METAL DROP EJECTING THREE-DIMENSIONAL (3D) OBJECT PRINTER HAVING AN IMPROVED HEATED BUILD PLATFORM
A three-dimensional (3D) metal object manufacturing apparatus has a build platform heater that is configured with a plurality of temperature sensors and heating elements distributed throughout the heater. The signals generated by the temperature sensors are monitored by a controller and when one of the signals is outside of a temperature range around a temperature setpoint for the heater, the controller adjusts a PWM signal operating a switch that connects the heating element corresponding to the temperature sensor that generated the signal outside of the temperature range. The temperature sensors and heating elements are distributed in a plurality of cells that border one another in a contiguous pattern.
1 . A heater for a platform assembly for supporting a workpiece in a three-dimensional (3D) printer comprising:
a plurality of sections that are positioned with respect to one another to form a structure encompassed by a single perimeter; and
each section including at least one independently controllable heating element and at least one temperature sensor.
2 . The heater of claim 1 wherein each section has a substantially similar shape.
3 . The heater of claim 1 wherein each section has substantially similar dimensions.
4 . The heater of claim 2 wherein each section has a hexagonal shape.
5 . The heater of claim 2 wherein each section has a ring shape.
6 . The heater of claim 1 further comprising:
a member positioned over an upper surface of the structure formed by the plurality of sections.
7 . The heater of claim 6 wherein the upper surface of the structure is essentially flat.
8 . The heater of claim 6 wherein each section consists essentially of a thermal conductive material.
9 . The heater of claim 8 wherein the thermal conductive material is a steel alloy.
10 . The heater of claim 9 wherein the steel alloy is molybdenum steel.
11 . The heater of claim 1 wherein the at least one temperature sensor is one of a thermocouple and a thermistor.
12 . The heater of claim 11 further comprising:
a plurality of switches, each switch being connected to one of the at least one heating elements in the plurality of sections to connect the at least one heating element to an electrical power source selectively.
13 . The heater of claim 12 further comprising:
a controller operatively connected to the plurality of switches, the controller being configured to:
operate each switch in the plurality of switches independently of the other switches.
14 . The heater of claim 13 , the controller being further configured to:
operate each switch with a pulse width modulated (PWM) signal that is independently generated for each switch.
15 . The heater of claim 14 , the controller being operatively connected to the at least one temperature sensor in each section in the plurality of sections and the controller being further configured to:
compare the signal from each temperature sensor to a temperature range about a temperature setpoint; and
change a duty cycle of the PWM signal operating the switch that corresponds to the at least one heating element in the section when the signal from the at least one temperature sensor in the section is outside of the temperature range.
16 . The heater of claim 15 , the controller being further configured to:
reduce the duty cycle of the PWM signal when the signal generated by the at least one temperature sensor in the section is below the temperature range.
17 . The heater of claim 16 , the controller being further configured to:
increase the duty cycle of the PWM signal when the signal generated by the at least one temperature sensor in the section is below the temperature range.
18 . A three-dimensional (3D) metal object printer comprising:
an ejector head configured to eject drops of melted metal;
a planar member positioned to receive the ejected drops of melted metal;
a plurality of sections that are positioned with respect to one another to form a structure encompassed by a single perimeter, the plurality of sections supporting the planar member; and
each section in the plurality of sections including at least one independently controllable heating element and at least one temperature sensor.
19 . The 3D metal object printer of claim 18 further comprising:
a plurality of switches, each switch being connected to one of the at least one heating elements in the plurality of sections to connect the at least one heating element to an electrical power source selectively; and
a controller operatively connected to the plurality of switches, the controller being configured to operate each switch in the plurality of switches independently of the other switches.
20 . The 3D metal object printer of claim 19 , the controller being further configured to:
operate each switch with a pulse width modulated (PWM) signal that is independently generated for each switch;
compare the signal from each temperature sensor to a temperature range about a temperature setpoint; and
change a duty cycle of the PWM signal operating the switch that corresponds to the at least one heating element in the section when the signal from the at least one temperature sensor in the section is outside of the temperature range.