Difference between revisions of "Laser-cutting Inspiration"

Revision as of 23:17, 21 April 2017

Overview

A good overview to a range of issues is provided by: https://www.instructables.com/id/Laser-Cutting-Basics/

Inkscape File Editing

Configuring Software

• File > Document Properties > Page - Width 600/ Height 400/ Units mm
• File > Document Properties > Snap - NOT 'Always Snap' (eg 20/10/20)
• Edit > Preferences > Tools > (tick) Geometric bounding box
• Edit > Preferences > Interface > Grids > eg x, y spacing 1, major grid every 10
• Edit > Preferences > Behaviour > Steps > 3.5433(07) px

Different Types of Cut

• Decide whether each part should be a drawn line (vector score), a filled area (raster engrave), or cut through - for overal outline or internal cut-outs.
• Set a stroke outline of a different colour for each, but no fill. The laser cutter software will be set later to apply a different treatment for each colour.

Text

• To allow lettering to be cut through material without parts falling out, download & install a stencil font, such as Awery.
• Text can be typed in, re-sized & moved.
• Once a piece of text is converted to a path (by Path > Object to Path), it’s no longer editable as text characters. Save file with different names before & after converting to path.
• Select a different stroke colour for a scored line vs filled ‘raster engrave’.

Source Image

• To transform a JPG line drawing, open the image, & copy to a blank template file: Edit > Select All (<Ctl> & ‘A’), Copy (<Ctl> & ‘C’), then Edit Paste (<Ctl> & ‘V’).
• Select All, then Path > Trace Bitmap, with settings Brightness Steps = 2, & Remove Background. The new path is overlaid directly over the original image. Click & drag the new top copy away, then select & delete the original version from underneath.
• Image may have unwanted lines around outline if scanned/ photographed from paper original. Remove by using 'Node' tool (2nd icon down left column): select each end of line, then Delete. Also for working with nodes/ segments, review dotty icons in bottom row at top of screen.
• Saving this file without altering could result in a large file, & long cutting time - depending on drawing's complexity. Use Path > Simplify Path to produce a smaller file with shorter cutting time.
• Where a 2-tone (eg paper cut) image is loaded, convert with Path > Edge Detection, colours = 2.

Converting File for Laser-cutting

Save file as DXF (Desktop Plotter Format) - no longer editable within Inkscape. Set options:-

• Base unit mm
• Uncheck LWPOLYLINE & ROBO-MASTER

Copy to USB stick for transfer to laser-cutter PC.

Design for 3D

• 3D forms may be made via 6 different construction methods: stacked slices/ interlocked slices/ curve/ radial/ folded panels/ 3D slices. See: http://support.epiloglaser.com/article/8205/47369/laser-3d-model-making-with-123d-make

Stacked Slices

• Horizontally sliced bowl: create 2 sets of rings, but 1 slightly bigger than the other, then stack by picking alternately from the 2 sets - each ring overlaps with the adjacent rings above and below it. The full method is described here: https://www.instructables.com/id/Stacked-Laser-Cut-Bowls/
• Create a shape & modify it. A polygon may be selected via polygon/ star icon, & the number of corners selected (eg 5 for pentagon) - see menus across top. Corners may be rounded, eg set to 0.15.
• Convert to Path (Path > Object to Path), then corners show as individual nodes. Use 'Node' tools to manipulate shape further - eg curving edges to be convex or concave, but avoid tight turns in the shape.
• Size, eg, to 100mm wide
• Right-click on shape & Duplicate. Drag duplicate away from original & size to, eg, 105 mm wide. To keep proportions, set top padlock icon to locked - height & width kept in same aspect ratio.
• Duplicate each of these 2, and re-size copies to 200 and 205 mm wide.
• Position each large shape around the smaller shape (200 & 100, 205 & 105 mm). In ‘Align & Distribute’, set ‘Relative to first selected’, then select small shape & large shape, & click icon to centre vertically & another to centre horizontally. Two pairs of shapes should be displayed, 1 pair slightly larger than the other.
• Extensions > Generate from Path > Interpolate, & (eg) 9 steps. This creates a series of rings around the smallest shape. Repeat for the 2nd pair. These 2 sets of rings are now ready for laser-cutting - with minimal material waste.
• After laser-cutting, alternate rings from the 2 sets may be stacked on top of each other to make a bowl.
• Star shape can be used to create stacked bowl from single set of rings. Experiment with number of corners (eg 20), amount of rounding (eg 0.04) and spoke ratio (eg 0.87).

Interlocked Slices

• Slices are positioned on edge at right angles to each other with 'slotted joints'. A cut-out in the bottom edge of the upper slice locks into a cut-out in the top edge of the lower slice. Cut-outs need to be altered to match the sheet material's thickness (or fractionally more?).
• The tightness of fit may be refined by altering slots to have slight lumps that press into the adjacent piece.
• [Method yet to be explored]
• This example shows how to make a bowl from interlocked slices, but not just using Inkscape: https://www.instructables.com/id/Fancy-Wooden-Fruit-Bowl-With-123D-Make/

Other Joints

• 'Finger joints' may be used for joining the edges of 2 pieces at right angles.
• 'Mortise & tenon' joints use slots in 1 of the pieces, and tabs in the other piece.

