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. Twenty-two steps and two mouldings, the frame and the arms, from heated tooling to a finished, wearable pair in recycled polypropylene with Oakley Holbrook, Frogskin, or Sutro replacement lenses.

V2 differs from the original guide in three ways. The lens slots are formed in-mold by removable inserts, so there is no Dremel routing step. The frame and the arms are separate mouldings from a matched pair of moulds. And each mould carries two locating pins that form the arm-screw holes, which have to be drawn out before the mould can be opened.

What you need Jump to the steps
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, in-mould lens slots, hinge-screwed arms.
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

  • Arbour Injection Machine V2 or Injection Mini V2. Either machine runs this build.
  • Sunglasses Mould V2 frame mould, in your chosen model, from the online store
  • Sunglasses Mould V2 arms mould, matched to the same model
  • Mould release spray
  • Main locking bolts and nuts, M2 x 10mm countersunk (supplied with each mould)
  • Two hinge screws, the same M2 x 10mm countersunk screw, one per temple
  • Two locating pins per mould, four in total (supplied with each mould)
  • Eight lens-area inserts, four per lens opening (supplied with the frame mould)
  • Parts tray, for the inserts and pins between cycles
  • Basic workshop tools, see Basic Workshop Tools
  • PPE: heat resistant gloves, safety glasses, see Basic PPE

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, and the same screw that holds the moulds shut, so there is only one size to keep track of.

Component Specification Notes
Hinge screws M2 x 10mm countersunk (x2) One per temple. The same screw as the main locking bolts, so there is one fastener size across the whole build.

Assembly tools

  • Cross-head (Phillips) screwdriver or hex key, whichever your screws take. The same M2 x 10mm countersunk screw closes the moulds and hinges the arms, so one driver covers the whole build
  • Soft, flat work surface (a folded microfibre cloth works)
  • Tweezers or flat-tip pliers (for lifting the lens-area inserts and drawing the locating pins)
  • 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 warms 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 one of the main locking bolts 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 two 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 main locking bolts and nuts. Tighten them in a cross pattern, finger-tight all round first, then a touch at a time on each until the seam closes evenly.

    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. Load approximately 25g of prepared recycled PP into the barrel and inject the full shot into the mold.

  5. The frame mould opened into two halves, the moulded frame still sitting in the lower cavity with its sprue and runner attached
    Step 5

    Undo the locking bolts and open the mould

    Undo the main locking bolts and nuts and lift the top half away. The moulded frame stays in the lower half, with the two locating pins and all eight lens-area inserts still in it.

    The mould opens first and the pins come out afterwards. Do not try to lift the frame yet: the locating pins still pass through it and it is held in place.

  6. A locating pin being drawn out of the closed frame mould with a hand tool, before the mould is opened
    Step 6

    Remove the two locating pins

    With the mould open, draw both locating pins straight out and put them in the parts tray. They pass through the moulded frame and form the holes the arm screws go into later.

    Nothing comes out of the mould until these are clear. Leave one in and the frame is locked in place, and pulling against it will damage the part.

  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 straight up out of the lens slot with tweezers or flat-tip pliers. No rocking, no prying.

    Repeat on the second lens opening. With North and South clear on both sides, the East and West inserts are free to move.

  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 each lens opening. Work them out squarely rather than twisting.

    Both eyes are now empty and the full lens channel is visible.

  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.

    Both moulds in a matched set are drilled to the same hinge spacing, which is why an arm from one set will not line up with a frame from another.

  3. The arms mould closed with both 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 charge the barrel with prepared recycled PP, the same as the frame in step 4. Both arms and the runner come from a single shot.

    The charge weight for the arms is not yet recorded. Weigh a shot and it goes in here.

  5. The arms mould opened into two halves, both moulded arms still lying in the lower cavity joined by the runner
    Step 17

    Undo the bolts and open the arms mould

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

    As with the frame, the mould opens first and the locating pins come out afterwards.

  6. A locating pin being drawn out of the open arms mould with a hand tool, the moulded arms still lying in the cavity
    Step 18

    Remove the arms mould's two locating pins

    Draw both locating pins straight out and return them to the tray. They form the screw holes in the arms, and they line up with the holes the frame pins made.

    The arms stay put until both pins are clear.

  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.

    They lift out by hand. The arms mold runs the same sequence as the frame mold with two things missing: there are no lens inserts, so nothing else has to come out first, and there are no pulling pins, so there is nothing to grip with pliers.

    The two arms are still joined by the runner at this point.

  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 an M2 x 10mm countersunk screw through the hole the locating pins formed. It is the same screw that held the moulds shut. Tighten with a small cross-head screwdriver to a firm hand-feel, no impact 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. 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

Let the mold cool a touch further before the next try. PP shrinks as it cools and a pin gripped tight in a hot mold frees off once shrinkage takes the pressure off. 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

First 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. Skip impact tools, they twist the mold halves and amplify the witness.

Finishing

Frame stuck in the cavity

Confirm all eight lens-area inserts are out (four per lens) and that both locating pins were drawn before the mould was opened. If the frame still resists, apply more release spray on the next cycle and re-check the mold was at 60 degrees Celsius before injecting. Do not pry with sharp tools, you will scratch the cavity.

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