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Exposure settings control how each layer is cured during the printing process. Proper configuration is critical for achieving successful prints with good layer adhesion and detail.

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ExposureConfig Structure

The ExposureConfig struct is defined in common/src/slice/config.rs:28 and contains five key parameters:
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exposure_time
Seconds
default:"3.0"
The duration that the UV light exposes each layer.Normal layers default: 3.0 secondsFirst layers default: 30.0 secondsLonger exposure times result in stronger curing but may cause over-curing and loss of detail. The optimal value depends on your resin type and printer’s UV intensity.
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lift_distance
Milimeters
default:"5.0"
The distance the build platform lifts after exposing a layer, allowing fresh resin to flow underneath.Default: 5.0 mmThis must be sufficient for the film to separate from the cured layer and new resin to flow into place.
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lift_speed
CentimetersPerSecond
default:"5.5 cm/s"
The speed at which the build platform lifts after exposure.Default: 5.5 cm/s (calculated as 330 mm/min)Too fast may cause parts to detach from supports; too slow increases print time unnecessarily.
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retract_distance
Milimeters
default:"5.0"
The distance the build platform retracts back down to the next layer position.Default: 5.0 mmTypically matches the lift distance but can be adjusted independently.
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retract_speed
CentimetersPerSecond
default:"5.5 cm/s"
The speed at which the build platform retracts back down.Default: 5.5 cm/s (calculated as 330 mm/min)This affects the force of impact when the platform returns to position.

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First Layer Exposure

First layers require significantly different exposure settings to ensure proper adhesion to the build plate. Mslicer maintains two separate ExposureConfig instances:

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Normal Exposure Config

Used for regular layers after the first layers and transition period: 
exposure_config: ExposureConfig {
    exposure_time: Seconds::new(3.0),
    lift_distance: Milimeters::new(5.0),
    lift_speed: CentimetersPerSecond::new(5.5),  // 330 mm/min
    retract_distance: Milimeters::new(5.0),
    retract_speed: CentimetersPerSecond::new(5.5),  // 330 mm/min
}

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First Exposure Config

Used for the initial layers that adhere to the build plate: 
first_exposure_config: ExposureConfig {
    exposure_time: Seconds::new(30.0),  // 10× longer than normal
    lift_distance: Milimeters::new(5.0),
    lift_speed: CentimetersPerSecond::new(5.5),
    retract_distance: Milimeters::new(5.0),
    retract_speed: CentimetersPerSecond::new(5.5),
}
The key difference is the exposure time: first layers use 30 seconds by default (compared to 3 seconds for normal layers) to create a strong bond with the build plate.

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Layer-Based Exposure Selection

Mslicer automatically selects the appropriate exposure configuration based on the current layer number using the exposure_config() method in common/src/slice/config.rs:38: 
pub fn exposure_config(&self, layer: u32) -> &ExposureConfig {
    if layer < self.first_layers {
        &self.first_exposure_config
    } else {
        &self.exposure_config
    }
}
Layers are zero-indexed, so:
  • Layers 0, 1, 2 use first_exposure_config (when first_layers = 3)
  • Layer 3 and above use exposure_config

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Transition Layers

Transition layers interpolate between first and normal exposure settings to prevent abrupt changes that could cause delamination. The number of transition layers is configured separately in SliceConfig.transition_layers (default: 10). During transition:
  • Exposure time gradually decreases from first layer values to normal values
  • Other parameters (lift/retract) also interpolate smoothly
  • This helps prevent stress on the part where settings change
The interpolation is calculated in the print_time() method, which averages the two configurations over the transition period. Total layer time includes:
  1. Exposure time: Duration of UV exposure
  2. Lift time: lift_distance / lift_speed
  3. Retract time: retract_distance / retract_speed
The complete calculation is implemented in common/src/slice/config.rs:56: 
let layer_time = exp.exposure_time
    + exp.lift_distance / exp.lift_speed
    + exp.retract_distance / exp.retract_speed;

let bottom_layer_time = fexp.exposure_time
    + fexp.lift_distance / fexp.lift_speed
    + fexp.retract_distance / fexp.retract_speed;

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Configuring in the UI

Exposure settings are configured in the Slice Config window through collapsible sections:
  • Exposure Config: Settings for normal layers
  • First Exposure Config: Settings for initial layers
Each section provides drag controls for all five parameters with appropriate units and ranges. The UI is implemented in mslicer/src/windows/slice_config.rs:154.
Start with default values and adjust exposure times based on your specific resin and printer. Most other values can remain at defaults unless you’re experiencing adhesion or separation issues.

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Units Reference

  • Seconds: Time values for exposure duration
  • Milimeters: Distance values for lift and retract
  • CentimetersPerSecond: Speed values (internally converted from mm/min)
All units are strongly typed in the source code to prevent unit conversion errors.

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