Experiments With A Bowden Extruder Filament Force Sensor

We were excited to learn that someone had started working with force sensors on filament extruders, especially after we posted about a recent development in filament thickness sensors.

[airtripper] primarily uses a Bowden extruder, and wanted to be a little more scientific in his 3D printing efforts. So he purchased a force sensor off eBay and modified his extruder design to fit it. Once installed he could see exactly how different temperatures, retraction rates, speed, etc. resulted in different forces on the extruder. He used this information to tune his printer just a bit better.

More interesting, [airtripper] used his new sensor to validate the powers of various extruder gears. These are the gears that actually transfer the driving force of the stepper to the filament itself. He tested some of the common drive gears, and proved that the Mk8 gear slipped the least and provided the most constant force. We love to see this kind of science in the 3D printing community — let’s see if someone can replicate his findings.

 

3D Printer Tool: Set Your Extruder Steps With Ease

My printer has other issues that i'm still tuning out, but the warping in PLA and excessive surface roughness has all the signs of over extrusion.
My printer has other issues that I’m still tuning out, but the warping in PLA and excessive surface roughness has all the signs of over extrusion.

I have an old Prusa i2 that, like an old car, has been getting some major part replacements lately after many many hours of service. Recently both the extruder and the extruder motor died. The extruder died of brass fill filament sintering to the inside of the nozzle (always flush your extruder of exotic filaments). The motor died at the wires of constant flexing. Regardless, I replaced the motors and found myself with an issue; the new motor and hotend (junk motor from the junk bin, and an E3D v6, which is fantastic) worked way better and was pushing out too much filament.

The hotend, driver gear, extruder mechanics, back pressure, motor, and plastic type all work together to set how much plastic you can push through the nozzle at once. Even the speed at which the plastic is going through the nozzle can change how much friction that plastic experiences. Most of these effects are somewhat negligible. The printer does, however, have a sort of baseline steps per mm of plastic you can set.

The goal is to have a steps per mm that is exactly matched to how much plastic the printer pushes out. If you say 10mm, 10mm of filament should be eaten by the extruder. This setting is the “steps per mm” in the firmware configuration. This number should be close to perfect. Once it is, you can tune it by setting the “extrusion multiplier” setting in most slicers when you switch materials, or have environmental differences to compensate for.

This little guy lets you tune the steps per mm exactly.
This little guy lets you tune the steps per mm exactly.

The problem comes in measuring the filament that is extruded. Filament comes off a spool and is pulled through an imprecisely held nozzle in an imprecisely made extruder assembly. On top of all that, the filament twists and curves. This makes it difficult to hold against a ruler or caliper and get a trustworthy measurement.

I have come up with a little measuring device you can make with some brass tubing, sandpaper, a saw (or pipe cutter), a pencil torch, solder, and some calipers. To start with, find two pieces of tubing. The first’s ID must fit closely with the filament size you use. The second tube must allow the inside tubing to slide inside of it closely. A close fit is essential.

Continue reading “3D Printer Tool: Set Your Extruder Steps With Ease”

Edible art from a Robot Pancake Printer

In case you didn’t know it, pancake art is a thing. People are turning out incredible edible artwork using squeeze bottles and pancake batter. But even if you’re not terribly artistic, you can still amaze your breakfast buddies with this robotic pancake printer.

At its simplest – and in our opinion its most impressive – pancake art involves making patterns with thin batter on a hot griddle. The longer the batter is cooked, the darker it becomes, and art happens. To capitalize on this, [Trent], [Kevin], [Sunny] and [Isaac] built a 2-axis gantry with a working area the size of an electric griddle. A bottle is pressurized with a small air pump and controlled by a solenoid valve to serve as a batter extruder, and an Arduino controls everything. Custom pancake design software lets you plan your next masterpiece before committing it to batter.

Sadly, the video below shows us that the team didn’t include an automatic flipper for the pancake, but no matter – that’ll make a great feature for the next version. Maybe something like this?

Continue reading “Edible art from a Robot Pancake Printer”

Hackaday Links: May 3, 2015

Everybody loves How It’s Made, right? How about 3D printers? The third greatest thing to come out of Canada featured Lulzbot in their most recent episode. It’s eight minutes of fun, but shame the puns weren’t better. Robertson drives and the Avro Arrow, if you’re wondering.

Speaking of 3D printers, a lot of printers are made of aluminum extrusion. Has anyone tried something like this? It’s an idea that’s been around for a while but we can’t seem to find anyone actually using 3D printed extrusion.

