Print Speeds

This guide explains the Vision Miner approach to setting print speeds in PrusaSlicer for the Vision Miner 22IDEX V4. The core philosophy is to configure relatively high nominal speeds and accelerations, understanding that the actual print speed is often dynamically limited by the material's maximum volumetric flow rate and the minimal layer time requirement for proper cooling and adhesion.

The goal is to achieve the fastest possible print times without compromising part strength or geometric accuracy. This involves understanding the interplay between slicer speed settings, acceleration capabilities, material extrusion limits, and cooling requirements.

This approach complements the strategies discussed in the Layer Times & Cooling Guide. Prerequisites include familiarity with basic PrusaSlicer navigation and an understanding of the concepts covered in the Minimal Layer Time and Volumetric Flow Rate guides.

Understanding the Hierarchy of Speed Limitations

Achieving the optimal print speed involves setting parameters in the slicer, but several factors create a hierarchy of limitations that determine the actual speed used during printing:

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1. Volumetric Flow Rate (Max Extrusion Rate): This is typically the primary limiting factor. It defines the maximum volume of plastic (in mm³) that can be reliably melted and extruded per second (mm³/s). Setting speeds that demand a higher flow rate than the hotend/material combination can handle will result in under-extrusion and failed prints.
2. Minimal Layer Time: As detailed in the Layer Times & Cooling Guide, this setting intentionally slows down the print speed on layers with small cross-sectional areas. This ensures adequate cooling time to prevent melting and deformation, preserving geometric accuracy and layer bonding, especially crucial for high-temp materials relying on ambient cooling. This is a deliberate slowdown for quality.
3. Acceleration Settings: Define how quickly the toolhead can change speed. Even if a high top speed is set, the printer may never reach it on short print moves if acceleration is too low. Think of it like driving in a city – acceleration matters more than top speed between short distances. The physical limit of acceleration on the Vision Miner 22IDEX V4 is 15,000 mm/s², but we limit it to 5,000 mm/s².
4. Configured Speed Settings: These are the target speeds you enter in PrusaSlicer for different features (infill, perimeters, etc.). They act as an upper bound, but the printer will only reach them if not limited by the factors above.

Configuring Volumetric Flow Rate

This critical setting caps the overall extrusion throughput.

1. Location: In PrusaSlicer, navigate to Filament Settings.
2. Advanced: Adjust the Max volumetric speed.
3. General Guidelines (Starting Points):
   • Extra High-Temp Materials (PEEK, PEKK, Ultem): Start around 5 mm³/s.
   • Standard Engineering Materials (Nylon, PC, ABS/ASA): Start around 10 mm³/s.
   • Faster/Lower-Temp Materials (PETG, PLA): Can often handle 15 mm³/s or more.
4. Tuning: These are safe starting points. The actual maximum depends on nozzle size, temperature, and specific filament brand. Refer to the dedicated guide for tuning procedures.

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Configuring Acceleration

Acceleration determines how quickly the printer reaches its target speeds.

1. Location: In PrusaSlicer, navigate to Print Settings → Speed → Acceleration Control (Advanced).
2. Philosophy: Higher acceleration generally leads to shorter print times, especially on complex models with many short segments (the "city driving" analogy).
3. Vision Miner Defaults: Our default profiles use conservative acceleration values known to produce high-quality results reliably.
4. Tuning (Optional): The Vision Miner 22IDEX V4 hardware is capable of significantly higher accelerations. You can cautiously increase values like Perimeters, Infill, and Travel acceleration. However, excessively high acceleration can cause ringing/ghosting artifacts, skipped steps, or increased machine wear. Increase incrementally and test print quality.

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Configuring Speed Settings

These are the target speeds for different print features.

1. Location: In PrusaSlicer, navigate to Print Settings → Speed.
2. Philosophy: Set generally high speeds for features like Infill (e.g., 200 mm/s or higher). Set moderately high speeds for internal Perimeters. However, use deliberately slower speeds for features critical to quality and strength:
   • External perimeters: Slower speed improves surface finish and dimensional accuracy.
   • Small perimeters: Slower speed helps with detail and prevents excessive heat buildup.
   • Support material / interface: Can often be printed faster, but interface layers might benefit from slower speeds for easier removal or better bonding depending on the type.
3. Avoid Excessively Slow Speeds: While specific features benefit from reduced speed, avoid setting all speeds extremely low (e.g., 50 mm/s). This negates the benefit of a fast machine and can sometimes cause issues due to prolonged nozzle heat exposure on the part. Rely on the Volumetric Flow Rate and Minimal Layer Time settings to impose limits where needed.

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The Role of Cooling Fans

Cooling strategies differ significantly based on the material type and desired part properties:

• High-Temperature Materials (for Strength): Part cooling fans are generally kept off. Strength relies on maximizing layer fusion, which requires keeping the previous layer hot. Cooling is managed indirectly by ensuring adequate Minimal Layer Time, allowing sufficient heat dissipation through ambient convection within the heated chamber. This slower, more controlled cooling promotes strong interlayer bonding.
• Low-Temperature Materials (PLA, PETG) or Draft Parts: Fans are often utilized to rapidly solidify the extruded plastic. This allows for printing finer details, steeper overhangs, and faster overall printing when maximum strength (especially Z-axis strength) is not the primary objective. Fan cooling is faster but generally less predictable than ambient cooling controlled by layer time.
• Specific Geometries (Bridges/Overhangs): Even with high-temp materials, minimal, targeted fan usage (dynamic fan control) might be necessary for severe overhangs or bridges to prevent sagging.

For detailed configuration of cooling parameters, including Minimal Layer Time and dynamic fan settings, refer to the Optimizing Layer Times & Cooling.

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