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OVERVIEW

The Department of Art has one Forest Scientific 3-axis Computer Numerical Controlled (CNC) router, managed by Technician Robin Schwartzman. Only technicians may start the CNC router, however once staff review and start your file, users are required to observe the router while it is in operation.

The CNC router is for use by enrolled students for coursework related projects only! If you intend to use the router for projects outside of course-related work there will be additional charges.

The CNC router can be used for cutting 2D part files, drilling and 3D machining or any combination of these functions. The CNC router has a 4'x6' bed with a 6" gantry clearance (Z height). A 4" maximum Z height is a good rule of thumb, but the maximum Z height depends on many factors including tool length, tool clearance and part geometry. For 2d cutting, there should be a 1" margin around the perimeter of your material stock in case we need to screw it into the router spoil board. The router is a 3-axis router, therefore it cannot make undercut or bevel cuts.

MATERIALS THAT CAN BE CUT INCLUDE:
Solid hardwood or softwood
Plywood, MDF, particleboard and other sheet stock
Plastics, such as acrylic and polyethylene (LDPE / HDPE)
Always be sure to bring extra material for test cuts and/or mistakes caused by possible shifting of material on the router bed.

Preparing files for the CNC Router

Step 1: Design
The software we use to design and toolpath files is EnRoute 4, however files designed other programs can be imported into EnRoute. Many designs can be made right in the EnRoute program, as well.

The following is the list of current formats EnRoute 4 supports: Adobe Illustrator 6 (*.AI) Adobe Illustrator 10 (*.AI) Windows Bitmap (*.BMP, *.JPG) CasMate (*.SCV) AutoCAD DWG (*.DWG) AutoCAD DXF (*.DXF) EnRoute 2x (*.ENR) Encapsulated Postscript (*.EPS) FlexiSIGN 5x (*.FS) HPGL (*.PLT) I-Script (*.iscript) Onyx XML (*.xml) STL (*.STL) STL (*.STL) to Relief 3D Studio (*.3DS) ModelMIll Relief (*.MMR) ModMill Object (*.mmo) G-Code Scan (*.cnc) WoodWOP.VARIANT (*.MPR) PDF (*.PDF)

2d cutting requires only 2d line drawings. 2d cut parts should have each part represented as a single closed curve, path or polyline. Be sure your lines meet exactly at endpoints and there are no duplicate, intersecting or overlapping lines. 3d machining requires a polygonal mesh, a surface or solid model. All files should be scaled to the actual size and units of the output that you require. If you need assistance designing your file, please contact Robin to set up an appointment, separate from your routing appointment.

Step 2: Toolpathing

Tool-paths need to be generated to program the machine to cut your part. You will be assisted in toolpathing your specific files based on material, type of cut and recommended bits. All toolpathing will be done in EnRoute 4.

WE WILL STOCK A VARIETY OF STANDARD TOOLS:
1/4, 3/8, 1/2" and 3/4" square endmill for roughing.
1/4" and 3/8" compression endmill for 2D profile cutting
and finishing.
1/8", 1/4" 3/8" and 1/2" ball endmill for 3D surfacing.
V-carving bits for 2-1/2D machining.
1/4" drill tip for drilling.

Selecting Cutting Tools
Generally, you should select the biggest diameter and shortest cutting tool you can safely use.
When selecting the tooling you're going to use, keep in mind that you want to use an appropriately sized cutter for your job. The cutter's diameter and length should be scaled for the amount and type of milling you plan on doing. The technician will help you select the appropriate tools for your project.

BASIC GUIDELINES FOR TOOL SELECTION:
The larger diameter the cutter, the more material it can remove per pass resulting in faster processing.
Smaller diameter cutters can get into tighter corners, but aren't suitable for hogging out a lot of waste material.
Long cutters are used where there are drastic slopes and deep pockets that might cause the collet to crash into the work piece.
Short cutters are robust; they allow for more material removal per pass.
Square end mills are ideal for roughing passes.
Ball nosed end mills are not for roughing passes. They are used for finishing passes.
For example, if you need to rough mill a stepped topography that is 24" square and 2" tall, you should choose an end mill that will remove a lot of material. A medium length .75" or .5" end mill will allow you to rough out the topography quickly. You may then run a finishing tool pass with a medium length .25" end mill to clean up any small corners where the larger end mill couldn't reach.

Step 3: Review

Before your part is cut, a Technician will assist you in designing, toolpathing and reviewing the file. Once your file has been cleared, we will schedule a time for you to run your part on the CNC router. Do not expect that this part can be run immediately. It is advisable to have your file reviewed several days in advance of your desired cutting time. Cutting times vary, but can range anywhere from 30 minutes to six hours, depending on the size and intricacy of the cut.

MATERIAL PREPARATION
Students must supply their own materials and be sure that they will fit on the 4' x 6' router bed. If you are using plywood, make sure to get as flat of a piece as possible. If your material stock is glued up, be sure that it has had sufficient time to dry. Use liberal amounts of glue spread evenly across the material to ensure complete adhesion when laminating materials. Also please note your actual material thickness, as this may effect your file settings. Calipers are located in the Workshop to get the exact thickness of your material. For example, if using 3/4" plywood, it is likely the actual thickness is .6875". These exact dimensions must be used for toolpathing. Always bring extra material for test cuts and/or mistakes due to possible shifting of material on router bed.

Step 4: Machine Set-up and Operation

The scheduling of CNC jobs is at the sole discretion of Workshop staff: we will prioritize jobs based on estimated cut time, staff workload and user preparation and availability.

We will advise you on how best to secure your stock to the router table. Be aware of where you are placing screws to ensure that they are not in the way of a tool path. If a tool path hits a screw, the bit can be destroyed. If bits are broken due to carelessness, students are responsible for the cost of the bit (which is as much as $80 depending on the bit).
Workshop Technicians will help you set the machine for your part and instruct you on how to make a tool change if necessary. Users are responsible for observing the machine while in operation. Please note that it is common for parts to take several hours to finish. The estimated time should be tripled for actual run time, including material attachment, etc.
Users are required to wear safety glasses while the machine is in operation: hearing protection is also strongly recommended. Earplugs are available in the woodshop.

CLEAN-UP
Users are responsible for leaving the area in a clean condition. There is a dust collection system that will pick-up the majority of dust. Then your part is completed, you should blow the majority of the chips off of the machine and sweep the floor, putting off-cuts and scraps into the scrap racks or the dumpster. Cut large scraps down to rectangles for reuse. Do not leave large scraps in the router room. You may lose your privileges to use the CNC router if you are negligent in your clean-up responsibilities.

QUESTIONS
If you have questions about the CNC router, please drop by the Workshop and speak to the Technician or e-mail Robin at schwa966@umn.edu.

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