How to make recycled plastic sunglasses, V2 build

A second-generation pair, with the lens slots formed in-mould.

The V2 build guide for the Sustainable Design Studio sunglasses mould contains 22 steps utilising the two moulds for the frame and the arms. Covering the full step-by-step process to create a wearable pair of recycled polypropylene sunglasses that utilise Oakley Holbrook, Frogskin, or Sutro replacement lenses.

V2 differs from the original guide in two ways. The lens slots are formed in the mould by removable inserts, so there is no Dremel routing step. The frame and the arm moulds both have two locating pins that form the arm screw holes. Making this one of the fastest moulds to create sunglasses yet.

The finished pair of recycled plastic sunglasses, marbled white, grey and black frame with orange mirrored lenses, arms open, resting on an OSB bench
Recycled polypropylene frame and arms that utilise a standard Oakley replacement lens and easy-to-repair hinge.
Before you start

What you need

Pick your model first. Holbrook, Frogskin and Sutro differ in frame shape, arm shape and lens, so each one has its own matched pair of moulds and you buy the set for the silhouette you want. Everything below is per pair once that choice is made.

Sustainable Design Studio equipment

Recycled plastic

Approximately 25 grams of injection-grade recycled polypropylene (PP) per pair. Good clean sources include:

  • Fishing nets
  • DVD cases
  • Food containers, cleaned and label-free
  • Bottle caps, PP only (check the recycling symbol)

The plastic must be clean, dry, and free of contamination. If you are unsure how to identify PP, see the Plastic Identification guide.

Choose your model

Three models, each a different Oakley-style silhouette. The difference is not only the lens: the frame profile and the arm shape change too, so each model has its own frame mold and its own arms mold. Choose before you order. All three lenses are 1mm thick, off-the-shelf replacements available from any specialist eyewear-parts supplier.

Model Frame shape Arm shape Replacement lens code Mould set
Holbrook Classic square, flat profile Straight, squared temple OO9102 (57mm) Frame mould + arms mould
Frogskin Round, retro Slimmer, tapered temple OO9013 Frame mould + arms mould
Sutro Wrap-around sport, single lens Wider, curved temple OO9406 (37mm) Frame mould + arms mould

Hinge screws

One per temple, securing the moulded arm to the frame through the hole the locating pins formed. Same hardware across all three models. The size is a choice, not a fixed spec. M2 is the larger of the two and the one to use on clean, strong plastic. On weaker or poorer quality plastic an M2 can split the hinge element, so drop to M1.6. The trade is that an M1.6 can leave the arms feeling a little looser in the hinge. Judge it on the plastic you are actually moulding with.

Component Specification Notes
Hinge screws, good plastic M2 x 10mm countersunk (x2) One per temple, countersunk, Phillips drive. Hex is available if you prefer. Holds the arms firmest of the two.
Hinge screws, weaker plastic M1.6 x 10mm countersunk (x2) The safer choice when the plastic is weaker or of poorer quality, where an M2 can split the hinge element. Expect the arms to feel a little looser than they would on an M2.

Assembly tools

  • Small Phillips screwdriver for the M1.6 or M2 hinge screws. Ours are Phillips, and hex versions are available if you prefer
  • Two 13mm spanners for the M8 mould bolts and nuts
  • Soft, flat work surface (a folded microfibre cloth works)
  • Flat-tip or needle-nose pliers, for easing the moulding out of the mould
  • Hex or Allen key, for removing the pin inserts
  • Plastic model snips, for cutting the sprues and gates
  • Lint-free cloth (for cleaning the inside of the frame and the lenses)
  • Fine craft knife or scalpel (for trimming any flash from the mold seam)
The build

Step by step build process

Twenty-two steps in three parts. The frame and the arms are separate mouldings, each with its own mould, and each mould follows the same cycle: assemble it, inject, then take it apart to get the part out. The last two steps put the pair together.

Part 1

Mould the frame

Assemble the frame mould, inject, then take it apart again and finish the frame. Steps 1 to 3 build the mold up, step 4 injects, steps 5 to 8 are the demolding sequence, and steps 10 to 12 fit the lenses and tidy the part while it is still warm.

