What's better... Skeinforge or CuraEngine?

This is a quick comparison of a deprecated slicer called Skeinforge and another slicer called Cura. Cura is a popular slicer and host that is currently updated.

My understanding is that the CuraEngine is based on a fork of Skeinforge. It's primary improvement is speed. Skeinforge has been the slowest slicer I have encountered, and I have tried just about all of them starting in 2011 when there were only about 3: Skeinforge, ReplicatorG and Sfact (which is just a dumbed down version of Skeinforge).


For this comparison test I'm using an object from Thingiverse called the Calibration Temple (thing:10199530). This has been my penultimate test for printers and profiles. Primarily because of the delicate size of the columns and the object's bridging requirements. It's 38mm tall.

I configured Cura as closely as I could to the Skeinforge Durbie-Normal profile. This is my best general all purpose profile. Slicing speed for Cura unsurprisingly won. It came in at about 4s. Skeinforge came in at about 16s. A considerable time difference.

Even though both slicers are set at 32mm/s, the print speeds are off by 2:11 with Cura printing at 29:28 and Skeinforge at 31:39.

Above are the results. The object on the left is sliced by Skeinforge. The object on the right is sliced by the Cura. Both are printed with PLA.

Skeinforge wins by far for best quality. It's hard to see, but the bridging with Cura is a messy tangle under the dome. The Skeinforge sliced object has a clear inner dome and the columns are straight and clean. There is but one off strand from bridging.

Why? Skeinforge took more time to print. The extra 2 1/2 min for printing was caused by a setting in the cooling profile.

Skeinforge allows for either a slowdown or an orbit when printing delicate areas that may be damaged by excessive heat in the printed parts. If the previously printed area hasn't had time to cool and solidify, the successive layers will began to distort.

In this case, the slowdown also helped by physically slowing the printer down and thus printing with greater care the delicate columns. This added time to the print job, but also greatly improved the finished product.

Skeinforge also has many more controls for dealing with bridging and other printing challenges. This is what makes this slicer still viable today.

Adding Skeinforge to Repetier-Host

Skeinforge has been my go to open-source slicer since the beginning. It has a rather intimidating interface, but with a little work, it can become quite easy to navigate.

What is important to realize is that most of the craft tools (image above shows Dimension selected), can be left alone once a profile has been made for your machine. And the profile is easily setup by using a profile called Durbie - Normal. Though this slicer hasn't been updated in about 5 years, it still creates a slice that's been dependable.... why change something that works?

I'm running Windows 10 and starting off with Repetier-Host version 2.1.3.

You'll need 5 programs for the install: 

• Skeinforge slicer
• Microsoft Visual C++ 2008 Redistributable Package (x86)
• Python 3.7.2
• PyPy 3.5.3
• Durbie Profiles

Each of the above programs should be installed in order. Skeinforge and PyPy are simply unpacked into a folder  and put into Program Files (x86) directory. Each of the files above are linked to the download page. If the link is broken, a Google of the following files will locate their depository:

• Skeinforge50plus-master.zip
• vcredist_x86.exe
• python-2.7.amd64.msi
• pypy2-v6.0.0-win32.zip
• master.zip

The master.zip file will contain the Durbie profiles in an older Skeinforge folder. Simply go through the directory \Skeinforge41-master\.skeinforge\profiles\ extrusion. Copy the Durbie profiles and add them into the profile directory of Skeinforge50plus.

Once the programs are installed, it's now time to set up Repetier-Host. Select the Slicer tab and then Manager. A popup window appears as below:

Type Skeinforge in the Name box and then click Add Slicer. Skeinforge will be added to the Slicer Manager list. The window will now display a configuration setup for Skeinforge.

