Duplication Array and Z-Stacking

Duplication Array Tool

Parts can be duplicated in the X, Y, and Z directions using the Array Duplication tool.

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1. Select the model you want to duplicate

2. Select the Array Duplication Tool on the left toolbar. The layout menu will pop up but it will be greyed out unless you select a model

3. Use the + button to increase the model count in each direction and adjust the spacing as needed. Use the "Alternate Flip" switch if you'd like for the models to alternate in direction when duplicating

4. Click duplicate to finalize the process

 

Tips:

  • Generate supports on your model before duplicating it. The tool will duplicate the model and its support. This is much faster than having your computer try to generate support for each model individually in the array.
  • Once you select a model, you will be able to change the following parameters for the X, Y, and Z-Axes:
    • Count - entails the number of parts
    • Spacing - entails the spacing between the two models' adjacent edges (bounding-box based) in millimeters. It is recommended you leave at least 10mm of spacing.
    • Be sure to press Duplicate to apply the changes! 
  • To maximize use of the build area, position the model in the front left corner of the build area before duplicating.
    • Move the part with the grab handles (the yellow square that appears when the model is selected) past the build area on both the front and left sides. It will snap to the bounds of the area. Then duplicate as described above. Afterwards, select all the models and position them in the center again

Z-Stacking

Stacking the parts in the vertical direction (Z-axis) provides maximum utilization of the build envelop on the NXE/NXD and XiP. The stacked parts are connected to each other using supports. There are a few further considerations to make when duplicating parts to stack in the z-axis.

The workflow is as follows:

  1. Import part
  2. Select a proper orientation and location on the build plate
  3. Select Array Duplication, click on the part and increase the Count to the number of parts desired in the stack. 
  4. Select Spacing (in mm)
  5. Click Duplicate
  6. Select the stack and click Auto-generate support
  7. Add cone supports to the base of the stack

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Duplicating parts so that they are z-stacking requires a few more considerations to make than duplicating in any other axis.

 

Slenderness ratio

The slenderness ratio of the stacked parts dictates the number of parts that can fit in a particular stack. NexaX calculates the slenderness ratio of the tower of stacked parts and limits the overall height of the stack accordingly. It will automatically stop adding parts in the stack once the critical slenderness ratio is reached. 

If the stacked parts have a significantly lesser lateral dimension (width) in comparison with the height of the stack, the whole tower can sway or bend during printing. The lesser width results in a smaller surface area to generate the base supports. 

In some cases, the stack can also collapse inside the resin vat due to a lack of balance in the stack. 

 

Support Strategy

Support strength will be automatically adjusted to be “High Strength” when parts are stacked in z-direction. The base of the stacked parts must be supported with cone supports to ensure proper adhesion to the build plate. The density of the support structure in between the parts in the stack depends on the resin used. 

 

Part Orientation

The parts need to be oriented in a way that allows the maximum area to put supports on. Proper part orientation can provide a well-supported base as well as the ability to create a strong support structure in between the parts within the stack

Weakly supported parts can separate off the stack and crumble inside the VAT during printing.

 

Spacing

A minimum of 1mm of spacing should separate the parts within a stack. This spacing depends on part size and geometry. Bigger parts with complex geometries will need 2-3mm spacing. Higher part spacing makes part separation easy during post-processing. But smaller part spacing allows for more parts to be stacked inside the printer.


If the part spacing is critically low between 2 stacked parts, there is a risk of both the parts getting cured into each other.   

 

Print Settings

The printing speed should be slowed down while printing Z stacked parts. High peel and lift speeds could cause separation of the part or part layers from the stack and cause delamination. Also high retract speeds cause vibrations which can also create interlayer delamination within the stack, resulting in weakening the stack. 

Increasing the wait times prevents the build from overheating, especially in long (>10 hours) prints. 

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