LPIM - Low Pressure Injection Molding

LPIM – Multi-Nozzle Low Pressure Injection Molding Technologies for Large Structural Plastic Parts


Milacron has set the standards, driven innovation and led the industry in Multi-Nozzle Low Pressure Injection Molding Technologies for more than four decades.  These machines can be used for Structural Foam, Structural Web, Gas Assist, Solid Molding, or combinations of these technologies depending on the application.

Ideal for injection molding large, lightweight, durable structural plastic parts, the Milacron LPIM – Structural Foam Technology creates a cellular foamed core surrounded by integral skins, forming a total integral and rigid structure.  In this process a foaming agent N2 is mixed with the polymer melt and short-shot through a modular multiple nozzle system into a mold (or multiple molds) in a volume less than is required to fill a solid part. Both the injection pressure and expanding gas/polymer cellular mixture act to fill the mold. The mold cavity pressures are 10 – 20 times lower than conventional injection molding which permits the use of lower cost aluminum molds with no hot runner, since the hot runner manifold & nozzle system is integral to the machine.  Many molds and large parts of different sizes can be molded at the same time.

The Milacron LPIM-Structural Web Technology is a proprietary multi-point gas assist process, with gas introduced through gas pins in the multiple nozzles feeding the plastic to the part that has similar light weighting advantages of Structural Foam for large parts.  The parts are solid without foam, but are packed out by low pressure internal gas pressure that produces hollow channels and hollow thick sections.  The LPIM Structural Web Process has the added benefits of an improved smooth solid molded in color surface for good cosmetics and hygienic products and faster cycles for parts that have very thick wall sections.

Milacron is also integrating other technologies into the LPIM machines such as Gas Assist Controllers, Cavity Pressure Controls Systems, Hot Runner Controls Systems, and Quick Mold Change Systems.

Milacron LPIM machinery is recommended for injection molding large structural plastic products such as material handling bulk bins, pallets, tool boxes, building products, pool panels and ladders, fencing, retail display racks, tote bins, storage sheds, shelving, cargo systems, in ground enclosures, recreational slides and toys, outdoor furniture, water storage tanks and drainage systems, burial vaults, garden lattice, dog houses, dock systems, janitorial and restaurant products, and industrial carts to name a few.



Model 500M 750MWP 1000MWP 1000MSWP 1500MHP 2500HMWP
Platen Size (H x W) (mm and in) 2489 x 2261 98 x 89 2184 x 4241 86 x 167 2616 x 4241 103 x 167 2616 x 4724 103 x 186 2712 x 4089 107 x 161 2794 x 5080 110 x 200
Maximum Shot Size PS/HDPE kg/lbs 68/54 kg. 150/120 lbs. 91/73 kg 200/160 lbs 91/73 kg 200/160 lbs 91/73 kg 200/160 lbs 91/73 kg 200/160 lbs 136/108 kg 300/240 lbs
Maximum Throughput cu.cm./ cu.in. 75380 cu.cm 4600 cu.in 98322 cu.cm 6000 cu.in 98322 cu.cm 6000 cu.in 98322 cu.cm 6000 cu.in 98322 cu.cm 6000 cu.in 150761 cu.cm 9200 cu.in
**Maximum Platen Configurations Shown, Consult Factory for Other Configurations**



  • Heavy duty fully hydraulic clamp infinitely adjustable.
  • Three (3) clamping cylinders for balanced force distribution. Center clamping cylinder has jack ram construction for fast energy efficient traverse.
  • Linear transducer for clamp positioning.
  • Proportional valve controls for clamp open/close speed; low pressure close, clamp tonnage and decompression.
  • Position based braking closed loop clamp control.
  • Recirculation filter and auto cooling system (5-micron) with independent pump and heat exchanger.
  • Overhead hydraulic reservoir with prefill valves for each cylinder.
  • Manually operated front and rear gates.
  • Mechanical knock-out plate with position adjustment.
  • Automatic central lubrication system.
  • Full ejection force on demand.


  • B&R Industrial PC control system.
  • Fast process control with 1 millisecond response time which exceeds the speed of the machine.
  • Same screen layout as Siemens/TI for operator convenience.
  • Fast screen updates.
  • Improved precision, accuracy and repeatability.
  • Closed loop injection speed controls.
  • Three injection speeds per shot size.
  • Larger 15 inch Color/touch screen operator interface with higher resolution.
  • Compact flash memory – no hard drive to wear out.
  • Unlimited recipe storage on USB memory stick or internal memory.
  • Improved data collection and storage capabilities.
  • Historical data management files.
  • Remote connectivity via the internet to Milacron for service support and upgrades.
  • USB port for program uploading/downloading.
  • Expanded diagnostics and alarms with time/date stamp.
  • USB port for transfer to PC for screen printouts.
  • “Set-back” control to lower all temperature zones to a lower idle temperature during mold change or maintenance.
  • Software for SPI standard core pull sequences A, B, C, D.
  • SPI-AN146/Euromap 67 Robot Interface with dual channel e-stop standard.
  • Heater band burn out detection.
  • Ladder logic for ease of trouble shooting.
  • Manual nozzle screen with platen graphics.
  • Nozzles can be operated independently for faster purging and color change.
  • Structural Web Gas Assist interface receptacle standard.
  • Position based braking closed loop clamp control.



  • Closed loop injection control.
  • Independent three-stage injection speed and pressure control.
  • 6000 PSI melt pressure per accumulator.
  • Injection speeds infinitely adjustable.
  • Linear transducers built into shot cylinders for shot accuracy and protection from heat and mechanical damage.
  • Melt shut-off valve between accumulator and extruder for accurate shot-to-shot repeatability.
  • Nozzle hydraulic manifold with ball valves for positive, leak free operation.
  • Horizontal melt manifolds.
  • Xaloy 800 or equivalent accumulator and plunger for abrasion resistance and long life with recycled materials.
  • Light weight tubular modular melt manifold extension blocks for ease of installation.
  • Longer inlet tubes for improved access during nozzle set up.
  • Eight (8) shot sizes per accumulator.
  • Thirty-two (32) independent nozzle sequences standard.

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