Bumbag customizable electronics enclosure system

Common placeable components are here, find other placeable components in this collection, or search for tag bumbagcomponent.

NOTE: The base enclosure is only compatible with the VC4 BOM V1 electronics enclosure (the version that has three side-mounted 50x15 cooling fans). It is not compatible with the new VC4 BOM V2 electronics enclosure with a single 120mm cooling fan in the lid, as this is 2.5mm taller and has different side panel mounting centres. I will publish V2-compatible base enclosure variants soon.

Important Documentation!

You can't just print this model - it's a user-configurable system. Please read this documentation carefully, particularly before asking questions.

Concept

The bumbag system allows you to use PrusaSlicer to arrange things like PCBs, power supplies, USB hubs and cable management just how you want it, then print an enclosure with all the mounting posts and other fixtures included. You can visualize how your layout will look and move things around easily. You don't need to know how to use CAD - it's all done in PrusaSlicer.

The bumbag system has been designed to extend the electronics enclosure attached to the rear panel of the RatRig V-Core 4 3D printer. This is often referred to as the “backpack” - and so the bumbag is an extension that typically goes beneath the backpack. Americans call this a fanny pack, but that sounds a bit odd to British people.

While the bumbag has been initially designed to integrate with the V-Core 4 backpack, the placeable components can be used with any enclosure with a 4mm thick base and 3mm thick walls. The original bumbag has an external height of 60mm which includes a 4mm thick lid, leaving 52mm between the base and lid. Placeable components will typically be designed to this specification, and wall cutouts are typically centred vertically to suit the 60mm external height. The outer width and height of the enclosure must be an even whole number of millimetres for alignment compatibility with placeable components.

Printables Models

This Printables model provides the enclosure shell that can extend the RatRig V-Core 4 electronics enclosure, and a few placeable components that are very specific to the V-Core 4. General-purpose common placeable components are here, find other placeable components in this collection, or search for tag bumbagcomponent.

Remixing and Sharing Layouts

If you want to share a particular layout, please do so as a 3mf PrusaSlicer project file that has not been merged*. This will allow others to tweak the layout for their needs. Single STL remixes of the bumbag enclosure are discouraged: this defeats the concept of being able to move things around. Please always include a link to this Printables model when you share your layout. [* see below]

Designing Placeable Components

There are some specific subtle requirements and challenges to designing placeable components that work properly. In time I plan to publish a guide for this. Until then, if you need a specific placeable component, I will consider designing it, or try to provide guidance on a case-by-case basis. Please message me, ideally by mentioning @tg73 in a message on the v-core-4-mods-discussion channel on the RatRig community discord.

Heatset Inserts

Where heatset inserts are required, the standard RatRig heatset insert hole profile is used, which suits standard RatRig heatset inserts with a M3 or M2.5 thread. The standard heatset insert sizes are:

• M3 x 4.6mm diameter x 4mm length
• M2.5 x 4.6mm diameter x 4mm length

M3 is used as standard unless a component requires a different size. For example, the holes on a Raspberry Pi are sized for M2.5.

The base requires 8 of M3 x 4.6D x 4L inserts (4 for the lid screws and 4 for attaching the original backpack side panel which is reused. All standard mounting posts require heatset inserts.

Getting Started

Download this Printables model, the common placeable parts model, and the this USB hub model. Paths starting enclosure/ come from this model, paths starting components/ come from the common placeable parts model.

This guide is written for PrusaSlicer 2.8.0. If you want to print with a different slicer, I recommend laying out your bumbag in PrusaSlicer, then exporting as a single STL, then print that STL in using the other slicer. Laying out a bumbag in another slicer might be possible, but this is not a supported or documented workflow.

A bumbag enclosure is designed to be printed as a single part. The V-Core 4 bumbag is 350mm wide. If you don't have access to a large enough printer, you can try designing the bumbag using a preset for a large printer (for example, a RatRig V-Core 4 400), exporting as a single STL, then cutting that STL up using your normal printer preset. You will have to work out how to glue the parts together after printing - there is no specific support for this in the design.

The basic steps are as follows:

• Start with an empty project in PrusaSlicer. Make sure you are using a printer preset that is large enough. The screenshots show a RatRig V-Core 4 500.
   
• First, let's add the bumbag base. Use Add (CTRL+I) and select enclosure/bumbag_130.3mf. The base model has two alignment guide parts, the long thin strips indicated:
  
  
  
  These are used to align certain placeable parts. The alignment guides are very thin, so they don't show up when sliced.
   
• Now we'll add a USB hub. Use Add (CTRL+I) and select components/device/waveshare_usb3_2-gen1-hub-2in-4out.3mf. The placeable component for the USB hub, along with the required mounting posts, is added:
  
  
   
• The objects list now looks like this:
  
  
  
  The USB hub object has several parts:
  
  
  • 4 post parts. These are “normal” parts. Each one is a mounting post.
     
