Method and Apparatus for Positional Reference in an Automated Manufacturing System

1 . An automated additive manufacturing system for forming a solid object upon a build surface disposed within a build space, the system comprising:

a multi-axis motion control system coupled to execute controlled relative movements between at least one tool head and the build surface;

at least one tool head, coupled to the motion control system, comprising at least one tool for acting to form the solid object and having a designated tool tip, the tool tip corresponding to a location at which the tool acts upon the solid object when the tool is engaged;

a contact probe, comprising a first contact-sensing element, coupled to move with the tool head in at least one direction corresponding to movement changing a distance between the first tool head and the build surface;

a second contact-sensing element disposed within the build space that is not coupled to move with the tool head in the at least one direction;

a controller configured to control the movements of the motion control system and to receive contact state information from the first contact sensing element and from the second contact sensing element;

wherein the controller is configured to direct the motion control system to execute a first movement to actuate the first contact sensing element by moving the tool head towards the build surface; and

wherein the controller is configured to direct the motion control system to execute a second movement to actuate at least one of the group of sensors comprising the first contact sensor and the second contact sensor by moving the contact probe towards the second-contact sensing element; and

wherein the controller is configured to direct the motion control system to execute a third movement to actuate the second-contact sensor by moving the tool tip towards the second-contact sensing element.

2 . The system of claim 1 further comprising at least one motion actuator controlled by the controller and configured to move the contact probe relative to the tool head.

3 . The system of claim 2 wherein the actuator changes the distance between the contact probe and the build surface.

4 . The system of claim 3 wherein the actuator controllably extends at least a portion of the contact probe closer to the build surface than the tool tip location.

5 . The system of claim 3 wherein the actuator moves the contact probe between a first position at which the contact probe is more distant from the build surface than the tool tip and into a second position at which the contact probe extends closer to the build surface than the tool tip.

6 . The system of claim 1 wherein the controller is configured to direct the motion control system to perform the first movement until the controller receives a signal from the first contact sensing element indicating contact between the contact probe and the build surface and the controller records at least one first positional coordinate applicable to the motion control system that corresponds to the detection of contact.

7 . The system of claim 1 wherein the controller is configured to:

direct the motion control system to perform the second movement until the first contact sensing element detects contact with the build surface;

record at least one second positional coordinate, applicable in the context of controlling the motion control system, that corresponds to the detection of contact;

direct the motion control system to perform the third movement until the second contact sensing element detects contact by the tool tip; and

record at least one third positional coordinate in the context of controlling the motion control system that corresponds to the detection of contact.

8 . The system of claim 7 wherein the controller is configured to calculate an offset value between the tool tip and the build surface as a function of the first, second and third positional coordinates.

9 . The system of claim 1 wherein the controller is configured to:

direct the motion control system to perform the second movement until the second contact sensing element detects contact and the controller records at least one second positional coordinate, applicable in the context of controlling the motion control system, that corresponds to the detection of contact; and to

direct the motion control system to perform the third movement until the second contact sensing element detects contact by the tool tip and the controller records at least one third positional coordinate, applicable in the context of controlling the motion control system, that corresponds to the detection of contact.

10 . The system of claim 9 wherein the controller is configured to calculate an offset value between the tool tip and the build surface as a function of the first, second and third positional coordinates.

11 . The system of claim 5 wherein the controller controls the actuator to move the contact probe from the first position to the second position in conjunction with performing at least one of the first movement and the second movement.

12 . The system of claim 1 wherein the system comprises a first tool head having a first tool tip and a second tool head having a second tool tip and the controller directs a first instance of the third movement to be performed by the motion control system for the first tool tip and records a first positional coordinate and for the second tool in a second instance of the third movement and records a second positional coordinate, and the controller calculates a differential offset value between the first tool tip and second tool tip as a function of the first and second positional coordinates.

13 . The system of claim 12 wherein the first tool head is an extruder having a nozzle as a tool tip and the second tool head comprises a rotatable chuck and the tool tip is a cutting bit mounted within the chuck.

14 . The system of claim 12 wherein the first tool head comprises a tool for depositing material onto the solid object being formed and wherein the second tool head comprises a tool for removing material from the solid object being formed.

