Patent Publication Number: US-9841750-B2

Title: Dynamic real-time slice engine for 3D printing

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to U.S. Provisional Application No. 61/992,617, filed on May 13, 2014. The disclosure of the prior application is considered part of and is incorporated by reference in the disclosure of this application. 
    
    
     BACKGROUND 
     This specification relates to three-dimensional (3D) printing. 
     3D printers use a variety of processes and materials for producing a 3D object. Materials used can be of the form of a resin (e.g., plastic) or other material that can be deposited so as to produce a desired 3D shape. A process of printing a 3D object can include, for example, printing a series of layers, each layer being two-dimensional (2D). 
     SUMMARY 
     In general, a method and system are provided for 3D printing that does not require external pre-processing of a computer-aided design (CAD) model to be printed, but rather provides real time parallel processing and printing functionality. A method includes receiving, by a 3D printer, a CAD model for a design to be printed by the 3D printer. The method further includes processing the CAD model to identify a first slice and generating instructions for printing the first slice. The method further includes using the generated instructions to start printing of the CAD model. The method further includes, in parallel with the printing, performing dynamic real-time slicing on a remaining portion of the CAD model. The dynamic real-time slicing includes receiving pre-processed data, model analysis information or real-time feedback during the printing of a respective slice or after the printing of one or more previous slices. The dynamic real-time slicing further includes identifying a next slice for printing including adjusting one or more slicing parameters based on the received pre-processed data, model analysis information or real-time feedback. Adjusting includes adjusting a slicing parameter for the next slice to be printed by the 3D printer. The dynamic real-time slicing further includes generating instructions for printing the next slice. The method further includes printing the next slice based on the generated instructions and, in parallel, repeating the performing dynamic real-time slicing to generate a then next slice and associated instructions for printing. 
     These and other implementations can each optionally include one or more of the following features. Adjusting one or more slicing parameters can include adjusting a slice thickness based on one or more of CAD model geometry or user input including slicing at least two different slice thicknesses when printing the CAD model. Adjusting the slice thickness can include increasing a slice thickness for a next slice to be greater than a slice thickness for a last-printed slice when printing a wall. Adjusting the slice thickness can include decreasing a slice thickness for a next slice to be less than a slice thickness for a last-printed slice when printing a curve. The user input can be received after the start of printing and can control a speed at which a remaining portion of printing occurs, with higher speed resulting in greater thickness slices. The method can further include processing an image taken from a camera including identifying one or more calibration errors and adjusting an alignment of a next slice. The method can further include identifying one or more delicate features in the CAD model that may result in print unreliability, and adjusting can include increasing a next slice thickness to increase print reliability and accordingly not printing the identified delicate features. The method can further include detecting an anomaly in a slice, determining a default configuration for the detected anomaly, and applying the default to the generated instructions to ensure no print error occurs when printing the CAD model. Adjusting one or more slicing parameters can include determining a default setting for at least one of the slicing parameters to print a first slice, and adjusting the at least one slicing parameter at a next slice or a subsequent slice based on feedback obtained during printing or an evaluation of the CAD model. 
     Particular implementations may realize none, one or more of the following advantages. Printing can occur directly from an original CAD model without the need for an external pre-processing. Printing can be started before all pre-processing of a CAD model is performed. Print speed can be manually adjusted by a user before or during a print. Slicing and instruction set generation can be performed in parallel to printing for at least a portion of the CAD model. Slice thickness can be automatically varied based on CAD model geometry and information determined when printing previous slices. Real time corrections can be made to compensate for detected anomalies, such as a result of mis-alignment or ambient conditions (e.g., temperature, humidity, build up of material on the print nozzle, cloudiness of the print window, vibration or movement of the printer body/platform). 
     The details of one or more implementations of the subject matter described in this specification are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages of the subject matter will become apparent from the description, the drawings, and the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A-1B  show two prior art systems for 3D printing. 
         FIG. 1C  shows an example system for 3D printing in accordance with this specification. 
