed part.

The most common ways to print metal use powders melted together, and these lead to tiny pores in the material that weaken the final product. Using Ti-6Al-4V, the researchers deliberately made a poor print that had more than the usual amount of defects. Then they applied extreme heat and pressure to the resulting piece. The pressure caused the pores to close up, and changed the material’s internal structure to be more like a composite.

Reports are that the pieces treated in this way have superior properties to parts made by casting and forging, much less 3D printed parts. In addition, the printing process usually creates parts that are stronger in some directions than others. The post processing breaks that directionality and the finished parts have equal strength in all directions.

The hot isostatic pressing (HIP) process isn’t new — it is commonly used in metal and ceramic processing — so this method shouldn’t require anything more exotic than that. Granted, even cheap presses from China start around $7,000 and go way up from there, but if you are 3D printing titanium, that might not be such a big expenditure. The only downside seems to be that if the process leaves any defects partially processed, it can lead to fatigue failures later.

We wonder if this development will impact all the car parts being printed in titanium lately. If you need something to print in titanium, consider hacking your rib cage.

3D Printering: Water-Cooled Hotends

January 31, 2022 by Al Williams 33 Comments

There’s an old joke about the Thermos bottle that keeps things hot and cold, so someone loaded it with soup and ice cream. That joke is a little close to home when it comes to FDM 3D printers.

You want to melt plastic, of course, or things won’t print, so you need heat. But if the plastic filament gets hot too early, it will get soft, expand, and jam. Heat crawling up the hot end like this is known as heat creep and there are a variety of ways that hot ends try to cope with the need to be hot and cold at the same time. Most hotends today are air-cooled with a small fan. But water-cooled hotends have been around for a while and are showing up more and more. Is it a gimmick? Are you using, planning to use, or have used (and abandoned) water cooling on your hot end?

Heat Break

The most common method is to use a heat-break between the heating block and the rest of the filament path. The heat-break is designed to transfer as little heat as necessary, and it usually screws into a large heat sink that has a fan running over it. What heat makes it across the break should blow away with the fan cooling.

High tech solutions include making heat-breaks out of titanium or even two dissimilar metals, all with the aim of transferring less heat into the cooler part of the hot end. More modern hot ends use support structures so the heatbreak doesn’t need mechanical rigidity, and they can make very thin-walled heatbreaks that don’t transmit much heat. Surely, then, this is case closed, right? Maybe not.

While it is true that a standard heat-break and a fan can do the job for common 3D printing tasks, there can be problems. First, if you want to print fast — time is money, after all — you need more power to melt more filament per second. If a heatbreak transfers 10% of the heat, this increases demands on the upstream cooling. Some engineering materials want to print at higher temperatures, so you can have the same problem there as well. If you want to heat the entire print chamber, which can help with certain printing materials, that can also cause problems since the ambient air is now hotter. Blowing hot air around isn’t going to cool as effectively. Not to mention, fans that can operate at high temperatures are notoriously expensive.

There are other downsides to fans. Over a long print, a marginal system might eventually let enough heat creep up. Then there’s the noise of a fan blowing during operation. True, you probably have other fans and noisy parts, but it is still one more noise source. With water cooling, you can move the radiator outside a heated enclosure and use larger, slower, and quieter fans while getting more cooling right where you want it. Continue reading “3D Printering: Water-Cooled Hotends” →

This Parametric Project Box Generator Is Super Easy

January 31, 2022 by Dave Rowntree 8 Comments

When it comes to taking an idea from concept to prototype reality, depending on the type of project, there can be quite a few sub-tasks along the way. Take for example, your latest electronic widget design. You’ve finished the schematic, and the PCB layout is a work of art (if you do say so yourself) but having that kicking around on the desk unprotected with wires dangling is not the end game. Now you’ve got to make an enclosure of some kind, and I don’t know about you, but this is the bit where this scribe struggles a little to get something to fit nice. Even if you’ve got the latest 3D printer dialed in to within a gnat’s whisker of perfection, you’ve still got to come up with the design, and those dimensions need to be really accurate. So, for those of us who are great at the PCB, but suck at the enclosure, [Willem Aandewiel] has been busy making the tool just for you, with his PCB-orientated Yet Another Parametric Projectbox generator (YAPP.)

Defining the PCB mounting points w.r.t. the PCB outline

Without hesitation you can head over to the YAPP GitHub, grab that sweet OpenSCAD code, and get cracking with the demos. Provided for your convenience are a number of examples for enclosing some common items, such as Arduinos and ESP32 modules, so you can use those as a springboard to get your own code in place. YAPP works based off the PCB — by specifying programmatically since this is OpenSCAD — outer dimensions, mounting post locations first. Next you define openings in the six faces of the box, and the tool happily spits out a platter with the base and lid ready to drop into Cura (or your slicer of choice) What could be easier?

And before you start on non-rectangular designs, this is a rectangular box generator for rectangular PCBs. That is all this is designed for, and as far as we can tell, it does that one job well.

Of course, this is by no means the first enclosure generator to grace these pages, far from it. Here’s one for starters. If you’re here for tips to help make better designs, check this out, and finally 3DHubs also has a nice guide for you. Happy printing!

That’s No Moon… It’s An Algae Robot

January 27, 2022 by Al Williams 10 Comments

When you think of a robot, you probably don’t think of a ball of underwater algae. But a team of university researchers used a 3D-printed exoskeleton and a ball of marimo algae to produce a moving underwater sensor platform. It is really at a proof-of-concept stage, but it seems as though it would be possible to make practical use of the technology.

Marimo are relatively rare balls of algae that occur in some parts of the world. A robot powered by algae runs on sunlight and could be electromagnetically quiet.

Continue reading “That’s No Moon… It’s An Algae Robot” →

Better Car Hinges By 3D Printing

January 25, 2022 by Al Williams 30 Comments

We often use 3D printing to replicate items we might otherwise make with traditional machining methods. Fraunhofer’s new door hinge for a sports car takes a different tack: it tries to be better than the equivalent machined part. The company claims that the new part is half the cost and weighs 35% less than the normal hinge.

Using tools in their 3D Spark software, the team analyzed different factors that led to manufacturing cost. Some of these were specific to the part while others were specific to the process. For example, orienting the part to minimize support and maximize the quantity that fit on the build surface.

Continue reading “Better Car Hinges By 3D Printing” →

One-piece Geared Hinge Can Take The Weight

January 24, 2022 by Donald Papp 31 Comments

3D printers have come a long way from cranking out things like bottle openers and coat pegs, and [E. Soderberg]’s Print in Place Geared Hinge is a pretty nifty demonstration of that. This hinge is designed as a print-in-place part, meaning it is 3D printed as a single piece, requiring no assembly. Not only that, but the herringbone gears constrain the sturdy device in a way that helps it support heavy loads.

Of course, hinges — even strong ones — are not particularly hard to find items. They’re available in a mind-boggling array of shapes and sizes. But what’s interesting about this design is that it shows what’s easily within the reach of just about any hobbyist nowadays. Not that long ago, designing and creating an object like this would not have been accessible to most home enthusiasts. Making it without a modern 3D printer would certainly have been a challenge in its own right.

It doesn’t always matter that a comparable (or superior) off-the-shelf part is available; an adequate part that can be created in one’s own workshop has a value all its own. Plus, it’s fun to design and make things, sometimes for their own sake. After all, things like 3D-printed custom switch assemblies would not exist if everyone were satisfied with the ability to just order some Cherry MX switches and call it a day.