Here the paths for each file will need to be specified. Starting with:

• Skeinforge Application:                                                                                                    C:\Program Files (x86)\Skeinforge50plus-master\skeinforge_application\skeinforge.py
• Skeinforge Craft:                                                                                                                               C:\Program Files (x86)\Skeinforge50plus-master\skeinforge_application\skeinforge_plugins\craft.py
• Working Directory:                                                                                                          C:\PC:\Program Files (x86)\Skeinforge50plus-master\skeinforge_application\profiles
• Profiles Directory:                                                                                                         C:\Program Files (x86)\Skeinforge50plus-master\skeinforge_application\profiles
• Python Interpreter:  C:\Python27\python.exe
• PyPy:  C:\Program Files (x86)\pypy2-v6.0.0-win32\pypy.exe

Then select Apply and close the window. 

Skeinforge will now have several errors when running:

The worst can be solved by simply turning off the Analyze tools in Skeinforge. Do this by selecting the Analyze tab and scrolling down the menu and selecting each of the tools:

• Interpret...
• Skeinsio...
• Skeinlayer...

Each new pop up window will have an Activate box that can be deslected. The following shows the Interpret Settings window.

Save the results. The only tool that does not have a save option is Skeiniso. This can be saved by selecting Save All at the bottom right of the main Skeinforge interface.

The last error has not been solved... at least not by me. It shows as follows:

Skeinforge does slice the object, but where is it? When Skeinforge is run as a stand alone program (do this by double clicking on skeinforge.py in the Application folder), the gcode is saved in the same directory as the object file. This is not the case when Skeinforge is run inside the Repetier-Host.

The gcode is actually found in the Repetier-Host working directory. In my case, its at C:\Users\richa\AppData\Local\RepetierHost and always labeled as composition.gcode. For some reason Repetier-Host cannot find it. 

To use the gcode, simply load the composition.gcode manually in Repetier-Host. 

Why go through the trouble of setting up Repetier-Host to run Skeinforge if the gcode still needs to be manually loaded? Running Skeinforge on its own will not allow the option to orient the object you are building on the build platform or add additional objects for simultaneous printing. These options and more are available on Repetier-Host, adding better functionality when using Skeinforge.

Solving firmware upload problems on GT2560

Problems changing or updating your firmware on a GT2560? There's a lot of nonsense concerning a knockoff GeeeTech board on cheap Prusa i3's. This solution may might help.

Earlier this year I was working out of town, so I purchased a knock-off version of the GeeeTech Prusa i3 3D printer kit. This gave me something to play with while I was there, but unfortunately not for long. The laser cut wood frame did not hold up well in a suitcase traveling through the airport system. Several areas broke.

I decided to use the GT2560 motherboard to upgrade my Prusa Mendel I built about 8 years ago.

Everything worked smoothly, but there was an issue with my stepper motors. Messy wiring has always been an irritation for me, so I was excited to be able to utilize the cable connectors on the stepper motors with the pre-configured cables that came with the Prusa i3 kit. But this would not work. The lead outs on my stepper motors are different than the lead outs on the kit's stepper motors.

My stepper motors on the Prusa Mendel are Minebea, a Japanese manufactured stepper motor with a good solid reputation. The stepper motors that came with the kit are slightly larger, but manufactured by RBstep motor. A generic Chinese manufactured product.

I decided to swap out my Minebea steppers with the generic ones so that I could keep the clean install of wiring.

 All of this is fine, but the GT2560 motherboard needs an updated firmware for the physical changes that I have made by the swapout. This is where the trouble lies. As I noted in my last blog entry, I could not seem to make any firmware changes. The board was not uploading.

After a lot of research I discovered that this is a very common problem with this particular board and specifically with the knockoff versions of the GeeeTech printer. The upload will just stall and eventually give a timeout error. Fortunately the fix is easy.

To keep it precise, here are the following specs of my system:

I'm using Windows 7 with the latest version of the FT232RQ driver. This driver creates a USB port for the GT2560 otherwise the device will not show up in your device list and thus be inoperable. (Note: Windows 7 requires a manual install of this driver... Windows 10 will install the driver automatically when the GT2560 is plugged into the USB port.)

Next, I'm using an older version of Arduino software. The version is 1.5.2. It's recommended to use an older version of Arduino to upload the Marlin firmware that the GT2560 requires.

