Family mold for both halves
- Base and cover come off the same shot, so they always arrive in matched sets
- Often less tooling spend than two separate tools
- Works best when the halves are similar in size and wall
Molded part guide: enclosures
Injection Molded Enclosures
An enclosure is two or more shells that have to close, stay closed, and look right from the outside. Where the halves split, how they are held together, and how the seal is made decide most of the tooling scope.
Start here
Decide how the box opens before you detail anything else
The direction the mold opens fixes the parting line, the draft, and where every snap and boss can go. Changing it late usually means reworking the whole model.
Most enclosures are a base and a cover that pull straight off their cores. Features that point sideways, like a connector cutout in a side wall or a latch window, need a side action or a lifter in the mold. Each one is a moving part in the tool and a witness line on the part, so it is worth asking whether the cutout could sit on a face that opens in the direction of draw.
Put the parting line on a sharp edge rather than across a rounded one. A parting line on a fillet has to match perfectly on both mold halves, and any mismatch shows as a step or a thin line of flash running around the whole product.
NetProto quotes the enclosure from your CAD and returns DFM feedback before tooling is released, so side actions, undercuts, and missing draft show up while they are still easy to move.
Closing the box
Ways to hold the halves together
Each method changes what goes into the mold and what happens on the assembly line.
| Method | Good for | What it asks of the molded part |
|---|---|---|
| Self-tapping screws into molded bosses | Covers opened a handful of times over the product life | Bosses tied into walls with gussets, and boss walls thin enough that they do not sink the outside face |
| Threaded inserts | Covers opened often, or screws that carry real clamp load | A boss sized for the insert, with the insert pressed in after molding, or molded in place |
| Snap fits | Consumer products assembled quickly without tools | Latches that flex without cracking, and a plan for opening the product without breaking it |
| Ultrasonic welding | Sealed products that are never meant to be opened | An energy director or shear joint on the mating edge, and resins on both halves that weld to each other |
| Overmolded soft seal | Handheld products that need a seal and a grip in one step | A second material bonded to the rigid shell, checked for adhesion to the base resin |
Sealing
A gasket only seals if the molded land under it is flat and clean
Water and dust get in at the joint, not through the wall. Most leaks trace back to the molded surface the gasket sits on.
- Keep flash off the gasket land by running the parting line beside the seal, not across it
- A tongue-and-groove joint locates the halves and traps the gasket in the same feature
- Stiffen the walls near the sealing flange so screw load does not bow the cover open between screws
- Put compression limiters in bosses that carry gasket load, so the plastic does not creep and let the seal relax
- Name the ingress rating you design to on the quote. Your test proves the rating; the drawing has to give the seal a surface that can pass it
Show surfaces
Keep the inside of the box from showing on the outside
Bosses, ribs, and thick corners inside an enclosure pull the outer skin in as they cool.
Sink marks and gloss shadows appear on the cosmetic face directly opposite heavy internal features. A texture hides a lot of this; a high-gloss finish hides almost nothing. If the product has a glossy show face, move bosses to the side walls, core out thick sections, and expect DFM review to question any feature sitting right behind the logo area.
Texture also changes the mold. Deeper textures need more draft on the textured walls, otherwise the part drags as it ejects and the texture streaks. Pick the texture before the draft is frozen, not after the first samples.
Logos and markings can be molded in, or applied after molding by pad printing, silk screening, or laser marking. Those run as secondary operations and are quoted with the part.
Tooling
One family tool for base and cover, or two tools
Both are options at NetProto. The geometry of the two halves usually decides.
A separate tool for each half
- Each half gets its own fill and cooling, which helps when one half is much larger
- Order quantities can differ, for example when covers are replaced more often than bases
- The cosmetic half can be tuned without disturbing the structural one
Drawing
What to put on the enclosure drawing
These details change the tool, so they belong on the drawing rather than in a later email.
Which faces are cosmetic, and the texture or gloss level on each
The ingress or drop requirement the product is designed to
Fastener type and size at every screw point, and where inserts are required
The gasket material or part number and its seat, if the enclosure seals
Resin, color, and any flame rating the product needs, taken from the resin supplier datasheet
Logos and markings, how they are applied, and where they go
Keep reading
Related guides
Housings for specific jobs, and the design rules behind the sections above.
Electronic enclosures
Board mounting, shielding, heat, and flame-rated resins.
Electronic enclosuresBattery housings
Holding cells in place and giving the pack room to move.
Battery housingsSensor housings
When the housing sits in the sensing path.
Sensor housingsBosses
Screw towers that hold without sinking the outside face.
BossesSelf-tapping screw bosses
Boss design for screws driven straight into plastic.
Self-tapping screw bossesSide actions
What sideways features cost in the mold.
Side actionsTexture and draft
Why textured walls need more draft.
Texture draft requirementsFamily injection molding
Base and cover in one tool, and when that makes sense.
Family injection moldingMolded parts hub
Every part-type guide, grouped by family.
Molded parts hubFAQ
Questions about molded enclosures
What wall thickness should an enclosure have?
It depends on size, resin, and how the part is gated, so there is no single number worth publishing. Keep the wall as even as you can and add stiffness with ribs rather than a thicker wall. DFM feedback on the quote checks the wall against your resin and flow length.
Do I need a side action for a connector cutout?
Only if the cutout faces sideways relative to how the mold opens. Sometimes it can be formed by a shutoff through the part, or moved to a face in the direction of draw. DFM review will point out which applies.
Can the same enclosure tool run different colors?
Yes. Color comes from the resin, not the tool, so the same tool can run different colors in separate production runs.
Who owns the enclosure tool?
You do, once the tooling charge is paid. The tool stays available for repeat orders, and you can request it at any time.
Next step
Quote the base and cover together
Upload both halves along with any gasket or insert details. You get pricing and DFM feedback on the pair, not on each shell in isolation. NetProto manufacturing is ISO 9001 certified.