Electrical discharge machining automated electrode changer

An electrical discharge machining (EDM) system including an automated electrode changer storing a plurality of electrodes for dispensing one at a time for insertion into the spindle of the system. The automated changer includes an electrode storage unit, an electrode insertion unit, and an electrode removal unit. The specification further discloses a method of electrical discharge machining utilizing, for example, the automated electrode changer.

BACKGROUND OF THE INVENTION

The present invention relates to electrical discharge machining (EDM) systems and methods, and more particularly to systems and methods for the handling of electrodes within such systems and methods.

Electrical discharge machining (EDM), also referred to as spark machining, spark eroding, burning, die sinking, wire burning, or wire erosion, is a manufacturing process whereby a desired shape is obtained using electrical discharges. Material is removed from the workpiece by a series of rapidly recurring current discharges between two electrodes. One of the electrodes is the tool, or simply the electrode, and the other of the electrodes is the workpiece.

The electrode is consumed during the EDM process. Consequently, spent electrodes must be replaced regularly with new electrodes. Obviously, the EDM system is not operating while the electrodes are being replaced, resulting in downtime and reduced machine utilization. The amount of downtime during the electrode replacement depends in part on how quickly the operator notices the need for a replacement and in part on the skill and the speed of the operator in making the replacement. When the EDM machining requires a relatively high rate of electrode consumption (e.g. speed drilling), machine utilization is particularly low.

Techniques have been developed in an effort to automate the electrode replacement process. These techniques include carousels and spring-loaded cartridges. Unfortunately, these techniques require an operator to load the carousels and/or the cartridges, resulting in undesirable labor. Further, these techniques produce inconsistent results and therefore inconsistent machine utilization.

SUMMARY OF THE INVENTION

The aforementioned issues are addressed by the present invention in which an automated electrode changer is provided for an EDM system. The automated changer reduces electrode replacement time increasing machine utilization.

The automated electrode changer includes an electrode storage unit, an electrode insertion unit, and an electrode removal unit. The storage unit is designed to store a plurality of electrodes and to dispense the electrodes one at a time to the electrode insertion unit. The electrode removal unit removes spent electrodes from the spindle. The electrode insertion unit inserts new electrodes into the spindle.

The automated electrode changer is incorporated into an EDM system including a spindle and a spindle transport system adapted to selectively align the spindle with the electrode insertion system, the electrode removal unit, and a workpiece. The system with the automated electrode changer reduces operator involvement to (a) the periodic loading of a tube of electrodes and (b) the periodic exchanging of workpieces.

The invention also includes methods of EDM machining utilizing the automated electrode changer and its functionality.

The present invention provides a number of advantages. Firstly, the system reduces machine downtime. Secondly, the system reduces the risk of damage to the electrodes that may occur during manual handling. Thirdly, the system reduces the time required to replace an electrode by automating the process. Fourthly, the system reduces possible health risks to an operator in view of the reduce exposure to the EDM environment.

These and other advantages and features of the invention will be more fully understood and appreciated by reference to the description of the current embodiment and the drawings.

DESCRIPTION OF THE CURRENT EMBODIMENT

An electrical discharge machining (EDM) machine constructed in accordance with a current embodiment of the invention is illustrated in the drawings and designated10. The EDM machine10includes a frame12, a workpiece support14, a spindle16, a spindle transport mechanism18, and an automated electrode changer20.

With the exception of the automated electrode changer20, the components of the EDM machine10are well known to those skilled in the art and do not require detailed description. The frame12provides a support structure for the EDM machine10. The workpiece holder14supports a workpiece P and moves about A and B axes. The spindle16releasably receives an electrode E. The spindle transport mechanism18moves the spindle15in the X, Y and Z directions. The spindle transport mechanism18is also known as an XYZ tool jig base. The workpiece holder14and the transport system18are operatively connected to a control system (not illustrated) of any type generally known to those skilled in the art.

The automated electrode changer20is one novel aspect of the present invention. As perhaps best illustrated inFIGS. 7, 7A, 8 and 8A, the changer20includes an electrode storage unit22, an electrode insertion unit24, and an electrode removal unit26. The changer20includes a riser block28supported on a frame member12a. The riser block28in turn supports, directly or indirectly, the remaining components of the changer20.

A main block30is supported on the upper end of the riser block28. The main block30supports the electrode storage unit22, the electrode insertion unit24, and the electrode removal unit26.

The electrode storage unit22is supported on a slide assembly32for reciprocating linear movement in an X direction (seeFIG. 2). The slide assembly32includes a slide cylinder34for moving the assembly. The slide assembly32enables the storage unit22to be transported between a rest position illustrated inFIG. 7and a load position illustrated inFIG. 8.

