Three Tier Rack

Three Tier Rack

This is a 3-tier display stand.

NOTE: Some of the images in this post are of prototype parts and may differ slightly in detail, form or fit from the final versions.  The STL files posted here are the latest and greatest and I'm not presenting this as a Work-in-Progress.  This is a done deal and should produce an acceptable assembled item.

The outside diameters of the plates are 12", 10" and 8".  Tier spacing is approximately 4".  The plates are 7.5 mm thick with a raised rim.  

The entire project was printed on a 3D printer with a 220 mm bed.  Don't let the large plate sizes make you think that a huge printer is needed.  

My rack was built with 7 mm thick plates and the screw pockets are visible when viewed from the top.  I've revised the three plate STL files, adding 0.5 mm to the thickness.  I haven't printed any of those modified files but I expect they'll be OK.

The circular plates are each printed in four segments, aligned by pins and holes that are part of the models.  They are joined by M3 machine screws with flat washers and Nylock nuts.  There are recesses in the underside of the plate segments for installation of the screws and hexagonal pockets for the Nylock nuts.

The bottom and middle Columns (identical) are simple cylinders but are somewhat faceted. That's pretty visible, giving the impression of fluted columns though they're really not.

The center of the assembled rack conceals a 5 mm threaded rod that clamps all the sections together vertically.

The Top Column (the tapered one) has an internal hexagonal pocket for an M5 rod coupler.  The rod coupler is recessed into the bottom of the column to make a space to cover the hex nut and flat washer at the top of the top plate when assembled.

The rod coupler in the Top Column screws on the central threaded rod but the top assembly wasn't designed to support the entire weight of the assembled rack.  The Loop and Finial are glued and will probably fail if used to lift the whole thing.  On the other hand, the assembled plates are quite rigid and lifting it by the 8" plate works fine.

All the parts are fairly easy prints but in the aggregate it's a big project, using over a 1 kg spool of filament.  I admit there were a fair number of prototype part throw-aways but still, a lot of plastic and a lot of printer time.  I'd weigh it to determine the actual amount of filament required but the lady requesting and specifying this piece already has it loaded and I'm far too wise to touch it.

Printing/Assembly Notes:

EDIT 4/12/25: A couple of the images show a rod coupler against the top of the top plate.  That was a test assembly during development and does not reflect the correct order of assembly.  See the stacking order details below.

Print the plate segments with supports turned on.  This is necessary because of the screw pockets on the undersides.

Poke a 4 mm drill in each of the alignment holes in the edge of the plate segments (2 holes per segment; not the screw hole).  Sometimes they come out a little too tight.  

Assure alignment pins and holes fit together properly before final assembly.  Some filing or sanding of the pins may be needed.  Fit should be snug but loose enough that the segments can be pushed together and pulled apart by hand. A too-tight pin will break off if you have to dismantle a plate for any reason.

IMPORTANT - DO THIS!: For the four segments of each plate (all identical), print the first two, then rotate the model 90 degrees on the bed and slice again before printing the other two.  Keep track of each pair (I used temporary stick-on labels) and alternate them when assembling the plate.  This will cancel out any out of squareness between X and Y axes.  I learned the hard way that a very tiny squareness error makes the plate want to "cup" when the screws joining the segments are tightened. I've never seen an out of square issue on my printer but as slight as it is, it caused a dramatically cupped plate on the first go-around. It's easy to avoid if you do it this way.

Install the M3 Nylock nuts into their pockets before assembling the plate segments.  A screw may be needed to pull them in and it's more easily done a single piece at a time, before assembly.

I learned that the screws joining the segments don't have to be torqued hard.  Just snug them up so there's no slack. The Nylocks will prevent loosening.  The assembled plates are quite rigid.  Do not use glue between plate segments nor in the alignment pin holes.

I recommend Allen head machine screws for joining the plate sections.  The pockets were made with those screws and an Allen wrench in mind.  The angles that result from reaching into the screw pockets with a screwdriver will make Phillips head screws difficult.

A ball-end Allen wrench helps in assembly but isn't completely necessary.  The screw pockets are long enough that it can be done with a standard Allen wrench.

The loop at the top is made in two pieces (Half Ring X 2) glued together.  

Ditto the "ball" feature (Finial Half X 2) at the bottom of the loop.  It's in two sections that have to be glued, capturing the loop.  That assembly has a downward facing square peg that mates with the square pocket in the top of the tapered column.  Glue that securely but avoid lifting the entire piece by the loop.

In 20/20 hindsight, the loop and finial halves could have been combined into a single part and the two halves glued together - two pieces instead of four. If it's within your capability to combine the models, go for it. If not, the way I did it works.

Glue an M5 rod coupler in the hex pocket in the tapered Top Column; assure that it's bottomed in the pocket.

The bottom and middle columns are identical; the flanges are at the top, against the bottom of the plate above. No glue is used here; just stack everything on the 5 mm rod.

There's a 5 mm Nylock and flat washer at the bottom of the central threaded rod. There's a pocket for them in the bottom of the assembled 12" bottom plate.  

I had bits and pieces of 5 mm threaded rod available but none long enough for the entire piece.  I used a couple of extra M5 rod couplers (you can't buy them one at a time anyway) to make three little ones into one big one.  The columns hide them.

Install a 5 mm flat washer and hex nut on the top of the middle and top plates.  The columns cover them.

- - - - - - - - - - - - - - - 
Assembly order on the central M5 threaded rod, bottom to top...

(M5 rod couplers can be used where needed if central threaded rod is not a single piece)

- M5 Nylock nut
- M5 Flat washer
- Assembled 12" plate
- [no flat washer and hex nut here]
- Column section, flange up
- Assembled 10" plate
- M5 Flat washer
- M5 Hex nut (tighten)
- Column section, flange up
- Assembled 8" plate
- M5 Flat washer
- M5 Hex nut (tighten)
- Assembled top section (Top Column, two Finial Half, two Ring Half) with embedded M5 rod coupler

- - - - - - - - - - - - - - -

Print Orientation:

Plate segments: Flat side down, supports on
Columns (2): Flange side down
Top Column: Big end down, supports on
Finial Half (2): Semicircular hole down, supports maybe
- - - - - - - - - - - - - - -

Print Details:

PLA
0.4 mm nozzle
0.2 mm layers except Half Rings, Finial Halfs; 0.15 or 0.1 mm for those
16% infill
0.8 mm shells

Bill of Materials:

- Lots of filament

= = = = = = = = = =

- Printed Parts:

 - 8" Plate (4 each)
 - 10" Plate (4 each)
 - 12" Plate (4 each)
 - Column (2 each)
 - Finial Half (2 each)
 - Half Ring (2 each)
 - Top Column (1 each)
= = = = = = = = = =

- 1 each, M5 threaded rod, ~ 265 mm long (can be in sections; add rod couplers as needed)

- 1 each, M5 rod coupler

- 1 each, M5 Nylock nut

- 3 each, M5 Flat washer

- 2 each, M5 Hex nut

- 12 each, M3 X 12 mm Allen head machine screw

- 12 each, M3 Nylock nut

- 12 each M3 Flat washer

- Cyanoacrylate gel