Once you have your Arduino software set up, navigate into the folder system. In my case, it was:

Arduino-1.5.2 folder
then
hardware folder
then
arduino folder
then
avr folder
then open the text file boards in a text editing program such as WordPad.

Here you will find a list of declarations for many different Arduino boards. Scroll to the bottom and add the following lines:

## GT2560 w/ ATmega2560 mega.menu.cpu.gt2560atmega2560=GT2560 w/ ATmega2560 mega.menu.cpu.gt2560atmega2560.upload.protocol=wiring mega.menu.cpu.gt2560atmega2560.upload.maximum_size=253952 mega.menu.cpu.gt2560atmega2560.upload.speed=57600 mega.menu.cpu.gt2560atmega2560.bootloader.high_fuses=0xD8 mega.menu.cpu.gt2560atmega2560.bootloader.extended_fuses=0xFD mega.menu.cpu.gt2560atmega2560.bootloader.file=stk500v2/stk500boot_v2_mega2560.hex mega.menu.cpu.gt2560atmega2560.build.mcu=atmega2560 mega.menu.cpu.gt2560atmega2560.build.board=AVR_MEGA2560

Save this to the text file and close.

Now open your Arduino 1.5.2 program and change your board selection to the entry
Arduino Mega (ATmega1280).

This is it. Simple and effective. The GT2560 will now upload whatever you choose . In my case, I'm using the file I3_pro_X firmware setup supplied by the GeeeTech website for the Prusa i3. This is similar to a Mendel Prusa configuration and will make a good base setup.

Prusa i3 Build

3D printers seem to cost a dime a dozen these days on eBay. When I sourced out all my parts for a RepRap Prusa Mendel in the last quarter of 2011, I spent nearly $700. Seven years later and I'm able to pick up a Prusa  i3 kit for 138 dollars! Everything needed to make a fully operable printer including tools and a spool of filament.

The printer I purchased (as in the image above), looks like a Geeetech 3D printer, but it isn't manufactured by that company.  Lately, I haven't paid much attention to the plethora of commercial open source 3D printers, so I wasn't aware I was getting a Chinese knock-off of a Chinese manufactured product.

I was to discover later that one indication of a Geeetech knock-off can be detected by the placement of the extruder motor. The motor on Geeetech printers is located on the right side of the extruder, the printer I purchased, the motor is on the left. Obviously, without considering the product name placement, the printers are very similar. Below is a Geeetech Prusa i3.

This may not seem to be an issue for concern, but there has been a problem in regards to the motherboard. This will be addressed in a later blog.

Overall, the item was shipped very nicely packed. And all of the components were intact.

The frame of the printer is a laser cut particle board. Not very strong, but rigid when assembled.

It was easily assembled in a day. And the initial testing-- before all cables were tied-- was successful.

The test prints were pretty good for PLA extrusion without a cooling fan.

These prints were made with the firmware settings supplied with the printer. Though, I had a hard time printing larger pieces. This was partly due to my inability of uploading firmware changes either by Repetier-Host commands or by uploading new firmware using the Arduino IDE. The motherboard refuses to accept uploading of any kind, so fine tuning firmware is impossible. I'll be looking into this at a later time.

Exhibition quality sculpture made on the RoboSculptor

Over 130 hours of print time and 53 individual parts were printed on the RoboSculptor.

 After the printing, the parts were sanded, filled, painted and polished.

 The title of the sculpture is Widget [W01]. It's the first in a series of four unique iterations.

 This piece was submitted in the juried art exhibition National Art Encounter in January of this year and was accepted. A write up can be found here: Naples

 During three months of this Summer, the sculpture was on display at the Alexandria Museum of Art in Alexandria, LA.

Interfaces

The most common human interface device with a computer is a mouse and keyboard. We’ll take a look at other useful interfaces for working with 3D modeling software.

