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Sunday, 21 September 2014 12:29

Finish

For many kinds of parts, the surface appearance of the part is of no great importance. For example, parts used deep inside a machine can be scratched or scuffed, and still work perfectly well. However, for many applications, having a regular, smooth appearance is important. In this category are things like car dashboard panels, musical instruments, and signs.

Several things can contribute to a blemished or uneven appearance in a waterjet cut part. To begin with, the stock material from which the part is cut may have surface scratches or marks. This is particularly true of aluminum and carbon steel plate, as these are often not considered as being for decorative use by their manufacturers. The waterjet cutting process itself can also cause irregularities. As mentioned above, parts cut on the waterjet will usually have frosting on them from stray particles from the cutting stream hitting the part.

Additionally, most parts waterjet cut from metal will have a small burr around the cut line on the bottom face. This is very undesirable in parts that must be touched or held, such as tools or handles.

  

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Illustration : Parts after waterjet cutting: Stainless steel which
began with a 2B finish on the left, aluminum on the right

 

In the photo above, you can see the "frosted" areas around the part's cut line, and the typical, slightly rough surface on the cut edge of a waterjet cut part. Parts with no finish may also have scuff marks due to handling and easily removed printed lettering from the mill that produced the raw material.
In the unfinished state, parts will typically have a small burr where the waterjet exits the part. Softer metals, such as aluminum, are more likely to have this burr. The burr can be easily removed with a sharp implement like a knife, or sandpaper. You can see an example of a burr in the photo below if you look very closely at the edge.

  

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Illustration : Closeup of the burr on 6061 aluminum

 

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Illustration : A waterjet cut part made from soft aluminum
showing burrs and frosting on the bottom face.


There are several techniques for cleaning up a waterjet cut part. The simplest is sanding with medium to fine grit sandpaper. This works well on most metals, including steel and aluminum. To get the most even surface, sand in only one direction, following the grain of the metal.

 

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Illustration : A waterjet cut aluminum part hand finished with sandpaper


You can remove burrs by hand using a sharp knife or deburring tool. The photos below show the process of removing the burrs from around the large circular hole in an aluminum part.

 

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Illustration : The bottom face of a part waterjet cut from soft aluminum.
Note the burrs around the cut lines.

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Illustration : Removing burrs from the part with a utility knife.

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Illustration : The large hole on the right is now free of burrs.

 

A faster way clean up the face of the parts and to deburr at the same time is to use a power rotary buffing or sanding tool loaded with a ScotchBrite or similar wheel. At Big Blue Saw, we call this “Basic Finish”.

This produces an even, fairly shiny finish as shown below on stainless steel (left) and aluminum (right). Like sandpaper, this process can remove all mill identification writing. It also removes any machining marks from the face of the part, including the waterjet "frosting". Some of the deeper marks which were present in the original raw material may be deeper than can be removed with this process.
With this treatment, burrs on the outside convex corners of your part are removed, and most other burrs are reduced somewhat. Burrs can still be left in small holes and in deep inside (convex) corners.

 

 

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Illustration : Parts cleaned up with a buffing wheel (Basic Finish).
A stainless steel part is on the left, an aluminum part on the right.

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Illustration : Aluminum finished with Basic Finish

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Illustration : Stainless steel finished with Basic Finish

 

One of the best looking ways to clean up small to medium quantities of parts is through the use of sandblasting or bead blasting. In this process, the parts are placed in a sealed cabinet and sprayed with a high pressure stream of sand or tiny glass beads. Finishing through bead blasting produces a more consistent surface finish the the Basic Finish, at the expense of some shininess. All machining and handling marks will either be eliminated, or made very hard to see. It is produced by spraying the parts with a high pressure, dry stream of tiny beads. The photo below compares the Bead Blast Finish on stainless steel (left) and aluminum (right).

With this process, burrs are reduced across the entire part, but may remain if there are large burrs in hard-to-reach places.
The Bead Blast finish also gives the face of the part an appearance consistent with the edges which were produced by waterjet cutting.

 

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Illustration : Bead blast finished parts with stainles steel on the left and aluminum on the right.

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Illustration : Closeup of Bead Blast on an aluminum part

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Illustration : Closeup of Bead Blast on a stainless steel part

 

Rotary tumblers or vibrators loaded with polishing media are a good hands-off way to clean up parts. Some thinner parts may be too delicate for this process, however. Larger parts will require an especially large tumbler.

When making signs with lettering, it can be tedious work to generate all the necessary bridges. This is true both when the letters are positive space (solid material) or negative space (holes). Fortunately, by using the correct font, you can save time and get a result that looks good.
When the letters form positive space, one good choice is to use a script font.


In the example below from David Kaufman, the Santa Fe script font was used to design two nameplates. The right hand side of the “f” had to be modified to connect with the “m”, but the rest of the letters naturally run together with this font.