The electrode storage unit22includes an electrode tube holder36a gate unit38, and a vibrating motor40. The holder36is adapted to receive an electrode tube42containing a plurality of electrodes E. As perhaps best illustrated inFIGS. 7A and 8A, the holder36defines a cylindrically shaped receiver bore44. The floor46of the receiver bore44defines a hole48through which electrodes E can pass. The diameter of the hole48is selected to be larger than the diameter of any one of the electrodes E, but less than twice the diameter of any electrode. Consequently, the electrodes E must pass through the hole48one at a time.

In the current embodiment, the floor46slopes downwardly toward the hole48. The vibrating motor40may be an eccentric drive motor or other suitable device for vibrating or shaking the electrode tube holder36. The angle of the floor46and the vibration provided by the vibrating motor40assist in the movement of the electrodes E to the hole48.

The gate unit38includes a slide50and a cylinder52. In its normal position illustrated inFIG. 7A, the slide50extends into the hole48to prevent an electrode E from passing through the hole48beyond the gate50. The cylinder52may be actuated to withdraw the gate50to the position illustrated inFIG. 8A, permitting an electrode E to exit the electrode tube42through the hole48.

The electrode insertion unit24is perhaps best illustrated inFIGS. 9-10. The electrode insertion unit24includes a roller mount54, a pair of rollers56,58, a spring60, and a cylinder62. The roller56is supported by the main block30and is selectively rotated by a motor57. The idler roller58is rotatably supported on the roller mount54, which in turn is pivotably supported on pivot64. The spring60biases the roller mount54in a clockwise direction as viewed inFIGS. 9-10to move the roller wheel58into contact with roller wheel56. Cylinder62may be actuated so that its plunger66pivots the roller mount54in a counterclockwise direction as viewed inFIGS. 9-10to disengage the roller58from the roller56.

The electrode receiver tube68and the electrode receiver guide70are supported within the load guide mount31. The tube68and the guide70are aligned with the rollers56,58to receive an electrode E.

The electrode removal unit26also is perhaps best illustrated inFIGS. 9-10. The electrode removal unit24includes a roller mount74, a pair of rollers76,78, a spring80, and a cylinder82. The roller76is supported by the main block30and is selectively rotated by a motor77. The idler roller78is rotatably supported on the roller mount74, which in turn is pivotably supported on pivot84. The spring60biases the roller mount54in a counterclockwise direction as viewed inFIGS. 9-10to bias the roller wheel78into contact with roller wheel76. The cylinder62may be actuated so that its plunger86pivots the roller mount74in a clockwise direction as viewed inFIG. 9to disengage the roller78from the roller76.

The electrode removal tube88and the electrode removal guide90are supported within the load guide mount31. The tube88and the guide90are aligned with the rollers76,78to receive an electrode E from the spindle16. A spent electrode tube92is supported on the riser block28by the tube holder94. The spent electrode tube92is aligned with the spent tube guide88to receive the spent electrodes for subsequent disposal or recycling.

A control system (not illustrated) is operatively connected to all of the described components to control their operation. The design and implementation of the control system will be readily apparent to those skilled in the art based on this specification. It therefore is unnecessary to describe the control system in detail.

An exemplary method of operation of the EDM system10will now be described. Other methods and/or reordering of steps within methods will be apparent to those skilled in the art.

While the description of the operation could begin at a number of steps, this description will begin with the loading of the electrode storage tube or cartridge42into the tube holder36. This loading is performed by an operator, who then takes further action to indicate that the electrode tube42has been loaded. Such further action may be as simple as shutting a door on the machine10. Such action may alternatively be entry on a keyboard or other input device.

With the electrode tube42loaded, the EDM machine10performs EDM machining until the control system determines that the electrode E within the spindle16is spent and requires replacement or until the program is complete. If the electrode E requires replacement, then the control system initiates an electrode change.

The electrode change sequence begins by transporting the spindle16into alignment with the electrode removal unit26. This position is identified by the numeral100inFIGS. 3-4. The position is further illustrated inFIGS. 11-12. The spindle16is unclamped to release the spent electrode, which drops by way of gravity between the open rollers76,78.

The control system then actuates the cylinder82to allow the roller mount74to pivot in a counterclockwise direction as viewed inFIG. 12. This movement allows the roller78to engage the adjacent roller76and to pinch or capture the electrode E. The roller76,78are then rotated to remove the electrode from the spindle16. The electrode E travels through the guide tube88into the spent electrode tube92.

