At Javelin we are constantly searching for areas where additive manufacturing can supplement or replace current manufacturing solutions for our clients. One of the leading areas in which additive offers an edge over traditional manufacturing is in low volume production of large-scaled parts, this can include Tier 1 automotive panels, large scale aerospace applications and heavy machinery replacement moldings.
Additive manufacturing is a perfect fit for these parts as the traditional manufacturing methods are usually costly and lengthy when large complex surfaces and features are involved. Utilizing additive manufacturing we are able to provide cost and time saving solutions for large parts in question. However, using additive manufacturing has its challenges, primarily due to the nature of plastics.
Warping and curling of plastics are issues that affect not only the additive manufacturing world, but plastic production on an industry wide scale. Warping plastics occur from a combination of two stimuli: thin/tall/unsupported geometry coupled with differential cooling/heating of the plastic part. As parts are being printed, heat can accumulate in areas with substantial mass vs areas that are thin walled and are able to cool more quickly, leading to differential cooling and warping. In the example part that we will be evaluating today, we can see that the majority of the part is thin walled except for the bulky geometry on the base corner pocket, which can allow for uneven heat accumulation and differential heating cooling.
Stabilization walls are a feature of Insight software that can greatly assist with the production stability of large parts. This feature allows for a vertical supporting structure to be built alongside the printed part for added stability during the printing process. Let’s take a quick look at how we can set these features to print large parts successfully.
Insight software feature: Stabilizing Walls
Once we have identified our preferred printing orientation, we can apply this feature to any areas that may be too tall to print without warping. In our part, we can see a combination of this walls that may warp as well as a large asymmetrical mass that can cause uneven heating on one side of the part. Navigating to Support -> Stabilize wall, we can see the parameters of this stabilization wall that we can adjust.
We can choose the width, height, thickness and the frequency at which the wall comes in contact with the part on a layer by layer basis. The general settings we use for successful stabilization walls can be seen in the screenshot above. Settings like Contact Interval (distance between adjacent supporting walls) and Penetration (depth of fusion between wall and printed part) can be adjusted as required based on the size of the section being stabilized. Once the parameters are selected, we can now select the intended start and end points of the stabilization wall, and generate a scaffolding supporting structure as such to support our part. As we can see below, we’ve generated stabilization walls on all of the thin walls of this part to offer extra stability.
Insight software feature: Anchor Columns
Flat planar parts are also at risk for warping while printing. Often, we see parts that are not properly stabilized start warping or curling as they are being printed. This is due to the thin nature of the part as well as the large opportunity for differential cooling along its surface area. Anchor columns are a great feature to stop part lift or part curling. Anchor columns ensure a secure connection between build platen and the printed part by using model material to create anchored material connections between the build tray and the printed parts. This allows for a more rigid connection when compared to the bed of support material that is used as default. These anchors can be clipped and sanded off from the bottom surface post print.
Navigating to Support-> Anchor columns, we can select the diameter of the intended column and start placing these anchors along the bottom layer of the part.
Once we are finished, we can reprocess the support and toolpaths and observe where the anchors are utilized. We utilize even spacing of anchor pins in order warping of the bottom surface does not occur. We can see that the anchor pins have created additional geometry that is printed in model material that is now projecting through the support base and providing a rigid connection directly from the part to the platen.
Controlling Airflow & Vibration
Our final tip for successfully printing large parts comes from the understanding of what causes part warping: uneven heating and part vibration. Machine vibration is an inherent part of the rapid FDM printing formula. If parts with thin sections/walls are being printed, the infill pattern as shown in Fig 7 can cause short, rapid cyclic movement of the gantry leading the machine and the parts inside it to vibrate during printing. In some cases of thin walls, we can eliminate the need for back and forth printing movement by utilizing the “Variable width remnant fill” option on insight. This can be found under Toolpaths -> Setup menu in the advanced settings. This option allows for one uniform toolpath to fill thin sections as opposed to a uniform width utilizing back and forth motion to for infill, minimizing opportunity for vibration of the machine and printed parts.
To keep vibration to a minimum, it is recommended that you check the rubber stopping legs at the base of the machine and ensure that it is extended to snugly meet the ground and dampen as much vibration as possible. This stops the machine from shaking and keeps the printed part as stable as possible during production.
To ensure even heating of the build chamber as much as possible we can be mindful of how we orient parts on the platen for printing, keeping in mind the direction of airflow from the heated fans.
With Stratasys FDM printers, airflow comes from both left and right walls and circulates downwards through the print chamber. If these air paths are obstructed by the printed part, the oven will not be heated evenly, therefore parts will not be heated evenly and will be at risk for warping. When printing large parts, ensure that they do not interfere with this airflow by orienting large features to align with airflow rather than obstruct the airflow. The above figure show that orienting so the walls are not perpendicular to airflow, will allow more uniform heat transfer during the printing process.
Additive Professional Services Team
We provide Designers and Manufacturers with a variety of custom-tailored 3D printing services, including high-performance prototypes, tooling and manufacturing aids, end-use parts, and low-volume production runs.
Feel free to reach out to our Print Services Engineering Team to find out how your parts can benefit from increased printing stability with these tips!
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