Abstract
Rescaling is performed by the software and is always necessary to compensate for any distortion that occurs when the resin is cured by the light source and goes through a phase transition, i.e., changes from a liquid to a solidified material.
During this phase transition, certain properties of the resin change due to differences in external conditions, such as temperature and pressure. The resins we work with usually experience some shrinkage during this phase transition.
Method:
In this experiment, we have removed the rescaling function that is applied by the software so that we can measure just how much of a difference it makes to the accuracy of the final print.
To do so, we simply adjusted the calibration that is usually applied for the tested resin, in this case CURO Model. This adjustment is made before the slicing process and exporting the print file. We maintain a controlled environment in our print lab to limit the effects caused by environmental conditions and are confident that we are able to produce consistent results.
When the print process is complete, we use a desktop scanner to generate a digital model of the physical object. The scanning process is performed two times: The first time is immediately after the print process is complete; The second time is 24 hours after the print process is complete.
When the object has been scanned, we then compare those scanned images to the original digital file to measure the level of distortion.I
Control group:
CURO Model 2.0 with re-scaling ratio
Testing group:
CURO Model 2.0 Without re-scaling ratio
Results:
| 3D Scan Accuracy | CURO Model
(with Scale Ratio) |
CURO Model
(without Scale Ratio) |
||
| Immediately after Post curing | 83.2% | 79% | ||
| 24hrs after post curing | 89.92% | 82% |
CURO Model – With Re-scaling Ratio
| Scan immediately after post curing |  |
 |
 |
| 83.2% | Lower Limit: 10.4% | Upper Limit: 93.6% | |
| 24 hours after post curing |  |
 |
 |
| 89.92% | Lower Limit:1.93% | Upper Limit: 91.85 |
| Observation immediately after post curing | Observation after 24 hours | Observation after 4 days |
| Smooth surface; No significant defects. | Smooth surface; No significant defects. | Smooth surface; No significant defects. |
———————————————————————————————————————————————————–
CURO Model – Without Re-scaling Ratio
| Scan immediately after post curing |  |
 |
 |
| 78.98% | Lower Limit: 11.80% | Upper Limit 90.78% | |
| 24 hours after post curing |  |
 |
 |
| 82.18% | Lower Limit 11.85% | Upper Limit 94.03% |
| Observation immediately after post curing | Observation after 24 hours | Observation after 4 days |
| Smooth surface; No significant defects. | Smooth surface; No significant defects. | Smooth surface; No significant defects. |
Conclusion:
Without the rescaling function, there would always be a noticeable amount of distortion and a distinct difference in size between the digital model and the printed object. The rescaling function that is applied for specific calibrated resins produces more accurate prints and eliminates the need for users to test and determine any adjustments that must be made.
There are other environmental conditions which play a role in the level of distortion, but it is the resin’s reaction to the polymerization process that is the most significant factor. All of the pre-calibrated resins are put through vigorous testing to determine the most accurate level of rescaling. Without this dedicated testing and the consequent optimization of the slicing software, it would be a laborious process to determine the level of adjustment that must be made to compensate for changes in the material.