SLQ Wiki engagement:grumpus:workshops:hugesigns

Huge Signs - Construction Techniques

anonymous@undisclosed.example.com (Anonymous) — Tue, 08 Jun 2021 18:20:47 +0000

Huge Signs - Construction Techniques

In keeping with the style and ethos of the Grumpus Project, these signs will be constructed mainly from cardboard (conductive cardboard being in short supply, the lights and controls will be various pieces of electronics).

In order to build a stable and strong frame for the 2 x 3m signs, new techniques were developed to make use of cardboard in this activity.

This documentation by Peter Musk, 2021.

Frame Building

In order to make construction sturdy and joining easy, some arbitrary specifications were adopted for the frame construction:

main members to be 100mm external dimension square section, with 90mm internal sides all round
material to be 6mm double ply cardboard (available in 1200 x 2400 sheets)
high temperature hot melt glue to be used in assembly and construction
folds are facilitated by crushing the cardboard along the inside of the bend - use a round tool, about 5mm diameter for best results (do not cut the surface layer if possible, to maintain strength).

Take note that the external fold of the 100mm beams needs to be at the back of the structure, giving a flat face for the sign to be placed on. This also avoids having too many layers of cardboard to cut through to make the joins described below (and pushing the joins out of square).

100mm beam fabrication

These elements will be joined using 90mm square section cardboard beams, and it soon became obvious that ensuring a consistent internal dimension of 90mm required special attention to measurements and fabrication of the 100mm main elements:

Mark out a series of lines, 30, 110, 100, 100, 100mm as shown

The measurements shown were found to work best for 6mm cardboard. The 110 mm side allows for the external fold of the final wall, as shown below

Glue is applied to the 30mm section, and the square tube rolled on to the line.

90mm internal connector fabrication

The internal connectors must have all sides at 90mm, which meant that the glued fold must be inside the section, as shown below:

Mark out lines at 30, 80, 90, 90, 90mm as shown

These measurements allowed for the inner fold to make a 90mm face, as shown below:

One dimensional, straight joins

100mm beams are easily joined by inserting a length of 90mm beam inside the cavity. A tight fit is best, and judicious crushing can get a slightly overlarge segment to push inside the 100mm beam, if necessary.

Glue one end in first, and apply glue to the exposed 90mm part, then push the other 100mm beam on.

Two dimensional, T-joints

These joins will be used where needed to support the 2m length of the frame top, with joins at top and bottom. Avoid making a t-join where 100mm beams are joined together by the means above.

A 90mm square hole is cut into the cross beam (the resulting flaps shown are best removed), and a straight 90mm joiner glued into the end of another beam. Apply glue to the free end of the 90mm beam, and push into the hole - glue will adhere to the top and bottom inner face of the perpendicular beam.

Three dimensional, corner joints

The sign frames will be deep enough to allow sandbagging for stability, and this means the corners will need to be connected in three directions. Rather than cut into a corner already weakened by the technique described above, a design for a 3-way 90mm joiner was developed, to be folded from a template (full sized design files available below).

Mountain folds (fold up from the page) need to be scored on the back of the cardboard. This includes the folds along the inner edge of each tab.

Valley folds (fold down into the page) are scored on the front of the cardboard.

Folding the 3-way joiner

Start by transferring the template to your material (this is a 1/3 size example)

Fold the tabs down first all around.

Do the internal folds, scoring along the back as required.

Begin at the top, pressing firmly as you glue to keep the external dimensions to 90mm. Keep the outermost section (3.1.2) until last - do not it glue yet.

Keep moving down the strip, gluing carefully as you go.

Almost there.

Hopefully yours is not this messy.

Design files

A4 and full sized templates (SVG format) are here: template.zip

Huge Sign 1 - Welcome to the Wonder

anonymous@undisclosed.example.com (Anonymous) — Wed, 02 Jun 2021 13:09:18 +0000

Huge Sign 1 - Welcome to the Wonder

As defined in the project brief, this sign was constructed using materials and techniques that could be readily available to anyone wanting to replicate the process.

