Casting a stroker sleeve

From printed mould and core to finished sleeve. For adults (18+). Every fact links to where it comes from.

Read this first. Nothing in this guide or in the tool proves that a home-cast sleeve is safe against the body. Skin-safe silicone, a clean mould and a good cure make it likelier, not certain. You choose the materials and you carry the risk. Sources for each claim: see the end.

• The process at a glance
• What the tool does today
• A cast, in photos
• Choose the silicone
• Print the pieces
• Prepare and assemble
• Mix and pour
• Cure and demould
• Clean, store, use
• Materials and links
• Privacy and terms
• Sources

The process at a glance

1. Design. Draw the canal, the shape a body slides into, along its length. The tool builds the plain outer sleeve body around it from the Sleeve panel. Fix anything the Checks panel marks. Start from a template if you like, or press Randomizer for a surprise. Texture puts a relief over part of the canal.
2. Render. Press Render, then download the three pieces, the two mould halves and the core, as STL or 3MF, and the print sheet. It lists how much silicone and filament you need.
3. Print the two halves and the core on your printer. The core prints bar down. Print the pieces
4. Prepare the halves and the core, then assemble: rubber bands round the halves, the core hung from the pour opening. Prepare and assemble
5. Mix and pour the platinum silicone, slowly, through the two openings beside the core's bar. Mix and pour
6. Cure and demould. Wait the full time, open the halves, then pull the core out through the entry. Cure and demould
7. Clean, store, use. Trim, wash it and let it dry before the first use. Clean, store, use

What the mould and core look like

Each part is explained on mould basics.

What the tool does today

You draw the canal: the profile (its width along the length) and its texture. Straighten and Smooth, Surface (waves, ripples, sawtooth, Smooth, Simplify) and Scale (width and height by a percent) save hand work. Randomizer makes a new canal from dice, and Undo brings yours back. In the preview you pick a colour or a base-to-tip gradient; that is for your eyes and does not change the print.

Texture. The Texture button lays a relief over part of the canal. Choose from seventeen patterns: pimples, spikes, bumps, balls, grooves, pyramids, diamonds, hexagons, woven, diagonal ridges, veins, scales, wrinkles, leather, warts, coral, tentacle suckers. Sliders set the height (0.2 to 6 mm), the tile (the size of one repeat, up to 100 mm), where it starts and ends and how it fades in. Stretch spreads the pattern wider round the body (fewer repeats, wider lines and veins). Twist leans it so lines run at an angle or follow a curve. Spin turns the pattern round the body. Mask hides a slice of it (Mask fade softens its two edges so the pattern blends out), leaving 360 minus the Mask degrees showing from the Spin point; the slice turns and leans with the pattern, so Spin and Mask together isolate a single vein. With a very wide Stretch the pattern gets less than one repeat round the body and shows a seam, which Mask can hide. Rotate turns it in quarter turns and Invert sinks a raised pattern. Every number in the tool is a slider (Surface, Scale and Texture); only the length and the printer volume are typed. You see it live; Apply keeps it, Cancel (or Esc) puts it back. The panel stays open when you click elsewhere. The relief is carried into the core and into the finished sleeve, so texture on the core becomes texture in the canal. Fine detail is hard to print and to pull a core out of once it's cast in silicone: the tool flags anything smaller than 1 mm, and deep or sharp patterns (spikes, coral) are the ones to pull slowly at demould. This is my advice, not a tested figure: try a small piece first. Each mould half has the name and size engraved on the outside.

Flatten. Near the bottom right of the preview sits a small toolbox with Flatten, Texture and Scale. Flatten cuts a flat chord into one or more sides of the round cross-section: Top and Bottom are the two sides in the plane of the path (front and back), Left and Right the two sides out of it. Tick one, two or all four; the Amount slider sets how deep the cut goes, shared by every side you ticked; Start, End and Fade zone it along the length the same way as Texture. It never cuts past a 5 mm radius. Flatten runs before Texture, so a relief such as the tentacle suckers sits on the flat bed rather than on the round body. Apply keeps it, Cancel (or Esc) puts it back, same as Texture.