         FIG. 1D  shows an architecture associated with functional elements performed by the dynamic processor of  FIG. 1C . 
         FIGS. 2A-2B  collectively show an example generation of variable thickness slices. 
         FIG. 3  shows an example of a flow for slice and instruction set generation in a 3D printer. 
         FIG. 4  is a flowchart of an example process for 3D printing. 
         FIG. 5  is a block diagram of an example computer system that can be used to implement the methods, systems and processes described in this disclosure. 
     
    
    
     Like reference numbers and designations in the various drawings indicate like elements. 
     DETAILED DESCRIPTION 
     Systems, methods, and computer program products are described for 3D printing without the necessity to externally pre-process a computer-aided design (CAD) model before delivery to a 3D printer. For example, 3D Printing, also known as Additive Manufacturing, is the process of additively fabricating a physical object from sequential layers. In the typical process, a CAD model is prepared and pre-processed to create an instruction set that the printer can read. This pre-processing typically consists of generating bitmap or vector data that defines where material should be deposited, cured, bound, or otherwise fabricated. 
     The practice of pre-preprocessing CAD models can have a number of disadvantages. For example, a slow processing time can result, as all preprocessing is done up front (i.e., before any portion of the underlying model is printed). In another example, a failure in pre-preprocessing a CAD model can prevent printing from even starting. Another example disadvantage is that preprocessed instructions are unable to accommodate dynamic feedback from the 3D printer during the print (e.g., such as related to detected or ambient conditions). In some implementations, these and other disadvantages can be solved, for example, by performing dynamic real-time slicing on the 3D printer itself, e.g., during the print. 
     Existing systems typically can take one of two approaches to process a CAD model into a 3D printer ready instruction set. In a first approach, for example, an entire model can be pre-processed and transferred to the 3D printer in advance of the 3D print. In this approach, for example, the entire instruction set can be stored in memory on the 3D printer, and the instructions can be carried out sequentially (as is represented by a prior art system shown in  FIG. 1A ). In a second approach, for example, a subset of slice instruction data can be pre-processed and streamed to the 3D printer from a network/attached computer. In this approach, the printer can store a given subset of data in a local buffer, and new data can be requested and received as layers of the print are completed (as is represented by a prior art system shown in  FIG. 1B , where acknowledgement is sent back to the pre-processor that only indicates completion of a last printed portion of the stream as opposed to any other type of feedback). 
       FIGS. 1A-1B  show two prior art example systems  100   a - 100   b  for 3D printing. For example, in the system  100   a , a 3D printing workflow uses pre-processing  102  (e.g., at a computer  104 ) and transfer  106  of completed instructions (e.g., for use by a printing engine  108  at a 3D printer  110 ). System  100   b , for example, pre-processes the model and streams ( 112 ) instructions to the 3D printer  110 .  FIG. 1C  shows an example system  100   c , for example, that uses a dynamic processor  114  on the 3D printer  110  for real time slicing and instruction generation that is performed in parallel with printing, which is a subject of this disclosure. For example, in the system  100   c , printing engine  108  can operate directly on the original CAD model  118  by dynamically slicing and processing the instruction set on the 3D printer  110  itself. 
     In some implementations, dynamic slicing and instruction set generation can enable a slice engine to adjust various slicing parameters in response to either pre-processed data, model analysis, or real-time feedback. Using this input data, for example, the slice engine output can be dynamically adapted in numerous ways. 
       FIG. 1D  shows an example architecture associated with the dynamic processor  114  of  FIG. 1C . In the example shown, the dynamic processor  114  can include plural engines  120 - 130 . In some implementations, each engine can be of the form of software instructions executed on one or more processors, dedicated hardware, firmware or combinations of the same. Other configurations and engines of the dynamic processor  114  are possible. 
