Advanced Metalworking Practices, LLC has a 50-ton injection molding machine for molding long, thin test bars from ADVAMET® MIM feedstocks. Our studies have determined that the following conditions provide a suitable starting point for molding ADVAMET® feedstocks.
Barrel temperature 350°F (approx. 175°C)
Nozzle temperature 375°F (approx. 190°C)
Mold temperature 110°F (approx. 43°C)
Mold clamping pressure 2700 psi (approx. 19 MPa)
Injection pressure 1700 psi (approx. 12 MPa)
Holding pressure 1125 psi (approx. 8 MPa)
Holding pressure duration 6 sec.
Cooling time 20 sec.
The processing parameters will very likely have to be adjusted and optimized for the specific component geometry, mold design, material type, molding machine and production rate.
The following cycle has been shown effective in dewaxing and debinding various steels and stainless steels with 6.0% - 8.3% binder in a 3" diameter ceramic tube furnace with nitrogen flowing at 7 CFH ( ~ 2.4 linear ft/min gas speed).
Samples were approximately 1" x ½" x 1/8" and were placed on ceramic paper on a flat ceramic surface.
| Temperature, Degrees C | |||
| Approximate Part Temperature | Heating Rate or Hold Time | ||
| From | To | ||
| R.T. 80 C 200 C |
80 C 200 C |
300 C / hour 75 C / hour Hold 30 minutes |
De-waxing complete |
| 200 C 240 C |
240 C | 75 C / hour Hold 30 minutes |
|
| 240 C 310 C |
310 C | 75 C / hour Hold 30 minutes |
|
| 310 C 360 C 510 C |
360 C 510 C |
150 C / hour 60 C / hour Hold 120 minutes |
Debinding complete |
Notes:
1. This schedule is intended as a guideline only. Debinding cycles are affected by type of equipment, part size and shape, quantity and spacing of parts and other factors.
2. Please note that the schedule refers to temperature as measured close to the part. Adjust temperature setting to compensate for any estimated difference between the set points and the part temperature.
3. Parts generally have enough strength for handling after dewaxing. If full debinding is carried out, parts must be at least pre-sintered in the same cycle before handling.
4. If cracking or distortion occurs, refer to the guidelines for thermal dewaxing of complex parts.
If cracking or distortion occurs when using guidelines for Thermal Debinding of Parts Molded from ADVAMET® MIM feedstocks, the following cycle is suggested.
| Approximate Part Temperature | Heating Rate or Hold Time | |
| From: | To: | |
| R.T. 140 C |
140 C | 200 C/hour Hold 6 hours |
| 140 C 165 C |
165 C | 90 C/hour Hold 1 hour |
| 165 C 205 C |
205 C | 90 C/hour Hold 5 hours |
Notes:
1. The oven should have sufficient air or gas flow to remove dewaxing products from the part vicinity. A perforated metal support may be adequate, but high purity porous alumina is preferred and will be necessary if the same setter is used for sintering. For more complex parts, particularly those with unsupported features, specially shaped setters may be required.
2. Please note that the schedule refers to temperature as measured close to the part. Adjust temperature setting to compensate for any estimated difference between the set points and the part temperature.
3. Parts generally have enough strength for handling after dewaxing. Final debinding is usually done in the initial phases of the sintering cycle.
4. The above table is a guideline for initial tests. Extending the hold at 140 C is most effective for minimizing cracks and/or distortion.
5. The dewaxing process should remove about half the binder. Achieving this may require increasing hold times at 165 C and/or 205 C, especially for thicker walls or higher oven loads.
6. Shortening the total cycle by reducing hold times may be possible, but care must be taken to ensure that part quality is not affected.
7. Protective (non-oxidizing) atmosphere should be used for subsequent processing above 205 C. Reducing atmosphere is preferred for completion of debinding through about 510 C. Furnace atmosphere and time-temperature-pressure conditions for sintering depend upon the material being processed.