MIM技術現狀及未來發展趨勢研討展示會.ppt

1、A Brief History of MIM,What is MIM? How did MIM Begin Ray Wiech, Inventor of MIM Licensees Problematic Formulations Secret Proprietary Information Who is MIMA? Viable Process,Current & Future Worldwide Market Situation,The Art of MIMThe MIM Process in Brief,What is Feedstock? Mixing Methods Primary

2、& Secondary Binders Shrinkage Volume Pelletizing Compression Ratio Screw Designs Check Ring Clearance,Feedstock Manufacturing,Pre-Alloyed Powder CIP/Master Alloy Elemental Powders Particle Size and Distribution Atomization (Water vs. Gas) Powder Shape,Particle Size and Distribution,Typical Laborator

3、y Equipment,Feedstock Mixer & Twin Screw,Turbula Dry Mixer Twin Screw,Injection Molding,The Importance of a Helium Pycnometer in Powder Metal Injection Molding,Why Write on this Topic What is a Pycnometer Monitoring Quality using a Pycnometer Use in Manufacturing Feedstock Use in different Manufactu

4、ring Steps Molding Debinding Sintering Use of Regrinds,Why? A brief Background,A MIM manufacturer sintered 316L MIM tensile bars in two furnaces A and B from different manufacturers. These parts failed both the Tensile & Elongation Values specified and was caused by improper Injection Molding,Fractu

5、re Surface of Tensile Bars shows Pre-existing Voids,There is a need for a Tool that Detects Flaws in the Green Parts BEFORE they are Sintered.,The Tool is a Helium Pycnometer.,A Typical Helium Pycnometer,Pycnometer with different sized sample cups and holders,Quality System using Pycnometer Density,

6、Feedstock Preparation & Quality,Measure Density of Metal Powders. Measure Density of Different Binders. Calculate Weight Requirement for each Constituent based on the Volume Fraction needed. Mix Feedstock and make Granules. Measure density and flow.,Molding,Mold design parameters (runner and gate si

7、ze, gate placement, venting, mold heating or cooling) and molding machine parameters (temperature, pressure, hold time, cushion, screw return speed) affect the part. A part not molded correctly will lead to poor density and /or distortion. You want to eliminate defective parts before the next step.,

8、Molding: Why not Weigh Green Parts?,Weighing Green Parts is Assuming: The mold is properly filled. No Voids. The volume is constant. No Flash. Gates break off exactly the same way with no variation. There is no feedstock deterioration.,Molding: Determining if you have Voids in the Green Part,Check t

9、he Density of the Feedstock used Measure the Density of the (Green Parts). Crush the (Parts) used for Density Measurement to powder and Check Density.,Typical Hand Grinder used to Grind Parts Back to Granular Form,Molding Characterization by Density Measurement,Molding: Why grind up parts?,Check for

10、 voids Another reason to grind up parts and check density is to ensure you did not deteriorate the feedstock during molding, for example, evaporate some of the wax by using too high injection barrel temperatures Use too high a screw return speed and cause binder separation.,Primary Debinding,Parts m

11、ust be properly Debound before secondary debinding and sintering. Most MIM operations use a weight loss between the green and brown stages. This does not take into account powder losses during handling the brown part which may be extra fragile. Feedstock manufacturers should provide the minimum brow

12、n density needed for further processing parts.,Primary Debinding by Density Measurement,Final Density,Easy to measure with a Pycnometer No sample preparation is needed No inaccuracies arising from trapped air bubbles as in case of using Archimedes Principle with water.,The MIM Quality Process,Regrin

13、ds,Check the density of the regrinds How close is it to that of the virgin and the theoretical feedstock density? If you are mixing virgin with regrinds, what is the density of the mixture? How much variation in the feedstock density will allow you to maintain the dimensional tolerance range for you

14、r part? Know the relationship between the density and shrink factor for your feedstock.,Conclusions,The Helium Pycnometer is a simple tool for evaluating the quality of: Raw materials during incoming inspection, Feedstock, Molding of green parts, Primary debinding, Sintering and To assess the usabil

15、ity of regrinds.,De-Binding,What is Debinding? Catalytic Debinding Solvent Debinding Thermal Debinding Super Critical Fluid Extraction,Secondary Binder Removal & Sintering,What is Sintering?,Materials used in MIM,Low Alloys (i.e. Fe2Ni, Fe8Ni) Stainless Steels (i.e. 316L, 17-4 PH 4140, 4340 8620, 8740 Copper Tungsten, Tungsten Copper, Tungsten Carbide Titanium Tool Steels (i.e. M2, M4, M42 & T15),Sintering Atmospheres & Profiles,Applications for Metal Injection Molded Parts:,Medical Applications: Orthodontics (Dental Implants & Brackets) Ordinance Applications: Watch Cases