You draw the canal, check it, and press Render. The tool designs a mould around your sleeve's outer body: a hexagonal block split along the centre line, with pins so the halves close one way, grooves for rubber bands, pry slots to open it, and vents where air could be trapped, plus a core that hangs inside to hold the canal shape while the silicone cures. Download the two mould halves and the core as STL or 3MF and print them; the sleeve itself is not offered as a separate download, since it only exists once the core is cast into place. The steps from "Choose the silicone" onward apply to that mould, or to any sleeve mould you make yourself.

The size limits in the checks (6 mm minimum silicone wall, 3 mm canal radius, 3 mm entry opening) are working defaults, not tested figures. They will be replaced by measured ones after a real print-and-cast run.

A hard outer shell, front cap and machine mount are planned but not built yet. Today the tool makes the mould, the core and the sleeve on its own; see the plan in the project docs if you're curious what's coming.

A cast, in photos

Photos below are from an earlier cast of a hex mould, before the hanging core was added, so they show the general mould steps, sealing, banding, pouring, curing, demoulding, rather than the sleeve-specific ones (hanging the core, pulling it back out). A full sleeve walkthrough, with the core, is still to be shot; the sections below have the sources for each claim either way.

1. The mould, as printed. Two halves, pins on one, sockets on the other.

2. Coat the inside with UV resin, thin and flat, and harden it under a UV lamp. It hides the layer lines and seals the print.

3. Smear petroleum jelly (Vaseline) on the flat faces where the halves meet. It seals the joint so the silicone does not leak out. Keep it out of the cavity.

4. Close the mould, put rubber bands in the grooves.

5. Weigh part A and part B on a kitchen scale, to the figure the tool gives, then stir in a few drops of silicone colour.

6. Pour slowly, in a thin stream from high up, into the funnel.

7. Leave it alone for 24 hours.

8. Take off the bands and pry the halves apart at the corner slots.

9. Done. Wash with dish soap to take off the petroleum jelly and any oil.

Choose the silicone

The short version is below. The long one, with what every label on the tin does and does not certify, is on which grades are body-safe.

• Platinum cure, not tin cure. The two differ in the metal that starts the cure. Platinum types shrink less and keep for decades; tin types cost less. Tin cure is never used for this. [Smooth-On FAQ 184]
• "Skin safe" is not "body safe". Smooth-On calls cured Ecoflex 00-30 and Dragon Skin 10 skin safe by an independent lab, gives no warranty, and leaves suitability to you. [FAQ 205] No page we read says such a grade is safe on mucous membranes, so this guide does not say it either.
• Read the labels carefully. USP Class VI is three animal tests on the material, pass or fail. It does not judge a finished device. [Elastostar] The US rule 21 CFR 177.2600 covers rubber for repeated food contact, not the body. [Cornell LII] Smooth-On itself says complying with it is not FDA approval. [FAQ 126]
• The trade runs on trust. "Body safe" often means only what the maker says, so ask for third-party test reports. [Dame] Pigments need their own tests. [SSP]
• Softness. Shore 00 is softer than A, and A softer than D. [Smooth-On] Reference sleeves run very soft, and 00-10 to 00-30 is the usual range for a canal. Full list and the case for going firmer at the entry: the silicone page.
• How soft (the author's tip). Very soft grades feel best on a canal but tear easily at the entry and neck; the author picks 00-20 as a default and reaches for a firmer layer at the entry (dual density) rather than a firmer silicone all through.

Print the pieces

The short version is below. The longer one, with what is sourced and what is not, is on printing a sleeve mould.

