Slotted rails to store steel sheets underneath Original Prusa Enclosure

Introduction

This is an OpenSCAD script to generate slotted rails to hold steel print sheets underneath the Original Prusa Enclosure.  The rails mount to the underside of the enclosure, using existing tapped holes in the base.  The pattern of holes is not symmetric, so you will need to print one left rail and one right rail.

Two sets of rails are included as STLs.  One set should fit below an enclosure that sits on the standard feet - this set will hold three steel sheets (I have not tested these ‘standard’ rails - I suggest maybe printing a short section of one rail to check the fit underneath the enclosure). The second set fits below an enclosure that's sitting on 25mm extended feet (e.g. as made with my customisable taller feet model).

Customisations

Many customisations are possible, but the height and number of slots are probably the most useful.

The script includes a section where the physical parameters are defined (screw hole locations, plate dimensions).  These should not be altered.  This is followed by a section of configurable parameters, where you can customise the rails.  Lastly, there is a section where various parameters are computed - again, these should not be altered.

Use the 'extra_feet' parameter to specify how much extra space there is below your enclosure. Specify zero if your enclosure is on the standard feet, but if you have used, for example, my customisable taller feet to add a given amount, say 25mm, to the height of the feet, then use the same value for 'extra_feet' to make slotted rails that fill the space available under the enclosure.

Change the number of slots ('n_slots') to suit your chosen height, making sure that you leave enough material below the bottom slot to print cleanly.  Note that the slots are angled backwards very slightly (by 'tilt' degrees) to stop the build plates from working their way out of the slots if the enclosure shakes during printing - probably not necessary in practice.  You can change ‘slot_thickness’ and 'slot-gap' to fit fewer or more slots in.  Note that there is a ‘taper’ option in the ‘slot’ module that aims to make the slots slightly thicker at the front.  This may break if the slot dimensions are changed significantly (lazy coding, sorry!) - in this case you can turn it off by setting ‘slot_taper’ to false.

Use 'f_offset_y' to move the rails in or out under the enclosure.  This value specifies the distance between the front of the slot rail and the first screw tab: increase it to bring the rails further forward, decrease it to push them further under the enclosure.

Printing

The only practical way to print these rails is 'end-on'.  If printed 'slots down' the long thin lines will almost certainly lead to lifting, 'slots up' isn't possible without a LOT of support material because of the screw tabs, 'top face down' or 'bottom face down' would require impossible supports for the slots. So I designed the screw tabs to suit printing ‘end on’.

However, the rails are too long to print vertically, so they need to be tilted over in order to fit within the maximum build height of a Prusa MK3S+ (210mm).  The script therefore generates rails with the rear end angled by 'build_tilt' degrees, so that the rear end sits flat on the build plate for good adhesion.  The 'check_build_height' module will echo the total build height to the console - if you vary the length or width of the rails, change 'build_tilt' until the echoed value is as close as possible to (but strictly LESS than) 210mm.  For the parameters in the uploaded script, I have used a ‘build_tilt’ of 21.5 degrees, which leads to a build height of 209.8mm.

Use the ‘rails’ module to generate the two rails laid out as they should be mounted underneath the enclosure.  This is for visualisation.

Use the ‘STL’ module to generate the two rails in the orientation suitable for opening in PrusaSlicer and printing.

If you only wish to print one rail, you can open the STL with the pair of rails in PrusaSlicer, then use the ‘Split to objects’ option - you can then delete the object that you don't want to print.

I have had no problem printing these, provided I use a brim of 10mm, and organic supports under the lowest screw tab to act as a prop (see photos) - use the ‘Smart Fill’ option when painting supports onto the edge of the screw tab.  With this configuration the rails stick to the build plate rather well, as you can tell from the last photo.

I printed my rails with PETG, 0.30mm DRAFT settings.

CJH, 02MAY23