Even after designing models with LSPc in mind, print files will need to be oriented and supported properly for more consistent print results. While orientation and supports will vary depending on the size, thickness, and shape of the model, here are some general tips:
Orienting Walls and Overhangs
- Allow a 30° minimum angle in order to build self-supported with typical wall thickness (up to about 25:1 span to thickness). Shallower angles are possible with shorter spans or ribs
- Horizontal overhangs beyond 2mm should be supported
Dealing with Cups
- If a cup-shaped feature is printing open to the vat, the resin will be pulled up by vacuum when the Z-axis lifts to separate, and the resin will pressurize when the axis returns to the platform
- Place a vent hole at the base of the feature or orient the cup opening at an angle which avoids the pressurization and increases stability
- Orient holes at the extremes of the part volume to allow for complete draining
Tall and Slender Parts
- When orienting tall and slender parts, limit the angle height to reduce movement on the build plate
- Widen support base and verify that there are no bend point in the support scaffolds
- Add supports to steep surfaces
Mitigating Layer Lines
Pronounced layer lines are usually caused by the part being under supported and sometimes from the print pausing during the printing process. The print itself will look more like layers in sedimentary rock if the print is under-supported. If it looks like there's a thick line drawn on the print, then this is likely due to a pause layer artifact. If the print needs more structure, there are a couple of options to try out:
Cones are a type of support that are larger and stronger than standard supports. The Base of the cone is what adheres it to the Build Plate, and the tip size is what's attached to print. Cones touch points should be larger than standard touch point tips, as they're meant to root the model to the build plate.
To add a cone, open the support tool window on the left-hand side of the NexaX window and choose Add/Edit Cone Support.
Once in editing mode, add the cone touch point(s) below the under-supported area, as they'll be holding the part in place to keep it stable while printing those layers. More than one cone support may be needed for very thick and large parts.
Changing the Critical Overhang Angle
The Critical Overhang Angle is the maximum angle of the part that will have supports on it. This can be adjusted by opening the supports tool on the left-hand side of the NexaX window, and clicking on Settings -> Critical Overhang Angle.
The angle can be adjusted by using the slider or by manually inputting the specified angle.
Note: Any sides with an angle larger than the number you adjust will not be supported properly. Supports or cones would have to be added manually.
Contact Point Adherence
There can be varying factors that may cause prints to separate from the contact points holding it onto the support structure, but usually it is due to:
- A lack of stability during printing
- An insufficient amount of contact points
- Contact points that are too small
- Part shrinkage that can cause brittle contact points to break.
Since material properties and print features vary widely, it may require a bit of trial-and-error to find the ideal strategy for successful builds with each print.
Partial Contact Point Tear
Sometimes a print will come out well, but some support touch points detached. While this may not be a major cause for alarm, there are some factors to consider when troubleshooting:
Thick and solid parts can detach from the contact points due to shrinkage during the print process. This may vary depending on the type of material, but there is always an amount of extra light exposure that causes the overall size of a solid part to shrink. This referred to as "cure-through".
Cure-through be mitigated by changing the length of the contact point beams for some give during the print process. This can be done by navigating to the supports menu on the left-hand side of your NexaX window and choosing Settings -> Minimum Distance To Part
Increasing this parameter will allow for some flexibility in the scaffolding below the contact points, allowing for the overall structure to maintain a better connection to the part.
Hollowed-out parts may also experience a similar issue, but for a different reason: suction cups. If a cup-shaped feature is printing open to the vat, the resin will be pulled up by vacuum when the Z-axis lifts to separate, and the resin will pressurize when the axis returns to the platform.
Hollow parts with improperly placed drain holes (or missing a drain hole entirely) will create a suction cup that pulls on the part due to the vacuum with each layer. These pulling forces can stress the touch points to failure, so it is always recommended to include a drain hole in the extremity of the part.
Note: with NexaX Pro for XiP, a drain hole can be added with the Perforation tool. To do this, select the model and using the toolbar on the left-hand side of the window choose Edit -> Perforation Tool. This feature is only available in NexaX Pro for XiP, and does not come with NexaX for XiP.
Complete Non-Adherence to Contact Points
If the peel forces applied to the part are too strong, it can be torn from the support structure entirely. There are many factors that can affect peel force, but here are some general tips:
Solid parts can rip off supports due to the amount of peel force applied during the peel of large-area slices. Larger parts will require a larger amount of touch-points, or may require an increase in contact point size. This can be changed by going to the Supports menu -> Settings -> Contact Width (mm)
Note: Larger contact points (or cones) will increase stability, but will require more post-processing. Smaller contact points make for simpler post processing, but it will likely require an increased amount of contact points to hold the same part on the scaffolding.
Hollow parts can rip off the supports due to an excessive suction cupping effect, an insufficient amount of contact points, or contact points that are too small. As previously mentioned, hollow parts need to have a drainage hole towards the first several layers so that there aren't excessive pull forces with each peel.