• Perimeters, not infill, give strength. Prusa: two perimeters minimum, three usual, four for strong parts; 10 to 15 % infill suits most models. [Prusa] [Prusa infill]
• The core's finish becomes the canal's finish. Print it at 0.12 mm layers, or in resin, then seal it. Grooves left by coarse layers in the canal are a hygiene problem, not just a cosmetic one. Detail.
• Layer lines show in the silicone. FDM moulds leave them in the cast. [Sinterit] [Formlabs] Sanding, then a thin coat of UV resin, smooths them and makes the cavity waterproof (the author's method). A self-levelling coat such as XTC-3D fills ridges under about 0.3 mm and sands smooth. [Smooth-On] Both sources sell competing methods, so treat the size of the effect as theirs.
• Cure inhibition. Some 3D-printing materials stop platinum silicone from curing: resin prints, some pigmented filaments, latex gloves, sulfur clay and CA glue. Fix it with a full UV post-cure, a sealing coat, or Inhibit X, and always run a test pour. Detail.
• Ironing the parting faces. Ironing is a second, slow pass over a flat top surface that smooths it; it does little on curved or sloped surfaces. [Prusa] The halves print with the parting face up, so it suits them. The Mould 3MF does not ask for it; switch ironing on for top surfaces in your slicer if you want it, and check it before you print.
• PLA and heat. PLA softens above 60 °C. [Prusa] Keep a PLA mould, and a PLA core, out of hot ovens and hot cars. We found no source for post-curing a cast in a PLA mould; more on the timing in cure and demould.

Prepare and assemble

Do these in order: smooth and coat, seal, release agent, assemble. Run the test patch (step 1) on the finished surface before the real pour.

1. Run a test patch first. Platinum silicone will not cure against some surfaces, and that includes some 3D-printing plastics. [Polytek] Test on a small area: wall it off, pour, wait the demould time, then check for a gummy surface. [Polytek]
2. Know what stops the cure. Dow lists amines, sulfur compounds, tin salts and phosphorus compounds. [Dow] Sulfur clay, latex, polyurethane rubber and some paints are named too. [Polytek] Do not use sulfur clay in the mould, and keep tin silicone away from platinum. [FAQ 104]
3. Smooth and waterproof the inside (the author's method). After printing, sand the inside of both halves until the layer lines are gone. Then smear a thin, flat coat of UV-hardening resin over the sanded surface and cure it under UV light. The coat fills the layer lines and makes the inside waterproof and very smooth. Sand and coat every half, and keep the coat thin so it does not blur the shape or the pin fit. This step comes from the author's own casting, not from a listed source. Cure the resin fully: an incompletely cured resin surface can stop platinum silicone from curing. [FAQ 210] So run the test patch on the finished coat, not on bare print.
4. Seal, then release. A porous print needs a sealer, then a release agent, on both mould halves. For PLA and ABS Smooth-On pairs XTC-3D with Ease Release 200. [Smooth-On] Give the sealer at least 30 minutes to dry. [FAQ 104] A sealer may not stop inhibition on its own. [FAQ 104]
5. Release on the core, except for dual density. For a single pour, release the core the same way as the halves. If you are pouring two layers, do not use release on the core between the two pours: platinum silicone only bonds to cured platinum silicone when the surface is clean, and a release agent stops that bond. Dual density.
6. Brush silicone into a textured core first. If the core carries a texture, brush a thin coat of the mixed silicone into the recesses before you close the mould and pour the rest. It works air out of fine detail that a straight pour can trap, and stops raised nubs forming where air was caught. This is the author's own method, not a listed source.
7. Seal the joint (the author's method). Smear a thin layer of petroleum jelly on the flat faces where the halves meet, not in the cavity. It stops the silicone leaking through the joint. This comes from the author's own casting, not from a listed source. Wash it off the finished sleeve.
8. Go light with the release agent. Too much causes pinhole bubbles. [FAQ 85] No page we read says release-agent residue is body safe, so wash the finished sleeve well.
9. Assemble. Close the two halves with rubber bands in the grooves. Hang the core from the pour opening: its two feet drop into the sockets at the rim corners, and its tip spigot into the socket at the bottom of the cavity. Seated correctly, the core can't turn or fall out during the pour.