     A slice engine  120 , for example, can determine slices to be printed using information from the CAD model  118 , a model analysis engine  122 , and user inputs from a user input processor  130 . The slice engine  120  can also base its determining on information received from a sensor engine  126 . Information associated with the determined slices (e.g., slice geometry) can be provided as an input to an instruction generation engine  128 . 
     The model analysis engine  122 , for example, can analyze the received CAD model  118  for an object to be printed and provide information to the either or both the slice engine  120  and the instruction generation engine  128  so as to enable adjustment of various print parameters (including slice parameters and/or instruction generation parameters) during the print process. 
     The sensor engine  126 , for example, can receive information from external sensors  132  (e.g., temperature sensor, humidity sensor, alignment sensor) and cameras  134  on the 3D printer and provide information associated with sensed conditions and images to the feedback engine  124 , or directly to slice engine  120  and instruction generation engine  128  (e.g., so as to enable dynamic adjustment of print parameters). 
     The feedback engine  124 , for example, can receive and process information from a user (by way of a mechanical or software control), sensors or the model analysis engine and provide feedback, such as a result of processing and printing a first set of plural layers for the model, to one or both of the slice engine  120  and the instruction generation engine  128 . 
     The instruction generation engine  128 , for example, can use information received from the model analysis engine  122 , the slice engine  220 , the feedback engine  124  and the user input processor  130  to generate printing instructions to be provided to the printing engine  108 . 
     The user input processor  130 , for example, can receive signals or other inputs from a user input control  136  (e.g., on the 3D printer or from another source), including information to be provided to the slice engine  120  and the instruction generation engine  128  to control printing. 
       FIGS. 2A-2B  collectively show an example generation of variable thickness slices  200 . Variable thickness slices  200  can be produced dynamically, for example, in real-time based on model geometry  202  or user input. Specifically, the variable thickness slices  200  are sized to conform to the model geometry  202 . Also, the thickness of the slices can depend on variability in the model geometry  202 . For example, larger thickness slices  204  can be used in places where the model geometry  202  remains relatively unchanged (e.g., in straight-walled portions). Smaller thickness slices  206  can be used, for example, in places where the model geometry  202  changes (e.g., in curves). In contrast to conventional slice engines, for example, that slice at a constant thickness, a dynamic slice-engine can output variable thickness slices  200  in response to incoming data. The data may take the form of real-time input (e.g., from a sensor or button), pre-processed metadata embedded in the CAD model, or dynamic analysis of the model. Variable thickness slices  200  may be desirable, for example, if certain areas of a CAD model require finer detail and other areas do not. For example, shallow curves may benefit from reduced layer thickness so as to reduce the prominence of steps forming in the physical print. Other simpler geometries, such as vertical walls, can be printed with thicker layers to speed up the print. 
     In some implementations, variable thickness slices  200  can also be used to adjust the speed of the print after the print has started. For example, a dial or other control may be presented to the user that, upon selection, increases the layer thickness and reduces the total print time. In some implementations, a user input is provided to allow for manual adjustment of the print process, such as to increase or decrease print speed. The manual control can be the form of a knob or selector for selecting or adjusting a parameter that controls slice thickness. Feedback can be provided to the user after input is received indicating, for example, time difference or remaining time required to print the CAD model given the change in the parameter setting. 
     In some implementations, the dynamic slicer can adjust the output (e.g., the bitmap or vector-based instruction set data) during the print based on pre-processed data, model analysis, or real-time feedback. For example, based on feedback from a camera, the alignment of a particular slice can be adjusted to compensate for calibration errors or for other reasons (e.g., based on an evaluation of one or multiple previously printed layers with their intended shape). In another example, delicate features that are considered too thin for printing may be adjusted (e.g., thickened or removed) to increase print reliability. Further, one or more sensors may be included or associated with the print environment. Sensors (or a camera) may be used to detect ambient temperature, ambient humidity, build-up of material on a print nozzle, cloudiness of a print window, movement or vibration of a print structure (e.g. the print platform). Feedback from the sensors can be provided to the dynamic processor  114  so as to enable adjustments to the print process for subsequent slices (e.g., to adjust slice thickness, another parameter or the instructions associated with the print process for next slices that are to be printed). In some implementations, feedback can be processed over time, such as to allow for adjustments to be made based on an evaluation of a plurality of previously printed layers. In some implementations, feedback can represent an average (mathematical or otherwise) over a plurality of previously printed layers. 