  1. The frame mould open in two halves on a workbench, both cavities clean and empty before a run
    Step 1

    Prepare the frame mould

    Clean both halves of the frame mould. Apply a light coat of mould release spray to every cavity surface, including the faces the lens-area inserts sit against.

    Heat the mould to 60°C using an oven, heat gun, or a mould heater if your setup includes one. A warm mold helps the recycled PP flow into the thin frame sections without short shots or cold lap lines.

  2. A gloved hand seating a locating pin into the frame mould, with a main locking bolt already through the block
    Step 2

    Seat the lens inserts and fit the two locating pins

    Every cycle starts here. Place the four lens-area inserts into each lens opening, eight in total. These form the lens slots in the mold, which is why the V2 build has no Dremel routing step.

    Then fit the frame mold's two locating pins. The pins form the holes that the arm screws pass through at the end of the build. Miss them and the frame comes out with nowhere to attach the arms.

  3. The frame mould closed and bolted, engraved Sunglasses Frame FS, with the locking bolts and flange nuts pulled up tight
    Step 3

    Close the mould and tighten the main locking bolts

    Bring the two halves together and fit the M8 x 80mm main locking bolts and nuts. Ideally, tighten them in a cross pattern. Tighten each one firmly but not to your maximum, because the injection pressure makes them harder to undo later.

    Uneven tightening flashes the parting line and leaves a visible witness around the finished frame.

  4. A gloved hand on the control of the Arbour Injection V2, with the machine's twin temperature readouts and power switch on the yellow panel
    Step 4

    Inject the frame

    Set your machine to 220°C, whether that is the Arbour Injection Machine V2 or the Injection Mini V2. Fully load the barrel with recycled PP and wait for it to melt. Then inject the full shot into the mold.

  5. A locating pin being drawn out of the closed frame mould with a hand tool, before the mould is opened
    Step 5

    Remove the two locating pins

    With the mould still bolted shut, draw both locating pins straight out. They pass through the moulded frame and form the holes the arm screws go into later. Place these in a safe location so that they are not damaged or lost.

  6. The frame mould opened into two halves, the moulded frame still sitting in the lower cavity with its sprue and runner attached
    Step 6

    Undo the locking bolts and open the mould

    Undo the main locking bolts and nuts and lift the top half away in a clean parallel motion. The moulded frame stays in the lower half with all eight lens-area inserts still in it.

    Do not lift the frame out by hand. It comes out on the four pulling pins, which is the next step.

  7. Pliers gripping one of the four pulling pins on the moulded frame, which is still seated in the lower half of the mould with its lens inserts in place
    Step 7

    Pull the frame out on the four pulling pins

    The frame has four pulling pins moulded onto it. Grip each one with pliers and lift the frame evenly out of the cavity. They are there so you never pull on the frame itself, which is what marks or distorts a part.

    Only do this once the locating pins are out. With a pin still in, the frame is locked into the mould and pulling on it will damage the frame.

  8. A lens insert being worked out of one lens opening in the moulded frame, held in a gloved hand
    Step 8

    Remove the North and South lens inserts

    The order matters. Take the North insert out first, then the South. Lift each one down and out, wiggling slightly, using your hands to remove. Don't use metal objects such as pliers to remove these as they can damage the aluminium inserts.

  9. A gloved hand drawing a lens insert out of the moulded frame to release it, the second insert still in place
    Step 9

    Remove the East and West lens inserts

    With North and South clear, the East and West inserts slide out of the lens opening. Work them out squarely rather than twisting.

    Now repeat steps 8 and 9 again for the second lens opening.

  10. The empty moulded frame held up to the light, both lens channels clear and ready
    Step 10

    Check the lens channel is clear

    There should not be any flash in the channel, but check both eyes every time before you go near a lens. The fit is snug by design, so a ridge you can barely see is enough to stop the lens seating flat.

    Run a fingertip or the back of a blade all the way round each channel. If you find anything, pare it back with a craft knife until the channel is smooth, then check again.