The Text was cut from 30mm extruded polystyrene (EPS) insulation foam (available at reasonable cost from hardware suppliers in 1200 x 2400 sheets). This material is robust, very light, cheap, electrically non-conductive and easy to cut and shape. While we used a CNC with an oscillating knife to cut the text directly from a 2D design file, cutting using a hot wire device, or a sharp boxcutter is also possible (letter templates can be printed and used to guide hand-cutting if necessary). Note that high temperature hot glue will melt this material (though low temperature glue guns work fine).
The Font chosen was devised to be readable by folks with dyslexia (and remains easily readable by those without). It can be downloaded from this site: https://www.dyslexiefont.com/en/typeface/
The Size was defined by the text used and the size of the letters as well as the material available. Using simple ratios of the material dimensions will reduce waste and save time. This sign will be 3600 x 2000mm.
The Materials used for the body of the sign were 6.7mm thick B/C double layer cardboard sheets (for beams and bracing) and 3mm single face corrugated sheet, available as a roll (for covering surfaces with a textured treatment). Some joiners were made from 3mm single layer pallet pads to test ease of fit during construction.
The Lights were strings of low voltage fairy lights (warm white) widely available from hardware outlets. Cutting and joining will be described, and can be done without the need for a licensed electrician since they operate at UltraLowVoltage (check your local laws about this - it varies with jurisdiction)
The Power comes from 18V lithium power tool batteries, with a inverter attachment. This makes the sign independent from 240V GPOs, and makes it easily deployable.

Constructing the Frame

Structural beams were made from 6.7mm B/C double layer sheets, using the techniques described in the page Huge Signs - Construction Techniques

Sheets were cut to 420mm wide lengths, with the corrugations running across the short side to maximise strength of the finished beam. Scoring was done using the measurements described previously, and the seams glued using hot glue. By using a bench and clamps, it was possible to glue an entire length in one pass, as shown below.

Beams were cut an joined as described to create the 3.5m x 2m frame required, with 3-way connectors at each corner. Clamping was used as needed to ensure a good join when supporting uprights were put in place.

When the frame had been securely glued together, it was placed face up across a couple of benches, adjusted to be square and the facing sheets were glued in place. These flat surfaces braced the frame, as well as providing a mounting surface for the corrugated finish and the letters.

Finally, a skin of corrugated sheet was glued to the flat surface using a quick-drying PVA glue. This was not an optimum adhesive because it is very viscous, and it proved difficult to get an even coating, even using improvised cardboard spreaders. In future the glue could be diluted first to make spreading easier, or a method of spray application used.

Erecting the finished sign

The front face of the frame was transported to the installation site before adding the back, since it was becoming too large to navigate the corridors. Unfortunately, corridor corners still proved an obstacle, and the vertical beams had to be cut through to allow the sign to bend in the middle for transport. Once in place, the cuts were repaired using cardboard braces, as shown.

Temporary hangers were made from foam offcuts with embedded zip-ties, and glued into the frame so that it could be suspended from a convenient overhead cable tray (and so prevent it falling on workers as the letters were added). The sides were also added to help stabilise the structure.

Mick's comments

Probably need to finish the frame and sheet the ends to give it some rigidity before sheeting the front
Height could be limited to length of a sheet so we don't have to patch top

Velcro applied to keep back flap closed for hidden access
If the height is limited to sheet size beam frame could be pre- constructed in 3 main components for quick installation

We had to make more beams to finish the sign and we made / conceptualised a few jigs to make building these easier and more true.

First we used the CNC and drag knife to quickly and acutely cut the cardboard. This doesn't need a NC file. you just line your cardboard up with the edge of the spoill board at 0 on the X dimension and move the head to 450 on the Y dimension. Set the depth of the drag knife to the correct Z depth and manually jog the up and down the x axis.

The 2 jigs are a folding jig

and a glueing jig

These can be set up on the 2 sides of a bench and people can work in two person teams to know out a pile of these really quickly if you can keep the cut beams up to them. .

Lighting the Letters

A prototype letter was made up and lit with different offsets - an offset of 25mm was decided to look the best.

Letters were cut from the 30mm EPS foam, and holes drilled around the back circumference at even intervals . The LED string lights have unidirectional bulbs, and to achieve a backlit effect it will be necessary to attach the bulbs to the letters in a way that directs the light towards the surface of the sign.

Initially, inserts were 3D printed to control the orientation of the bulbs, and each bulb pushed in before mounting the whole system into the holes. After some time this method was abandoned as being too time consuming, and a bulb with wires pushed directly into each hole - the foam was found to be spongy enough to grip the bulb in place without the mount..