     In some implementations, a dynamic real-time slice engine (e.g., as part of the dynamic processor  114 ) can be implemented inside the 3D printer hardware itself. For example, a slice engine included in the dynamic processor  114  in the 3D printer  100   c  can receive a CAD model directly as input, e.g., as shown in  FIG. 1C . The slice engine, for example, can generate slices dynamically from the CAD model during/in parallel with portions of the printing process. 
       FIG. 3  shows an example of slicing and instruction set generation performed in parallel to printing. For example, an initial slice of the CAD model may be processed (including slicing and instruction generation) over an initial time period t 1 . Printing of the initial slice can occur over time period t 2 . For example, in parallel to a print  308  for the first layer  302   a  in time t 2 , slicing  304  and instruction set generation  306  can occur for the second layer  302   b . Subsequently, in parallel to a print  308  for the second layer  302   b  in time t 3 , slicing  304  and instruction set generation  306  can occur for the third layer  302   c , and so on for the other layers. Other patterns of time delays and parallel processing can be used. 
     In some implementations, error handling can be used in printing. For example, because slicing and instruction set generation can be performed in real-time during the print, robust error handling can be used to ensure that any CAD geometry can be printed. Typical 3D printers may have only a limited range of acceptable 3D geometry. As such, failure cases commonly include (but are not limited to) inverted normals, intersecting triangles, self-intersection, non-manifold surfaces, among other errors. In some implementations, abnormalities in the input CAD model data can be handled by the dynamic processor  114  to produce a printable instruction set. In cases in which the CAD model abnormalities are ambiguous as to the correct way to print, the processor can analyze the model to decide a default configuration. For example, if the slice engine encounters a model with significant holes, it can decide between printing the model as a solid or as a shell with a given wall thickness. In some implementations, the processor can be implemented in such a way as to minimize failure (e.g., a situation in which printing does not complete). 
       FIG. 4  is a flowchart of an example process  400  for 3D printing. The 3D printing can occur, for example, without the necessity to pre-process a CAD model before delivery to a 3D printer.  FIGS. 1A-3  are used to provide example structures for performing the steps of the process  400 . 
     A CAD model is received by a 3D printer, the CAD model for a design to be printed by the 3D printer ( 402 ). For example, referring to  FIG. 1C , the 3D printer  110  can receive the CAD model  118 . 
     The CAD model is processed to identify a first slice, and instructions are generated for printing the first slice ( 404 ). As an example, referring to  FIG. 2 , the dynamic processor  114  can identify a first one of the variable thickness slices  200 , such as the bottom slice associated with the model geometry  202 . The initial slice may be selected based on one or more default settings, such as a default thickness. 
     The generated instructions are used to start printing of the CAD model ( 406 ). For example, the dynamic processor  114  can pass instructions associated with the slice to the printing engine  108 . The printing of the first slice can beginning while a next slice of the model is identified and instructions are generated. 
     In parallel with the printing, dynamic real-time slicing is performed on a remaining portion of the CAD model ( 408 ). For example, the dynamic processor  114  can perform processing for subsequent layers, e.g., in parallel with printing, as shown in  FIG. 3 . 
     Pre-processed data, model analysis information or real-time feedback is received during the printing of a respective slice ( 410 ). For example, as the first layer  302   a  is being printed, the dynamic processor  114  can receive information associated with printing the first layer  302   a . Other examples of data, information or feedback include: data associated with a static analysis or a more detailed analysis of the CAD model, sensor data, camera data, print data, or user input (such as from a manual control to adjust print speed). 
