Nov 30, 2015 | By Kira

Warping is one of the most frustrating yet common issues when it comes 3D printing with plastic filaments, particularly when using ABS. You’ve calibrated your starting Z height, cleaned your build surface, used a heated build platform and even tried 3D printing with a raft, yet nothing seems to stop those bottom corners from pulling loose from the build platform, curling upwards, and completely ruining your print.

Though warp is difficult to measure and almost impossible to avoid, in order to help users of all levels determine the warp-index of their chosen filament and achieve the best possible 3D printing results, ‘Filament Wizard’ and inventor Kai Parthy has developed a repeatable, standardized test for measuring warp across various 3D printing filaments that requires nothing more than an FDM 3D printer and a flatbed scanner.

Warping occurs when plastic parts cool at different rates, causing uneven shrinkage and bends where the print should be straight. Although PLA is less susceptible to shrinkage than ABS, both can warp and curl. The most common tips for minimizing warp include 3D printing on a heated build platform, printing slower, and printing cooler. In addition to these tips, many manufactures now claim that their 3D printing filaments offer ‘low’ or ‘near to zero’ warping properties—however as Parthy explains, these are mostly “empty marketing phrases,” as nobody is able to exactly define the warp.

“To measure warp is not that easy. You cannot just apply a ruler and read out any index!” Parthy told 3Ders.org. “It is a common misunderstanding to use the provided shrinkage values give by the polymer-producers as indication for the expected warp. The values for the shrinkage of a plastic, however, cannot be used 1:1 as an indicator for the warp of a 3D printed plastic, because layer-wise printing is a complex thermal process depending on more than a dozen parameters.”

His solution, therefore, was to create a simple, open-ended scale (0 = good; 10 = bad, with the possibility of even higher values for more extreme materials) that identifies how much a given filament will actually warp.  Importantly, Parthy reminds us that his method will not describe how to print with less warp—rather, it is a tool that can help makers compare and determine which 3D printing filaments are more suitable for their chosen project (especially for larger 3D prints) based on the material’s tendency to warp.

The low-bondage warp index can be measured in a few simple steps. First, 3D print a warp-test object (Parthy has provided a few free, downloadable examples). Next, draw a thick line with a permanent market at the Z-levels that are relevant for the measurement of the (2D) scan. Scan the object at (at least 1200 x 1200 dpi), and then measure the flexion of these layers using a graphics software (i.e. Inkscape) to 1/100 mm. The value of this flexion will be between 0-10, meaning it can then easily be compared to other values using the given scale.

For example, for the “Curtain” test object, the print parameters are:

  • 0% filling, 0 solid at top, 0 bottom
  • 1 perimeter > ~ 1 mm wall
  • 0.25 layer
  • Object fan off
  • Platform and environment unheated (20-25 C)
  • 0.4 – 0.5 nozzle
  • Print speed: 30 mms/sec

Parthy explains that rather than using a heated 3D printing platform to measure the warp-index, it is crucial to conduct the test on a cold print platform. This is because cold conditions (20-25°C) are a common denominator for almost all 3D printers, and because hot conditions are not always reproducible across different 3D printer models and setups. The non-heated platform thus makes everything standardized and repeatable, resulting in much more reliable findings.

This fundamental finding certainly isn’t the first time Kai Parthy has made waves in the world of 3D printing.  Back in 2012, the German inventor released LAYWOO-D3, the first filament of its kind to combine natural wood with thermoplastics. Since then, Parthy has developed LAYWOOD FLEX, BENDLAY, MOLDLAY, PORO-Lay, and LAYBRICK—all of which have rightly earned him the title of the 3D Printing Filament Wizard. For this project, Parthy also thanked Joerg Draheim / innovativaggregat for more than five years of help in 3D printing know-how and software consulting.

Though even the Wizard admits that the problem of warping will still keep makers busy for a long time to come, his new method for measuring the warp index of plastic 3D printing filaments may have brought us one step closer to undoing one of the most fundamental, and certainly most frustrating, obstacles for 3D printers. Warping: your time is almost up.

 

 

Posted in 3D Printing Materials

 

 

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