Assembly tray (2)

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(1)

A faster procedure to glue and cut blocks of scintillators is to assemble them first into 50+cm assemblies, held by clips, and then put glue along the centers of the sections, and then cut them apart.

tray_new.stl
tray_new_cap.stl

(2)

Cut files (dxf):
cutfile_a
cutfile_b
cutfile_c
cutfile_d

(3)

Put a stripe of gel superglue next to each clamp. Cure for few minutes

(3)

Cut with on the Boss LS 3655 laser cutter, at 95% power (of 150W) at 10 mm/s

Outgassing outside

(4)

Start of the 48x50 cm panel.

We need a stiff, lightweight base: honeycomb core panel

How to cut carbon-fiber honeycomb panels

(5)

Tray for layer A. The prototype is 48x50 cm, and will be printed in sections, since the printer has a working area of 20x20 cm.


STL for layer a bottom left
STL for layer a bottom left
STL for layer a bottom left

(6)

The cross ridges hold the bottom bars in place. The fibers from upstream bars pass underneath. This is better than trying to hold the fibers down in the channels with tape, as I did in the previous prototype.

(7)

Bridges in red. They are 1/4 of the width, the tray sections (grey, green, yellow) are ~1/3 of the width (cuts at 16, 32 cm from the origin.

layer a bridge 6.0 cm
layer a bridge 12.5 cm
layer a bridge 5.5 cm

(8)

Scintillating bars are glued in bundles of 16, then laser-cut into blocks. 4 layers (A,B,C,D) × 6 blocks long × 12 blocks wide × 16 bars = 4600 channels for the 48×50cm prototype.

(9)

Beginning construction of layer A; The trays are mounted on a 1/8" honeycomb core panel. From the left 3, 6, 9, 12.5, 14, 5.5cm blocks. The even blocks are raised on bridges. The bridges for 12.5 and 5.5 are supported by mylar, which lays over the grooves where the fibers go.

(10)

Removing the '6' block shows the bridge. It is shorter than 6cm to allow the fibers from '3' to bend down into their groove.

Removing the bridge shows 2 fibers going into their groove:

(11)

Middle and right sections done, with small tweaks: ridges to keep blocks from sliding sideways increased from 0.3→0.6 mm. Added mising ridge at 3cm.
layera_botleft.stl
layera_midleft.stl
layera_topleft.stl
xxxx layera_botmid.stl
layera_midmid.stl
layera_topmid.stl
xxxx layera_botright.stl
layera_botright.stl
layera_topright.stl

WLS fiber connector

(12)

New connectors: there is no reason to maintain the triangular pattern in the connectors as I did before. The piece that joined the two in the previous prototypes was too weak and tended to split. Here I line up all fibers, spaced 2mm apart. The total width of the connector is 39mm (to fit at 40mm pitch), and the walls of the joiner are sturdier. The joiners stack on top of each other, with a height corresponding to the total height of a layer (11.9mm). You can see half-circular cutouts, so the stacks can be screwed down.

linker.stl
connector_v3.stl

(13)

I printed a few to see how the fibers might want to be routed. Here you see some A input conectors, some with wls fibers coming in, joiners B, some stacked. and C output conncetors, no clear fibers attached. The wls fibers pass through the open space on the top of the joiners, which makes the assemblies want to be tilted.
Top view.
Note that we want 6 of these assemblies, here 3 are shown.

(14)

For the next round, I will therefore tilt the assemblies, and also add open space below for the outgoing clear fibers.

Next, flip the tilt angle, so that the wls fibers come in along the bottom. This way you can assemble the scintillators, insert the wls fibers and connect them to the joiners. Later, you can connect the outgoing fiber connectors.

(15)

Tilted by 8°, for a ~5cm pitch between the six connector groups.

connector_angled.stl

(16)

If the connectors are tapered as shown, there is just enough space to route the 1mm fibers along the bottom. The gap there needs to be 3mm (once), 2mm (twice) and 1mm (twice). The last one needs no gap.

(17)

The layers are paired (AB, CD) and the pairs are spaced 5cm apart.

Even though the connectors and fibers now fit inside of 12mm, I cannot get my fingers in between layers A and B to connect output fibers (same for C,D).

Note: the y-scale is stretched by ×5

(18)

But if I flip A and C, maybe there is finger space to connect outgoing fibers to layers B and C, but likely not.
So during installation, one would mount AB first, and connect outgoing fibers on the two sides, next mount CD in a temporary position such that there is enough space to connect the outgoing fibers to surfaces C and D, and finally move CD into the final position close to AB.



