Square tube arc punching machine is widely used in guardrail and fence workshops to produce arc‑shaped notches for tube‑to‑tube lap welding.The final notch quality,service life of wearing parts and anti‑deformation performance of tubular workpieces largely rely on reasonable die design,rather than only the hydraulic power of the host machine.Arc punching dies for square tubes have special requirements on geometric profile,die material and hardness,matching clearance,positioning‑support structure and anti‑deformation auxiliary mechanism,which are quite different from ordinary flat‑plate punching dies.
First of all,the geometric profile of upper arc punch and lower die cavity must strictly match the outer diameter of the mating tube.The arc radius of the punch should correspond to the pipe outer circle,and transition fillets shall be set at the junction of straight edge and arc section to avoid sharp stress concentration points.Sharp corners will cause local tube wall cracking during arc notching.Each specification of square tube and matched connecting pipe needs corresponding dedicated arc punch‑die set;universal one‑size‑fits‑all dies cannot guarantee notch fitting accuracy.For galvanized square tubes,the punch edge shall adopt micro‑chamfer treatment to reduce zinc‑chip adhesion and burr formation.
Die material and heat‑treatment hardness are critical for long‑term mass‑production.For ordinary Q235 galvanized carbon‑steel square tubes,alloy tool steel with hardness reaching HRC 52‑58 is the mainstream selection.When processing stainless‑steel square tubes,high‑hardness alloy steel or surface‑coated punch is required to resist material sticking and abrasive wear.Low‑hardness dies will produce rapid edge collapse,resulting in rough arc notches and frequent die replacement,which greatly reduces workshop production efficiency.
Reasonable punch‑die clearance matched to tube wall thickness cannot be ignored.Too‑small clearance increases punching resistance and accelerates tool wear;excessive clearance leads to large burrs,arc‑edge tearing and local tube‑wall collapse.For carbon‑steel square tubes,single‑side clearance is generally controlled at 8%‑12%of wall thickness,while aluminum square tubes adopt 5%‑8%single‑side clearance.Clearance value needs fine‑tuning according to actual material after sample test punching.
Special internal supporting structure is another core requirement for square‑tube arc punching die.Hollow square tubes are prone to inward collapse and indentation under stamping force.Therefore,the lower die must be equipped with inner supporting mandrel or split‑type supporting blocks inside the tube cavity during arc punching,to support the tube wall at the punching position.Without effective internal support,even high‑tonnage machine and high‑quality punch cannot avoid workpiece deformation defects.
Besides,the die assembly needs reliable guiding and stripper mechanism.Precise guide posts and guide sleeves ensure punch‑die alignment during reciprocating stroke.The stripper plate can separate the workpiece from the punch smoothly after arc punching is finished,preventing the tube from sticking to the punch.Users should also notice that excessive wall‑thickness will bring heavy load to arc‑shaped punch.If wall thickness exceeds machine allowable range,punch fracture risk rises sharply.
Before formal batch production,sample arc punching with real square‑tube samples is strongly recommended.Operators should check arc fitting degree,burr height and whether tube wall appears collapse or crack,and adjust clearance and supporting mechanism accordingly.In short,qualified arc punching dies need correct arc profile,proper material hardness,wall‑thickness‑matched clearance and effective anti‑deformation inner supporting structure.
References
APA 7th
Li,M.,&Yang,C.(2023).Die structure design and parameter optimization for arc notching of square hollow steel tubes.*IOP Conference Series:Materials Science and Engineering*,1278(1),012059.
MLA 9th
Li,Ming,and Chao Yang.“Die Structure Design and Parameter Optimization for Arc Notching of Square Hollow Steel Tubes.”*IOP Conference Series:Materials Science and Engineering*,vol.1278,no.1,2023,p.012059,
GB/T 7714‑2015
LI M,YANG C.Die structure design and parameter optimization for arc notching of square hollow steel tubes[C]//IOP Conference Series:Materials Science and Engineering.IOP Publishing,2023,1278(1):012059.
