G5 and G9 melamine tubes are produced by lamination molding and tube rolling. Understanding the process explains why melamine tube behaves the way it does, why inner diameter affects the maximum producible length, and which of the two methods suits your part. This page covers both production routes and the quality checks that keep melamine tube consistent.
Why Melamine for Fuse Bodies
Melamine is a hard, dense thermoset built from melamine resin and glass cloth reinforcement. Compared with phenolic or generic polyester laminates, it offers high tracking resistance, so a conductive path is less likely to form across the surface after contamination or moisture. It also holds its shape at temperature and provides strong dielectric strength in a thin wall, which is exactly the combination EV, PV, and communications fuses need. That is why G5 and G9 melamine tubing dominates compact high-voltage fuse bodies.
Lamination Molding
Melamine tube is based on lamination molding, a process in which prepreg tape is cut and laminated according to the shape and size of the product, then placed between two polished metal molds and heated and pressurized to form the composite. This gives precise control over the finished geometry. It suits short, thick-walled, or complex parts where dimensional accuracy and a fine surface finish matter more than continuous length.
Tube Rolling
The rolling process works as follows:
- Hot rollers on the tube rolling machine soften the adhesive tape so the resin on the tape melts.
- Under controlled tension, the rollers use friction against the core mold to wind the tape continuously onto the core tube until the required thickness is reached.
- Cold rollers cool and set the tube.
- The tube is removed from the machine and sent to a curing oven.
- After curing, the core mold is removed, leaving the composite rolled tube.
Rolling is the more economical route for long, straight, thin-walled tubes, and it is how most G5 and G9 fuse bodies are made. Its weakness is length control as diameter grows, explained in the next section.
Molding and Rolling Compared
| Consideration | Lamination molding | Tube rolling |
|---|---|---|
| Best suited to | Short or thick-walled parts, complex geometry | Long straight tubes, thin walls |
| Dimensional control | Set by the mold, very repeatable | Set by mandrel and winding tension |
| Length capability | Limited by mold size | Long, but constrained at larger IDs |
| Surface finish | Polished mold finish both sides | Good, dependent on mandrel condition |
| Tooling cost | Higher per geometry | Lower for a range of lengths |
| Typical use | Insulating blocks, formed sections | Fuse bodies, tubes in volume |
Why Inner Diameter Limits Length
Because melamine resin is water-soluble, larger inner diameters are harder to control. When the inner diameter is greater than about 12 mm, the tube can only be rolled to roughly 500 to 530 mm long, so it stays manageable by hand. Otherwise, the melamine resin tends to form bubbles in the middle during heating and hot pressing, which lowers performance.
The mechanism is worth understanding rather than just accepting. Solvent and moisture have to escape from the laminate as it cures. In a large-diameter tube the wall is thicker relative to the curvature, and the escape path is longer, so vapor that cannot leave is trapped as voids. Voids reduce dielectric strength and create initiation points for tracking. Capping the length keeps the diffusion path short enough that the laminate cures sound.
Where G5/G9 Melamine Tube Is Used
- New-energy EV fuses: battery pack, inverter, and charger circuits where a compact body must hold DC dielectric strength.
- PV solar fuses: string and array protection at 1000 V to 1500 V DC, where long-term UV and thermal endurance matter.
- 5G and communications fuses: small bodies with tight tolerance for automated assembly.
- Industrial control: where tracking resistance on a contaminated surface is the governing requirement.
Our EV and PV fuse requirements and melamine tube selection article covers the application side, and the UL standard PV fuse and melamine tubing page covers the standards angle.
Quality Control Points
- Prepreg condition: resin content and volatile content within window before rolling, since both drive void formation.
- Winding tension: held consistently along the length, because tension variation shows up as wall thickness variation.
- Cure profile: time and temperature recorded per batch, since undercure leaves residual volatiles that re-appear as bubbles later.
- Bore roundness and concentricity: measured at both ends and mid-length, not only at the ends.
- End face quality: square and burr free, so the tube seats in the cap without rocking.
- Surface tracking test: verified on sample parts where the end application demands high tracking resistance.
Availability and Custom Work
We stock common inner diameters in G5 and G9 melamine tube, which keeps lead time short for standard fuse sizes. For anything outside the stock list, we run the same rolling and curing process to your drawing, and we can machine openings, threads, chamfers, tapers, and multi-hole features after cure. Because machining after cure is the standard route, features should be dimensioned from a stable datum rather than from a raw edge.
Why Source From a Direct Manufacturer
Tianze Electrical builds G5/G9 melamine tubes from electronic-grade glass cloth and melamine resin, with ISO 9001 certification and SGS material testing available, and stocks common IDs. Because rolling, curing, and machining happen in one plant, the length limit, bore tolerance, and feature geometry we quote are the ones production can actually hold at volume.
Frequently Asked Questions
Q: Why is my long melamine tube limited in length?
A: Above roughly 12 mm ID, the water-soluble resin makes long rolls hard to control, so length is capped to avoid bubbles and performance loss.
Q: Can you machine custom features?
A: Yes, including openings, threads, chamfers, tapers, and multi-hole work.
Q: What is the difference between G5 and G9?
A: Both are melamine glass laminates; the grades differ in resin formulation and the resulting temperature and mechanical performance. Tell us the duty and we will confirm which grade fits.
Q: Do you supply tubes with the end caps fitted?
A: We supply the tube to drawing. Caps and contacts are usually added by the fuse maker, but we can machine the seating features to the dimensions their caps require.
See the G5/G9 melamine tube page or email sale@fusestube.com.
