Warping - Mass Loss

11min

Mass Loss Warping
Parts curling or bowing during secondary curing.
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How to Identify
Mass loss warping can be diagnosed as follows:
Thin-walled parts
Curling edges
Bowing ends
Parts with varying thickness
Misshapen, bowing edges
Mass loss warping is the most common type of warping, and is typically the reason for warping. 
Reference also Warping - Print-Stress﻿ and Warping - Solvent﻿ for less common types of warping that can occur under very specific circumstances.
Cause - 
Differing Wall Thicknesses
Solution - Print Preparation or Part Design
Cause - Differing Wall Thicknesses
Solution - Print Preparation or Part Design
Cause - Differing Wall Thicknesses
Solution - Print Preparation or Part Design
Cause - 
Inconclusive
Troubleshooting
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Process, Material, and Hardware Checks
If any of these conditions apply to your print, take the corrective action and reprint to see if the problem is resolved.
Ensure parts have been fully dried after washing with solvent.
Wait at least 3-5 minutes at a bare minimum, even if you can't see any surface wetness.
Try drying parts longer up to the resin's cure start time. 
Reference resin protocol﻿.
Adjust baking method to apply even heat around the part
Bake flat surfaces on a raised mesh
Hang parts and/or use a baking fixture to hold parts in place during the bake
Pack parts in saltfNote: Only select resins are compatible with salt packing. Reference resin specific protocols﻿ or more information.

Reference Thermal Curing﻿ for more information.
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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.
Redesign part
Thicken walls of your part to reduce mass loss. 
Reference recommended feature sizes﻿ for guidelines per resin.
The example on the upper left is printed at 1.0 mm thick, below the recommended unsupported thickness for RPU 70 resin. Loss of mass, relative to surface area is high, and the loss of mass occurs randomly throughout the part leading to the curling you see here.
The version on the lower left is 2.5 mm thick, the recommendation for RPU 70, which is correctly flat.
Match wall thicknesses to mitigate differential shrinkage.
Or if unable, make changes in thickness as similar and gradual as possible.
The example on the upper right has a thin walled honeycomb pattern in the center and a thicker frame around the exterior. The thin honeycomb loses mass more quickly than the thicker frame, which pulls in the edges to produce the bowing you see here.
The version on the lower right adjusts the frame to be thinner, more closely matching the honeycomb dimensions, which keeps the edges straight.
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If problems persist, please reach out to Carbon Support.
Explanation & Causes
Explanation
Warping is the manifestation of mass loss, which is a form of shrinkage. Mass loss is a natural and expected side effect of the thermal curing process, but it leads to warping when that mass loss occurs unevenly. Uneven mass loss can occur for a few reasons:
Parts not fully dry after solvent washing
Uneven exposure to heat
Thin walls
Differing wall thicknesses
Reference DLS Printer Dynamics﻿ for more information about shrinkage in DLS production.
Causes
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Root Issue
Problem
Why Defect Presents
Drying
Wet parts
Parts must be fully dried after washing per protocol. If solvent has not completely evaporated from the part prior to baking, mass loss could be uneven.
Secondary Thermal Curing
(Baking)
Uneven exposure to heat
Monomers escaping the part will take the easiest path. When some surfaces become hot more quickly than others, such as surfaces sitting directly on the baking tray, the molecular structure will change more quickly making it harder for monomers to escape. Therefore monomers will take the easier path out of surfaces that are still getting hotter, such as those openly exposed.
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Root Issue
Problem
Why Defect Presents
Design
Thin walls
Thin walls have more surface areas exposed for unlinked monomers to escape.
Design
Differing wall thicknesses
Thinner walls will lose more monomers than thicker ones, which can distort the intended shape of the part.
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Root Issue	Problem	Why Defect Presents
Drying	Wet parts	Parts must be fully dried after washing per protocol. If solvent has not completely evaporated from the part prior to baking, mass loss could be uneven.
Secondary Thermal Curing (Baking)	Uneven exposure to heat	Monomers escaping the part will take the easiest path. When some surfaces become hot more quickly than others, such as surfaces sitting directly on the baking tray, the molecular structure will change more quickly making it harder for monomers to escape. Therefore monomers will take the easier path out of surfaces that are still getting hotter, such as those openly exposed.

Root Issue	Problem	Why Defect Presents
Design	Thin walls	Thin walls have more surface areas exposed for unlinked monomers to escape.
Design	Differing wall thicknesses	Thinner walls will lose more monomers than thicker ones, which can distort the intended shape of the part.

Warping

Warping - Print-Stress