OpenFab PDX Modular Fiddle Quick start guide

Modular Fiddle Assembly Instructions
A modular, open source, 3D printed acoustic violin.
www.openfabpdx.com
#ModularFiddle
Body
Tuners
Bridge Strings
Neck
Truss Rod
Tail Piece
Chin Rest

Assembly Process
The Modular Fiddle is easy to assemble and requires no adhesives, fasteners, or other joining parts.
The assembly process takes about an hour.
1. Gather Materials
2. Prepare Body –deburr and prep Body part.
3. Prepare Neck –deburr and prep Neck part.
4. Prepare Pegbox –deburr and prep Pegbox and install tuners.
5. Clean joints and join parts –gently file joints on all parts to achieve a smooth, consistent fit. Assemble Pegbox, Neck, and
Body parts together, install truss rods.
6. Install tailpiece and strings –install stock violin tailpiece and 4/4 strings.
7. Install Bridge and chin rest
8. Final Setup WEAR SAFETY GLASSES AS NEEDED

1. Gather Materials
Modular Fiddle BOM
Buy your parts locally whenever possible! Tell your local music shop about the project and what you're up to. You never know
what kind of collaboration, feedback, or support could result.
9/25/2018
Amazon links on this BOM are affiliate links. I have mixed feelings about this. It means that OpenFab gets a small percentage
of the Amazon sale (usually about 4%) if the product is purchased via the
link. If you plan to buy on Amazon, please use these links to support further development. Please purchase your parts locally
if possible. Thank you!
Part Name Quantity Type Manufacturer
Mfg Part Number
Supplier Supplier Part # Unit Cost Total Cost Notes (lead time, print settings, etc)
Neck 1 Printed OpenFab PDX OpenFab PDX
Print 3 loops with .4mm nozzle (skin thickness at least 1mm). Infill >= 15%.
Pegbox 1 Printed OpenFab PDX OpenFab PDX
Print 3 loops with .4mm nozzle (skin thickness at least 1mm). Infill >= 15%.
Body 1 Printed OpenFab PDX OpenFab PDX 363g
Print 3 loops with .4mm nozzle (skin thickness at least 1.2mm). Infill >= 15%.
Bridge 1 Printed OpenFab PDX OpenFab PDX 1g
Print 3 loops with .4mm nozzle (skin thickness at least 1mm). Infill >= 15%.
Ukelele Friction Tuners,
Grover 88B or Sta
-
Tite
4W 1 Purchased Grover 88B, 4W Amazon
88B ASIN:
B000X31R4W $35 $35
Sta
-
Tite 4W also an option. ASIN B003A67WHU, link: https://amzn.to/2Ih2RAy
Medium Tension
Synthetic Core 4/4
Violin Strings 1 Purchased
Thomastik-
Infeld
Alphayue AL100 Amazon
ASIN: B012BMSANS
$22 $22
Any 4/4 (full size) set of violin strings will work
4/4 Violin Tail Piece 1 Purchased Wittner 918119 Amazon
ASIN: B00HGDRSB8
$17 $17
Other 4/4 tail pieces should work just fine
4/4 Violin Chin Rest 1 Purchased Wittner 250111 Amazon
ASIN: B0009SXWLC
$23.0 $23.0
Other 4/4 chin rests may or may not work. Test before you buy if possible.
Carbon Fiber Tube,
6x8x330mm 2 Purchased Arris N/A Amazon
ASIN: B00TF8UW9C
$7.5 $15
It seems like only one tube is necessary (through the neck). Time will tell if the
body is stiff enough.
TOOLS
•Needle-nose pliers
•Small files (triangular is particularly helpful)
•Deburring tool (much easier and safer than a
knife for cleaning parts)
•Exacto knife
•Sandpaper (I use 220 and 600 grit)
•Safety glasses
•Calipers or a decent ruler
•Sharpie

2. Prepare Body
Remove supports from Body using needle
nose pliers. Use a deburring tool, exacto,
or file to remove any leftover bits from
supports. Gently clean up F holes.
Clean off skirt and deburr edges where
they contacted your build plate.
Check truss rod holes at front and rear.
The carbon fiber tube should enter the
holes by hand with moderate force. I drill
mine out (significantly) with a 5/16” bit.

3. Prepare Neck
Remove supports from Neck using needle nose
pliers. Use a deburring tool, exacto, or file to
remove any leftover bits from supports.
Clean off skirt and deburr edges where they
contacted your build plate.
Gently file fingerboard edges to round them
off. Then sand the fingerboard and neck as
much as desired. The smoother the
fingerboard the better!
Check both truss rod paths (fingerboard truss
and body truss) to make sure the carbon fiber
tubes slide in and out without much force.
These holes are sized larger than the Body’s
and should not require drilling.

4. Prepare Pegbox
If needed, clean off skirt and deburr edges
where they contacted your build plate.
Check peg hole fit –if needed, use a
deburring tool or exacto to open up the
holes a bit.
The Ukelele friction tuners are very easy to
install. If needed, press in the bushings for
the tuners. The Grover 88B (shown, left) do
not use bushings, and simply tighten down
on the Pegbox. The Grover 4W uses
bushings you press in.
Fasten the tuners to the Pegbox and
tighten them until they are seated and
turn with firm force. You will probably
need to re-tighten the tuners several times
as the parts settle. (Less true for the 88B)

5. Clean Joints and Join Parts
All parts should slide together with some
friction, but should not require high force
or impact to install or remove parts. That
said, it is OK to remove the Neck by
tapping it carefully near the joint with a
small hammer (or tapping it on a table).
Carefully file the joints on all parts as
needed to achieve a good fit. Do not file
too much!
Slide all parts together –feeling good?
Great! Slide the carbon fiber truss rod
through the Pegbox and to the end of the
Neck.
Slide the Body truss rod entirely through
the Body. Make it flush with the Neck
interface, then slide the Neck into place.
Push the truss rod the rest of the way,
until just sub-flush at the endpin. R5 and
later Necks have an open through hole so
you can push this rod back out as needed.

6. Install Tail Piece and Strings
Install strings from lowest to
highest. (G to E)
Hook the ball end into the tail
piece, then set the tail piece
loop around the end button.
Pass the string through the left
close tuner and tighten
counter-clockwise. Tighten,
without the bridge, until there
is enough tension to hold the
tail piece in place.
The two left tuners tighten by
turning counter-clockwise. The
two right tuners tighten by
turning clockwise. This is also
shown in the image at right.
Repeat process with D, A, and
E strings.

7. Install Bridge and Chin Rest
Slide the bridge under the strings and
pivot it up to support string tension. The
bridge should be centered, and the
distance from nut to bridge should
measure about 330mm.
Check that the strings sit OK in the nut and
bridge grooves. You may need to file these
down to hold the strings securely or to
lower the action of the strings. Don’t worry
about that just yet.
Fasten the chin rest in the appropriate
position.

8. Final Setup
Tighten the strings to full tension,
tuning from G to E. Then check the
height of your strings at the end of the
fingerboard.
While these heights are not critical, your
instrument will play better and sound
better if string heights are properly
adjusted. Ideally your highest (E) string
is 3.5mm above the fingerboard and the
lowest (G) string is 5.5mm.
File the bridge grooves as needed to
improve the string heights. I file my nut
grooves as well, but I do it by feel and
not by measurement.
Record your string height
measurements. In a week, check them
again and file the bridge as needed.
Additional design work may be
needed for the bridge to attain
proper string height!
This is the nut. It prints with
grooves, but you may want to
file them a bit deeper.