Part Defects

Witness Line

10min

Witness lines
Changes in resin flow dynamics cause witness lines.
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How to Identify
Witness lines can be diagnosed as follows:
Thin lines on part surface.
Lines appear horizontal (parallel to the build platform).
Lines appear on all sides of the part.
Visual artifacts that can be seen but not felt by hand.
Cause - Inconclusive
 
Cause -
Sudden change in print speed via Print Plan Adjustments
 
Cause - 
Sudden change in print speed via Print Plan Adjustments
 
Cause - 
Sudden change in print speed via Print Plan Adjustments
 
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Troubleshooting
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Print Preparation or Part Design Adjustments
The following solutions will address print or part-related causes of the defects. Choose among the suggested actions below and select the best approach for your application. Usually only one type of adjustment is needed.
Tilt parts at an angle.
Keep multiples of the same part in the same orientation.
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Avoid printing different part geometries simultaneously.
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Reference Print Plan Adjustments﻿ for guidance on the following parameters.



Stages 1-4

If changes to speed or platform movement have been made in the print plan already, ensure you have ramped up/down to the changed slices to prevent witness lines.

3 Pump Down Stage

Platform Speed Parameters
Motor Down Speed

4 Settle Down Stage

Delay Timing Parameters
Minimum Pre-Exposure Delay
Minimum Time Force Slope Down Settled
If problems persist, please reach out to Carbon Support.
Explanation & Causes
Explanation
Changes in resin flow dynamics affect the speed and direction of resin flow, which can cause subtle changes on the surface finish of the part. The primary conditions where this can occur:
Flow changes caused by different part configurations:
Printing different part geometries simultaneously. 
Or printing the same part in multiple orientations.
Platform moving above the surface of resin in the cassette.
A sudden change in the print plan.
Different Part Configurations
As these part of varying height finish printing, a new resin flow condition is created.
Platform Position
Early in the build, the platform is immersed in the resin, which has a large influence on the dynamics of resin flow. Later in the build, the platform exits the resin and only the parts themselves influence resin flow, which is less turbulent than than the platform.
Print Plan Sudden Change
When the print plan suddenly changes in speed or platform movement, the resin flow also changes suddenly.
Causes
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Root Issue
Problem
Why Defect Presents
Orientation
Change in cross section is parallel to platform
When a cross section changes suddenly from one slice to the next, the dynamics of resin flow also change suddenly. Tilting parts at an angle so cross section changes gradually can mitigate the issue.
Parts are in different orientations
Keeping all parts at the same orientation keeps flow conditions consistent.
Layout
Different geometries on one build.
Different part geometries will change the resin flow dynamics as different parts finish printing.
This can be an efficient way to test different part geometries to save resin and printing time, but is it not an advised production solution.
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Printing Stage
Parameter
Type

Type of Adjustment
Why Defect Presents
1 Pump Up
2 Settle Up
3 Pump Down
4 Settle Down
Any
Sudden increase or decrease
Sudden changes in flow dynamics can follow any sudden change in speed or platform movement.
3 Pump Down
Platform Speed
﻿Increase﻿
A quick pump down speed can cause more disturbance in resin flow.
4 Settle Down
Delay Timing
﻿Decrease﻿
Less time for the settle down stage means resin has not had enough time to recover from changes in flow dynamics.
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Root Issue	Problem	Why Defect Presents
Orientation	Change in cross section is parallel to platform	When a cross section changes suddenly from one slice to the next, the dynamics of resin flow also change suddenly. Tilting parts at an angle so cross section changes gradually can mitigate the issue.
Parts are in different orientations	Keeping all parts at the same orientation keeps flow conditions consistent.
Layout	Different geometries on one build.	Different part geometries will change the resin flow dynamics as different parts finish printing. This can be an efficient way to test different part geometries to save resin and printing time, but is it not an advised production solution.

Printing Stage	Parameter Type	Type of Adjustment	Why Defect Presents
1 Pump Up 2 Settle Up 3 Pump Down 4 Settle Down	Any	Sudden increase or decrease	Sudden changes in flow dynamics can follow any sudden change in speed or platform movement.
3 Pump Down	Platform Speed	Increase	A quick pump down speed can cause more disturbance in resin flow.
4 Settle Down	Delay Timing	Decrease	Less time for the settle down stage means resin has not had enough time to recover from changes in flow dynamics.

Warping - Solvent

Printer Health Checks