     A next slice is identified for printing including adjusting one or more slicing or instruction parameters based on the received pre-processed data, model analysis information or real-time feedback, wherein adjusting includes adjusting a slicing or instruction parameter for the next slice to be printed by the 3D printer ( 412 ). For example, the dynamic processor  114  can identify the second layer  302   b  as the next layer to be printed, and the dynamic processor  114  can adjust printing parameters for the second layer  302   b  based on information received. Printing parameters can include slice generation parameters or instruction generation parameters. Slice generation parameters can include slice thickness. Instruction generation may include as well use of default settings or parameters, which may be adjusted over time and during the print as herein to compensate for real time detected/received input. For example, instruction generation parameters can include print temperature (e.g., to compensate for ambient temperature or other detected conditions), flow rate (rate at which material exists the nozzle), speed of the print head movement, a cleaning parameter (to control timing of cleaning of the nozzle such as after detection of excess material), brightness parameter or other illumination parameter (e.g., to control a brightness pattern of a light source based on detection of a cloudy print window), or an alignment parameter (e.g., to shift a start of print location relative to some point of origin to compensate for misalignment). Other parameters relating to slice generation or for use in generating print instructions are possible. 
     In some implementations, adjusting one or more slicing parameters can include adjusting a slice thickness based on one or more of CAD model geometry or user input including producing slices having at least two different slice thicknesses when printing the CAD model. For example, the dynamic processor  114  can adjust printing parameters for the second layer  302   b  so that the slice thickness of the second layer  302   b  is different from the slice thickness of the first layer  302   a.    
     In some implementations, adjusting the slice thickness can include increasing a slice thickness for a next slice to be greater than a slice thickness for a last printed slice when printing, for example, a wall. For example, the dynamic processor  114  can determine that larger thickness slices  204  can be used in places where the model geometry  202  remains relatively unchanged (e.g., in straight-walled portions). 
     In some implementations, adjusting the slice thickness can include decreasing a slice thickness for next slice to be less than a slice thickness for a last printed slice when printing, for example, a curve. For example, the dynamic processor  114  can determine that smaller thickness slices  206  can be used, for example, in places where the model geometry  202  changes (e.g., in curves). 
     In some implementations, user input is received after the start of printing and controls a speed at which a remaining portion of printing occurs, with higher speed resulting in greater thickness slices. For example, as the user watches the printing of a respective slice, the user can provide information that is used by the dynamic processor  114  to control the speed of printing and thicknesses of subsequent slices. Other user inputs can be used to change other aspects of printing. 
     In some implementations, adjusting one or more slicing parameters can include determining a default setting for at least one of the slicing or instruction generation parameters to print a first slice, and the at least one slicing or instruction generation parameter can be adjusted at a next slice based on feedback obtained during printing or an evaluation of the CAD model. For example, the first layer  302   a  can be printed using default settings for the printing engine  108 . Subsequent slices can use settings that are changed by the dynamic processor  114  based on information received by processing the CAD model  118  and information received from printing previous slices. 
     Instructions for printing the next slice are generated ( 414 ). For example, the dynamic processor  114  can generate the instruction set for the second layer  302   b.    
     The next slice is printed based on the generated instructions and, in parallel, dynamic real-time slicing is repeated to generate a then next slice and associated instructions for printing ( 416 ). As an example, the second layer  302   b  is printed, and during that time, the dynamic processor  114  can determine and generate instructions for the next slice (e.g., the third layer  302   c ). 
     In some implementations, the process  400  can include processing an image taken from a camera including identifying one or more calibration errors and adjusting an alignment of a next slice. For example, by analyzing image information captured by a camera during printing the second layer  302   b , the dynamic processor  114  can determine that calibration errors (e.g., alignment, spacing) exist. Using this information, the dynamic processor  114  can provide information to the printing engine  108  to correct alignment or other issues. 