Mix and pour

How much to mix: the quick calculator.

• Most Ecoflex and Dragon Skin grades mix 1 A : 1 B by volume or weight. [Smooth-On] The tool's Quantities panel shows part A and B for your shape. Always follow your own product's sheet.
• Mix A and B separately first, then combine, scraping sides and bottom until the colour is even. [Smooth-On]
• Work inside the pot life: 45 minutes for Ecoflex 00-30, 20 for Dragon Skin 10 Medium. [Ecoflex 00-30] [DS 10] Warmth shortens it, cold lengthens it and can stop the cure. [FAQ 136]
• Colour (the author's tip). You can buy silicone colours, made to mix into silicone, to tint the whole sleeve. Mix a little into part A or the combined mix until the colour is even. For a gradient, tint separate small batches and pour them in stages. For swirls, pour two colours together and stir once, lightly. This comes from the author's own casting, not from a listed source. Use a colour sold for silicone: other colorants can stop a platinum cure, and a pigment is not covered by the base silicone's certificates. Why. Run the test patch with the colour in it.
• Degas if you can. Skipping it leaves air pockets and surface flaws. [Smooth-On tutorial] The tutorial pulls about 29 inHg, lets the mix rise and fall, then runs a minute more. Thin, runny silicones may not need it. [FAQ 111]
• No vacuum chamber? Pour slowly (the author's tip). Most hobby silicone is thin enough to degas itself: the bubbles rise and pop if you give them time. Pour slowly, in a thin stream, from about 10 cm above the opening, so the silicone stretches thin as it falls and lets the air out on the way down. The 10 cm is what the author uses, not a tested figure. This comes from the author's own casting, not from a listed source. A thick silicone traps more air, and then a vacuum chamber is worth it.
• Pour through the two gaps beside the bar. The core's bar crosses the pour opening, leaving a gap on each side. Pour into one, then the other, keeping the level roughly even on both sides of the bar, and let it find its level round the core.
• Dual density (the author's plan, not yet built or tested at full scale). Pour the harder silicone first, around a core sized to the canal plus a soft-layer margin, and let it cure. Swap in the full canal core without release agent, and pour the soft silicone into the gap within about 24 hours, so it bonds to the cured hard layer instead of pulling away from it. More.

Cure and demould

• At 23 °C Ecoflex 00-30 cures in 4 hours and Dragon Skin 10 Medium in 5. Dragon Skin 30 takes 16. [Ecoflex] [DS 10] [DS 30] Do not cure Dragon Skin 10 below 18 °C.
• Wait a day (the author's tip). The author leaves every cast 24 hours before opening the mould, longer than the datasheet asks. A full cure costs nothing and a torn sleeve costs the silicone.
• Let it cure fully before you pull it. Very soft grades such as Ecoflex 00-10 cure with a tacky surface. [Smooth-On]
• Open the mould. Twist a flat screwdriver or a coin in one of the pry slots at the corners, then work round to the others. Do not lever against the cast. Why the slots. The sleeve comes out of the open halves with the core still inside it.
• Pull the core out through the entry. Go slowly, past any narrow sections of the canal, and don't tug on the sleeve itself to speed it up. The tip vent hole lets air in behind the core as it comes free, which breaks the suction holding it in; a little soapy water round the core makes it slide easier. Soft silicone can be turned inside out without tearing (Dragon Skin 10). [Smooth-On] The tool's 6 mm wall check is a rule of thumb about thin sections tearing as the core comes out; it is not from a source.
• Trim. Cut away any flash at the parting line and the two pour openings with sharp scissors before you wash it.
• Post-cure only after demoulding. A PLA mould, and a PLA core, soften around 55 °C, well under most heat post-cure schedules. [Prusa] Pull the parts from the mould first, then post-cure the sleeve alone if your silicone's maker gives a schedule for it. We found no source for a specific post-cure time or temperature, so this guide does not invent one; ask your silicone's maker.

