SURFCAM & CNC MILLING

Transcription

1 SURFCAM & CNC MILLING Panelization and manufacturing of the Predator by Greg Lynn and Fabian Marcaccio University for Applied Arts, Vienna Studio Prof. Lynn Drawings & compilation by Nathalie Rinne With special thanks to Oliver Bertram & David Erdman

2 Basic Introduction to the software SurfCAM: In this lab students will be utilizing a number of modeling softwares prior to using SURFCAM. Alias, Maya, FormZ, Rhino, 3D Studio, none can be directly read by SURFCAM. The data must be translated into a standard format that can be understood by SURFCAM. The Initial Graphics Exchange Specification (IGES) can transfer CAD data from one system to another. SurfCAM is therefore the software program that we use to take a geometry file (in our case the IGES file from Maya), interpret the surfaces within the context of the milling machine, develop a set of tool paths that will carve out the intended geometry, and then it post processes the toolpaths into G-code that is specific to the Precix 3axis Mill. The progression of file formats is as follows: IGES (exported from MAYA) >.NCC (SurfCAM format) >.gc (G-Code for the mill) The clean and precise manufacturing of a piece depends on many factors, chief among them being, the quality of the CAD file or model, the parameters and translations used in creating the toolpaths, and a successful understanding of the resulting G-code sent to the Machine. The more information the data of transfer, the more likely the information will be distorted in the second party software. In order to minimize interface distortion one should limit the transfer of information to NURBS or curves. When possible, avoid trimming, stitching, blending operations. If these are unavoidable be prepared to leave time for adjustments as a result of transferring.

3 File Preparation for SurfCAM in Maya: One of the major constrains of the 3 axis CNC mill is that it can t perform undercuts. CNC mills can basically cut an infinite number of variations of a bowl. It means that the machine can mill a U, but not a C -like profile. Ensure that all surfaces are free of undercuts. Ensure that the file you have generated in MAYA has been done with the Z axis set to up. (the default is for Y to up from the animation industry!) Ensure that the model is in the positive x, y and the negative z area. - The (0,0,0) coordinate will be your origin on the milling machine, with z=0 as the top of your material.

4 Create a reference line, because SurfCAM will import your model in a wrong scale. You may want to set up a bounding box around your project. The bounding box is a box that should be a 2D series of lines which describe a perimeter within which a part is placed. The area between the part and the bounding box with be excavated. This should be drawn on the Z=0 plane of your file. It will act as the reference for the material and a corner could possibly be the origin point for the Mill. Your bounding box can also act as your scale reference marker. Export the active items (file> export selection) as an Iges file. - If iges doesn t exist in the setting, cancel the export action and check the export-setting. (windows> settings/preferences>plug-in manager>highlight MayaToIgesDxf.mll ) - Repeat the export action. - Once you have saved the.iges file manually rename iges to.igs.

5 File Preparation for Milling in SurfCAM: Launch SurfCAM, click once on the image in the center of the screen = ready! - >File>Open your igs file in the file command - Save the file as DEM Format - NOTE, in SurfCAM there is NO UNDO!!!!! Please SAVE as often as possible!!! View port configuration: SurfCAM has basic viewport configuration. The basics of Zoom, Rotate view, Pan and Fit are all present on the Main toolbar. - There are two different views : V View is the Visual View (what you see on the display), C View is the Construction View (what your model sees): You must be careful to always match the views (usually to TOP = #1) when processing new tool paths. - This is easily accomplished by double clicking on either view, selecting the view and clicking both buttons at the bottom of the selection window: VIEW + CVIEW

