### Dual Extrusion with BVOH

#### Note

This article does not replace the use of manual or full training!
Brief description

This article explains how to print with the water-soluble material BVOH as support material. In particular, the adhesion between the print material and the support material will be improved by applying the points listed and therefore significantly increase the success rate for dual extrusion prints.

Filament Handling

Soluble support materials like BVOH have a high moisture uptake. If the moisture content is too high, the material behaves differently during print.

Store Filament in a dry environment. It is strongly recommended to use the filament directly out of the box or stored in a "keep dry environment", for example, a dry cabinet like the BigRep SHIELD.

BVOH can be used safely for about one day after unpacking before the processability might underlay some changes due to moisture uptake. There will be a filament housing for the BigRep ONE coming soon. The BigRep PRO already consists of a filament keep dry system.

You get the best results when printing BVOH in combination with PLX and PA666, but by conducting the manual points also for other combinations, the success rate will increase. If you want to combine it with other material, please contact us for further information. A table for the compatibility of materials and support materials will be available soon.

Print Preparations

Put the filament on the filament holder. Calibration is crucial for the success of dual print and good printing quality.

Start with the bed levelling and calibrate the flowrate as well as the z height precisely. Most importantly for dual extrusion is the x-y-calibration. If you print two lines next to each other with different extruders, the x-y-calbiration ensures that they are exactly next to each other, that they meet but do not overlap.

Settings in Blade

The latest Blade Version already includes improved dual extrusion settings but still, some settings need to be adapted manually (the manual steps will be eliminated with one of the upcoming Blade Releases). The following procedure requires either 1 mm nozzles with a 0.6 mm layer height or 0.6 mm nozzles with a 0.3 mm layer height.

To make adjustments for dual extrusion, you need to make all parts of the menu visible. Click on 'Custom' in the print settings. Click on the three lines next to the search field and select 'All'. Note that there will show up a lot of settings. Do not change any settings unless you are sure about its effects on printing processes. If you are looking for a specific setting within the wide selection, you can always use the search field.

Extruder selection

1. Click on the extruder menu on top of the window, select the tab with the correct extruder and enable the extruder. The extruder is enabled when there is a checkmark in the box next to 'Enabled'. On top of the tab, it shows the name of the extruder when it is enabled.

   Select BVOH as Material for the support extruder (in this case T1) and your main material (preferably PLX or PA666) for the wall extruder (T0). Make sure you selected the correct nozzle size and both extruders have the same nozzles.

2. Make sure the extruder for which you selected BVOH is also selected as support extruder (in this case T1). Everything else should be printed with the other extruder.

Note that for Studio.2 (aka G2) the part has to be assigned to T1 whereas T0 has to be the support extruder!
Speed settings

1. Go to 'Speed' Menu and adjust the speed settings for the support as following:

   | 1 mm nozzle 0.6 mm layer height | 0.6 mm nozzle 0.3 mm layer height
   --- | --- | ---
   Support speed |  |

Temperature settings

1. The printing temperature for BVOH should be 200° C. Make sure you selected the correct tab (T0 or T1) and find the temperature within 'Material'.

2. Check the 'Cooling' settings for the BVOH extruder. The fan speed should be on 0, or you remove the checkmark for 'Enable Print Cooling'.

3. Go back to 'Support Menu' and make sure the settings for the fan speed of both extruders are correct. The fan speed override must be enabled (set a checkmark). The supported skin fan speed> should be 0.0 to ensure a good interface strength.

   The setting for the supported skin fan speed is absolutely crucial for a successful dual extrusion print!

   To switch between both extruder settings, click on the tabs on top.

Support settings

1. There are two approaches for the support settings. Either you chose settings that ensure print success or you chose settings that enable fast printing and dissolving of the support structure. Adapt the settings in the support menu.

   - Printing with Triangles as support pattern with a support density of 30% delivers a higher success rate for a high variation of geometries. This support pattern has higher stability. Though, the print, as well as the dissolving of the support structure, will take longer.

   - A faster way of printing BVOH is with the Zigzag pattern for support with a density of 15%, which is the default setting in Blade at the moment. These settings will reduce printing time and time for dissolving support structures but are not suitable for all print objects.

2. Adapt the support distance in x, y, and z. Go to the 'Support' Menu.

   - Set 'Support Top Distance' and 'Support Bottom Distance' to 0.

   - If you work with a 1 mm nozzle, set 'Support X/Y Distance' to 0.5 to enable good support. Set the 'Minimum X/Y Support Distance' to 0.2 mm. You can use default settings with a 0.6 mm nozzle.

3. You need to check and adjust the settings for the support interface if necessary. For a 0.6 mm nozzle, the Support Interface Pattern has to be Concentric. It is as well recommended when using a 1 mm nozzle. Set the Support Interface Density, Support Roof Density, and Support Floor Density to 95%.

Dual Extrusion settings

1. Set the Nozzle Switch Retraction Distance to 16 mm.

Troubleshoot: Clogging of support extruder

1. If BVOH is clogging, adapt the retraction count for the support extruder. Type retraction count into the search field or go to the 'Travel' Menu. Set the Maximum Retraction Count to 1 and the Minimum Extrusion Distance Window to 5.