(19)

Back one step: How to connect wls fibers to the tilted joiners? In the top drawing, you see the 1mm wls fiber needs to go from the far end of the scintillstor bar into the connector which inserts to the center of the joiner, which needs to be mounted to the board. The fibers are stiff, and come in groups of 16, so I can't' back off the connector in order to insert it into the joiner.

[A]
If I split the support board, and separate the parts so that I can connect the fibers, they get pulled out several mm. Then I have to slide them back together. But there are 6×16 fibers, and I can probably not slide all of them in at the same time.

[B]
So I leave the joiners loose until the fibers are inserted, and mount them onto the board later.

(20)
joiner_latch_0gap.stl
joiner_latch_1gap.stl
joiner_latch_2gap.stl
joiner_latch_3gap.stl

connector_tapered_in.stl
connector_tapered_out.stl
New versions: The bumps should click into dimples in the joiner to hold them in place. Also, no more stacking, and the connectors are tapered so that fibers can pass under and over. The joiners have different gaps on the bottom: 3,2,2,1,1,0 mm.

19 oct 21

(21)
joiner_latch_gap0b.stl
joiner_latch_gap1b.stl
joiner_latch_gap2b.stl
joiner_latch_gap3b.stl

connector_tapered_inb.stl
connector_tapered_outb.stl
Previous version was too tight. Shrunk the connectors by .1mm, and enlarged (half)holes on the joiner to 3.8mm (+6-32).
Here the assemblies are spaces by 4cm.

26 oct 21

(22) Start test assembly:
- cut 16 fibers to length (
see 13 here)
- epoxy fibers into connector
- print new polishing blocks
- polish the ends (see 14, 15 here)

polisher

(24) First block: remove the upstream connectors (this works only because the nylon screws bend).
(25) You have to pass the fibers (in order) underneath the bridges. This is tedious. In the process I discovered that 2 of the 16 fibers were 1.1mm, and the other 14 were 8.8-9.2mm diameter. The thicker fibers will not pass, and I had to cut them off.
(26) The connector is inserted into the joiner first, and then screwed down.

Note the 2 cut fibers.

(27)
This is how the assembly of one 16-fiber row of blocks goes:

A: 16 fibers for block 1 get routed under the bridges in the base plate and inserted into block 1. Screw down connector 1.

B: Fibers for block 3 get routed and inserted in block 3, connector 3 screwed down, over the fibers from 1.

C: Same for block 5. over the fibers from 1 and 3.






D:Place block 6. When fiting, put connector joiners 4 and 2 in place.

E: Place block 4. Fibers pass over the top of block 6.

F: Place block 2. Fibers go over 6 and 4.


(28)
Once the connectors snap in place, they are hard to loosen. I added a pair of holes, and made a spreader tool to facilitate easy loosening of the connectors.
connector tapered input with holes
connector tapered output with holes
(29)
I made a 80/20 frame, with clips to hold the 1/8" carbon fiber boards. I also printed H-channels to join the boards.
H-channel panel joiner
80/20 clip
6-32 tap cap. The connector joiners are screwed down on a 4×4cm grid of holes tapped in the carbon.
6-32 tap guide
(30)
2 rows of layer A finished. Fibers that pass over blocks 4 and 6 are held with mylar 1mm-high brackets.
(31)
The first third of the top cover of layer A. Various nubs hold down the blocks, slipping in between the fibers. The flange will be drilled to hold it down with 6-32 screws.

layeratop_left_bot.stl
layeratop_left_mid.stl
layeratop_left_top.stl
layeratop_mid_bot.stl
layeratop_mid_mid.stl
layeratop_mid_top.stl
layeratop_right_bot.stl
layeratop_right_mid.stl
layeratop_right_top.stl

(32)
Prepare for tray B. I made a parametrized version of the tray, so I can quickly make A, B, C and D.
        A   B   C   D
  -------------------
  dd1  30  30  30  60 
  dd2  90  90  90 120 
  dd3 180 180 150 210 
  dd4 305 305 240 340 
  dd5 445 445 375 500 
  dd6 500 500 500 500 
For now, we need the rgb parts:
b_right_bot.stl
b_right_mid.stl
b_right_top.stl
(33)
4 groups of 6 in place. Only the bottom two have fibers.
(34)
Top covers in place

(35)
Partial top: 3 covers held in place with a carbon fiber panel. The panel is not the full width, it was a left over piece. Needs to be replaced

Now layer A can be flipped over and layer B will be constructed on the other side.



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Hubert van Hecke
Last update June 2022