Low Pressure Injection Molding
Dennis Walker, Retco Tool Co.Inc
PIM 2001 Conference paper, presented in Orlando, Florida
I. Why Low Pressure Molding (LPM)?
- Less Start-up Capital
- Semi-Auto machine $30-40K
- Auto machine $40-60K
- Tooling costs substantially lower
- normally less than $10K usually less than $5K for single cavity semi-auto molds
- Tooling can be Aluminum
- High Volume is feasible.
- Can hold tolerances
- normally +/- 0.005' (0.1 mm) per inch (25.4 mm), some current projects being held to +/-0.001' (.02 mm)
II. What geometric and mass capabilities are viable with LPM?
(slide 2) Mach Nozzle
- Parts less than a gram.
- 0.300' (7.6 mm) length
- 0.075' (1.9 mm) OD
- 0.011' (0.3 mm) venturi
- 200 point CAD Curve
- Approx. yearly usage 15000 pcs, 3 details
- 6% Co sub-micron
(slide 3) TJK Nozzle
(slide 4) Mixing chamber
- Parts less than 50 grams.
- 20° angle, 0.058’ (1.5 mm) small orifice from 0.150’ (3.8 mm) dome configuration.
- weight 35 grams, Rockwell A 95+
- epoxied into a 17-4PH stainless steel casting and mechanically fixed with 2 ea. 6-32 1/8 set screws
- Approx. yearly usage 10000 pcs.
- 4.5% Co ultra grain
(slide 5) Nova Nozzles series
- Parts less than 100 grams.
- one through hole
- one feed chamber
- 2 O-rings and 1 flat
- weight 70 grams
- 4.5% Co sub-micron
(slide 6) Nova Nozzles series core rods
- Parts from 100 to 500g.
- Gas Seat Check
- 3 series, 28 details per series
- details are to venturi size
- Constant 6° angle on ID for all details
(slide 7) Bent feed tube
- 6% Co sub-micron
- Parts more than 500g.
- 90° exit orifice
- 5° angle in shank
- 17-4 PH stainless steel shovel epoxied on
- weight 735 grams
- 12% Co 3-5 µm grain
- Parts more than a kilo
- currently molding a 7.8 Kg disk, 11' (279 mm) diameter
III. Are ceramics viable with LPM?
(slide 8) Burner block
- Ceramic materials that have been low pressure molded by Retco
- Yttrium Stabilized Cubic Zirconia
(slide 9) YES
- High volume is feasible
- 25K per week
IV. Does LPM have a place in today’s market?
- Yes, today’s technologies are creating new and unusual wear and corrosion problems that only a cemented carbide can solve.
- Serious "wear" problems can cause costly shut-downs and customer dis-satisfaction. LPM Carbide can be an effective means to solve this.
- The lower cost of LPM allows the user to seek a better solution for his wear problems. In a lot of situations the user knows that WC is right for the application but it can’t be pressed and would be cost prohibitive to Preform.
- The current development of the Ultra and Nano-grained Tungsten Carbides will send more users to carbide wear parts due to the cost effectiveness in terms of longer usage and less shut-downs.