Graphics tablet

A graphics tablet is a special drawing board that works with a pen-like stylus. It’s been the primary interface for use with graphics and digital painting software and it can be useful for 3D sculpting as well.

A graphics tablet system is similar to writing with a traditional pen on paper. A stylus has a pressure sensitive nib which responds to the pressure exerted on the graphic tablet’s surface. This allows a more natural method of manipulating brushes and sculpting tools within 3D modeling software.

Some software is not capable of utilizing the pressure sensitive capabilities (such as Meshmixer), but can be still used as a mouse type device. Hard modelers (such as Sketchup Make or Fusion 3D) are cumbersome to work with while using a stylus. They are better suited with a traditional mouse.

Wacom is one maker of the graphics tablet. The Bamboo Capture Pen and Touch Tablet is featured here and costs 100 USD. Newer models are available and they vary in price depending on the size. It’s fully compatible with 3D-Coat.

Space mouse

Most 3D modeling software requires toggling (by way of menu selection or by keyboard) in order to use the mouse to navigate the camera view. This interrupts the primary work in order to gain a better view.

The space mouse is an additional peripheral device that works in tandem with other peripherals such as a mouse or graphics tablet. It allows navigation with the left hand and mouse usage with the right hand (or vice versa). This allows for 360° of navigation freedom with zooming and panning. It also relieves wrist fatigue by separating the work load between two hands.

3Dconnexion is one maker of the space mouse. They have various models, some incorporating an ergonomic platform that has programmable keys and LCD displays.The SpaceMouse wireless is featured here and it’s available for about 125 USD. It’s fully compatible with 3D-Coat, Sketchup Make and Fusion 360.

Next: 3D scanning. There has to be an easier way of creating 3D models, right? 3D scanning may provide you with the solution.

3D Modeling

There’s a variety of 3D modeling software offering many types of approaches for creating three-dimensional forms. Deciding which one to use will depend primarily on the style of work, the steepness of the learning curve, and how much the software costs.

Optimizing the 3D modeling experience

3D modeling software can be divided into two kinds of modelers, hard and soft modeling. Both approaches have their advantages and disadvantages, yet by combining the software a workflow can be created that will optimize the 3D modeling experience.

For example, the concept is hard modeled as a geometric form with Sketchup Make. And then soft modeled with Meshmixer. By using these two different software programs, the basic structure could be quickly built with precision and then modeled further into a natural organic form. Utilizing these two approaches, virtually anything can be modeled.

Let's take a closer look at this concept.

Soft modeling

Soft modeling works best for creating organic forms. By using an assortment of tools, such as flatten, pinch and smooth, the surface of a model can be shaped into realistic forms and textures. The following soft modeling software is recommended for its functionality and modest learning curve.

Meshmixer

Meshmixer has a good variety of sculpting tools that can be adjusted for different characteristics, such as strength, size, and depth. It also utilizes a stencil feature which allows for the application of physical textures on the surface of the model. One of the most significant features of Meshmixer is its collection of parts. 

A variety of primitives, shapes, and human and animal parts can be added together and transformed in countless configurations. These parts can be utilized to create base forms that can be reshaped later with the sculpting tools.

Meshmixer is provided free by Autodesk and it can be downloaded at their site http://meshmixer.com/download.html.

3D-Coat

3D-Coat is a professional digital sculpting program that works more like real clay than most other programs. Using a voxel (volumetric) system, it actually carves into the model as a solid, rather than displacing the topological surface. This allows for digging into the actual form (creating negative space and holes) with much better results than other soft modelers.  

3D-Coat also has a powerful layers system called a voxtree. This allows modeling of complicated forms that have many parts. Individual parts of the model can then be isolated for specific modeling or they can be exported as individual parts for 3D printing. This creates the possibility of creating sculptural assemblages larger than the build volume of a 3D printer.

3D-Coat incorporates a 3D painting system as well. The model can be rotated and digitally painted with tools that work very similar as the tools in photo editing software. If your sculpture is to be painted with traditional materials, this can be a very quick means for pre-visualization.