The spindle16is then raised to position102(seeFIG. 13), and then the spindle16is moved in a transverse direction to the position104(see againFIG. 13) in which the spindle is aligned with the rollers56,58of the electrode insertion unit24. The spindle is then lowered to a position closely proximate the spindle insertion unit24.

The rollers56,58are then rotated to transport a previously staged electrode E (as described below) upwardly through the guide tube68and into the spindle16.

The spindle16is then actuated to clamp the electrode inserted therein.

The control system then actuates cylinder62to extend the plunger66, thereby pivoting the roller mount54in a counterclockwise direction as viewed inFIG. 12. This pivoting disengages the roller58from the adjacent roller56to release the electrode E.

The spindle16then is transported upwardly to completely withdraw the electrode E from the electrode insertion unit24. The spindle16is then transported back to its operating position106illustrated inFIGS. 2, 4 and 16. The machine10then resumes EDM machining until the workpiece P is completed or until another electrode change is required.

While the machine10resumes EDM machining after the electrode replacement, another electrode is staged within the electrode insertion unit24. This process begins by actuating the slide cylinder34to move the electrode storage unit22from its normal position illustrated inFIGS. 2 and 7to a position aligned with the electrode insertion unit24as illustrated inFIG. 8. When in position, the cylinder62is actuated to withdraw the plunger66, which permits the roller mount54to pivot counterclockwise as viewed inFIG. 9. This motion enables the roller58to engage the adjacent roller56and to trap or pinch the electrode E. The cylinder52in the gate unit38is actuated to withdraw the gate50to the position illustrated inFIG. 8A. Additionally, the vibrating motor40is actuated. The combination of the sloped floor46and the vibrating motor40causes one of the electrodes E within the tube42to become aligned with, and to fall through, the hole48and between the rollers56,58as illustrated inFIG. 9. The rollers56,58are then rotated to draw the electrode E downwardly through the guide tube68until the leading end of the electrode is sensed by sensor (not illustrated). At that time, the rollers56,58are stopped; the cylinder52on the gate unit38is actuated to return the slide50to its position illustrated inFIG. 7A; and the vibrating motor40is turned off. The rollers56,58are then rotated once again to draw the electrode E fully downwardly into the insertion unit24. At this point, none or relatively little of the electrode E extends upwardly above the electrode insertion unit24. The slide cylinder34is then actuated to return the electrode storage unit22to its normal position. At this point, the electrode E within the guide tube68is staged for a subsequent electrode change as described above.

As will be appreciated from this specification, the present invention essentially fully automates the electrode changing function within an EDM environment. Essentially the only operator involvement required is (a) the periodic loading of the electrode tube42, (b) the periodic exchange of workpieces P, and (c) the periodic removal of spent electrodes from the spent electrode tube92. The present invention thereby accelerates electrode changes and increases machine utilization.

The above description is that of a current embodiment of the invention. Various alterations and changes can be made without departing from the spirit and broader aspects of the invention as defined in the appended claims, which are to be interpreted in accordance with the principles of patent law including the doctrine of equivalents.

This disclosure is presented for illustrative purposes and should not be interpreted as an exhaustive description of all embodiments of the invention or to limit the scope of the claims to the specific elements illustrated or described in connection with these embodiments. For example, and without limitation, any individual element of the described invention may be replaced by one or more alternative elements that provide substantially similar functionality or otherwise provide adequate operation. This includes, for example, presently known alternative elements, such as those that might be currently known to one skilled in the art, and alternative elements that may be developed in the future, such as those that one skilled in the art might, upon development, recognize as an alternative.

The invention is not limited to the details of operation or to the details of construction and the arrangement of the components set forth in the above description or illustrated in the drawings. The invention may be implemented in various other embodiments and practiced or carried out in alternative ways not expressly disclosed herein. Also, the phraseology and terminology used herein are for the purpose of description and should not be regarded as limiting. The use of “including” and “comprising” and variations thereof is meant to encompass the items listed thereafter and equivalents thereof as well as additional items and equivalents thereof. Further, enumeration may be used in the description of various embodiments. Unless otherwise expressly stated, the use of enumeration should not be construed as limiting the invention to any specific order or number of components. Nor should the use of enumeration be construed as excluding from the scope of the invention any additional steps or components that might be combined with or into the enumerated steps or components.

The disclosed embodiment includes a plurality of features that are described in concert and that might cooperatively provide a collection of benefits. The present invention is not limited to only those embodiments that include all of these features or that provide all of the stated benefits.

Any reference to claim elements in the singular, for example, using the articles “a,” “an,” “the” or “said,” is not to be construed as limiting the element to the singular.