15 . In an automated manufacturing system comprising a motion control mechanism configured to create motion of at least one tool head relative to a build surface, a method for calibrating the position of a tool tip portion of the tool head relative to the build surface comprising:

providing a first contact probe, comprising a first contact sensing element, that moves with the tool head;

providing a second contact sensing element that does not move with the tool head;

using the motion control mechanism, moving the tool head closer to the build surface to cause contact between the first contact probe and the build surface;

determining a value for a first coordinate, indicative of positioning by the motion control mechanism to create relative motion between the tool head and the build surface, at which the first sensing element detects contact between the first contact probe and the build surface;

determining a value for a second coordinate, indicative of positioning by the motion control mechanism to create relative motion between the tool head and the second contact sensing element, at which the first contact probe and second contact sensing element make contact;

determining a value for a third coordinate, indicative of positioning by the motion control mechanism to create relative motion between the tool head and the second contact sensing element, at which the second contact sensing element detects contact with the tool tip portion of the tool head; and

calculating an offset value between the build surface and the tool tip portion of the tool head as a function of the first, second and third coordinate values.

16 . The method of claim 15 wherein contact between the first contact probe and the second contact sensing element is detected by the first contact sensing element and not the second contact sensing element.

17 . The method of claim 15 wherein contact between the first contact probe and the second contact sensing element is detected by the second contact sensing element and not the first contact sensing element.

18 . The method of claim 15 wherein the providing a second contact sensing element comprises providing the second contact sensing element at a fixed coordinate along an axis normal to the plane of the build surface.

19 . In an automated manufacturing system comprising a controller, a build surface, at least one first tool head and a motion control system, controlled by signals from the controller, acting to cause relative motion, among at least the build surface and the tool head, according to positional coordinates within a finite build space, a method for indirectly establishing an offset between the build surface and a tool tip portion of the tool head comprising:

with the motion control system, initiating a first motion that reduces distance between the tool head and the build surface;

receiving a first signal, from a first contact sensing probe attached to the tool head, indicating that the first motion has brought the contact sensing probe into contact with the build surface;

storing a first positional coordinate value describing a position of the motion control system that corresponds to receiving the first signal;

with the motion control system, initiating a second motion of the tool head towards a second contact sensing probe that is not attached to the tool head;

receiving a second signal, from at least one sensor in the group consisting of the first contact sensing probe and the second contact sensing probe, indicating that the second motion has brought the first contact sensing probe in contact with the second contact sensing probe;

storing a second positional coordinate value describing a position of the motion control system that corresponds to receiving the second signal;

with the motion control system, initiating a third motion of the tool tip portion of tool head towards the second contact sensing probe;

receiving a third signal, from the second contact sensing probe during the third motion, indicating that the tool tip portion has contacted the second contact sensing probe;

storing the value of at least one third positional coordinate, describing a position of the motion control system that corresponds to the third signal; and

calculating and storing an offset value for the tool tip relative to the build surface as a function of the first positional coordinate value, the second coordinate value and the third positional coordinate value.

20 . The method of claim 19 further comprising providing the second contact sensor to be positioned at a fixed coordinate, along at least one axis, within the build space.

21 . The method of claim 19 wherein the first contact sensing element is coupled to a movable probe member, which may be moved by an actuator, under control of the controller, to selectively move between a first state wherein the probe member is distant from the build surface and a second state wherein the probe member is closer to the build plate.

22 . The method of claim 21 further comprising controlling the actuator to move the probe member to the second state as the first and second motions are performed.

23 . The method of claim 21 wherein, when the actuator is in the second state, the probe member extends closer to the plane of the build surface than the tool tip portion.

24 . A non-transitory computer-readable medium containing instructions which, when executed on a controller of an automated manufacturing system, performs a method for indirectly establishing an offset between a build surface and a tool tip portion of a tool head, the method when executed comprising:

sending signals to the motion control system to cause a first motion that reduces distance between the tool head and the build surface;

detecting a first input signal, from a first contact sensing probe attached to the tool head, indicating that the first motion has brought the contact sensing probe into contact with the build surface;

responsive to detecting the first signal, storing a first positional coordinate value describing positioning of the motion control system upon detecting the first input signal;

sending signals to the motion control system to cause a second motion of the tool head towards a second contact sensing probe that is not attached to the tool head;

detecting a second input signal, from at least one of the group consisting of the first contact sensing probe and the second contact sensing probe, indicating that the second motion has brought the first contact sensing probe in contact with the second contact sensing probe;

responsive to detecting the second signal, storing a second positional coordinate value, describing positioning of the motion control system upon detecting the second input signal;

sending signals to the motion control system to cause a third motion of the tool tip portion of tool head towards the second contact sensing probe;

detecting a third input signal, from the second contact sensing probe during the third motion, indicating that the tool tip portion has contacted the second contact sensing probe;

responsive to detecting the third signal, storing the value of at least one third positional coordinate, describing positioning of the motion control system upon detecting the third input signal;

calculating and storing an offset value for the tool tip relative to the build surface as a function of the first positional coordinate value, the second coordinate value and the third positional coordinate value.