Please Leave Us A Message
Privacy statement: Your privacy is very important to Us. Our company promises not to disclose your personal information to any external company with out your explicit permission.
EN
Structural frames are the one interior part where dimensional stability is a functional requirement, not a cosmetic one. They sit at the high-precision end of the Automobile Molds range — 6 t of steel, four insert nests, and a CMM report delivered with the tool. The frame carries the glass, locates against the roof aperture, and often becomes the welding substrate for a second frame — so every tenth of a millimetre propagates into wind noise, water ingress and weld strength.
Because three effects add up: coefficient-of-thermal-expansion mismatch between PA66-GF30 and steel, packing differences around each insert, and the release of moulded-in stress in the first 48 hours.
The numbers are not subtle. A 1.4 m frame cooling from an 80 °C mould to a 23 °C inspection room would contract about 3 mm in the plastic if it were free; the steel insert contracts about 1 mm over the same length. That 2 mm difference cannot disappear — it converts into bow, twist or clip-position error, depending on where the inserts sit.
| Contributor | Effect on a 1.4 m frame | Control |
| CTE mismatch, plastic vs steel | 1.0–2.5 mm bow | Insert preheat to 80–100 °C, symmetric insert layout |
| Insert position in the tool | ±0.15 mm at each insert | Two fixed pins plus one spring pin per insert |
| Pack difference around inserts | 0.2–0.5 mm local sink or bulge | Gate at least 15 mm from any insert edge |
| Stress relaxation, 48 h | 0.3–0.8 mm additional drift | Fixture check at 24 h, not at ejection |
Glass fibre makes it worse and better at the same time. Thirty percent GF drops the flow-direction expansion to 25–35 µm/m·K but pushes cross-flow to 60–80, so a frame that is stiff along its length is soft across its width. Gate position therefore decides which direction the bow appears in — and moving a gate to fix a weld line can move the bow to the other axis.
Insert layout matters more than any process setting. Put inserts symmetrically about the frame centreline, never clustered on one side, and never within 20 mm of a gate. An asymmetric insert pattern guarantees a twist that no cooling change will remove.
The same insert logic appears in smaller parts: metal inserts in Home Appliance Parts such as hinge housings and handle mounts fail in exactly this way when the insert sits off-centre.
✅ Bottom line: Insert position and preheat decide frame flatness; CTE mismatch sets the floor you cannot go below.
Locate each insert on two fixed pins and one spring pin, preheat to 80–100 °C, gate 15 mm away from any insert, and cut the cavity to the conditioned part rather than the nominal drawing.
Tooling decisions, in the order they matter:
Welding frames add one requirement that catches most first-time programs: the weld joint needs flatness under 0.5 mm across the whole mating face, and a 1.0–1.2 mm weld rib with a 0.3 mm interference. If the frame bows 1.5 mm, the welder compensates with pressure and the joint fails in peel rather than in shear.
Measurement closes the loop. Fixture the part at 24 hours in a 23 °C / 50% RH room, measure insert positions and perimeter flatness on a CMM, and compare against the conditioned model — not the drawing. PA66 absorbs moisture and grows 0.3–0.6% between dry-as-moulded and equilibrium, which on a 1.4 m frame is another 4–8 mm of length that has nothing to do with the tool.
Jusheng builds frame tools in 1.2738 with H13 gate inserts, spring-loaded insert nests and mirror-image cooling, and reports insert position on a CMM at T1 and again after 24 hours. Zhejiang Jusheng Intelligent Technology Co., Ltd. cuts frame cavities on five-axis gantry centres to hold perimeter flatness within 0.05 mm before polishing, which leaves the process budget for the CTE effect rather than spending it on machining error. The insert-nest approach is shared with Home appliance molds for hinge and bracket parts, where the same 0.05 mm bore clearance decides whether the insert cracks the boss.
✅ Bottom line: Build the cavity to the conditioned part, not the drawing; moisture and CTE together move a frame further than any machining tolerance.
Q: How much does a sunroof frame mold cost? A: A single-cavity frame tool with four insert nests and H13 gate inserts runs 85,000–160,000 from a China factory. Adding a second frame for welding, or a family tool with the reinforcement bracket, pushes it past $200,000.
Q: How long does it take to reach a stable dimensional report? A: 14–18 weeks at Jusheng: 3–4 weeks DFM and flow analysis, 8–10 weeks machining and insert fitting, then 3–4 weeks of tryout, CMM reports at T1 and 24 h, and a conditioned-part correlation.
Q: Can an existing frame tool be corrected for bow? A: Yes, within limits. We re-cut the cavity to a pre-bent profile of 0.5–1.5 mm opposite the measured bow, adjust insert pin positions, and re-verify. Beyond 2 mm of correction the wall thickness starts to drift, and a new cavity insert is the honest answer.
Send the STEP file, insert drawings, resin grade with glass content, and the flatness and insert-position callouts, and Jusheng returns a gate layout, insert-nest design and factory price within three working days. OEM and ODM programs include a conditioned-part CMM report, so dimensional approval is based on parts measured the way the customer measures them. Ask for the CTE and moisture allowance in writing — it is the number most frame programs discover too late.
Mobile: +86 13516880625
Email: info@zjjsmould.com
Website:www.zjjsmould.com
January 07, 2027
Email to this supplier
January 07, 2027
Privacy statement: Your privacy is very important to Us. Our company promises not to disclose your personal information to any external company with out your explicit permission.
Fill in more information so that we can get in touch with you faster
Privacy statement: Your privacy is very important to Us. Our company promises not to disclose your personal information to any external company with out your explicit permission.