Adaptive Layer Height on the Monoprice Select Mini

If you’ve used a desktop 3D printer, you’re likely familiar with the concept of layer heights. Put simply: thicker layers will print faster, and thinner layers will produce better detail. Selecting your layer height is making a choice between detail and speed, which usually works well enough. For example, prints which are structural and don’t have much surface detail can be done in higher layer heights to maximize speed with no real downside. Conversely, if you’ve got a model with a lot of detail you’ll have to just deal with the increased print time of thinner layers.

At least, that’s how it’s been up till now. Modern slicer software is starting to test the waters of adaptive layer heights, which change the layer height during the print. So the software will raise or lower the layer height depending on the level of detail required for the current area being printed. [Dylan Radcliffe] wanted to experiment with this feature on his Monoprice Select Mini, but it took some tweaking and the dreaded mathematics to get Cura’s adaptive layer height working on the entry-level printer. He’s documented his settings for anyone who wants to check out this next-generation 3D printing technology without forking out the cash for a top of the line machine.

While Cura is a popular slicer, the fact of the matter is that it’s developed by Ultimaker primarily for their own line of high-end printers. It will control machines from other manufacturers, but it makes no promises that all the features in the software will actually work as expected on lesser printers. In the case of the Monoprice Mini, the issue is the rather unusual Z hardware. The printer uses a 7.5° 48-step motor coupled to 0.7 mm thread pitch M4 rod. This is a pretty suspect arrangement that was no doubt selected to keep costs down, and results in an unusual 0.04375 mm step increment. For the best possible print quality, layer heights should be a multiple of this number. That’s where the math comes in.

After enabling adaptive layers in Cura’s experimental settings, you need to define the value which Cura will add or subtract to the base layer height. In theory you could enter 0.04375 mm here, but while that’s the minimum on paper, the machine itself is unlikely to be able to pull off such a small variation. [Dylan] recommends doubling that to 0.0875 for the “variation step size” parameter, and setting the base layer height to 0.175 mm (4 x 0.04375 mm).

[Dylan] reports these settings reduced the print time on his topographical map pieces from 12 hours to 7 hours, while still maintaining high detail on the top surface. Of course print time reduction is going to be highly dependent on the model being printed, so your mileage may vary.

If Cura isn’t your style, our very own [Brian Benchoff] gave us a tour of “variable layer height”, the Slic3r version of this technique. Perfect for that Prusa i3 MK3 you finally spent the cash on.

3D Printering: Which Raspberry Pi is Best at Slicing in Octoprint?

OctoPrint is arguably the ultimate tool for remote 3D printer control and monitoring. Whether you simply want a way to send G-Code to your printer without it being physically connected to your computer or you want to be able to monitor a print from your phone while at work, OctoPrint is what you’re looking for. The core software itself is fantastic, and the community that has sprung up around the development of OctoPrint plugins has done an incredible job expanding the basic functionality into some very impressive new territory.

RAMBo 3D controller with Pi Zero Integration

But all that is on the software side; you still need to run OctoPrint on something. Technically speaking, OctoPrint could run on more or less anything you have lying around the workshop. It’s cross platform and doesn’t need anything more exotic than a free USB port to connect to the printer, and people have run it on everything from disused Windows desktops to cheap Android smartphones. But for many, the true “home” of OctoPrint is the Raspberry Pi.

As I’ve covered previously, the Raspberry Pi does make an exceptional platform for OctoPrint. Given the small size and low energy requirements of the Pi, it’s easy to integrate into your printer. The new Prusa i3 MK3 even includes a header right on the control board where you can plug in a Raspberry Pi Zero.

But while the Raspberry Pi is more than capable of controlling a 3D printer in real-time, there has always been some debate about its suitability for slicing STL files. Even on a desktop computer, it can sometimes be a time consuming chore to take an STL file and process it down to the raw G-Code file that will command the printer’s movements.

In an effort to quantify the slicing performance on the Raspberry Pi, I thought it would be interesting to do a head-to-head slicing comparison between the Pi Zero, the ever popular Pi 3, and the newest Pi 3 B+.

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PrusaControl: The Beginner’s Slicer

There are two main applications for managing 3D prints and G-Code generation. Cura is a fantastic application that is seeing a lot of development from the heavy hitters in the industry. Initially developed by Ultimaker,  Lulzbot has their own edition of Cura, It’s the default software packaged with thousands of different printers. Slic3r, as well, has seen a lot of development over the years and some interesting hacks. Do you want to print non-planar surfaces? Slic3r can do that. Slic3r and Cura are two sides of the CAM part of the 3D printing coin, although Cura is decidedly the prettier side.

The ability to combine the extensibility of Slic3r with the user interface of Cura has been on our wish list for a while now. It’s finally time. [Josef Prusa] has released PrusaControl, a 3D printing CAM solution that combines the best of Slic3r into a fantastic, great looking package. What are the benefits? What’s it like? Check that out below.

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3D Internal Structure For Better 3D Printed Objects

Makerbot is in the gutter, 3D Systems and Stratasys stock is only a shadow of their 2014 glory, but this is the best year 3D printing has ever had. Machines are now good and cheap, there’s a variety of various thermoplastic filaments, and printing useful objects – instead of just plastic trinkets – is becoming commonplace.

Gradient-Grid
The standard rectilinear infill from Slic3r

There’s one area of 3D printing that hasn’t seen as much progress, and it’s the software stack. Slicing, the process of turning a 3D object into a Gcode file for a printer has been basically the same for the last few years. Dual extrusion is still a mess, and automated bed leveling is still in its infancy.