6 Checking the scale of the object: Measure the known distance of the line that was created in MAYA and calculate the scaling factor. NOTE: ALL MEASUREMENTS IN SURFCAM ARE IN MILIMETERS!!! - >Analyze> Distance> Sketch( or Endpoints) - The line that you created in MAYA should be the same measured value in SurfCAM. - If required apply a scaling factor to the entire drawing, be careful to maintain the position and orientation of the piece scale about the origin! - >Edit> Transform> Move> Scale> visible> Keyboard (...,...,...)>Keyboard (0,0,0,) (+SAVE) Check the Surface Direction of your object: Check the surface side the surface should be pointing up, towards the +Z of the mill. - >Display> Shade> Undercut (red=wrong/ green=right) In this mode you ll also see if your model has undercuts. - >Edit> surface> side> click on red surface > direction (influence the fine cut direction-important for the pattern) > corner r (determine the starting point of the fine cut) (+SAVE) Create bounding box (if not already done in the maya file) For any object that will have 2 or more sides milled (top and bottom), a bounding box with bridges will be required to stabilize the milling. For other (flat) jobs, a bounding box is often a good idea, so as to demarcate the piece from the material, or to set up even & square cutting or post-finishing lines. - >Create> line> string> polyline> sketch (don t forget the bridges, if you are milling two sided) the minimal distance between the line and the model should be at least the diameter of the milling bit. - >Create> rectangle> draw a rectangle around the part where the bridges hit the model (only for hard materials such as MDF and Acryl). Prepare the file settings > Operations Manager The complete tooling of a single piece may often require several different toolpaths. To organize the files and toolpaths set up the job in the operations manager. - Click the operations manager icon on the toolbar. (right-most button on the first bar) - Here you can set up folders for Z-rough cut, Z-fine cut,. - left button creates new folder> create a fine- and a rough- folder)> - activate the rough folder. It will automatically put your NC jobs in this folder. The Operations Manager allows you to view the structure of the job and do graphical verification of the milling jobs, means it post process, simulate, hide and group NC routines.

7 Generating toolpaths using SurfCAM: Once a job has been set up in SurfCAM the toolpaths can be calculated. There are several different toolpath types that can be run on a 3 axis Precix mill. To get best results for a piece several toolpath types may be combined and run in order. Information may appear in control windows which is not included of discussed in this manual. All information which has been bypassed is not relevant to the following procedures and therefore should not be manipulated. If a student would like to investigate more complex procedures which would require the manipulation of omitted parameters, he/she should be familiar with the procedure outlined in this manual. Different types of cutting supported on the Precix Mill: 2d contour cutting: Cutting along a line at a prescribed depth. This will result in etching or cutting of material in 2d. A sacrificial layer under the material should be used if the cut is to be completely through the material. Z-Rough: Used to mill off the bulk of the material to a set height above a surface. This is a rough operation and is often used in conjunction with a finishing operation. It produces a topographical modell. Z-Fine or cut: Used as the fine tuning after a Z-Rough cut. It will fine cut the surface (or surfaces with steep angle s) and should be set to use a different endmill to increase precision. It produces a mill path along the geometry of the surface. Planar: a linear fine milling of the project surface, all toolpaths are parallel and the mill moves with the surface in the Z axis. Planar Flow: A fine milling of the surface, however the toolpaths are calculated based on the inherent geometry and orientation of the U&V geometry within the NURBS surfaces.