More Complex 3D Design

• Rather than using Inkscape, 'l23D Make' looks to be free download software offering a means of designing 3D forms, then producing all the sliced pieces ready for laser-cutting. Certainly worth investigating . . .

Laser System Software

• Laser System 5.3 is the software used to operate the laser-cutter. This is installed on a dedicated Windows 10 PC connected to the machine.

Preparing File for Laser-cutting

• A '.DXF' file needs to be created in Inkscape/ Adobe Illustrator/ other vector graphics software, and transferred to this PC on a USB stick.
• 'New' file (top left most icon)
• 'Import' file (3rd from left top icon), & select DXF file from USB stick. Doesn't always work - software seems erratic. Should display image properly. Otherwise, repeat or close & re-open software. Doesn't always show within frame of laser-cutter bed area - can zoom out to check.
• 'Centre to Table' icon (halfway down left column) displays image within 600 x 400 laser-cutter bed window.
• Select All, then Tools > Unite Lines (eg 0.1 threshold)
• Optional - right-click 'Set array output > check properties - check image size. Select all & click ‘Size’ icon halfway down left column. Click on X or Y dimension & enter a new size, if appropriate. To retain original image proportions, click series of dots to right of the other dimension - 2nd dimension is re-calculated.
• Set sequence of cuts - select each colour at top right of screen, & move ‘Up’ or ‘Down’ to amend the sequence. Complete all raster engraves & scored lines before any cut throughs. Do an internal cut-through before cutting through the outline shape - in case material moves.
• Set speed & power per cut type - dependent on material & thickness. A line may be drawn by moving the laser quickly and/ or setting the laser bulb to a low power. To cut through the material, move the laser more slowly and/ or set the laser to a higher power. See table [** to be created **] for recommended settings for different materials/ thicknesses. To amend settings, double click on speed/ power for a specific line colour at top right. Re-select cut type of 1 colour to pick up latest speed/ power settings created.
• Optional - timer icon at top checks cutting time - useful check of whether settings are correct. Sometimes it’s possible to use a faster cut speed, combined with a higher power. Avoid setting power above 90.
• When ready to cut, at lower right of screen, Download > Delete All (clears buffer) > Download Current. Wait until the file has completed downloading to laser-cutter before operating the machine.

Speed & Power Settings

[to be created]

Laser-cutter Operation

• The machine is a Laserscript LS6040, supplied by HPC Laser of Elland.

Normal Operation

• To switch on, simply turn the key on top of the laser-cutter.
• The laser needs to be set to a specific height above the sheet material for its beam to focus correctly. Ensure material bed is sitting flat in frame – lift up & brush away any debris if necessary. Place the sheet material on the rail bed. Use small square acrylic gauge tool, placed on edge, to check the laser height. Place the gauge next to the laser head, and press green <Up> & <Down> buttons until gauge is a snug fit between the material and the thin rim ‘shoulder’ of the laser head. It’s better to have a little slack than for the gauge tool to be clamped hard between laser head and sheet material.
• Set start position for cutting: cutting starts at the top right corner of the overall cut shape. On laser-cutter, press <Esc> then use cursor arrows to navigate up/ down/ left/ right. Hold cursor arrow for 3 seconds to move quickly.
• Testing cut area: on laser-cutter, press <Esc> then <Test>. The laser head moves around the cutting area in a rectangular motion, pointing a red LED onto the sheet material to indicate the area to be cut. Re-position the cutting start point if cutting extends beyond the material boundaries, or if there's a whole in the material anywhere that's going to be cut, or if a ‘SOFT STOP’ message displays (if cutting goes outside material bed size). Also re-position the start point if cutting goes very close to the edge of flammable material like cardboard – as FRAYED EDGES MAY SET ALIGHT.
• Cutting: first ENSURE LID IS CLOSED. On laser-cutter, Press <Esc> then <Start>. NEVER LEAVE MACHINE UNATTENDED EVEN BRIEFLY – in case of fire. To take a break from cutting, press PAUSE, and again later to resume.
• If an error occurs, eg settings clearly wrong, press STOP.
• Press EMERGENCY STOP (big red button on top of machine) if a major problem occurs, eg something catches fire. Afterwards, reset by rotating & releasing the big red EMERGENCY STOP button.

Varying Line Thickness

• With the laser beam properly focused, using normal settings, vector scored lines are very thin. Sometimes, artwork requires bolder/ thicker lines.
• Just as a torch beam is wider further from the bulb, the laser can create a thicker line from a wider beam by spacing it further away from the sheet material.
• Move the material bed down, ie further from laser. To ensure settings may be repeated, experiment with settings at various distance intervals. The square acrylic gauge for focusing laser is 3mm thick. Multiples of these may be stacked on top of each other in addition to holding 1 on edge. It's worth testing the effect using 1, 2, 3 or more thicknesses. For each height, test speed & power settings - speed needs to be slowed and/ or power increased as the laser distance increases.
• [example settings to be documented]