If you need a silicone part, a gasket, a grip, a seal, a custom bumper, a soft keypad, or a one-off prop, the slow and expensive part has never been the silicone. It is the mold. Traditional molds for silicone parts are CNC machined from aluminum or steel, and when those metal tools are used for prototypes or short runs, Formlabs' guide to casting silicone puts the lead time at several weeks and the upfront tooling cost at hundreds to thousands of dollars. That is a lot of money and calendar to find out whether your gasket seals.
There is a faster route, and we run it at DC Additive Pros in Rockville, Maryland every week: we 3D print the mold. No metal, no machining queue, and a mold in your hands in 1 to 5 business days depending on complexity and quantity.
I need a silicone mold but I do not want to pay for metal tooling. Can a 3D printed mold actually do the job?
Yes. A rigid 3D printed mold in PETG, ABS, ASA, or PCTG will cast room temperature vulcanizing (RTV) silicone just fine, because RTV silicone cures with no heat and no pressure, so the mold never has to survive a press or an oven. That is the whole trick. The metal tooling in mass production exists because liquid silicone rubber injection and heat cured rubber compression run hot and under pressure. Two-part RTV silicones, the tin cure and platinum cure kits sold by the pint, cure on a bench at room temperature. Formlabs notes that because RTV silicone does not require high heat or pressure, it can be formed with limited equipment in a prototyping lab, and that most castable silicones are not chemically adhesive, so the cured part peels away from the mold surface. A stiff plastic mold is all you need to hold the shape.
We design the mold around your part, print the halves, and ship them with registration features so they line up every time. You mix, pour or syringe, clamp, wait for cure, and pop the part out.
Already have a mold that is worn, cracked, or was made from a drawing nobody can find? Ship it to us. We 3D scan your current mold, rebuild the cavity in CAD, fix anything that was wrong with the original, and print the new molds from that model. You do not need the original part, only the mold you have been using.
Which mold style fits your part
There are four styles, and the same guide describes each. A compression mold is two printed halves; you pack silicone putty in and clamp, the closest match to production gaskets. An injection filled mold has a fill gate and vents; you syringe liquid silicone in and gravity fills the cavity, the workhorse for grips, seals, and any single continuous part. An overmold suspends hardware in the cavity so silicone forms around it: a soft sheath over a sensor, magnet, or electronics module. An eggshell mold is a thin sacrificial shell cracked away after cure, used once for parts with deep undercuts. Tell us what the part does and whether you need one, ten, or a hundred, and we pick the style. The first three are good for dozens of casts; an eggshell is single use by design.
What about layer lines? I do not want my silicone to look 3D printed.
Silicone copies whatever surface it cures against, so we treat the mold cavity as the finished surface: fine layer heights, orientation that keeps the cavity face smooth, and a sealing coat before the first pour. This is the real limitation of a printed mold and we would rather say it up front. Formlabs' guide points out that RTV silicone captures fine surface detail, including defects, and that an FDM mold will leave layer impressions in the silicone if the cavity is left raw. So we print the cavity side at the finest layer height the geometry allows, orient it so the critical surface is not a stepped overhang, and seal it with a clear coat so the grooves are filled before silicone touches it. For a gasket inside an enclosure, the raw cavity is usually fine. For a part someone will hold or see, we seal and smooth, and the quote states which finish you are getting.
One more compatibility note for the platinum cure crowd: platinum silicones can be inhibited by certain surfaces and leave a tacky skin. Rigid thermoplastics like PETG and ABS are generally friendly to them, but any sealing coat or release agent is a new variable. That is why we recommend ordering one mold first: run your test pour with your exact silicone, confirm the fit, finish, and cure, and then order the rest. The test pour is yours to run, in your shop, with your material, so there is no guessing about how it will behave once you are casting in volume. Tell us which silicone you are using and we will match the coating to it.
Why this changes the math for small companies and makers
Metal tooling forces you to get the design right the first time because a second tool costs the same as the first. A printed mold flips that. If the first gasket is 0.3 mm too thin at the lip, we change the CAD, reprint the half that changed, and you have the revised mold in days. Iteration stops being a budget line and becomes a normal step. It also puts silicone parts within reach of people who never had a tooling budget: a hardware startup that needs 50 sealed enclosures for beta units, a restorer who needs a rubber bumper for a discontinued machine, a robotics team that wants a soft gripper pad, or an Etsy seller building a product line without a factory order. If the original part exists but the drawing does not, our 3D scanning and reverse engineering service captures the old part so the new mold matches it. When the mold is done, our build and ship process gets it out the door from Maryland with tracking.
How to get a quote
Send us one of four things: a CAD file of the silicone part, a physical sample we can scan, your existing mold so we can scan it, or a sketch with dimensions. Tell us the silicone you plan to use (or ask us to pick), the quantity you expect to cast, and whether the surface is cosmetic. We come back with a mold style, a material, a finish level, and a ship date inside the 1 to 5 business day window. Start with one mold, run your test pour, then order the set. Email info@dcadditivepros.com.
And if you make silicone kits, mold releases, sealing coatings, or pressure pots and want a real shop to run them against printed molds and write up what happens, we review products. Same address.
Frequently asked questions
Can you 3D print a mold for silicone casting instead of machining it from metal?
Yes. RTV silicone cures at room temperature with no pressure, so a rigid 3D printed mold in PETG, ABS, ASA, or PCTG holds the shape without metal tooling. DC Additive Pros ships printed silicone molds in 1 to 5 business days depending on complexity and quantity.
How long does a 3D printed silicone mold last?
Compression, injection filled, and overmolds are typically good for dozens of casts before the cavity wears, according to Formlabs' silicone casting guide. Eggshell molds are single use because they are cracked away to release the part.
Will layer lines show up on my silicone part?
They can, because silicone copies the mold surface. We print the cavity at fine layer heights, orient it so the critical face is smooth, and seal it with a clear coat before the first pour. For cosmetic parts we smooth further and state the finish level on the quote.
I have an old mold but no drawing. Can you copy it?
Yes. Ship us your existing mold and we 3D scan it, rebuild the cavity in CAD, correct any wear or damage, and print new molds from that model. Order one first, run your test pour, then order the rest.
What silicone works in a 3D printed mold?
Two-part RTV silicones, both tin cure and platinum cure, in a wide range of durometers. Platinum cure silicones can be inhibited by some surfaces, so order one mold first, run your own test pour with your exact silicone, and then order the rest. Tell us which silicone you use so we match the coating.
Sources: Formlabs, "How to Cast Silicone Parts in 3D Printed Molds" (blog guide); Cimquest, "Overview of Silicone Molding 3D Printed Tooling." Lead times stated are DC Additive Pros shop figures for typical mold sizes.