     In some implementations, the process  400  can include identifying one or more delicate features in the CAD model that may result in print unreliability, and adjusting includes increasing a next slice thickness to increase print reliability and accordingly not printing the identified delicate features. As an example, the dynamic processor  114  can determine that small or complicated features in the CAD model  118  may not be printable by the printing engine  108  (e.g., due to constraints or capabilities of a given printer), and that these features should not be attempted by the printing engine  108 , as the features fall outside a limited range of acceptable 3D geometry. As a result, the dynamic processor  114  can override a thickness parameter to effectively disregard the complicated features. 
     In some implementations, the process  400  can include detecting an anomaly in a slice, determining a default configuration for the detected anomaly, and applying the default to the generated instructions to ensure no print error occurs when printing the CAD model. The dynamic processor  114 , for example, can determine failure cases associated with a particular slice (e.g., inverted normals, intersecting triangles, self-intersection, non-manifold surfaces, among other errors), and the dynamic processor  114  can automatically account for the failure cases when generating the instruction set for the slice. 
       FIG. 5  is a block diagram of example computing devices  500 ,  550  that may be used to implement the systems and methods described in this document, as either a client or as a server or plurality of servers. Computing device  500  is intended to represent various forms of digital computers, such as laptops, desktops, workstations, personal digital assistants, servers, blade servers, mainframes, and other appropriate computers. Computing device  500  is further intended to represent any other typically non-mobile devices, such as televisions or other electronic devices with one or more processors embedded therein or attached thereto. Computing device  550  is intended to represent various forms of mobile devices, such as personal digital assistants, cellular telephones, smartphones, and other computing devices. The components shown here, their connections and relationships, and their functions, are meant to be examples only, and are not meant to limit implementations of the inventions described and/or claimed in this document. 
     Computing device  500  includes a processor  502 , memory  504 , a storage device  506 , a high-speed controller  508  connecting to memory  504  and high-speed expansion ports  510 , and a low-speed controller  512  connecting to low-speed bus  514  and storage device  506 . Each of the components  502 ,  504 ,  506 ,  508 ,  510 , and  512 , are interconnected using various busses, and may be mounted on a common motherboard or in other manners as appropriate. The processor  502  can process instructions for execution within the computing device  500 , including instructions stored in the memory  504  or on the storage device  506  to display graphical information for a GUI on an external input/output device, such as display  516  coupled to high-speed controller  508 . In other implementations, multiple processors and/or multiple buses may be used, as appropriate, along with multiple memories and types of memory. Also, multiple computing devices  500  may be connected, with each device providing portions of the necessary operations (e.g., as a server bank, a group of blade servers, or a multi-processor system). 
     The memory  504  stores information within the computing device  500 . In one implementation, the memory  504  is a computer-readable medium. In one implementation, the memory  504  is a volatile memory unit or units. In another implementation, the memory  504  is a non-volatile memory unit or units. 
     The storage device  506  is capable of providing mass storage for the computing device  500 . In one implementation, the storage device  506  is a computer-readable medium. In various different implementations, the storage device  506  may be a floppy disk device, a hard disk device, an optical disk device, or a tape device, a flash memory or other similar solid state memory device, or an array of devices, including devices in a storage area network or other configurations. In one implementation, a computer program product is tangibly embodied in an information carrier. The computer program product contains instructions that, when executed, perform one or more methods, such as those described above. The information carrier is a computer- or machine-readable medium, such as the memory  504 , the storage device  506 , or memory on processor  502 . 
     The high-speed controller  508  manages bandwidth-intensive operations for the computing device  500 , while the low-speed controller  512  manages lower bandwidth-intensive operations. Such allocation of duties is an example only. In one implementation, the high-speed controller  508  is coupled to memory  504 , display  516  (e.g., through a graphics processor or accelerator), and to high-speed expansion ports  510 , which may accept various expansion cards (not shown). In the implementation, low-speed controller  512  is coupled to storage device  506  and low-speed bus  514 . The low-speed bus  514  (e.g., a low-speed expansion port), which may include various communication ports (e.g., USB, Bluetooth®, Ethernet, wireless Ethernet), may be coupled to one or more input/output devices, such as a keyboard, a pointing device, a scanner, or a networking device such as a switch or router, e.g., through a network adapter. 