  • 4 cut parts. These are negative parts. Each one cuts a cylinder into the base of the enclosure to make space for a heatset insert and M3 screw.
     
  • The usb3… part. This is a modifier part, but does not have any special settings. This is the 3d model of the USB hub itself which is useful for alignment and considering cable routing. As a “does nothing” modifier part, this will disappear when sliced.
     
• Let's move the USB hub somewhere else:
  
  
  • Click on an empty area of the build plate (or press ESC) so that no object is selected:
    
    
     
  • Important: if you simply click on the USB hub, you will select only the usb3… modifier part, which will look like this (other objects go dark grey):
    
    
    
    Instead, you must SHIFT+CLICK so that the whole object is select, which will look like this:
    
    
     
  • Important: placeable parts that need to be aligned to the enclosure edges are designed to align when moved on a 1mm grid. Always use the cursor (arrow) keys to move placeable parts. Don't click and drag with the mouse.
     
  • Once the USB hub is selected, make sure the mouse cursor is somewhere over the main view of the model (inside the red box below). If the mouse cursor is over the object list, the cursor keys will not work as expected.
    
    
     
  • Now use the cursor (arrow) keys to move the USB hub, and PageUp/PageDown to rotate it. The cursor keys will move the object by 10mm, SHIFT+cursor key will move the object 1mm. The USB hub should move along with its posts. If the posts don't move, then you have not selected the whole object (see above).
    
    Move the USB hub to roughly this position, in the orientation shown:
    
    
     
• The USB hub is next to the high voltage AC section of the main backpack. The AC section should be isolated from the low voltage DC section. There is a partition object for this purpose. Let's add it.
  
  
  •  Use Add (CTRL+I) and select enclosure/ac_partition.3mf.
    
    
    
    Placeable parts that are intended to be aligned with the edges of the base are carefully designed to be automatically aligned to a whole 1mm grid when added., and where applicable to remain aligned to the grid when rotated by any multiple of 90 degrees. You should see whole numbers for the X and Y position below the object list:
    
    
    
    If you are trying to align a part and it won't align perfectly, if the unaligned X or Y coordinate is not a whole number, try editing the number and rounding it to the nearest whole number. This can also help if the placeable part gets moved off the 1mm grid by dragging with the mouse.
    
    Note: this only applies to parts designed to be aligned to the edges of the enclosure - things like vent holes, panel-mounted connectors and so on. 
     
  • Use the cursor keys to move the ac_partition object into place. You should only need to use the up/down keys as the partition object should already be correctly aligned in the left/right direction. Use SHIFT+cursor key to move by 1mm when required. Do not use the mouse to click and drag the object.
    
    The ac_partition object has an alignment strip (red arrow) just like the base object (pink arrow). When correctly aligned, the ac_partition alignment strip should perfectly overlap the base alignment strip. Here they are not aligned correctly:
    
    
    
    And here they are aligned correctly:
    
    
     
• Let's see what the sliced/printed layout will look like.
  
  
  • Press CTRL+A to select all objects:
    
    
     
  • Now right click on any selected part (either in the main view or the object list) and then click Merge:
    
    
     
  • The object list will be “flattened” so that there is only one root object with lots of parts:
    
    
     
  • Then click Slice now or switch to the Preview view to see the result:
    
    
     
  • When your layout is in the merged state, you can right-click on the root Merged object in the object list and select Export as STL/OBJ… to save the printable result as a single STL. For example, you can then load this STL into a different slicer.
    
    As noted above, please do not share models as single merged STLs: instead, if you want to publish your layout, publish it as a 3mf PrusaSlicer project in the unmerged state. Then other users can tweak the layout if they need to. Please always include a link to this Printables model when you share.
     
  • Important: Once you have inspected the sliced result, you must go back to the 3D editor view, then press CTRL+Z (undo) so that object list shows the original objects again:
    
    
     
  • Important: always save your layout in the unmerged state. Only merge when you need to slice the layout, then remember to immediately undo. If you want to share your layout, always share it in the unmerged state. If you save in the merged state, it will be impossible to edit the layout again.
     
• Now let's add a cutout to the AC partition so it's easy to run wires to the DC unput of the USB hub from the existing power supply (PSU). Note, this particular USB hub has terminals for 7-36V DC.
  
  
  • Go back to the 3D editor view and make sure you've returned to the unmerged state (see above).
     
  • We can't easily decide where to put the cutout because we don't know exactly where the existing components in the main backpack are positioned. Luckily, there is a component just for this. Use Add (CTRL+I) and select enclosure/vc4_electronics_enclosure_v1.3mf.
    
    For some unknown reason, this component may not be properly centered on the 1mm grid when inserted by PrusaSlicer. Correct it if needed (this is covered above).
     
