#cell-BqXGxD5EB2vr4IZ{order:0;}
The science of injection molding machine tonnage: the watershed between small tonnage and large tonnage
#cell-fHQ5jUgy5pMfjtn{order:0;}
In the field of plastic injection molding, the "tonnage" of an injection molding machine directly determines its capacity limit. Tonnage does not refer to the weight of the entire machine, but the size of its clamping force, measured in tons (T). This parameter represents the maximum closing force that the clamping system of the injection molding machine can exert, which is used to resist the huge expansion pressure generated when the molten plastic is injected into the mold. If the clamping force is insufficient, the mold will be stretched open, resulting in flash burrs; and excessive tonnage will cause energy waste and equipment loss.The calculation of clamping force follows the core formula:Clamping force (T) = product projection area (cm²) × mold pressure (kg/cm²) × safety factor / 1000The mold pressure depends on the material properties:Ordinary plastics (such as PP, PE): 250-350 kg/cm²Engineering plastics (such as PC, nylon): 350-500 kg/cm²The safety factor is usually 1.1-1.2.
#cell-hsscrAED38AdJ8k{order:0;}
1. The core differences between injection molding machines of different tonnages
#cell-e851tz2HjaVj4vP{order:0;}
Injection molding machines can be divided into four categories according to tonnage, which have significant differences in mechanical structure, application scenarios and technical requirements:（1）Small machine (30-100 tons)Structural features: mostly vertical or angular design, mainly fully electric drive, small footprintInjection volume: usually ≤200 grams (based on PE)Typical applications:Electronic connectors (USB interface, SIM card tray)Precision gears (clocks, micro motor parts)Medical equipment (syringe needles, test tubes)Advantages: high precision (repeat error ±0.01mm), energy saving (60% less power than hydraulic presses), no oil pollution（2）Medium-sized machine (150-500 tons)Mainstream machine: hydraulic or hydraulic-electric hybrid drive, horizontal structureInjection volume: 300-2000 gramsApplication scenarios:Household appliance housing (rice cooker, vacuum cleaner housing)Daily necessities (washbasin, chair, toy)Automotive interior parts (dashboard frame, door handle)Technical highlights: Can be equipped with multi-color injection molding system (such as P-type/L-type double shot) to achieve dual-material composite molding（3）Large machine (600-1000 tons)Structural features: two-plate clamping mechanism, enhanced rigidity and mold opening spaceInjection volume: 2500-5000 gramsTypical products:Logistics pallet (1200×800mm standard size)Automobile bumperLarge trash canChallenge: Need to cooperate with mold temperature control system to prevent shrinkage of thick-walled parts（4）Ultra-large machine (>1000 tons)Representative models: Haitian 1600T, Fuqiangxin 1900T three-color machineCapacity indicators: up to 4000 tons, injection volume exceeds 20kgApplication areas:Automobile instrument panel (one-piece molding)Yacht deck partsLarge turnover box (volume>1000L)Innovative design: horizontal two-color machine (H type) with overlapping mold technology, production capacity increased by 70%
#cell-D3NF3Sn854EGgPg{order:0;}
Table: Comparison of injection molding machine tonnage and key parameters
#cell-ymhY2qqWYKNO3bx{border-style:solid;border-width:1px;order:0;}#unit-hgDkEFU5pvC77ly [ce-data-type="text"]{text-align:center;border-width:1px;}
Tonnage range
#cell-W74J7ujeySj2HUF{border-style:solid;border-width:1px;order:0;}#unit-r2NPKcpb0NvsOKy [ce-data-type="text"]{text-align:center;}
