Orientation and Supports
Orienting and supporting parts is a challenging process with multiple considerations at play. There may be more than one solution for a successful print. Determining the best option for any given geometry is a process of balancing priorities with the dynamics of the printer.
Example assessment exercises are provided on the following pages in this guide:
Features that may not print properly if left unsupported:
Example Corner Cube Part
Overhangs
On the dark gray background, you can see how the part is sitting on the platform.
Viewed from below in the main image, the overhang detection tool highlights overhangs/bridges in red.
The dark gray surface is sitting on the platform.
Islands
Two islands emerge partway through the print that require supports.
Cross section is the XY slice of the part being printed at a given point in time, which can be seen when you view slices for the project.
Goals
- Small cross sections (less than 50 x 50 mm recommended)
- Consistent cross sections throughout the print
- Gradual changes in cross section from slice to slice
Risks
Parts with a large cross section on the platform will have strong adhesion and may be more difficult to remove from the platform. For especially rigid and brittle resins (ex: EPX), this can result in chipping the part during removal.
Parts with a large cross section late in the print, in conjunction with a small cross section on the platform, can be susceptible to an adhesion failure due to suction forces.
- Small cross section on platform
- Large cross section late in print
- Slices during printing
- Adhesion Failure from Suction Forces
Abrupt changes in cross section, especially when a bridge suddenly closes, results in a geometry flow band: a line in the printed part when the cross section changes suddenly.
- Slice just before an abrupt cross section change
- Abrupt cross section change
- Resulting cross section line
Prints are most successful when the resin can flow freely and consistently.
Risks
As with cross section described above, abrupt changes from one slice to the next cause a change in resin flow which results in a cross section line: a line in the printed part when the cross section changes suddenly. (see example above)
Resin flow can also cause a shallow line to appear on your part when the speed and direction of resin flow changes during printing. This can happen with parts of varying height on one build or when the platform moves above the resin surface. This is most common with elastomeric materials.
If resin is trapped in the part during printing, you could end up with an inadequate amount of liquid resin in the cassette to finish the print (when the minimum amount of required resin is in the cassette).
This is most common with unvented volumes.
The example here, printed directly on the platform, trapped resin in the six holes and didn't have enough liquid resin left in the cassette to properly flow where needed to finish the print.
See Unvented Volumes below for more information.
Fringing
This example shows the fringing defect, but the same solutions can apply to all defects caused by an unvented volume.
Project Analysis in the Printer UI will look for unvented volumes in your part(s) and provide a warning for areas of trapped volume.
You can view the warning areas in red with a sliding scale that simulates the part through printing.
Stability is needed to counter the suction forces of printing.
Parts susceptible to stability issues are top heavy or asymmetrical in their orientation, with a relatively small footprint on the platform. The resulting print defect is usually under-adhesion.
Suggested solutions for print success in this lesson focus solely on how orientation and supports can help. Additional options may be available for the print defects described here, including but not limited to design solutions. Reference the Part Defects documentation for full troubleshooting options.
Surface finish may be important on parts that have highly visible surfaces, such as name plates or the exterior of housings. Orientation & supports strategies can be utilized to achieve the best surface finish where needed.
Supports Location
Cosmetic surfaces can be oriented to avoid the need for supports.
On Cosmetic Surface
Off Cosmetic Surface
Medial Axis Flow Lines
Large cross sections parallel to the platform, facing the window, will manifest resin flow lines as a result of fluid dynamics.
Reorient cosmetic surfaces out of the ending XY plane to mitigate the effect.
Pixel Lines
Vertical surfaces can show vertical lines manifested from the corners of pixels in the slice image.
Reorient cosmetic surfaces out of the Z plane to mitigate the effect.
Reference DLS Design Guidelines for more information on resolution.
Slice Lines
Shallow curved surfaces can show the edges of slices as the slice image's edges shift from one slice to the next.
Reorient cosmetic surfaces to minimize shallow curves to mitigate the effect.
Reducing the slice thickness can also reduce this effect but will increase the print time. Reference Print Controls.
Reference DLS Design Guidelines for more information on resolution.
Consistency
Angled surfaces have the best consistency in surface finish as the combined effects of resin flow, pixels and slices average together.
It is particularly useful to match the print angle on multiple surfaces so they all share the same finish.
Fence Support Nubs are Smaller
There are two types of supports.
- Bar supports The break line is farther from the surface of the part and therefore leaves behind a larger nub.
- Fence supports The break line is close to the surface of the part, leaving smaller, consistently spaces nubs.
Your parts may have critical features where tolerance is tight and accuracy is important. Orientation & supports decisions can be made to ensure the most critical features have the best outcome for your application.
Overcure and cure-thru are optical effects resulting from how UV light interacts with the resin as it's curing. Resin is not completely opaque to UV light, and some light passes through features edges where the material is thin, curing a small amount of additional resin.