One aspect of slicing that has been severely overlooked is infill. Obviously, you don’t want to print plastic trinkets completely solid – only the outside surface matters, and a part with 100% infill is just a waste of plastic. Different slicers have come up with different ways of filling the inside of a print, usually with a grid of squares, triangles, or hexagons.

While the most popular methods of filling in a 3D printed objects do the job of adding a little bit of strength to a print and supporting the top layers of a print, it’s not an ideal solution. The desired strength of the finished part is never taken into account, print artifacts are sometimes visible through the side of a print, and the spacing of the infill grid is completely arbitrary. You can only set a percentage of infill, and telling a slicer to make an internal support grid with 10mm spacing is impossible.

Type A Machines just changed all of this. With the release of their public beta of Cura Type A, the infill for a 3D printed part is also 3D. The dimensions of the infill are predictable, opening the door to stronger and better looking parts.

From the Type A press literature and white paper, this new type of ‘infill’ isn’t; it’s more properly referred to as ‘internal structure’, with proper dimensions between infill features. Instead of a grid of squares or triangles stacked one layer on top of each other, it’s a true structure, with the infill following the perimeter of the 3D printed object.

Generating 3D Infill

3D
Infill generated from Type A Machine’s Cura beta. Note the 3D structure of the infill.

Right now, infill is generated in a slicer by specifying a percentage. Zero percent infill means a hollow object, and 100% infill is a completely solid part. These two edge cases are easy, but anything else means the slicer must fill the part with filament in a grid of tessellating shapes, either rectangles, triangles, or hexagons. With current slicers, the dimensions of this internal structure are, for all practical purposes, random. Printing an object with 20% infill might mean a grid of squares with 5mm or 2mm spacing. Telling the slicer to infill a part with a grid of squares spaced 10mm apart is impossible.

Type A Machine’s latest Cura release changes all of this, allowing a designer to set a precise distance between rows and columns of infill. By defining infill in absolute dimensions, this allows for stronger parts using less infill.

Absolute dimensioning is only one feature of the Type A Machine’s latest release of Cura. Even more exciting is the development of 3D internal structure. Instead of stacking layers of squares, triangles, or hexagons on top of each other, Type A Machine’s Cura uses an infill of cubes turned on their side. While each individual layer of infill looks like a series of triangles and irregular hexagons, when assembled into a printed 3D object, this infill forms a true 3D structure.

The closest comparison to this sort of structure is the difference between graphite and diamond. Both of these materials are made out of the same element, carbon. The physical structure of graphite is just, 1-atom-thick layers of graphene, producing a relatively weak material. Diamond, on the other hand, has a true 3D structure and is one of the hardest materials known to man. While adding 3D structure to the infill of 3D printed objects won’t make the objects any stronger, it will drastically reduce delamination, and be much more resistant to stresses in all three dimensions.

While Type A Machines has done some great work here, it does mean there’s yet another version of Cura to deal with. Type A Machine’s Cura, in addition to the LulzBot edition and the original are now the defacto standard for turning 3D objects into printed parts. Having an open source solution is great, but forking the development this much surely can’t be ideal.

Better 3D Prints by Mixing Slicing Techniques

Most 3D printing projects start with a 3D model of some kind. Slicing programs transform the model into gcode. The gcode file contains the commands that actually drive your printer. There are different ways to slice a model and sometimes you want to use more than one on a single model. I’ve been working on a way to make that easier.

When you slice a 3D printing model, you can select different attributes for the resulting gcode file. For example, you might set the slicer to produce different infill density, temperatures, or print speeds. These settings can have a big impact on your printing results. For example, a piece that needs high strength might require a denser infill  than some trinket or key chain. You might want an artistic piece to have a finer layer height than some internal part for some gadget no one will ever see.

One Size Fits All?

The problem is that for most open source slicers, these settings will apply to the entire model. Cura has some plugins that can change settings at different Z heights, and Slic3r can vary layer height, but in the general case, what you set for the slicer will apply to the entire model. Of course, a gcode file is nothing more than a text file, so if you are industrious, you can manually merge two or more files into one.

A manual merge is a pain, which is why I wrote gblend. It can stitch together gcode files to get various effects. The program takes multiple gcode files in as inputs and can combine them in different ways. The most useful feature allows you to get a certain number of layers from each source file and combine them into a single print. Measurements are in millimeters, so you don’t have to worry about layer numbers. The entire process is much easier than anything else I’ve come across.

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An interview with [David] of Ultimaker

cura

After interviewing the creator of Slic3r and the folks at Shapeways, [Andrew] is back again with his adventures in 3D printer videography and an interview with [David Braam] of Ultimaker

About a year ago, [David] looked at the state of the art in 3D printer control and Replicator G. While Replicator G, along with Pronterface and Repetier-Host both convert 3D models into G-code files as well as control the printer while its squeezing plastic out onto a bed. [David] thought the current state of these RepRap host programs were janky at best, and certainly not the best user experience for any home fabricator. This lead him to create Cura, a very slick and vastly improved piece of host software for the Ultimaker.

Cura isn’t just a fancy front end on an already existing slicer engine; [David] created his own slicing algorithm to turn .STL files into G-code that’s immensely faster than skeinforge. Where skeinforge could take an hour to slice a complex model, Cura does the same job in minutes.

There are also a bunch of cool features available in Cura: you can rotate any part before sending it to the printer, as well as pulling voxels directly from your Minecraft world and sending them to your printer. Very, very cool stuff, and if you’re running a Ultimaker or any other RepRap, you might want to check it out.

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