Strings were pushed into the holes, one bulb at a time.

Separating the letters

Since these strings operate at a very low (and therefore safe working) voltage of 31V, we decided to cut the strings between each letter. So that the wires could be joined again accurately after mounting, the wires were individually marked using different coloured paint pens:

Skinning the letters

After the bulbs had been fixed in place, each letter was skinned with corrugated sheet material (do the front first). The side banding was 40mm wide - giving a bit of overlap that helped to hide any loose wiring. This material was glued on to the foam using a low temperature hot glue gun (high temp will melt the foam, and masking tape can be applied to the foam surface before gluing to prevent this - a time consuming process).

Mounting the letters using stand-offs

The aim was to achieve the effect of back-lighting each letter, and since the bulbs were focussed downwards, each letter needed to be mounted on the wall with a stand-off. Strips of foam were prepared at 25x30mm using a hot wire cutter, and glued as required using the low-temperature hot glue. Each letter had more than one stand-off, arranged for best support.

To fix these letters to the face of the sign, strips of corrugated cardboard were prepared, and the approximate location of the stand-offs marked for each letter (the corrugated strips were reversed so that the ripples interleaved, and glued with the corrugations down, giving a flat surface to take the stand-off).

The small hole at the bottom is for the wiring to be threaded through to the back of the sign.

Wiring

The wiring harness logic is to cut strands of LED fairylights, making note of the colours and the sequence, then solder extension leads (in this case cat5 cable) to connect the letters. Each letter has two extensions - with 4 wires. The wiring from the letters to the Cat5 is:

Letter harness	Cat5 colour
Blue paint	blue
White Paint	blue-white
black (no mark)	Brown
tape (or light blue)	brown-white

Connecting the LEDs to Cat5 cables

The lighting behind the letters was joined together by soldering the colour coded wires from the LEDs to the assigned colours of the Cat5 inner wires. The exposed core of the wires was bent to form hooks to join the 2 ends together before adding solders to solidify the joints.

Insulating the solder joints

Hot glue and masking tape were used to insulate the connections as a quick and simple method to keep the exposed joints from touching each other, resulting in a short circuit and also from being touched, and electrocute someone. The method: - Lay down a piece of masking tape, sticky side up on a flat surface - Put the soldered joints on top of the masking tape, hold them down with the sticky side of the tape. Keep the exposed joints separate from each other as much as possible - Apply hot glue onto the joints, keeping the joints separate as the glue starts to dry. Make sure to cover a bit of the sleeve of the wires with hot glue to prevent any exposed connection - Wrap the masking tape onto itself and cover the joints.

Stabilising the Cat5 wires

Once the Cat5 cable being used to link the letters was attached, it was soon found that the extra mass pulled the strings of LEDs out of the foam when they were stood upright. This was addressed by hot-gluing the sign end of the cable to the back of each letter (this was done for both the incoming and outgoing cable)

Labelling is Essential!

The ends of the Cat5 extensions were labelled as shown to prevent confusion when they were connected at the back of the sign. The fundamental idea was to maintain the linear sequence of the wiring as the Cat5 was inserted between letters. The colour coding described above meant that the integrity of the circuit could be maintained even though the actual function of each wire remained obscure.

Letters were similarly labelled to avoid confusion that might arise due to having more than one example of each letter in the sign (there were 3 E's, for example)

Connecting the letters

The Cat5 cables were joined using press connectors so that they won’t have to be soldered together. (Note that these connectors are cheap, and widely used in telecommunications, but only work with solid core wire (braided wires will not hold). The exposed ends of the cables were bent to form a small hook as a backup measure in case the wires want to slide out from the connectors.

Behind the sign, excess cable was looped and tied up for safety and neatness.

Mounting the Letters

Some calculations were done to determine the kerning and margins for each line of text, and some appropriate jigs prepared to make this easier. Having stand alone jigs made attaching the letters much easier, since both hands were needed to hold the letter in place while the glue set.

Here you see the cardboard jigs used to keep even spacing between the lines of text.

Finished View

You can see a difference between the light effect of the top line and the bottom line of text - this was because the small (top) letters had a 60mm stand off, and the lower line (large letters) used 90mm standoffs

Design Files

The text used is shown here:

and here are the design files used:

giant_sign.zip