Clean, store, use

Before you use it: safety.

• First wash (the author's tip). Wash a new cast with dish soap and warm water. It takes off the petroleum jelly, the release agent and any oil from the mould.
• Wash with liquid soap or toy cleaner and air dry. [Healthline] Health sites say silicone toys without motors can be boiled: 3 minutes [Healthline], up to 10 [WebMD]. Those apply to finished toys; for a home cast, ask your silicone's maker and use the shorter time. A textured canal traps residue in the grooves: warm water, mild soap, a soft brush, then dry it fully with the canal held open so the inside air-dries too. More.
• Store the sleeve apart from other soft toys. Non-silicone soft toys can melt into each other. [Healthline]
• Lube: water-based only. Silicone lube is not compatible with silicone toys. [Planned Parenthood Toronto] It can wear the surface and leave damage where bacteria live. [Healthline] One platinum-silicone maker says otherwise, so this guide takes the cautious view of the health sources.
• Suction and pressure. The tool only makes passive suction, the grip you feel as you stroke, not a powered vacuum. Keep a vent open the first few times you use a new sleeve, and never fit it to a pump. Stop straight away if you feel pain, numbness or discolouration. More.
• Do not share a sleeve without a barrier (a fresh condom) between uses, and wash it fully between people.
• Stop if anything hurts, tears or looks damaged. See a doctor if anything feels wrong and doesn't pass.

Materials and links

You need: platinum silicone, mixing cups and sticks, a release agent and sealer, a vacuum chamber (optional), filament for the mould and the core, water-based lube. Shop links on this site, when there are any, sit in boxes marked Ad. They are affiliate links: if you buy, the site may earn a commission, at no extra cost to you. Read the datasheet before buying, whatever the box says.

Learn more about silicone casting

Read on 2026-09-20; pages change. These are outside sites, not endorsements.

• Formlabs: casting silicone from 3D printed masters (manufacturer guide, from print to pour)
• Instructables: two-part silicone casting (hobby walkthrough with photos)
• Polytek: test cures for platinum silicone (how to run the test patch)
• Smooth-On: sealers and release agents (what to put on a 3D printed mould)
• Smooth-On FAQ: cure inhibition (why silicone stays sticky)
• Sinterit: finishing printed moulds for silicone (FDM, SLA and SLS compared)

Privacy and terms

• Adults only. The site asks you to confirm you are 18 or older, or of legal age where you live. It cannot check.
• Privacy. The site sets no cookies and has no accounts. Your designs stay in your browser unless you press Publish. Publishing sends the design file (the shape, its colour and its texture, nothing else) to the public gallery. The name you typed is dropped and the gallery gives the design a name of two words, like brave-chocolate; no personal data is stored. To limit abuse, Cloudflare counts publishes per connection address for a minute; the site does not keep that address. Published designs cannot be edited or removed by their author. The site saves three things in your own browser: your saved designs, your settings and the age confirmation. Clearing site data removes them. Visits are counted with Cloudflare Web Analytics, which sets no cookie and keeps no identifier for a person.
• Not for commercial use. What you make here (designs, exported files, moulds and casts) is for personal use only. You may not sell it, or use it in a product or a paid service. If you want to use it commercially, ask the author for a licence: the address is in the footer of every page. The mould files carry the same notice, engraved on one half.
• No guarantee. The tool and this guide come as they are. Shapes are checked against rules of thumb that have not been tested by a real cast yet. Nothing here is medical advice. You are responsible for materials, hygiene and use.

Sources

Read on 2026-09-20. Pages change; check the current datasheet. The full list, with what each page says and where the sources disagree, is in docs/GUIDE-SOURCES.md in the project. Health pages: WebMD (medically reviewed), Healthline (medically reviewed), Planned Parenthood Toronto. Manufacturer pages: Smooth-On, Dow, Polytek, Prusa, SSP, Mann. Retailer and hobby pages are marked as such in the text.