  11. An orange mirrored lens being pressed into the frame, seated along the outer edge with the nose-piece end still to go
    Step 11

    Fit the lenses while the frame is still warm

    Do this straight away. Recycled polypropylene stays slightly flexible while it is warm, and the lens is a tight fit, so a warm frame gives far more than a cold one. Leave it until later and the same lens becomes a fight.

    Push the outer edge of the lens into the channel first, then work round and bring the nose-piece end in last. Starting at the nose end is what makes it hard. Lens codes for all three models are in the table in What you need above.

  12. Flush cutters trimming the sprue away from the finished frame, both orange lenses already fitted
    Step 12

    Snip away the sprues, vents and pulling pins

    With both lenses in, cut away the sprue, the vents and the four pulling pins. Plastic snips or a sharp craft knife both work, whichever you have to hand.

    The frame is finished at this point. It goes back on the bench while you mould the arms.

Part 2

Mould the arms

The arms mould runs the same assemble, inject, demould cycle, with its own pair of locating pins and no lens inserts.

  1. Both halves of the arms mould open on the bench, cavities and runner channels clean and empty
    Step 13

    Prepare the arms mould

    Clean both halves of the arms mold, spray the cavities, and bring it up to 60°C the same way you did the frame mold.

    The arms mold has no lens inserts, so there is less to seat than on the frame.

  2. A locating insert being driven into its seat on the open face of the arms mould, with the two arm cavities and the T-shaped runner alongside
    Step 14

    Fit the two locating pins

    Fit the two locating pins. They form the screw holes in the arms, and they are set to line up with the holes the frame pins made in step 2.

    Please note that the locating pins for the frames are different to the arms and must not be mixed up.

  3. The arms mould closed with the locking bolts through it, being tightened by hand in a cut-resistant glove
    Step 15

    Close the mould and tighten the main locking bolts

    Bring the two halves together, check they are seated square, and tighten the main locking bolts and nuts evenly.

    Same hardware and the same even tightening as the frame mold in step 3.

  4. A gloved hand on the control of the Arbour Injection V2, with the machine's twin temperature readouts and power switch on the yellow panel
    Step 16

    Inject the arms

    Set the machine to 220°C and fill the barrel with prepared recycled PP, the same as the frame in step 4. Both arms and the runner come from a single shot.

  5. A locating pin being drawn out of the open arms mould with a hand tool, the moulded arms still lying in the cavity
    Step 17

    Remove the arms mould's two locating pins

    With the mould still bolted shut, draw both locating pins straight out. They form the screw holes in the arms, and they line up with the holes the frame pins made. Place these in a safe location so that they are not damaged or lost.

  6. The arms mould opened into two halves, both moulded arms still lying in the lower cavity joined by the runner
    Step 18

    Undo the bolts and open the arms mould

    Undo the locking bolts and nuts and lift the top half away in a clean parallel motion. Both arms stay in the lower cavity, joined to each other by the runner.

    The pins are already out, so nothing holds the arms but the cavity itself.

  7. The pair of moulded arms lifted clear of the mould, still joined to each other by the runner and sprue
    Step 19

    Release the arms

    Start at the end furthest from the nozzle injection point, not at the sprue end. Lift gently and slowly, rocking the arms back and forth rather than pulling straight up, and they will come away without stressing the part.

  8. Flush cutters separating the moulded arm from its runner and sprue
    Step 20

    Cut the sprue off the arms

    Cut the runner and sprue away and separate the two arms. Plastic snips or a craft knife, the same as the frame.

    Trim the cut ends flush so the hinge end sits flat against the frame later.

Part 3

Assemble the pair

The finished frame and the two arms become a wearable pair.

  1. A small cross-head screwdriver driving the hinge screw through the arm into the frame, the orange lens visible below
    Step 21

    Attach the arms and finish

    Line each arm up with the frame and drive a 10mm countersunk screw through the hole the locating pins formed. Use M2 if your plastic is clean and strong, M1.6 if it is weaker or of poorer quality, because an M2 can split the hinge element in that plastic. An M1.6 can leave the arm feeling a little looser, which is the trade for not splitting the hinge. Tighten with a small cross-head screwdriver to a firm hand-feel, no power tools.

