CNC Milling at the AA Digital Prototyping Lab Procedure The CNC machines at the AA are operated by the Digital Prototyping Lab staff. AA Students can submit 3D models for production in one of the machines at the lab between 10.00 am and 1.00 pm, monday to friday. After delivering the file and material or paying for high-density foam which is supplied by the DPL, your model is placed in the queue. At this time the lab staff can give you an estimation of the date and time your model will be finished, please be aware that there usually is a waiting time between 1 and 8 working days (in busy periods). Sizes and Materials The maximum cutting size of the big CNC machine is 1220x1220 mm. The maximum cutting size of the small CNC machines is 500x400 mm. The maximum thickness in all machines is 50 mm.* This has to do with the standard thickness of the high density foam sheets and also the length of the cutters. (*We have one cutter with a length of 75mm for use in the big CNC machine, with a diameter of 12 mm.) When considering sizes for a model produced in the big CNC machine it is advisable to work with the standard sheet sizes of high-density foam to avoid waste of material and high purchase cost: The high-density foam comes in sheets of 1500x500x50 mm. Other materials that can be used in the CNC machines are: MDF Plywood Bluefoam Other types of soft foam Cast-acrylic Modeling wax All these materials need to supplied by the individual student or can be ordered through the DPL. In all cases when considering materials other than high-density foam it is strongly recommended to discuss your project with the DPL staff beforehand. In the DPL are also sample boxes of several different types and grades of medium and high-density foam available. Cost of Materials Two grades of High-density foam are usually kept in stock at the Digital Prototyping Lab (M300 and M450), larger amounts can be ordered for delivery on the next day. The prices fluctuate slightly due to exchange rates and other factors, the price for a block 500x400x50 mm M300 grade (yellow) is currently 34.00 pounds (Jan2009). You only pay for the material, if you bring your own material there is no charge. Guidelines for File Preparation The staff at the Digital Prototyping Lab will set up your digital file for CNC milling using ArtCam or Mayka software. To enable the preparation of your 3D model you will need to ensure the following guidelines are met: - the 3D model must be in millimeters, in 1:1 scale of the final physical model; - the model must fit within the maximum cutting size of the machine; - the model must be submitted in the .3DS (3d studio) format; - separate blocks must be submitted as separate files; (for instance 'studentname_model5_01.3ds', 'studentname_model5_02.3ds', etc) - doublesided models can be submitted as one 3d model; - models for the big CNC machine consisting of multiple sheets of high-density foam can be submitted as on 3d model; - please supply 'clean' files: not other information, geometries, hidden objects/layers/ etc. As guideline for the thicknesses of double-sided milling projects keep a minimum of 3mm in all directions. With regard to the minimum dimensions of detail please keep in mind that we can use different cutters: 12, 6, 3 mm and the 1 mm Vbit. Holes, gaps or grooves within your model will not be milled if they are smaller than the size of the drill. Please note that for the CNC milling software you do not need to submit a fully closed, watertight model (as opposed to modeling for 3D printing). A 3D model can contain intersecting surfaces or solids, as the software will only consider the top surfaces. Be aware that the AA only has 3-axis milling machines, which means if your model features undercuts these will not be machined. Double-Sided Milling - Submit a single .3DS file containing a clean model considering minimum thicknesses; - Include a frame around the parts to be milled, with a minimum thickness of 20 mm and a height of 50 mm; - Include frames in between separate parts if those parts cannot be joined to the edge frame on all sides; - Include 'bridges' in between the frame and the parts, with a minimum thickness of 5 mm, height of 50 mm; - Leave a distance slightly smaller than the size of the intended drill bit in between the bridges and the part. (This will allow easy cutting and finishing after the pieces have been milled.) 2D cutting of large size sheets (big CNC machine) - Submit a 2D drawing file in .3DM (Rhino) format; - Combine multiple sheets in one drawing, clearly labeled; - Drawing must be in mm in 1:1 physical model scale; - Apply a maximum sheet size 1200x1200 mm; - Text, areas and outline cut shapes need to be in separate layers; - Each shapes that will be cut or areas that will be 'engraved' to a certain depth needs to be marked with a single, closed polyline; - Holes that will be drilled need to be marked with a circle; - Separate shapes need to be at a minimum distance of 20 mm from eachother and from the edges of the sheet. For additional guidelines and illustrations see our new CNC tutorial in the 'tutorials' section!