September 2011 Archives

Creating Texture

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IMG_0333.JPGThe CNC router can be used to create a variety of textures out of a surface. These can range from faux wood grain, stone, pounded metal, bricks, basket weaves, honeycombs, etc.

Bitmaps can be useful in creating a texture that makes up part of your design. EnRoute utilizes the colors or grayscale shading in a bitmap image to modify the height of the relief using parameters that you provide. The lightest or white areas will be the tallest part of the relief, black areas will be the lowest, and all grayscale areas will adjust accordingly between the two dependent on their value.
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EnRoute has the capability to create textures for a relief without the aid of bitmaps. A number of texture tools have already been defined and entered in as templates. This is a good starting point for several different textures. There are several types of textures available. The categories include: basic noise, brick, cellular, dots, flgstone, flame, hammered, hexes, marble, mudpot, multicell, multifract, terrain, veneer, weave and wood. Each of these textures can be used as defined or further refined to achieve the precise texture for your design.

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Vector Cuts

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IMG_0229.jpgThe router is a great tool for cutting out solid shapes of material. This is also known as a vector cut, because the shape is designed within the program with what is called a vector graphic. A vector graphic uses a system of points, lines, curves, shapes and polygons which are based on mathematical equations to represent images in computer graphics. Unlike pixellated images, vector graphics can be scaled up or down to any size without becoming blurry or distorted.

The cut can be as simple as a circle or as complicated as the outline of a text or a country. It can involved multiple shapes next to, inside or outside of each other. Shapes can also include strategically place drill holes. Cutting out vector shapes can also be combined with dimensional cuts.

Materials

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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)
High-Density Urethane (HDU), also referred to as SignFoam
*Insulation foams such as extruded polystyrene CANNOT be cut on the router!
Always be sure to bring extra material for test cuts and/or mistakes caused by possible shifting of material on the router bed.

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.

Material Suppliers

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The following are a list of local suppliers for wood and sign related products.

Youngblood Lumber
1335 Central Avenue N.E.
Minneapolis, MN 55413
612-789-3521
Hardwoods, exotics, big (8" x 24" x 24' mahogany) and little. Students buy at wholsale prices! This is where woodworkers in the Twin Cities buy hardwoods.

Forest Products Supply
2650 Hwy 61
Maplewood, MN 55109
651-770-2834
FPS has a large selection of hardwoods and exotic woods. There are over 70 species of wood in stock. We also have a great selection of sheetgoods, plywood, melamine, hardboard, etc. FPS sells shorts cheap.

Siwek Lumber & Millwork
2536 Marshall Street N.E.
Minneapolis, MN 55418
612-781-3333
Close-outs, odd lots, used stock, common grade; the most for the least.

Natural Built Home
4020 Minnehaha Avenue
Minneapolis, MN 55406
612.605.7999
Natural Built Home is your one-stop shop for eco-friendly building supplies in Minneapolis and St. Paul. They carry bamboo floors, non-toxic paint, recycled glass tile and much more.

Midwest Sign and Screen
45 East Maryland Avenue
St. Paul, MN 55117
651.489.9999
Commercial sign supplies including HDU Sign Foam, sign paints, urethanes, tapes and adhesives, cutting tools and rulers.

Coastal Enterprises
Manufacturers of Precision Board Plus HDU

Dimensional Cuts

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The router is a great tool for creating dimensional low-relief cuts which can include a variety of textures, shapes and text. In this example, a drawing was created in EnRoute where it was given dimension and woodgrain texture. The piece was cut out of MDF in two passes, the first to clear out excess material and the second to cut the fine detail work. The MDF was then primed and painted to create a finished work.

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Flat reliefs can be assembled together to create unique 3-dimensional objects.

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The following are examples of signs created by Dan Sawatzky at the Imagination Corporation in Yarrow, B.C. Note that the text and textures are all done using the router, however the dimensional objects mounted to the signs are hand-sculptured with a 2-part epoxy putty.
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Woodcut Prints

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The CNC Router can be used to create intricate and beautiful woodcut prints. There are two ways to utilize the router for woodblocks:
1. Scale up an existing smaller-scale woodcut image to create a larger version.
2. Scan an intricate drawing or text to create a woodblock of an image that would be impossible to carve strictly with hand tools.

In the fall of 2010, the Department of Art's router was used to cut a 4' x 6' version of Artemio Rodriguez's linocut print entitled Pinata. The original print was scanned, converted into a vector file, enlarged and then cut in low relief out of a sheet of MDF. Due to the size and intricacy of the image, this woodblock took over 30 hours of cutting time.

In-progress cut.
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Detail of cut in-progress.
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Original linocut print, approximately 10" x 15".
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Full scaled routed woodblock print, approximately 4' x 6'.
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CNC Router Links

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EnRoute Software
An overview of the software used by the Department of Art including videos, photo galleries, training and support.

EnRoute User Guide
Downloadable EnRoute User Guides for all your file designing questions.

Feeds and Speeds
Suggested feed rates and spindle speeds for a variety of cutting tools and commonly milled materials.

Forest Scientific
Information about the Department's Forest Scientific 3-axis router.

SU DesignWorks You-Tube Channel
Great comprehensive step-by-step RhinoCam instructions from our friends at Syracuse University. Other good stuff, too!

Google Earth to SketchUp
Step-by-step streaming tutorial for importing topography from Google Earth to SketchUp to prepare for CNC machining.

EnRoute Thoughts is EnRoute's blog, full of projects, tutorials and workshop dates and info.

Contact the Router Tech

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E-mail: umnlaser@gmail.com
Locaiton: E153, XYZ Lab
Regis Center for Art
405 21st Ave. S.
Minneapolis, MN 55455

CNC Router Access Use and Policy

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The CNC Router is available for use by enrolled students, faculty and staff in the Department of Art at a cost of $5/15 minutes (machining time).

The Router is available for use by non Department of Art students, faculty and staff at a cost of $25/15 minutes (machining time).

Appointments must be made for both consultations and machining time. Please e-mail Anthony at umnlaser@gmail.com to setup an appointment. No machining will be done without a preliminary consultation to set up files, create toolpaths and select correct bits. After we review and start your file, users are required to observe the router while it is in operation. Only lab technicians are allowed to start the CNC Router.

Overview

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OVERVIEW

The Department of Art has one Forest Scientific 3-axis Computer Numerical Controlled (CNC) router. 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 some 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 email umnlaser@gmail.com.