Panel (homebrew)

The panel, front panel or faceplate is where most or all of the controls and displays are mounted. Usually it is the primary user interface for patching, control and operating besides actually playing notes.

Aesthetics
Fabricating attractive front panels for a synthesizer can be a real challenge. Great care should go into creating an attractive synthesizer. The quality of work put into a guitar build, chrome fittings, pearl inlays, exotic woods all help inspire the musician and so it should be with the synthesizer. The design of a good-looking system requires much time spent mentally going over the various relationships of the modules and how the instrument will be used.

Layout
Having elements too close together can introduce noise and crosstalk, spaciousness helps towards reducing unwanted problems. Choose between having jacks easier to read placed near their associated controls, or below where patch cables are then easier to keep out of the way.

Design the panel so that behind the panel the potentiometer and jack bodies have enough clearance from each other and that in front both the controls and the users fingers have enough room to operate. Also check that any parts close to an edge won't interfere with mounting the panel into its enclosure. Check the angle of rotation of the pot will match the scale going to be marked on the panel. Components laid out on a grid can use a half grid distance from their edge on adjacent panels.

Modular synthesizer panels
With a modular synthesizer module the front panel is also a structural element. Except for the power supply and power rails, the rest of the synth module internals are supported by the panel. Panels are usually made of thicker aluminum or have flanges to give extra stiffness, for example to withstand the forces of plugs being inserted and removed from the jacks. The PCB when attached parallel to the panel can be done by mounting pillars or via the pots and jacks soldered to the PCB, but check how this might strain the the solder joints. When attached perpendicularly the PCB is held in place usually with a stooge bracket and fastened against the panel by the pots and jacks, or simple 4-40 steel mounting brackets.

Material
Usually aluminium; T3 or T6 6061 1.59 mm (0.0625") aluminium sheet. This is easy to machine and isn't too soft. Sometimes other materials are used such as some sheet metal, acrylic (aka Lucite or Perspex), glass-reinforced epoxy laminate (FR4 PCB), plywood or formica.

Drilling
Use a center punch to mark the panel for drilling. This will stop the drill bit from wandering. First drill a pilot hole, then use increasingly larger size drill bits until the correct hole diameter is reached. However it's more efficient to use a unibit aka step drill bit. Also check for correct mounting against the data sheet, e.g. hole dimensions and maximum panel thickness.

Labelling
Controls for particular functions can be grouped together by panel graphics. Individual controls labels can be with text and others with graphics. Scales can be indicated with tick marks. Signal routing can be indicated. Besides writing or painting directly on the panel by hand, there are a number of different methods to add labelling. Traffolyte laminate or Dymo embossed labels were once common. Adhesive labels tend to fall off after a while. Laser printed graphics are common now, as well as a variety of iron-on transfer methods.

Note that for some of the methods listed here panels can be given a protective coating of matte or gloss clear lacquer after labeling. Some materials are attacked by acrylic or vinyl coatings. Vinyl resists flaking and chipping better than acrylic.

Adhesive polyester
A4 polyester sheets that can be printed on a standard laser printer. Available in a range of different colours and also as sheets of peel-off labels. Very durable because the laser toner goes into the surface of the sheet.

CNC engraving
Requires a large investment to produce panel drilling approaching commercial quality. It's more efficient to use a drill press for making holes and use CNC for engraving. Engravings in anodised aluminum panel can be blackened with Birchwood Casey Aluminum Black or coloured using a Markal Lacquer-Stik.

Dry transfer lettering
Dry transfer lettering will adhere to smooth clean surfaces. The ink contains a pressure-sensitive heat-resistant adhesive. First remove the protective backing sheet then hold the symbol or letter firmly to the panel surface and rub around it with a wooden burnisher, pen or pencil. Take care to avoid rubbing adjacent letters/symbols. Gently lift an edge of the film to check transfer has been sucessful. The backing sheet can be used to further burnish the transfered characters. A wax residue remains on non-porous surfaces. This can be removed with thinners and a soft cloth. To improve durability apply a coat of protective lacquer after. Custom transfers can be produced by inkjet or laser printer using dry rub off decal paper.

Etched
With chemical etching using Press and Peel transfer film, toner transfer or lacquer, masking areas of the panel from the etchant. A variety of etchants can be used, taking into consideration what type of metals is used for the panel. This can be hazardous, so some care is needed in dealing with whatever chemicals are used as well as with the process itself. Safer methods are described at Non-toxic method for etching copper and brass.

After 1965 all Moog modules panels were etched using black anodized aluminum coated with a photosensitive resist, known as Fotofoil. Where the panel had been exposed through a photographic film the resist remained. Immersing the panel in lye (sodium hydroxide) then etched the parts not protected.

Laminated
The panel overlay is laminated in a plastic pouch, which is attached to the panel with contact adhesive. Print two copies of the overlay and use one of them as a drilling guide. Laminate pouches are also available in different finishes which you might be preferable. A problem with this method is that with the edges catching on other panels the platic laminate might lift at the corners.

Laser etching
Anodized aluminum can be laser etched to create fine bright markings against a darker background. Plain aluminum can be etched through paper masking.

Lazertran
Water-slide decal paper from Lazertran is a flexible method for producing a hard wearing transparent finish, approaching silk screen for quality. The image for transferring is printed mirrored with a toner based laser printer. The sheet is then soaked in water to detach the decal which is then placed on the panel toner side down. Heating the panel later in an oven bonds the toner to the surface. Otherwise use an aerosol lacquer to protect it.

Paint infilling
Acid etched or engraved panels can be infilled with Revell enamel model or automotive touch up paint and the excess paint cleaned up after it's cured.

Paint stick
Similar to paint infilling but easier and inexpensive. Using a Markal Lacquer-Stik. Dificult to apply to large etched areas where the appearance will be dull. Remove dried paint film from tip before use. Rub into the engraving and wipe off the excess around engraving with a soft cloth. On rough surfaces excess wet paint can be removed by lightly rubbing with a cloth dipped in mineral oil. When dry use mineral spirits or alcohol. Tack free after 12 hours, completely dry after 24 hours.

Painted
MOTM panels finish is baked-on two part Polane paint, giving it a crinkly look, and with labeling and scales in screen printed epoxy-ink.

Printed paper
A laser print is made, of the same size as the panel and then glued onto it.

Quick-Mark Digital
QMD is a clear self-adhesive film on which the panel markings are laser printed in mirrored image, up to A3 size. This is then wet laminated to double sided adhesive white, silver, yellow, transparent or 0.2 mm aluminium base sheet. Low cost high quality panels with full colour labeling are easily produced.

Screen printed aka silkscreen
Screen printing uses a stencil supported by fine polyester mesh about 1 mm above the panel. First a blade or squeegee moves ink into the exposed mesh, then a reverse stroke causes the inked areas to momentarily make contact with the panel. It can take many attempts to perfect the process.

Toner transfer
Similar to the toner transfer method of printing PCB etch resist. Printing the mirrored image with a laser printer onto glossy paper then using an iron to heat the reverse of the print bonding the toner onto the panel.

Designs

 * Front Panel Express Templates by David Brown, ModularSynthesis.com
 * Modular Synth Panels files, Yahoo group
 * fpd files by Richard Brewster

Finishing

 * Finishing Aluminum Panels, syinsi.com

Etching

 * Etching Innovation, nontoxicprint
 * faceplate etching thread, Muff Wiggler forum, March 2009