CastARs are shipping out, and someone made a holodeck with retroreflective material. It’s an inflatable dome that’s attached to a regular ‘ol tent that works as a positive pressure airlock. If you’re looking to replicate this, try it with hexagons and pentagons. That should be easier than the orange-slice gores.

For some reason we can’t comprehend, USB ports are now power ports. There’s still a lot of stuff that uses 9 and 12V, and for that there’s the USB 912. It’ll work better with one of those USB battery packs.

Want to see what the Raspberry Pi 2 looks like with a Flir? NOQ2 has you covered.

Remember the Speccy? In the manual, there was an exercise left to the reader: reproduce [Mahler]’s first symphony with the BEEP command. It took a Raspberry Pi (only for synchronizing several Speccys), but it’s finally done.

WirePrint is a Physical ‘Print Preview’ for 3D Printers

3D printers may be old news to most of us, but that’s not stopping creative individuals from finding new ways to improve on the technology. Your average consumer budget 3D printer uses an extrusion technology, whereby plastic is melted and extruded onto a platform. The printer draws a single two-dimensional image of the print and then moves up layer by layer. It’s an effective and inexpensive method for turning a computer design into a physical object. Unfortunately, it’s also very slow.

That’s why Hasso Plattner Institute and Cornell University teamed up to develop WirePrint. WirePrint can slice your three-dimensional model into a wire frame version that is capable of being printed on an extrusion printer. You won’t end up with a strong final product, but WirePrint will help you get a feel for the overall size and shape of your print. The best part is it will do it in a fraction of the time it would take to print the actual object.

This is a similar idea to reducing the amount of fill that your print has, only WirePrint takes it a step further. The software tells your printer to extrude plastic in vertical lines, then pauses for just enough time for it to cool and harden in that vertical position. The result is much cleaner than if this same wire frame model were printed layer by layer. It also requires less overall movement of the print head and is therefore faster.

The best part about this project is that it’s a software hack. This means that it can likely be used on any 3D printers that use extrusion technology. Check out a video of the process below to see how it works. Continue reading “WirePrint is a Physical ‘Print Preview’ for 3D Printers”

Blobless Printing With Velocity Extrusion

velocity

The current crop of 3D printers are technically four-axis machines, with three axes of movement and a fourth for the position of the filament. [Bas] had an entirely different idea – why not link the speed of the extruder to the speed of the nozzle? It turns out this technique gives you more ‘plasticy-looking’ prints and a vast reduction in blobbiness.

[Baz] has been working with LinuxCNC, a BeagleBone Black and the BeBoPr-Bridge cape, and there’s been a lot of development with that system in turning many straight lines into one smooth arc. This led him to adjusting the flow rate of a nozzle while the printer is running, but this is difficult if the extrusion is controlled by position as in a traditional printer setup. A new configuration was in order.

What [Baz] ended up with is a config that calculated the speed of the extruder based on the speed the nozzle is moving over the print surface. This gave him the ability to add live nozzle pressure adjustment, and as a result, a near complete disappearance of the little blobs that appear at the start of each layer.

For a well calibrated machine, it’s only a small difference between the ‘normal’ and ‘velocity’ methods of controlling an extrusion rate. It’s a noticeable difference, though, and one that vastly improves the visual quality of a print.

 

DIY Filament: The Filabot Wee

filabotwee

Now there’s yet another option for making your own 3D printer filament: the Filabot Wee. It looks like their once open source model that they pulled from Thinigiverse earlier this year has received a significant makeover, though we aren’t sure what parts may have changed. (EDIT: Filabot says the Wee is still open source, and that once they’ve updated the files they will be available again.)

As you would expect, the Wee has a PID temperature controller and is capable of extruding both ABS and PLA pellets into either 1.75mm or 3mm-diameter filament. Speed varies depending on materials and thickness, but can reach 5 to 20 inches per minute of filament extrusion. Though the Filabot gang is selling the extruder as a kit, you can probably save a few bucks if you have access to a laser cutter and some other basic materials.

You should expect to spend more for Filabot parts ($649) than you would for the original Lyman extruder, though perhaps a more fair comparison would be the new third version of the Lyman extruder, whose bill of materials approaches $900. Considering Lyman’s recent comments that indicate an extrusion rate of 40-50 inches per minute, the extra bucks may be worth it. You can check out a demonstration video of the Filabot Wee after the break.

Continue reading “DIY Filament: The Filabot Wee”