Hollow Castings: Measure the Wall and Hold the Core
A 5 mm wall with no measurement map is how one side goes thin and the buyer calls it a mold error. If you are locking a hollow resin or concrete tool, this page is the validation: nominal wall, allowed variation, and locators that stop float and tilt. A core that only has a top strap can still walk sideways under wet load.
RUUIPON pours platinum RTV skins and locates cores in Bao'an, Shenzhen (Licheng Technology Industry Park, Xinhe Blvd, Shajing; USCC 91440300MA5FAXCN9W) since 2018. Simple 3D is USD 50 when that CAD scope applies. Prototype is 3-7 business days after CAD lock. Production is MOQ 20 pieces per design.
Where this page sits
How to design the core, buoyancy, and demold path lives on hollow inner-core design and silicone mold inner cores. A large planter load lives on large concrete planter molds. This page covers wall measurement and locator proof on the first hollow casting.
Write nominal wall and variation
Do not stop at "target wall = 5 mm." Write measurement locations, allowed variation, base thickness, rim thickness, and whether a miss is cosmetic or structural. A flexible skin needs a measurement state: seated in the jacket, core locked, or after the pour. Soft rubber changes under a caliper.
Float and tilt are different
A core can rise, walk sideways, or rotate. A top restraint can stop float and still leave a 2-3 mm side shift that thins one wall. Pick locators that lock the degrees of freedom you actually need. Top bridge, bottom pin, keyed shell, removable spacers, or a through-rod - choose from load, access, and the witness mark you will accept.
Typical shop values
Reference values only. Confirm material-specific limits against the supplier’s technical data and agree project acceptance criteria before production.
| Item | Typical shop value |
|---|---|
| Quote inputs | Nominal wall, allowed mm, dump (resin / concrete), locator marks you will accept |
| Core shift that changes the wall | About 2-3 mm side walk is enough to reject a thin side |
| Locator jobs | Stop float, tilt, and rotation - not only "hold it down" |
| First-cast proof | Section, rim caliper, or go/no-go at named stations |
| 3D / CAD | USD 50 when that modeling scope applies |
| Prototype after CAD lock | 3-7 business days |
| Production after written pass | MOQ 20 pieces per design |
| Contact | [email protected] · +86 135 3006 2969 |
Witness marks are a choice
A locator can print a pad, hole, or ridge on the casting. Place it where it is hidden, easy to fill, or already a drain. If the hero face cannot take a mark, use another support route. Do not discover the witness on the first painted part.
Pour around the core
Map the annular path. Narrow gaps, a flow split, air at the rim, a bridge that blocks fill, and high-point vents all change the casting even when the core is centered. A well-located core can still leave a void if the dump cannot close around it.
Section the first casting
On a high-risk hollow, measure the first pour. Cut a sacrificial piece, use a rim caliper, or run a go/no-go. Record wall at rim, four quadrants, and base. One thin side is core walk. A fat-and-thin pair that follows the pour path is fill, not location.
Worked example: hollow planter
Typical job, not a named PO. Buyer wrote "5 mm wall." We required rim and mid-height stations plus or minus 1 mm, a bottom pin plus a top bridge, and a sacrificial section. The first pour was thin on the handle side. The pin had stopped float; it had not stopped tilt. The second locator closed the map before MOQ 20.
When this page does not apply
This measurement page does not replace inner-core design or planter tooling. It does not apply to a solid figurine with no core. HCR compression products and molds stay on a RUUIPON HTV RFQ. High-volume LSR cold-runner part tools are a different RFQ - ask us. A slush / rotational hollow with no inner core is a different process.
RFQs we will not accept as-is
"5 mm wall" with no stations or tolerance. A top strap only on a tall wet pour. Approving the empty mold with no section. Sending an HCR / LSR part through this RTV hollow page.
Matched next step
Send outside and inside geometry, nominal wall, dump material, and where a locator mark is allowed. We will name locators and the first-cast map. "Hollow mold, keep it light" is not enough.
Send wall, dump, and locator limits · Inner-core design · Inner cores · Planter mold
[email protected] · +86 135 3006 2969 · Licheng Technology Industry Park, Xinhe Blvd, Shajing, Bao'an, Shenzhen. USCC 91440300MA5FAXCN9W.
FAQ
Is this the inner-core design page? No. Design lives there. Measurement lives here.
Can we skip the section cut? Only if you have another way to prove wall at named stations.
Does a top bridge stop tilt? Not by itself. Add a second locator if the core can walk.
Do you hang food papers on a resin hollow? No.
What is MOQ after a pass? 20 pieces per design.