Other

Joseph K Kelly

Jyoti Mazumder

Timothy Walter Skszek

Joohyun Choi

Multiple criteria are monitored and controlled to enhance the success of direct-metal deposition, including greater control over factors such as deposit layer height/thickness, sub-harmonic vibration, contour path shape, powder mass flow, and deposition speed, and stress accumulation. Sensors are used to monitor some or all of the following parameters during the deposition process: deposit height, width, temperature, and residual stress. A predetermined limit with respect to the yield strength of the material is preferably set. If the stress exceeds that limit sensors will automatically introduce one or more remedial measures, the priority of which is established using a look-up table generated in accordance with prior experimental knowledge. To control temperature induced distortion and stress, an infrared temperature detector may be used in conjunction with a controller to reduce temperature, increase speed and decreased power for purpose of stress management.

Closed-loop, rapid manufacturing of three-dimensional components using direct metal deposition

The laser duty cycle in a direct metal deposition (DMD&trade;) system is monitored and used to control another device to keep the duty cycle within a desired range. In the preferred embodiment, the duty cycle is used to control powder flowrate to keep the duty cycle between 75 to 95%. For example, the powder flowrate may be increased or decreased by stepping up or stepping down the angular velocity of the feed-rod. The duty cycle of the laser is preferably measured by sampling the output signal of the feedback device at a sufficiently high rate, at least twice as fast as the on/off switching speed of the feedback device. The sampled data is stored in a memory buffer, and an algorithm is used to calculate the duty cycle over a period of time specified by the operator. The current duty cycle is preferably displayed on the screen of the operator's computer along with the values of the periodic measurements stored in the process history database.

Duty cycle stabilization in direct metal deposition (DMD) systems

The temperature of the deposition tip in a direct metal deposition (DMD) apparatus is monitored to circumvent problems due to tip clogging. Both the inner and outer nozzle tips are monitored utilizing appropriate sensors, which are interconnected to a controller programmed to detect a predetermined rise in tip temperature. If an unacceptable condition is sensed, the equipment may be configured to sound an alarm, display a warning condition, or enter a controlled shut-down of the deposition apparatus. Use of the invention accordingly permits the detection of even partial clogging when it occurs, allowing an operator to take immediate corrective measures both to protect the nozzle from damage and to insure the highest possible deposition quality.

Direct-metal-deposition (DMD) nozzle fault detection using temperature measurements

Overhang and undercut features, as well as cavities, channels, pipes and three-dimensional voids and other structures are fabricated using a laser-aided direct-metal deposition (DMD) processes. In the preferred embodiment, this is accomplished through the selective deposition of a lower melting point sacrificial material. Following the integrated deposition of both sacrificial and non-sacrificial materials using DMD, the part is soaked in a furnace at a temperature sufficiently high to melt out the sacrificial material. As preferred options, the heating is performed in an inert gas environment to minimize oxidation, with a gas spray also being used to blow out remaining deposits. Using this technique, articles having integral sensors and cooling channels may be used as part of an automated system for controlling the temperature, stress and strain during the shaping or forming of a product using the resultant smart die or mold. Such a system would preferably include means of controlling the inlet flow of coolant and means for controlling or terminating the forming or injection process. The control is preferably mediated through a computer which analyzes and evaluates the inputs from the sensors and transmits the resulting information to a flow controller and to a process controller or logic gate, so that appropriate actions are carried out on a continuous basis.

Growing community of inventors

Plymouth, MI, United States of America

Joseph K Kelly