Clamping force (T)
#cell-V2rRDHJSAkPOMbz{border-style:solid;border-width:1px;order:0;}#unit-SG06MOxRUFyWMpy [ce-data-type="text"]{text-align:center;}
Injection volume (g)
#cell-dvT4RKZi3VeJLqN{border-style:solid;border-width:1px;order:0;}#unit-Rz3yUFgWAAnUkAU [ce-data-type="text"]{text-align:center;}
Screw diameter(mm)
#cell-gVAiog8UnQTZXKc{border-style:solid;border-width:1px;order:0;}#unit-I72x5ugT9Jyh4jz [ce-data-type="text"]{text-align:center;}
Typical mold structure
#cell-SetIUkBX7NsJaLL{border-style:solid;border-width:1px;order:0;}#unit-nJ4C7ce0oiBJGwO [ce-data-type="text"]{text-align:center;border-width:1px;}
Minicomputer
#cell-3jOplLs77PTASVs{border-style:solid;border-width:1px;order:0;}#unit-hnu5ZHqhZ8XOfk7 [ce-data-type="text"]{text-align:center;}
30-100
#cell-g7wxIHdF5KpfXUO{border-style:solid;border-width:1px;order:0;}#unit-ai8ljYdtz7vRZZJ [ce-data-type="text"]{text-align:center;}
≤200
#cell-xyH2cPuVQajF80N{border-style:solid;border-width:1px;order:0;}#unit-zzLZqrQFQ4o9uCe [ce-data-type="text"]{text-align:center;}
25-40
#cell-O2F7C2tiSLFb0jA{border-style:solid;border-width:1px;order:0;}#unit-Mz4OGHOiUdHOQzX [ce-data-type="text"]{text-align:center;}
Toggle
#cell-rHZwOD3QqBt9nn9{border-style:solid;border-width:1px;order:0;}#unit-p5oIcMgWDJpXIef [ce-data-type="text"]{text-align:center;border-width:1px;}
Medium-sized machine
#cell-nkn40vHWXHdijef{border-style:solid;border-width:1px;order:0;}#unit-LRSYmz3wG3zK57t [ce-data-type="text"]{text-align:center;}
150-500
#cell-iABR01rVNQO8g0n{border-style:solid;border-width:1px;order:0;}#unit-uLyXuDFLkEISUDH [ce-data-type="text"]{text-align:center;}
300-2000
#cell-95ogqjSA9yEwNWg{border-style:solid;border-width:1px;order:0;}#unit-j6CDSw8YyyWBycL [ce-data-type="text"]{text-align:center;}
45-70
#cell-R8lBMyftGVdl3zd{border-style:solid;border-width:1px;order:0;}#unit-GxQJgfKzBU2xufr [ce-data-type="text"]{text-align:center;}
Toggle/Two-Plank
#cell-N1rL2ny80dlZreZ{border-style:solid;border-width:1px;order:0;}#unit-36ZuNmxgp6Q44DF [ce-data-type="text"]{text-align:center;border-width:1px;}
Mainframe
#cell-8sIQsUa1IS8C2Xf{border-style:solid;border-width:1px;order:0;}#unit-g0KhaGnlIj61h3c [ce-data-type="text"]{text-align:center;}
600-1000
#cell-F3vs5wQsK3BurMn{border-style:solid;border-width:1px;order:0;}#unit-PUpVQZrfE4299x1 [ce-data-type="text"]{text-align:center;}
2500-5000
#cell-Z4X9aSrGXpfswzq{border-style:solid;border-width:1px;order:0;}#unit-mrucr4UOSyD2ZPq [ce-data-type="text"]{text-align:center;}
75-110
#cell-eT6BLEb8QrgYkAU{border-style:solid;border-width:1px;order:0;}#unit-QfBnlDmZJyE3CDg [ce-data-type="text"]{text-align:center;}
Two-plate
#cell-OqQMacB9NK7jusG{border-style:solid;border-width:1px;order:0;}#unit-YFapAlGYKCko6TM [ce-data-type="text"]{text-align:center;border-width:1px;}
Large Scale Machines
#cell-o2fyyJC3oQmgoQB{border-style:solid;border-width:1px;order:0;}#unit-mL55eGSCNuzrF0G [ce-data-type="text"]{text-align:center;}
>1000
#cell-VpalpMFQv91VFVz{border-style:solid;border-width:1px;order:0;}#unit-imqbXfwL1Sabk3b [ce-data-type="text"]{text-align:center;}
>5000
#cell-9TS0jyacCv23tET{border-style:solid;border-width:1px;order:0;}#unit-o2cLcRBH7Ly48qi [ce-data-type="text"]{text-align:center;}
≥120
#cell-6tfE5j6yWufb90H{border-style:solid;border-width:1px;order:0;}#unit-VhvNxRSLi3WBe6h [ce-data-type="text"]{text-align:center;}
Two-plate enhanced
2. Core principles and application scenarios of tonnage selection