- Overcure occurs in the XY plane
- Cure-thru occurs in the Z axis
Critical features maintain better accuracy when oriented in the XY plane because overcure behaves equally across that plane. A vertically oriented feature will experience cure-thru only from the bottom (where the UV light shines from), causing a feature to be marginally oblong.
The overcure and cure-thru illustrated here have been exaggerated for graphic readability. The actual dimensional difference is smaller at scale. Reference DLS Design Guidelines for more information on optical effects as well as recommended compensation factors for holes.
Supports
Features that serve a functional role may require special considerations to ensure proper fit in their application. Examples include:
- Holes that require a press fit or will serve specific hardware
- Surfaces that will be bonded to another component
- Snap fit features
Orient Strategically for Function The function of this bracket requires a smooth interface on all flat faces to ensure a tight fit with construction components. Orienting the part such that supports are only on the edges of the part, the function of the bracket is improved.
Functional assembly of the bracket
Orientation with supports on a flat face Orientation with all supports on edges
Orient for No Supports on Features Orient your part to eliminate overhangs and the need for supports on critical features.
Choose Fence Supports If the preferred orientation* requires supports on critical features, choose fence supports to leave behind smaller support nubs.
*For example, this example orientation may be preferred for cosmetic reasons: to keep supports off of hero surfaces (see above).
When parts will be assembled, it is recommended to orient each part consistently relative to how the components will fit together. Every axis, in each part, will then be exposed to printing forces in the same manner, leading to the best fit.
Supports are printed in the same material as the part. The more supports a part needs, the more cost is associated with the part. Utilize orientations that minimize the needs for supports to save on cost.
Reference the Unsupported Features Print Success example for minimizing unsupported features.
Reducing print time is desirable to increase throughput. Orientation of the part can have a measurable impact on the print time.
Note that ultimately what matters most for cost is the print time per part. The shortest print time is often at odds with the number of parts per build, so it makes sense to look at both factors in tandem and calculate the best value per part. Reference the Tall vs Short Cost Comparison below.
Part Height The most influential factor on print time is the height of the part. Drastically reduced print times can result from a short orientation.
Note that print time rarely changes from one part to a fully packed build, unless parts are packed too closely. The examples below have the same print time for one part and for the full build.
Estimates shown from an M3 Printer. Other printers will vary due to build size, or on an M2 Printer (which has the same build volume as an M3) due to M3's force feedback feature that usually yields faster print times.
Maximizing the number of parts per build is desirable to get as many parts through production as possible. Orientation of the part can have a great impact on how many parts fit on the build platform.
The Minimize Footprint tool in the Printer UI is the quickest way to get an orientation to maximize parts per build. This example yields 42parts per build with a minimal footprint, compared to 10 in a short orientation. Remember to follow part spacing recommendations: reference Layout.
Tall vs Short Cost Comparison Note that while maximizing the build can often provide a good value, it is important to look at all factors affecting cost on a per part basis, notably those mentioned above: material and print time per part.
The example above fares better in the short orientation for print time per part and material cost per part (due to fewer supports). The deciding factor may come down to other factors. Reference the Example Orientation Assessment for full considerations at play.
Orientation & Supports decisions can have a noticeable impact on the effectiveness of washing methods and the ease of removing supports. Improving these aspects of post-processing can save labor time and therefore cost.
Washing Exposure
Avoid Touch-Up For parts to wash without the need for touch-up, orient parts to ensure all surfaces are exposed to the full agitation of solvent.
In the example below, the layout on the left orients the inside of the housing face-down on the platform. Solvent will have very little agitation on the interior surfaces when washed on the platform, and the parts will need touch-up. The layout on the right exposes all surfaces to solvent agitation and parts will come out clean after washing without touch-up.
Easy Access for Touch-Up If touch-up is not avoidable, ensure that features needing touch-up are easily accessible.
Part Washer Spinning
Using the Smart Part Washer is recommended for the best washing results. The part washer primarily works with centrifugal force, spinning parts both inside and outside of the solvent during the wash cycle.
When laying out parts on the build platform, consider the effects of spinning to achieve consistently clean parts.
Avoid the Center The only area of the platform that doesn't get the benefit of centrifugal force is the center.
Best wash results avoid the center as can be seen in this layout example.
Take Advantage of Spinning Features such as blind holes often require touch-up after washing.
Use centrifugal force to your advantage and aim blind holes outwards so the spinning pulls out resin for you.
This example aims the blind hole towards the platform edge on both sides
Supports
Ensure that supports are easy and quick to remove to save labor costs. When supporting parts, consider how they will be removed in post-processing.
Make sure all supports are accessible for removal.
Consolidate Supports Supports will be quicker to remove when they can be pulled off all at once.
In the example
- The left part has a series of fence supports, which may be difficult to grab all at once.
- The second part uses bar supports which automatically truss together as one when possible.
- The last part uses one fence support instead multiple.
