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湜莪趉措孒蕗，啝嚡莈関係 

Using An Indexing Jig For Laser Engraving

Laser engraving specialists are sometimes faced with the often daunting job of engraving on a curved or cylindrical surface. One example of this is engraving a two line message on a pen where, for example, it??s necessary to engrave one line of text parallel to the pen??s axis and then rotate the pen to bring the next portion of the pen??s circumference into position to receive the second line.
As most laser owners are aware, one way to laser engraver cylindrical surfaces is to use a cylindrical attachment, a device which is available with most lasers, which rotates the item as you engrave. Cylindrical attachments are great, especially if you want to engrave a line of text or a design reading around the circumference rather than parallel with the center line. However some of the cylindrical attachments are better suited for holding wine bottles and other large items than they are for pens and the like.They are also an expensive extra that is rarely needed in the average shop.
In any event, I have found that a number of laser engraver involving limited-coverage engraving on cylindrical surfaces can be done with excellent accuracy and repeatability using an inexpensive home-made indexing fixture I created myself. The principle used in my fixture is that you hold the cylindrical item ??between centers?? so that it can rotate on its axis. You set up a line of text or other graphical element (not extending too far out from the top of the curve) and then engrave the item as if it were a flat engraving job. To engrave a second line of text, you rotate the item on its axis to provide the desired spacing between lines and engrave that set up, again treating it as a ??flat?? layout.
What triggered my invention was my experience as a woodworker for over 20 years. I immediately thought of an indexing pin on a wood lathe as a good starting point for my fixture. This utilizes a disc with holes equally spaced around it and a pin that creates a stop when it??s inserted in the hole.
Because my fixture would be fabricated from acrylic and vector cut on the laser engraver, I was able to easily make several interchangeable indexing wheels to accommodate virtually any number of steps around a cylinder. For example, Figure 1 shows three separate indexing wheels which contain 10, 14 and 8 indexing notches, respectively. Using a wheel containing a greater number of notches provides a greater number of rotary indexing steps having a smaller angle and reduced line-to-line spacing between set ups.
The indexing wheels can then be mounted to the fixture, allowing the pen or other item to be rotated between notches (Fig. 2).cnc router Instead of using a pin, I mounted a ??knife?? which slips into the notches I cut around the indexing wheels.
To more easily understand how to set up the computer files to work with this fixture, we??ll use the U.S. Flag pen shown in the opening photo as an example. This set up is much more complicated than a couple lines of text but it really demonstrates the operation of the fixture. Let??s start with the lower barrel of the pen (stripes).
The first thing we do is measure the diameter of the cylinder. I use dial calipers for this. Note: The more accurate this dimension is, the more uniform the widths of the alternating red and white stripes will be.
We know that the U.S. flag has 7 red stripes so let's divide the cylinder into 14 equally spaced parts. We??ll use the 14 step indexing wheel for this since 7 can be divided equally into 14.
The diameter of this particular pen barrel when finished is .613". Draw a circle of that diameter and then divide it into 14 equal segments. Then measure the width of the segment. The length of the pen barrel is 2.375". Figure 3 shows how we transfer these dimensions into a framework suitable for drawing wavy stripes.
For clarity, I drew only two stripes in the grid. Normally we would only need to draw one because it??s a repeat pattern. If the pattern around the pen were totally different or non-uniform, we??d have to use the whole grid.
The next step is to set up the laser engraver. Position the indexing jig in the engraver with the wooden barrel mounted to it, and align the first segment of the grid exactly on top of the barrel in the laser engraver. In CorelDRAW create a box that represents the engravable area on the pen barrel (.25" high x length of segment). With the red dot pointer activated on the laser engraver, vector trace the outline of the box (with the engraver lid open of course). Adjust the location of the engraving box until it traces accurately onto the pen barrel. Now position the grid with all segments so that your first segment is centered within the engraving box. Once we??re aligned, set up your layers. This is essential with complex patterns but not really necessary if the pattern doesn??t change from one segment to the next.
In our Corel layout, the first stripe in the pattern will be assigned to a layer we will call ??PRINT.?? All of the layers in the file will have the print function disabled except for this one. Also set up a layer called ??STRIPES.?? This layer will accommodate the stripes or segments of the pattern that aren??t being printed (engraved). When we get to the upper barrel of the pen (stars), the reason for this will become clearer.
Before you begin cutting, make sure that the indexing knife on the jig is engaged in the 14 step indexing wheel. With the pen barrel mounted to the indexing jig and accurately aligned inside the engraver, you can now engrave your pattern.
link:http://www.iehk.net/