Is it unreasonable to expect 3D print perfection? Indeed it is, but end users are quick to blame the machines.
Let me begin by stating that I’m not a plastics engineer, but I do know that thermoplastics have a glass transition temperature, meaning they will become liquid and solidify again at certain temperatures. This is the reason certain plastic items can be melted and used again repeatedly. As you may already know, this is exactly how FDM technology works: the materials are heated to their glass transition, extruded, and then solidify again. The process is quite simple, but obviously there’s much more to consider.
While thermoplastics, such as ABS, have relatively low shrinkage rates, we still see issues with distortion and curling due to material characteristics, especially when printing large geometry with thick cross-sections. This can be accredited to differential cooling rates of materials. Exterior surfaces tend to cool faster, while the interior mass stays hotter, which can cause undesirable results.
There’s nothing more frustrating and discouraging than removing a 25, 50, or 100 hour build only to find that some geometry has distorted well beyond tolerance. These overlooked yet quick and easy processing steps, within Stratasys’ Insight software, can help reduce that heartbreak.
Option 1: Give the model a bigger base
Increasing the base geometry will allow more bonding area with the foundation. This also doubles as a heat sink.
These controls can be accessed under the Support menu by selecting Setup and then clicking the advanced settings parameters icon. One or both of these values can be modified as needed.
Base Oversize - Think of this as the foot print of the support base. The setting refers to the dimension around the perimeter between the part and support. It defaults to 0.050” but it can be increased up to a maximum of 0.5”. The blue and white layers, in the pictures below, represent the base layers (support material).
Base Layers - This straightforward setting controls the thickness or number of base layers. The default is 5 layers and the drop down will give you choices of 5, 10, and 15; however you can also type in a layer height of your choice even though we haven’t experienced a situation that required more than 15.
The default base oversize setting of 0.050” (shown below) cradles the model footprint tightly.
Shown below, the base oversize is set to the max of 0.5”. You’ll notice the base area increased by about 16% which provides a larger base to bond with the tray and sinks some heat away from the large cross section.
Shown below, I’ve set the parameter to 15 base layers with the 0.5” base oversize. Using combinations of these options often produces the best results.
Option 2: Remove Perforations (Breakaway Supports)
This setting refers to support parameters, which add single model layers at specific intervals within support columns. Insight will automatically activate this when a material with breakaway support is used. The design intent of the perforations is to help remove supports. But here’s the rub: if the geometry has large areas of support, they can curl and separate at these perforations. Thus, removing the perforation layers will help reduce part curl, but make it more difficult to remove the supports.
These controls can also be accessed under the Support menu by selecting Setup and then clicking the advanced settings parameters icon. The controls are just below the support base controls. Uncheck the box and you’re done!
The above example shows default perforation layer lines (light blue).
Option 3: Add Anchor Columns
Anchor Column - This feature can create columns of model material that connect and secure the bottom facing surface of the model directly to the substrate through the base support. The caveat is that these additional features will later need to be mechanically removed. Keep this in mind if the bottom surface of the part is critical.
Placement and quantity are fully customizable, but will depend on the geometry. Obviously, you’ll want to focus on areas of the build that may have had issues in the past.
Prior to generating supports, begin the process by accessing the Support Menu, and select Anchor Column.
From the top view, select the desired center point and click OK. Insight will add a circular contour, which locates the anchor column. Once you confirm the placement and create supports, step down into the base support layers and notice the anchor columns. This process can be repeated for as many additional anchor columns as needed.
After supports and toolpaths are generated, you will notice the column in all its glory.
As I mentioned earlier, using combinations of these options will produce the most favorable results. In a recent application, our customer combined both parameters from Option 1, as well as added several anchor columns. They were able to reduce part curl down from 0.020” to 0.009”; which was well within their tolerance.
If you’re experiencing part curl, even after utilizing these options, we can provide additional application support and advanced Insight training. Please contact us for more information.
Happy processing!