  • Use the cursor keys to align the alignment strip of the the inserted component with the existing bumbag base:
    
    Not aligned:
    
    
    Correctly aligned:
    
     
  • Now we can see where the components in the backpack are. We will add a cutout in the area indicated (red line):
    
    
     
  • To add the cutout, we will simply use PrusaSlicer's built-in box-shaped negative part. Right-click on a solid part of the bumbag base (eg, red arrow), then select Add negative volume, then Box.
    
    
    
    PrusaSlicer adds the negative volume cube (seen on the right) and selects it:
    
    
    
    It shows up as Generic-Box in the object list:
    
    
     
  • An 8x8 mm hole should be big enough. Make sure only the negative volume box is selected. Change the size of the box in the Part manipulation section under the object list so it looks like this:
    
    
     
  • Make sure the mouse cursor is over the main object view, then press M or select the Move widget, then move the negative volume box into position so that it will cut a hole in the AC partition. Be sure to avoid the existing components inside the backpack.
    
    
    
    Press ESC (escape) or click a blank area of the built plate to deselect, then it will look like this:
    
    
     
  • Repeat the merge procedure described earlier and check the sliced result:
    
    
    
    Important: remember to unmerge immediately after checking the sliced result.
     
• Now we can add a cable tie mount so the DC power wires to the USB hub can be routed neatly. Use Add (CTRL+I) and select components/cable_management/cable_tie_mount_10.stl. Use the cursor keys to move the cable tie mount into place. If you want more than one cable tie mount, use Add instance (+ key) when the mount is selected. The mount is a single-part model so you don't need to SHIFT-click to select it, a simple click is ok. There are other useful cable management parts in the cable_management folder.
  
  
   
• Finally, lets add some vent holes. Use Add (CTRL+I) and select components/ventilation/vent_hex_24.3mf. The vent part has a small triangle which is used to align to the outside of the enclosure (red arrow):
  
  
   
• We will add some vent holes to the left of the USB hub.
  
  •  Use Page Up (PgUp) and Page Down (PgDown) to rotate the vent part so that the alignment triangle is on the left. Move the vent into place to the left of the USB hub. The alignment triangle must be outside the bumbag base, and the point of the triangle should perfectly align with the edge:
    
    Rough position:
    
    
    
    Not quite aligned:
    
    
    
    Perfectly aligned:
    
    
     
  • Use Add instance (+ key) to add another section of vent. The vent part is designed to be easy to repeat, with a 2mm gap between the parts. Using the cursor keys, move the second vent part into place next to the first instance with the correct gap. It's easy to see when you've got the correct spacing.
    
    
    
    Add third instance and position it:
    
    
     
  • It would look neater to have a column of three vent holes at both ends of the vent. The vent part is designed to make this easy: the columns of vent holes are joined by thin lines which don't affect the sliced result, so it's easy to select one column of holes. However, first we need to make each instance be a separate object so that we can delete a column of holes from only one of them.
    
    Right click on the root vent_hex_24 item in the object list, then select Set as a Separated Objects:
    
    
     
  • Then (not SHIFT) click to select the outer column part with only two holes:
    
    
     
  • Then use Delete (DEL key) to delete that column:
    
    
     
  • To make it easy to move the whole vent as one object rather then three separate objects, SHIFT-click to select all the sections, then right click on one of the selected vent_hex_24 objects in the object list, and select Merge:
    
    
    
    All the parts of the three vent objects are now grouped together under a new object called Merged:
    
    
     
  • Double-click on the Merged object name in the object list and rename it to my_big_vent:
    
    
     
  • Use Add instance (+ key) to create another instance of the my_big_vent object, then place it on the opposite side of the bumbag. Note that PrusaSlicer's merge operation might slightly mess with the placeable part. This shows up as irregular clipping. However, the sliced result should still be correct:
    
    
    
    The sliced result:
    
    
     
• Summary
  
  This Getting Started guide has hopefully covered most, if not all, the key concepts involved in laying out a bumbag. Adapt these techniques as needed. 

Bumbag Sizes

The maximum size depends on the printer size to which the bumbag will be fitted:

• V-Core 4 300: 130mm
• V-Core 4 400: 230mm
• V-Core 4 500: 330mm
   
• For a side-mounted bumbag, the maximum is 100mm, and a different round cutout to clear a mounting bolt on the rear panel is required. You can use a negative volume cylinder for this.
   
• For a top-mounted bumbag, the maximum is 190mm.

License

The following files which are remixed from RatRig printed parts and/or published CAD designs, and are licensed under a Creative Commons (4.0 International License) Attribution—Noncommercial—Share Alike license:

• enclosure/vc4_electronics_enclosure_v1.3mf
• enclosure/vc4_reused_panel_from_electronics_enclosure_v1.3mf

Updates