AutoPass Endless Pattern: Double Helix

Instructions

To cut this pattern, we use the ramp phase of the AutoPass extension in a somewhat creative way. AutoPass plunges the cutter deeper into the workpiece with each pass in a linear motion. The length of this ramp phase varies depending on the depth of cut and the selected plunge speed. Since we can calculate this length relatively well, you get great opportunities to create three-dimensional patterns with Origin. For the beginning, it might be good to try cutting a simple star to familiarize yourself with the general process – it's pretty easy! Have a look here: http://community.shapertools.com/t/autopass-patterns-star-and-spiral SOME BASICS: (1) Since AutoPass does not work with open paths (lines), this pattern consist of several shapes, of which we always cut only the curved segment (= our cutting path). The remaining straight segment of the shapes are only a means to an end to be able to use AutoPass (= irrelevant path segment). (2) We simulate an online cut by setting the negative half cutter diameter as the offset. So for my V-cutter with a maximum diameter of 3 mm, I choose "-1.5 mm". (3) In order to have good control over the start and end when cutting, the shapes are designed in a way that they always have a hard angle at the start and end points. This makes it easy to prevent Origin from cutting into the straight segment of the shape that we want to leave out. Be sure to avoid using Auto-Lock during cutting! (4) If you want to adjust the size/height of the helix, you can scale the SVGs proportionally. After that you have to recalculate the plunge speed. The same applies if you want to change the cutting depth. See below how this works. (5) You can use a trick to test whether you have set the correct parameters to get the perfect ramp length. Since the usual AirCut is not suitable for this purpose, let's use the manual Z-Touch. Start the manual Z-Touch function and move down the bit juuuust a little and set this value to zero. Now you can test without turning on the spindle resp. without cutting into your material. The behavior of AutoPass is the same as real cutting. During (air) cutting our patterns, Origin should always display a light blue line. This is an indicator of the ongoing ramping phase. When the line turns dark blue, the ramp phase is over and the maximum cutting depth has been reached. If the line turns dark blue near or better directly at your the end point, you have set the perfect plunge speed. PLACING AND REPEATING THE SVG: The double helix pattern consists of a 45 mm wide segment that can be lined up as often as desired. The easiest way to do this is to first place a segment of the helix where you want it on your workpiece. Then click the round Copy button at the bottom Origins screen and then select the Position menu. To extend the pattern to the right, now simply enter "+ 45 mm" for the x position. When lining up, please always place the full segments next to each other with no gaps, otherwise the pattern may not look right. For simplicity, the pattern has a custom anchor in the center on the left edge. HOW TO CUT: (1) Prepare your workspace and Origin: mount the cutter, z-touch, set spindle speed, scan the workspace, grid, load and place the SVG and place it next to each other as many times as you like. (2) Do the settings: Activate AutoPass. Open the AutoPass settings and deactivate the "Pass Depth" toggle as well as the "Roughing Passes" toggle. Set the cut depth to 3 mm, your offset to minus (!) half cutter diameter and the plunge speed to 249 mm/min. (3) Bring Origin near the starting point of the first segment to be cut. Make sure that you bring Origin a little above the starting point and on the opposite side of the segments that should not be cut. Please see my visualized explanations in the picture gallery to make this more clear. (4) Start cutting and don't active Auto-Lock! Cut slowly along your segment until you reach the end point. Stop cutting. Repeat this process for each stroke of you helix. Do not be surprised, because an optical line of the helix consists of two cuts. They are always cut from the outside to the inside and meet in the middle, at their deepest point. This gives the impression of one single line that first becomes deeper and wider and then thinner and flatter again. CHANGE THE CUTTING DEPTH: To change the cutting depth of the helix, you need to recalculate the plunge speed. The length of the cutting path will not change and remains 15.156 mm. You can calculate the plunge speed precisely with Beau's calculator (see link at the bottom of this page) or use my quick and easy to remember formula. If you use my formula, you get a good approximation but may need to do some fine tuning: Plunge speed in mm/min = ( cutting depth in mm * 1300 ) / length of cutting path in mm With integer scaling, this is very simple, since doubling the depth of cut results in doubling the plunge speed, and vice versa: For a cutting the helix 2 mm deep set the plunge speed to 166 mm/min. For a cutting depth of 4 mm, set the plunge speed to 332 mm/min. SCALING THE PATTERNS: The SVGs can be scaled proportionally directly on tool. After scaling, the plunge speed must be recalculated (see above). For this calculation you need the length of the segment to be cut. You can either measure the length with a graphics program or simply calculate it by multiplying the height of your SVG by 0.842 mm. So if you want to cut the helix 25 mm in height, the length of cutting path is 21.05 mm. FURTHER READING: – General discussion about RampArt: http://community.shapertools.com/t/autopass-ramp-art – Beau's pretty cool calculator: http://community.shapertools.com/t/engraving-and-autopass-ramping-and-calculators – Discussion regarding this project: https://community.shapertools.com/t/autopass-endless-pattern-double-helix MORE PATTERNS: – – 5-Point Star: https://hub.shapertools.com/creators/623dae1dfb4d27f71b9ebdb0/shares/65dfa95a3c4f43b001f32a70 – Star and Spiral: https://hub.shapertools.com/creators/623dae1dfb4d27f71b9ebdb0/shares/63b8145350c65c5f829171b5 – Moulding Style: https://hub.shapertools.com/creators/623dae1dfb4d27f71b9ebdb0/shares/63dbca43e086cc02ed83c3ef