---
title: Vacuum Line
slug: troubleshooting/vacuum-line
description: Discover effective solutions for addressing the "Vacuum Line" part defect from Carbon DLS printing. This comprehensive document explains how to identify, troubleshoot, and understand the root causes.
docTags:
createdAt: 2024-06-14T00:57:10.266Z
---
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**Vacuum Line**
An unvented volume creates lines on a surface by moving thin walls under the pressure differential.
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# How to Identify
Vacuum lines can be diagnosed as follows:
- Vacuum lines are a defect specific to unvented volumes.
- The line(s) appear horizontal relative to the platform.
- Thin walls are most likely to present this defect. The walls will appear to be pulled in towards the trapped volume along the vacuum line.
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When the geometry transitions from a thin wall to a large cross section surrounding an unvented volume, a [Cross Section Line](docId:7TYKEfAqK6hnwMvjVW6Xj) can occur in conjunction with the [Vacuum Line](docId\:uIA3VrtjsNOqvyXwL8VxS) defect. Both defects may need to be addressed.
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In extreme conditions, the [Blow Out](docId\:ygAbVQOmuTwYuvDOvnBfN) defect may also occur along vacuum lines.
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**Cause -** **Unvented Volume**
**Solution** - Print Preparation or Part Design
- The upper line is occurring in conjunction with a **cross section line **defect.
- The lower lines are vacuum lines only.
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**Cause -** **Unvented Volume**
**Solution** - Print Preparation or Part Design
- The upper line is occurring in conjunction with a **cross section line **defect.
- The lower lines are vacuum lines only.
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**Cause -** **Unvented Volume**
**Solution** - Print Preparation or Part Design
- The **blow out **defect is also occurring in this example.
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# Troubleshooting
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It is recommended that you review all the possible solutions before taking action to ensure you are pursuing the best course of action.
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If the best course of action is not apparent, try the troubleshooting options in the order listed. Refer [here](docId\:pPm8gmeGCY_0fkFwgTCyj) for more tips.
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Verify if your project contains an unvented volume.
- [Project Analysis](docId\:gfR-GoC-Irq_L9_KanC-X) in the printer software will alert you if you have an unvented volume.
- If you do have an unvented volume, proceed to the **Print Preparation or Part Design Adjustments** troubleshooting options below.
If you do not have an unvented volume, refer to the** Identify a Defect** guide to identify a different defect.
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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.
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### Orientation
- **Unvented volume**
- Reorient the part to vent the trapped volume (supports may also be needed)
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### Supports
- **Unvented volume**
- Lift the part above the platform on supports to vent the trapped volume
- Use bar supports, or break up fence supports into shorter sections with gaps in between, to provide venting
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### Design
- **Unvented Volume**
- Add vent holes in the part, at or near the platform, to vent the trapped volume
Reference [DLS Design Guidelines](docId\:t94PR-A-C0pIhY6LJsWk7) for drain/vent hole guidelines.
::Image[]{src="https://api.archbee.com/api/optimize/xcOI3p6O5jO0MVhoHv9rO-hRnOq3snOPNxzp7rO57yO-20240801-162827.png" size="80" width="1680" height="824" position="center" alt="Unvented Volume Design Fix" showCaption="false"}
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### Print Plan Adjustments
[Print Plan Adjustments](docId\:NxUK0dltz_vemEAU0DIpN) are not applicable for this defect.
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If problems persist, please reach out to [Carbon Support](mailto\:support@carbon3d.com).
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# Explanation & Causes
## Explanation
An [unvented volume](docId\:U7XYytjyDp3BvsYy2qKcU) has a pressure differential inside versus outside the trapped volume. The walls surrounding the trapped volume will be pulled inwards by the low pressure as the platform moves up during pumping, causing wall deformation. Some of the pressure may relax as the platform pumps back down to the curing position, thus the walls continue to deform as the print progresses often resulting in more than one vacuum line as the print proceeds.
*Reference *[DLS Printer Dynamics](docId\:U7XYytjyDp3BvsYy2qKcU)* for more information on pumping up and down during printing.*
- Thin walls in conjunction with a large trapped volume are the most likely to experience vacuum lines.
- More susceptible to unvented volumes:
- EPU due to its low green strength.
- L1 printer due to larger suction forces.
## Causes
### Print Preparation or Part Design
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How the part is **oriented**, **supported**, or **designed **is causing the defect.
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| **Root Issue** | **Problem** | **Why Defect Presents** |
| --------------- | --------------------------------- | --------------------------------------------------------------------------------------------------------------------------------------- |
| Unvented volume | A horizontal line along the part. | The pressure differential causes the walls surrounding an unvented volume to move while the platform moves up and down during printing. |