     The computing device  500  may be implemented in a number of different forms, as shown in the figure. For example, it may be implemented as a standard server  520 , or multiple times in a group of such servers. It may also be implemented as part of a rack server system  524 . In addition, it may be implemented in a personal computer such as a laptop computer  522 . Alternatively, components from computing device  500  may be combined with other components in a mobile device (not shown), such as computing device  550 . Each of such devices may contain one or more of computing devices  500 ,  550 , and an entire system may be made up of multiple computing devices  500 ,  550  communicating with each other. 
     Computing device  550  includes a processor  552 , memory  564 , an input/output device such as a display  554 , a communication interface  566 , and a transceiver  568 , among other components. The computing device  550  may also be provided with a storage device, such as a micro-drive or other device, to provide additional storage. Each of the components  550 ,  552 ,  564 ,  554 ,  566 , and  568 , are interconnected using various buses, and several of the components may be mounted on a common motherboard or in other manners as appropriate. 
     The processor  552  can process instructions for execution within the computing device  550 , including instructions stored in the memory  564 . The processor may also include separate analog and digital processors. The processor may provide, for example, for coordination of the other components of the computing device  550 , such as control of user interfaces, applications run by computing device  550 , and wireless communication by computing device  550 . 
     Processor  552  may communicate with a user through control interface  558  and display interface  556  coupled to a display  554 . The display  554  may be, for example, a TFT LCD display or an OLED display, or other appropriate display technology. The display interface  556  may comprise appropriate circuitry for driving the display  554  to present graphical and other information to a user. The control interface  558  may receive commands from a user and convert them for submission to the processor  552 . In addition, an external interface  562  may be provided in communication with processor  552 , so as to enable near area communication of computing device  550  with other devices. External interface  562  may provide, for example, for wired communication (e.g., via a docking procedure) or for wireless communication (e.g., via Bluetooth® or other such technologies). 
     The memory  564  stores information within the computing device  550 . In one implementation, the memory  564  is a computer-readable medium. In one implementation, the memory  564  is a volatile memory unit or units. In another implementation, the memory  564  is a non-volatile memory unit or units. Expansion memory  574  may also be provided and connected to computing device  550  through expansion interface  572 , which may include, for example, a subscriber identification module (SIM) card interface. Such expansion memory  574  may provide extra storage space for computing device  550 , or may also store applications or other information for computing device  550 . Specifically, expansion memory  574  may include instructions to carry out or supplement the processes described above, and may include secure information also. Thus, for example, expansion memory  574  may be provide as a security module for computing device  550 , and may be programmed with instructions that permit secure use of computing device  550 . In addition, secure applications may be provided via the SIM cards, along with additional information, such as placing identifying information on the SIM card in a non-hackable manner. 
     The memory may include for example, flash memory and/or MRAM memory, as discussed below. In one implementation, a computer program product is tangibly embodied in an information carrier. The computer program product contains instructions that, when executed, perform one or more methods, such as those described above. The information carrier is a computer- or machine-readable medium, such as the memory  564 , expansion memory  574 , or memory on processor  552 . 
     Computing device  550  may communicate wirelessly through communication interface  566 , which may include digital signal processing circuitry where necessary. Communication interface  566  may provide for communications under various modes or protocols, such as GSM voice calls, SMS, EMS, or MMS messaging, CDMA, TDMA, PDC, WCDMA, CDMA2000, or GPRS, among others. Such communication may occur, for example, through transceiver  568  (e.g., a radio-frequency transceiver). In addition, short-range communication may occur, such as using a Bluetooth®, WiFi, or other such transceiver (not shown). In addition, GPS receiver module  570  may provide additional wireless data to computing device  550 , which may be used as appropriate by applications running on computing device  550 . 