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Illustration : Nameplate signs from David Kaufman
https://www.flickr.com/photos/thevaportrail/sets/72157642700926135/

 

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Illustration : The font used in the examples above: Santa Fe LET
http://www.fonts101.com/fonts/view/Script/28879/Santa_Fe_LET


When the letters are negative space, you can use a stencil font. Below are a few examples of the varieties of stencil fonts which might be useful for your project.

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Illustration : AG Stencil http://www.dafont.com/ag-stencil.font

 

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Illustration : Bodoni Becker Stencil Bold
http://www.fonts101.com/fonts/view/Uncategorized/43971/Bodoni_Becker_Stencil_Bold

 

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Illustration : Stencilia http://www.dafont.com/stencilia.font

 

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Illustration : Tomorrow People. Note: some numbers and symbols may not
have appropriate bridges in this font. http://www.dafont.com/tomorrow-people.font

 

Friday, 05 September 2014 12:56

Turning a Logo Into a Sign

Below is an example logo for “thegymnasium”.

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Illustration : The original logo to be turned into a sign.


Now let's take a look at four different approaches to turning this logo into a sign. Below you will see renderings of two variations with the logo as positive space and two variations with the logo as negative space.

 

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Illustration : A rendering of the sign with the logo as negative space.
Note that the centers of the letters "e", "g", and "a" are disconnected
parts and must be mounted separately.

 

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Illustration : A sign with the logo as negative space. In this design, the centers
of the letters "e", "g", and "a" have been bridged. This makes mounting and alignment easier,
but produces a logo that is less faithful to the original.

 

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Illustration : The logo with the letters as positive space in the sign. In this variation,
the letters have been bridged with a baseline. Also note the bridge connecting
the dot above the "i". Since it is one piece, it is relatively easy to install.

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Illustration : The logo as a sign in positive space with separate pieces for each letter.
This would be the most accurate rendition of the logo when installed on a wall or other
background of contrasting color. However, it is the most difficult configuration
to install, as each letter must be aligned and mounted separately.

Signs are another popular application for waterjet cutting, as they typically convey their information in two dimensions. Logos, pictures, and lettering can all be cut using the waterjet. Most of the signs we make at Big Blue Saw are either stainless steel or aluminum. I prefer the look of stainless steel; its darker color gives the sign a more solid, serious look. Signs can be made from very thin material, but for more visual impact close up, you can go with a thicker stock.

There are generally two approaches to cutting a sign or logo:

  • Making the individual letters out of solid material and assembling them together.
  • Cutting the lettering or design from within a solid outer frame.

In other words, you must decide whether you want the design to appear as positive space (material) or negative space (holes).

The second approach can result in a sign that's easier to install. If designed correctly, you can hang up the sign as a single piece without having to worry about fastening separate letters or their alignment. In order to do this, you must be sure to join any separate islands within the design using bridges. This often comes up when adding certain letters that naturaly contain islands: A, B, D, O, etc. Note the bridging on the letters in the sign shown below.

This sign was easy to assemble, with just a few screws needed to hold the upper layer onto the lower layer, and 4 screw holes in the corners to allow the sign to be hung up.

If you want professional sign design work, you should contact RoPro Design, as they designed the sign for us shown in the picture below. At Big Blue Saw, we've worked with them on a number of projects, and they're highly professional and will do a great job.

 

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Illustration : A sign in two layers, with the logo and lettering waterjet cut from wood.

If you want the letters to be made from solid material rather than holes, you can still keep them in one piece, but you will have to come up with a scheme for joining them together. The photo below shows one possible aproach.

Note also that this sign is designed to be cut in a single pass with only one pierce of the material. This helps reduce costs (for more information, refer to our cost reduction article).

 

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Illustration : A nameplate sign with the letters as positive space and joined together.

If you want the most accurate representation of a logo, you will probably choose to have each section of the design and each letter cut out as separate pieces. This allows, for example, letters to be exactly the shapes you want them to be without having to worry about bridging. Since you don't have to worry about designing bridges or connecting elements of the logo, design can be easier. The chief downside of this kind of sign is that each piece must be hung separately. You must also take great care when installing the sign to make sure that the position and alignment of each piece is correct.

When designing a sign, you should consider how the sign is to be hung on a wall or otherwise mounted in place. If you are mounting to a wall or other flat surface, the design can include holes for mounting screws in each piece of the sign. If you don't want visible screws, you can mount the sign using adhesive or by welding attachment points to the back. Make sure that whatever attachment method you use is strong enough to hold up the sign (Big Blue Saw gives you a weight estimate for your design in the ordering process.)

 

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Big Blue Saw
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Waterjet and Laser Cut Custom Parts.
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Phone: (678) WAY-SAW4 (678) 929-7294

 

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