  2. The finished pair of recycled plastic sunglasses, marbled white, grey and black frame with orange mirrored lenses, arms open, resting on an OSB bench
    Step 22

    Check the finished pair

    Trim any flash along the mold seam with a sharp blade and wipe the lenses with a lint-free cloth.

    Fold both arms in and out a few times. The hinge screws should feel firm without binding, though a little more play is normal if you went with M1.6. Check both lenses are sitting flat in their channels, with no gap at the nose-piece end.

    That is a wearable pair, made from recycled plastic in two mouldings.

When things go sideways

Tips and troubleshooting

Six common gotchas on the V2 build, with the fix that usually clears each one. The first three are specific to the V2 moulds.

V2 inserts

Lens-area inserts will not lift out

Check the order. North and South must come out first, on both lenses. If you have tried East or West first they will bind against the molded frame, because the geometry interlocks until N + S are clear. Re-seat N + S if they have shifted, then take them out in the right order before the East and West will release.

V2 pins

Locating pin will not draw out

Check you are turning it anticlockwise, and draw it while the mould is still warm. PP shrinks onto the pin as the part cools, so the longer it sits the tighter the grip gets. Letting it cool makes a stuck pin worse, not better. Never open the mould to get at a stuck pin. The pin runs through the part itself, so opening the halves with it seated bends the pin and tears the hole it just formed.

V2 lenses

Lens too tight or too loose in the slot

Fit the lenses while the frame is warm and freshly injected. That is when the channel gives, and a frame left to go cold can make a correctly sized lens feel far too tight. If that is not it, check the lens matches the mould set you used. A Sutro lens will not seat into a frame moulded in the Holbrook tooling, and the arms will not match either, because the models differ in frame shape and arm shape as well as lens. With the right model in hand, a tight lens is almost always flash on the parting line: trim it with a fine craft knife and try again. A loose lens points to the wrong model or a worn mold insert.

Injection

Short shots or thin frame sections

The barrel temperature is the first thing to check. Push the barrel up by 5 to 10 degrees Celsius and try again. Also confirm the mold is warm before injection: cold tooling produces short shots and patchy surface finish in PP.

Mould

Visible witness around the frame

The main locking bolts were tightened unevenly. Work in a cross pattern, finger-tight all round first, then snug each one a touch at a time.

Finishing

Frame stuck in the cavity

Make sure the locating pins are removed. Confirm release spray was used at the preparation step. Work quickly while everything is still warm, a warm frame lifts where a cooled one grips. Do not pry with sharp tools, you will scratch the cavity. If it keeps happening, check the mould was at 60 degrees Celsius before injecting.

Custom designs

Need a different silhouette?

Three Oakley-style models are available as matched mould sets: Holbrook, Frogskin, and Sutro. Each set is a frame mould and an arms mould, because the models differ in arm shape as well as frame shape and lens. If you want a silhouette we do not make, or a fully custom mold set for a private label run, get in touch.

Start a custom mould enquiry
Keep going

Resources that pair with this guide

Three picks from the Sustainable Design Studio resources library. The V1 design for the original Injection Machine, the watch guide as a sister-template build, and the mould-use fundamentals.

V1 sunglasses guide from Sustainable Design Studio V1

How to make recycled plastic sunglasses (V1)

If you are looking for the V1 design, you can find it here. Same three shapes on the original Injection Machine, kept available for anyone still running that hardware.

Intermediate 2 hours Compare
How to make a recycled plastic watch guide from Sustainable Design Studio How-to

How to make a recycled plastic watch

A second sister build using the same template. A watch case in recycled PP with an NH35 movement and a domed glass crystal.

Intermediate 26 hours Build
How to use your mould guide from Sustainable Design Studio Guide

How to use your mould

The fundamentals of setting up, heating, injecting, and maintaining your Sustainable Design Studio Premium Mould.

Beginner 8 min Learn

First V2 pair come out wrong? Send a photo.

Show us the failed shot, which lens model you tried, and what plastic you used. We have walked plenty of first builds through the same steps and can usually point at the fix.

Contact us All resources