     Computing device  550  may also communicate audibly using audio codec  560 , which may receive spoken information from a user and convert it to usable digital information. Audio codec  560  may likewise generate audible sound for a user, such as through a speaker, e.g., in a handset of computing device  550 . Such sound may include sound from voice telephone calls, may include recorded sound (e.g., voice messages, music files, etc.) and may also include sound generated by applications operating on computing device  550 . 
     The computing device  550  may be implemented in a number of different forms, as shown in the figure. For example, it may be implemented as a cellular telephone  580 . It may also be implemented as part of a smartphone  582 , personal digital assistant, or other mobile device. 
     Various implementations of the systems and techniques described here can be realized in digital electronic circuitry, integrated circuitry, specially designed ASICs (application specific integrated circuits), computer hardware, firmware, software, and/or combinations thereof. These various implementations can include implementation in one or more computer programs that are executable and/or interpretable on a programmable system including at least one programmable processor, which may be special or general purpose, coupled to receive data and instructions from, and to transmit data and instructions to, a storage system, at least one input device, and at least one output device. 
     These computer programs (also known as programs, software, software applications or code) include machine instructions for a programmable processor, and can be implemented in a high-level procedural and/or object-oriented programming language, and/or in assembly/machine language. Other programming paradigms can be used, e.g., functional programming, logical programming, or other programming. As used herein, the terms “machine-readable medium” “computer-readable medium” refers to any computer program product, apparatus and/or device (e.g., magnetic discs, optical disks, memory, Programmable Logic Devices (PLDs)) used to provide machine instructions and/or data to a programmable processor, including a machine-readable medium that receives machine instructions as a machine-readable signal. The term “machine-readable signal” refers to any signal used to provide machine instructions and/or data to a programmable processor. 
     To provide for interaction with a user, the systems and techniques described here can be implemented on a computer having a display device (e.g., a CRT (cathode ray tube) or LCD (liquid crystal display) monitor) for displaying information to the user and a keyboard and a pointing device (e.g., a mouse or a trackball) by which the user can provide input to the computer. Other kinds of devices can be used to provide for interaction with a user as well; for example, feedback provided to the user can be any form of sensory feedback (e.g., visual feedback, auditory feedback, or tactile feedback); and input from the user can be received in any form, including acoustic, speech, or tactile input. 
     The systems and techniques described here can be implemented in a computing system that includes a back end component (e.g., as a data server), or that includes a middleware component (e.g., an application server), or that includes a front end component (e.g., a client computer having a graphical user interface or a Web browser through which a user can interact with an implementation of the systems and techniques described here), or any combination of such back end, middleware, or front end components. The components of the system can be interconnected by any form or medium of digital data communication (e.g., a communication network). Examples of communication networks include a local area network (“LAN”), a wide area network (“WAN”), and the Internet. 
     The computing system can include clients and servers. A client and server are generally remote from each other and typically interact through a communication network. The relationship of client and server arises by virtue of computer programs running on the respective computers and having a client-server relationship to each other. 
     While this specification contains many specific implementation details, these should not be construed as limitations on the scope of any inventions or of what may be claimed, but rather as descriptions of features specific to particular implementations of particular inventions. Certain features that are described in this specification in the context of separate implementations can also be implemented in combination in a single implementation. Conversely, various features that are described in the context of a single implementation can also be implemented in multiple implementations separately or in any suitable sub-combination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a sub-combination or variation of a sub-combination. 
     Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Moreover, the separation of various system components in the implementations described above should not be understood as requiring such separation in all implementations, and it should be understood that the described program components and systems can generally be integrated together in a single software product or packaged into multiple software products. 
     Thus, particular implementations of the subject matter have been described. Other implementations are within the scope of the following claims. In some cases, the actions recited in the claims can be performed in a different order and still achieve desirable results. In addition, the processes depicted in the accompanying figures do not necessarily require the particular order shown, or sequential order, to achieve desirable results. In certain implementations, multitasking and parallel processing may be advantageous.