The cost of failed selectionInsufficient tonnage: product flash and size deviation (a mold that is stretched 0.1mm can lead to scrapping)Tonnage is too large: energy consumption increases by 30%-50%, the risk of mold deformation increases, and mold exhaust difficulties lead to burning
Four-step scientific selection methodCalculate clamping forceTake the car bumper as an example: the projected area is 1200×600mm=7200cm², and the pressure in the PC mold is 400kg/cm²Theoretical clamping force = 7200×400×1.2/1000≈3456T → Select the 3500T modelTest toleranceMold size ≤ tie rod spacing (such as the tie rod spacing of the 1000T machine is usually 1200×1200mm)Mold thickness ∈ [minimum mold thickness, maximum mold thickness] (for example: the mold thickness range of 350T machine is 150-450mm)Ensure demoulding spaceMold opening stroke needs to be > product height×2 + runner length (deep cavity parts need to add an additional 20% margin)Match injection systemFinished product weight should be ≤ Theoretical shot volume × 75% (leave a safety margin)For thin-walled parts, choose a small screw (high pressure and high speed), and for thick-walled parts, choose a large screw (high plasticizing capacity)Industry scenario applicationElectronic industry (below 100T): Connectors use a 30mm diameter screw, and the shot speed ≥300mm/s ensures fillingHome appliance industry (300-800T): Air-conditioning panels use hot runner molds + 650T machines to reduce runner wasteAutomotive industry (>1000T): Door panels use a double-station turntable three-color machine to achieve one-time molding of substrate + soft glue + logoMedical industry (50T fully electric): Syringe production is equipped with a Class 100 clean room to avoid hydraulic oil pollution
3. Future trends in technology evolution and tonnage selection
The selection of injection molding machine tonnage is undergoing three major technological changes:Energy-saving driveAll-electric injection molding machines (such as FANUC Roboshot) replace hydraulic presses below 100T, reducing energy consumption by 60%; the penetration rate of hybrid technology in large machines increases (such as Haitian MA series)Intelligent control systemIoT module monitors clamping parallelism in real time (deviation of >1000T machine needs to be ≤0.1mm/m)AI algorithm dynamically optimizes the pressure holding curve, reducing the molding cycle of large-tonnage machines by 15%Specialized developmentMicro injection molding machine (<10T): used for medical microfluidic chips, injection accuracy ±0.002gMulti-component large machine: such as Fuqiangxin FB-1900R three-color machine, turntable diameter 2250mm, serving the integrated molding of automobile lampshadesIn the future, with the application of new materials (such as carbon fiber reinforced plastics), the clamping accuracy requirements for high-tonnage machines will be further improved, and modular design will make tonnage adjustment more flexible-by replacing the screw assembly, the same clamping unit can cover the injection range of ±30%.
4. Conclusion
The selection of injection molding machine tonnage is like deploying troops for a battle: too little will not be enough, and too much will be a waste of money and effort. From a connector the size of a fingernail to a car bumper several meters long, the difference in tonnage is the result of the deep collaboration of material science, mechanical design, and control algorithms. In the future, with the advancement of energy-saving technology and intelligence, tonnage selection will no longer be based solely on empirical formulas, but will be dynamically optimized based on real-time data, pushing plastic molding into a new era of "tailor-made".