3D-Coat is a commercial program offered by Pilgway and it can be downloaded at http://3dcoat.com/download/. A 30 day trial is available with all features intact. An amateur version with less features is available for 99 USD. Full professional version is 379 USD.

Hard Modelers

Hard modelers work more like CAD drafting programs. They create straight lines and curves with the precision of real world measurements. Because of these traits, they can be useful for creating parts that need to be precisely integrated with objects. They also model complex geometric forms with far greater ease than a soft modeler. The following hard modeling software is recommended for its functionality and low cost.

Sketchup Make

Sketchup Make has one of the lowest learning curves for a hard modeler. It works by drawing lines and basic shapes (such as rectangles and circles) and then extrudes these drawn shapes into a 3D model. 

It has an intuitive approach to modeling that makes it easy to build complex mechanical parts or geometric constructions that can be exported into other programs for soft modeling.

Sketchup Make is a free program offered by Trimble and it can be downloaded at http://www.sketchup.com/download. It begins with a 30 day trial as the Sketchup Pro version. The pro version costs 695 USD and adds more functionality, such as solid modeling tools.

Fusion 360

Fusion 360 is a powerful tool for creating industrial and mechanical designs. It models with a system of T-splines, which are mathematical representations of curves and surfaces. The learning curve for this software is moderately difficult due its many features.

One of it’s most significant features is its ability to create a shape around an imported mesh (such as a 3D scanned model) and copy the contour of the form. This provides the artist with a means for creating precise parts that can be attached to real world objects.

For an artist who works with hard edged forms that rely on geometric precision, Fusion 360 will provide the best tools for creating a 3D model.

Fusion 360 is a commercial cloud based program offered by Autodesk. It has a 30 day free trial with all features intact. Professional usage has a 30 USD cost per month or 300 USD cost per year. Hobbyist and startup companies can register for free use.

Up Next: Interfaces. Working with a 3D modeler is more enjoyable if it becomes more accessible as a tool in an artist’s hands. We’ll look at some affordable human interface devices.

How 3D printing works

3D Modeling

3D printing begins with conceptualizing an idea as a digital model. There are many different methods for creating digital models. The most common method is by using  3D modeling software or by 3D scanning physical objects. The 3D models generated with this software must be a solid (more on this at the Mesh Tools page) and exported as a .stl (STereoLithography) file. This is the file format for 3D printing.

The slicer

For 3D printing, the .stl file has to be prepared with software that’s called a slicer. The slicer works by taking your 3D model and cutting it up into many thin horizontal layers.

At each layer the slicer also adds the instructions your 3D printer needs in order to fabricate this layer. After slicing, this new information is saved as a .gcode file.

The Host

The host is simply a software program that allows you to manually control your 3D printer and it communicates the

information stored in your .gcode file to the 3D printer’s onboard computer. There are many different hosts available. They all have a basic user interface (UI) with some sort of graphical representation of your 3D model.

What is a 3D printer?

A 3D printer is a robotic device that’s controlled by an onboard computer system.

 It can move precisely in all three dimensions of space and control aspects of its functions by monitoring its components by the use of sensors. Ideally, once a 3D model is prepared and loaded, you can walk away and the 3D printer will fabricate your model without further human assistance.

The FFF process

There’s more than a handful of unique 3D printing technologies in use today. This site explores a process called fused filament fabrication (FFF). The FFF process works by heating a thermoplastic filament by way of a toolhead called an extruder. Guided by the instructions provided in the gcode of the 3D model, the extruder will create a thin horizontal layer of plastic that follows the contour of the model. It then lifts slightly and builds another layer on top of the previous layer. The 3D printer will continue to build these layers, one on top of another until the entire 3D model is fabricated.

This method of fabrication can create virtually anything by using many types of thermoplastics. Thermoplastics can consist of an assortment of fillers such as, carbon fibers, wood, stone, kiln ready clay and metal, providing the artist with a variety of materials to work with.  Even transparent and flexible materials are available for 3D printing.