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How many times did your 3D printer’s nozzle bump into extruded parts during retraction? Whether it’s often or just some times, the Z hop feature could help. Cura Z hop is a slicer feature that, when enabled, raises the nozzle higher during retractions. In this way, the nozzle can safely travel from one extrusion place to another without damaging already built parts. The Z hop can reduce blobs and printing failures. Importance of Z-Hop in 3D Printing Z hop is a Cura feature (you may find it in other slicers too, including the PrusaSlicer) developed to ensure a smooth movement of the print head when it is not extruding. When enabled, the Z hop causes the print head to move up (or the bed to move down) so that the nozzle doesn’t bump into previously printed parts. In this way, you avoid scaring top solid layers, especially when you have a tall model (e.g., a tower feature). Considerations Before Using Z-Hop Just because this option can help you avoid scratching the object’s solid layers, it doesn’t mean that you have it automatically enabled. One of the Z hop’s downsides is that it adds a lot of extra movement to the Z-axis. Due to this, your machine will take longer to print the model. An enabled Z hop could also affect multi-material or multi-color printing. This happens because the firmware determines the number of printed layers by detecting the print head’s height. When the Z hop is enabled, the printer raises the print head automatically. As a result, the firmware can wrongly believe that the determined number of layers have already been printed, pausing the process and prompting you to switch filament. Sure, you can resume printing at this stage. Yet, if you opted for G-code assisted filament switch, the firmware has likely ordered the printer to retract as much filament as possible. If you wish to resume, chances are the next layer will be under-extruded, which comes with quality consequences. It could also happen that you change the filament at this stage. Thus, you’ll be printing a few layers with the wrong color or material. In a similar fashion, the firmware may also get confused by the ever-changing height of the nozzle and trigger an error instead of activating the M600 command to change the filament. How To Configure Z-Hop in Cura Z hop is a useful feature to use when printing tall objects. You may also want to use this setting regardless of the object’s size and shape if you must produce a flawless print. The settings below can help you get it right. Z Hop Height This value determines how far up the hot end will rise during non-extrusion movements. Cura sets the Z hop height to 0.2mm by default, which is also the default height of a layer printed with a 0.4mm nozzle. Hence, the printer will leave an empty space equivalent to a layer’s height between the nozzle and the last printed layer. Using the default setting works well for most purposes, but you might want to change this number in the following instances: When you’re setting a greater layer height for your print. In this case, the 0.2mm Z hop might be insufficient, leaving the nozzle in contact with the top layer. If you’re using melty materials that might ooze or drip, such as PETG. A higher Z hop in this case can prevent blobbing or stringing. While there is no option to disable Z hop in Cura, you can do so by setting the height (and all other parameters) to zero. Z Hop Speed Contrary to popular belief, the Z hop speed is not the travel speed of the arm, but the speed at which the nozzle will raise. By default, this speed is set to 5mm/second. You should increase this number if you’re printing with materials that might ooze or that are prone to stringing. If you have to change this setting, double the speed in the first instance, then fine-tune until you find the sweet spot for the material you’re working with. Note: There is a limit to the maximum Z hop speed you can set. On Cura/Ender 3, the max speed is 10mm/s. Simplify3D and PrusaSlicer allow for higher speeds up to 20mm/s and 30mm/s, respectively. Travel Speed Pretty self-explanatory, the travel speed is the speed at which the printer moves the arm during non-extrusion movements, when the Z hop is enabled. In Cura, the default value is 150mm/s. This speed is faster than the printing speed of most filaments, and it is set to be faster to speed up the entire printing process. The problem is that a too fast travel of the arm during non-extrusion movements could lead to stringing issues. You should lower this speed to the printing speed for your chosen material (e.g., 60mm/s for PLA, etc.) and, ideally, slightly lower than this if you don’t mind waiting a bit more for the printer to complete the entire printing process. Z Hop When Retracted In Cura, Z hop when retracted is disabled by default. When enabled, this setting moves the build plate down by a set value when a retraction is performed, allowing the head to move over the print without touching it. This setting’s main downside is that it increases print time, especially if the project involves many retractions. You can keep it disabled to fasten up the process when printing prototypes or other objects that don’t have to be highly accurate. If you need high accuracy and quality, enable this option. Z Hop Only Over Printed Parts Cura’s Z hop only over printed parts allows you to speed up the printing process while maintaining the quality of the print. Basically, the printer will only raise the arm if, during non-extrusion movements, it can’t avoid traveling over the part. When traveling over empty parts of the bed, the arm won’t be raised. As a rule of thumb, it is good practice to keep this option enabled. Wipe Nozzle Between Layers When working with oozy or stringy materials, another setting that you want to enable is called wipe nozzle between layers. This setting moves the hot end to an indicated location (you can only choose an X-axis parameter) and “park it” there. It is meant to allow you to wipe the nozzle’s tip with a cloth or brush to remove excess filament before resuming printing. As you can imagine, it adds a lot of extra time to the print. Z Hop After Extruder Switch This Cura setting is only useful if your printer uses multiple extruders. In this case, the nozzle will hop only after an extrusion switch is performed, preventing the extruders not in use from brushing over the printed model. Pros and Cons of Using Z Hop in 3D Printing https://www.youtube.com/watch?v=CZowfbkz0pw Knowing how to set the Z hop correctly doesn’t mean that you should really enable this option. Here are Z hop’s pros and cons. Pros Reduces blobs and other defects caused by the nozzle scraping over the printed surface Prevents the nozzle from knocking over a taller print Can solve oozing issues Cons Could cause more stringing if settings are incorrect Slows down the entire printing process Commonly Encountered Issues With Cura Z Hop Z hop is a useful feature in most cases, but it could run in some issues. Here’s how to solve them. Z Hop Not Working One of the most annoying issues is noticing that Z hop isn’t working even if the settings seem right. Despite what you might think, this issue is generally caused by human error. Enabling the Z hop only over printed parts option means that your hot end won’t hop up for most of the printing process. This function might also be disabled automatically if the combing mode is enabled. Speed Error As mentioned above, all slicers limit the Z hop speed, which is the speed at which the arm raises. In Cura, this limit is 10mm/s. Simplify3D and PrusaSlicer allow for higher limits, but you still can’t go over 30mm/s. If, due to some bug or internal error, you manage to set the speed higher than the limit, the slicer will signal an error. Extruder Jams If the height, speed, and travel speed are not properly set, the Z hop motion could jam the extruder. With a clog stuck inside, new filament might struggle to come out. In the best-case scenario, you’ll have to deal with under-extrusion. In the worst, you’ll have to take everything apart to unclog and clean the nozzle. Your print will likely be destroyed in both cases. Final Thoughts Cura Z hop is a setting that enables you to raise the nozzle during non-print movements so that it doesn’t scratch or damage the print. Enabling Z hop can reduce blobbing, scratching, and – sometimes – stringing. At the same time, it increases the total printing time. Ideally, you should use Z hop whenever your print must be perfectly accurate. Otherwise, you might want to disable it.