Drawing or measured sample
Representative part: molded cuff with a named convolution.
Key axis: closed and open length with ID/OD.
Ask: whether the factory will quote from the drawing or from a recut sample.
Same-basis request
custom molded rubber bellows
Turn the requirement into a request several factories can quote on the same basis. Custom molded rubber bellows need a cavity story: compression molding or transfer molding, the drawing that locks the convolution, and the compound the buyer will still own after the first lot.
Rubber Bellows Sourcing is an independent sourcing partner. We issue one written list. We do not claim a tool shop, a press count, or an authorization. Gather the axes below before anyone talks about a unit number.
Request Factory QuotesWhat the buyer should gather before the request leaves the plant
These six cards are application-to-request translations. They are not promised results and not a plant map this desk owns.
Compound shortlist
Representative part: NBR, EPDM, silicone or FKM cuff.
Key axis: Shore A hardness the supplier must confirm.
Ask: ASTM D2240 condition, not a colour guess.
Medium and temperature
Representative part: boot around a rod or a pump shaft.
Key axis: service temperature in °F or °C with the fluid named.
Ask: continuous versus excursion, not a brochure range copied here.
Tooling ownership
Representative part: new cavity versus a reused insert.
Key axis: who stores the tool and who pays the first shot.
Ask: gate design / runner system only if the factory proposes a new mold.
Lot documents
Representative part: first-article plus production lot.
Key axis: dimensional report and named ASTM method.
Ask: PPAP only when the receiving plant already runs that file.
Equivalent offer
Representative part: a substitute convolution when the exact item is unavailable.
Key axis: what changed on wall, hardness or compound.
Ask: write the substitution; do not treat it as a courtesy upgrade.
Questions each supplier should answer on the same custom molded rubber bellows line
Hardness and compound
Which Shore A number is a question, not a reprint?
Ask the factory to confirm Shore A on the quoted compound. This desk will not convert a black photo into 70A. Shore A and Shore D stay on different scales.
When is silicone the wrong first call?
Hydrocarbon splash and many solvents swell silicone while FKM holds sealing force. Silicone still wins on a wide temperature window and many food-contact files. The buyer names the medium; the factory names the swell it will stand behind.
Process and equivalent lines
Compression molding versus a thermoplastic substitute
Vulcanized rubber still wins on compression set and continuous heat above many TPE windows. A TPE or TPU over-mold can cut cycle time, but it is a different request. Do not let a salesperson silently swap thermoset for thermoplastic elastomer.
How is an equivalent treated when the exact item is unavailable?
Re-issue the line with the changed axes visible. Keep the original configuration on file so a later batch can be compared with the approved item. An unnamed “close enough” convolution is not yet a competitor.
Notes you can request with the brief
- Request-writing checklist — axes factories need on one page.
- Quote-reading notes — how to send an incomplete offer back.
- Sample acceptance sheet — what to record on a molded piece.
- Application translation — site conditions without a promised duty cycle.
These are page notes, not downloadable certificates this desk issues. Factory files stay with the named supplier and the quoted lot.
Issue the custom molded rubber bellows list once
Optional budget and supplier preference can be added. Preference is a buyer label, not a verified factory rating. No existing quotation is required.
- Same ID/OD and compound to every factory
- Shore A asked, not assumed
- Substitution written, not implied