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Warping in 3D Printing – Solutions with a twist

Warping in 3D Printing – Solutions with a twist 15 APRIL 2018

In this article, let us share our take on how to reduce and prevent twists and distortions for excellent 3D printing results

Print failures are not only a huge problem that result in cost and time wastage, but are also a tough nut to crack. Very often, 3D Printed parts experience warpage issues. This results in either prints being distorted and even coming off the print bed for Fused Deposition Modelling (FDM) printers, or simply final printed parts being geometrically inaccurate on other modes of printing.

The HP Jet Fusion 3D 4200, which is based on the novel idea of a multi-jet fusion technology has taken over the polymer 3D Printing world by storm. With its superb 3D Printing quality as well as rapid print speeds of up to 4500 cm3, we have had much success printing a wide spectrum of parts with it. From models and prototypes to end-use engineering components, the MJF 4200 has served us well.

Nonetheless, as with all 3D Printing, we have encountered occasions of part warpage. This has proven costly due to the excessive waste of materials as well as resulting in production delays. This has also thrown up a wide array of questions such as:

  • What wall thickness would be optimal for printing?
  • Would the overall dimensions of the part result in greater warpage?
  • How would the orientation of the print affect the overall quality?

While we do not have all answers to these questions yet, we have found a couple of ways to mitigate and reduce the issue of warping. Typically, warping occurs during the cooling phase of the 3D Printing. As the part cools, it contracts and shrinks and this causes uneven lateral stress on the part. Some of the main ways to reduce warping for FDM prints would be to increase ambient temperature, perhaps with a heated bed or even improving the print bed adhesion. However, the MJF 4200 is unable to do either.

Playing with the various parameters such as choosing a standard print over a fast print or even natural cooling as opposed to fast cooling has not churned desirable results. We have found that the Glass Transition Temperature (Tg) of the HP 3D High Reusability PA 12 is between 90 – 95 ˚C, with the melting point at 350 ˚C. Armed with that knowledge, we have tried a variety of ways to bring the temperature of the final printed part to approximately 95 ˚C and holding the temperature there to soften the material, allowing it to be malleable enough to be reshaped to the desired and actual shape.

Some of the ways include letting the part sit in a water bath to ensure that the heating is uniform and allowing the part to warm up gradually, reducing any possible non-uniform stresses. The alternative would be to place the part in our in-house furnace to bring the temperature up to 95 ˚C and hold it there for approximately 20 minutes or as long as needed for the part to be soft enough to be reshaped. The holding time at the glass transition temperature would depend greatly on the dimensions of the part as well. For large flat pieces, the part would be weighed down with solid metal blocks to keep the straight form of the part.

Moving Forward – our plans to innovate warpage resolution

Our current methods, whilst somewhat primitive at this stage, have enabled us to achieve the original goal of producing an accurate part. However, this is only correcting the symptom after a part has been produced. We are currently experimenting with a number of other ways to reduce warpage during printing. One such better way would be to create supports for the part, such as ribs and a mesh with nodes to anchor the part to a firmer shape. These intended nodes would simply be broken off or post processed after.

3D printing is a both a complex and exciting process and we are eager to continue on this educational journey of exploring novel ideas to solve daily problems. Look out for our next related article on the new methods we will create to resolve warpage issues!

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