8 Creating a NC job (ROUGH CUT) Operations Manager: Highlight the Fine Cut folder - >NC mode> 3axis> z-rough> visible(or within) - A window will appear requesting the Material Height and the technique for locating the endmill. >top profile> set material height (-2mm to be sure not to mill into the table) - >chain (click twice on your bounding box, to snap the first and the endpoint of your line) - Once selected, the Surfcam 3axis Z rough window will be displayed on the screen Tool Information:> select the endmill size and type (12mm flat or round nose bit) - Cut control:> conventional (method to be cut) - Stock to leave:>2mm (the rough cut leaves material, that the fine cut is going to remove in the second job): - Rapid plane: >3mm-5mm (this is the height of retraction above the top surface of the model the bit will maneuver while executing routines. This option has to be double-checked when editing or redoing NC sequences as it will change back to variable defaults) - Z-step size:> 6mm ( this is the depth the endmill plunge in a material. As a rule of thumb, endmills typically plunge a maximum of half of their diameter): - XY-step size: >6mm (max. half of the diameter of the bit this will determine the texture and smoothness of the surface. The greater the step over, the rougher the texture.) - Plunge Point Selection:> Select (you ll select points where the mill is able to plunge into the material between the sequence. This is important for hard material like MDF and Acrylic, as plunging into the material outside of the bounding box might break the bit) - >OK - Draw plunge points using the >SKETCH setting (between the bounding box and your model and in the deep areas of your model) - >Done - The program now calculates the toolpath and saves it into the Operations Manager. Simulation - >Operation manager> highlight the toolpath> click Simulation button (Errors will be shown red in the simulation) Creating a NC job (FINE CUT) Operations Manager: Highlight the Fine Cut folder. Check the direction of the surfaces. There are several different modes that can be used for the fine cutting of a surface, experiment with each to find texturing and finishing processes for your design. - >NC mode> 3axis> cut> select the surface (Surfcam will only allow individual sequences for finish cuts. These can be grouped later on in the operation manager) - Tool Information: > select the endmill size and type (6mm/ 3mm Endmill, rounded milling bit) - stock to leave: >0 (as one is not excavating a surface from the material, but finishing it) - step type: >2 (this is the finish of the surface, its grooviness. Typically, 2 will give adequate results. For extremely smooth surfaces this should be set higher, but will increase the run time. Strong pattern can be produced with a thicker bit and half the diameter of the bit.) - step type:> increment - retrace: >bi-directional (how often the bit is cutting. Typical, means it is cutting one stroke, then retracing, returning near the beginning of the prior stroke and cutting again. Bidirectional means the bit is always cutting. Bidirectional is typical as it minimizes cutting time.) - rapid plane: >3mm-5mm (this is the height of retraction above the top surface of the model the bit will maneuver while executing routines. This option has to be double-checked when editing or redoing NC sequences as it will change back to variable defaults) - For more complex procedures the gouge check might be useful. For instance, if there are adjacent surfaces which may get gouged. >Multi surfaces will check the adjacent surfaces and determine which surfaces should be avoided. Click first on the surface, which has to be cut and then click on the adjacent surfaces. - >OK

9 Flipping the material for a double-sided model: If you are creating a piece that has 2 sides then it is imperative that you have very good control over the placement of the XYZ origin in both SurfCAM and on the Milling table! - Set both the VIEW and your current view (CVIEW), which is the view in which you work, to right side view. - >Click views> right view> click cview+ click view >ok - >Edit> transform> copy (just in case, remember there is no undo command) - >Rotate> keyboard (0,0,0) (the model has been flipped around the origin. You ll have to do the exact action at the milling table, just flipping your working piece around the origin.) It is often helpful to mark the material BEFORE milling to ensure that the origins will line up with the zero-points for the file. Repeat the set up for both rough and fine cut for the other side of the piece don t forget to name your folders in the operations manager with the side number as well. Post processing: Simulate your job before post process, to make sure that you didn t do any errors! Once all the toolpaths have been calculated the job can be post processed. Post processing is the act of translating the SurfCAM toolpaths format into the native Precix.gc (G-Code format). - Open up the Operation manager. Simulate your NC jobs and check for any errors. Highlight the Rough folder (Fine folder), containing the jobs for one side, with the same milling bit. They can be grouped for one job on the milling machine. - Ensure that the Precix mill is set in the machine selection box. - >Post - A window will be opened with your job written in g-code. - Select >file> save as> save file as filename.gc (make sure you type the.gc end) G-Code is a standard used in the CNC machining industry. It is a small set of relatively simple commands for moving from one coordinate point to another. With a very brief introduction it is possible to read and edit G-Code manually. It is also possible to program directly in G-Code using script generators. There are several graphical verification tools available for native G-Code. Send file to the mill: - Check that the milling machine is switched on. - Start> find computer> Precix - double click the precix> double click files> copy your gc-files into the folder of the current month. - Please ensure that all of your work including the Milling codes are backed up on CD or onto your personal account. Ready for Milling