"Eject core" that's a key you don't want to hit by mistake
"Eject core" that's a key you don't want to hit by mistake
Monday was largely an exercise in laser cutting; Tuesday was an exercise in snow.
The Lasersaur cutter at the Artisan's Asylum has been down for some time, so on Monday I enlisted the generous help of Brian Johnson (the digital fabrication lab steward at the AA) in making a custom set of printer settings for the Epilog Helix, in hopes that I could finally cut styrene. I prefer styrene to acrylic for scratch building because styrene is very easy to sand and weld. Unfortunately, acrylic is excellently laserable, styrene not so much. However, though took a couple of hours of fiddling around with tiny little two-second cuts of 1mm test squares, I'm happy to report that I was largely successful in finding some workable settings for styrene (detailed settings and information below), at least on the Epilog.
But first a bit of back story. I have been working with @Eric Ardros on a build of the the Subspace Beacon from TNG "Schisms."
This prop also appears in TNG "Cause and Effect" as a dekyon field modulator.
Thanks to Elvis's hand-drawn plans and my translating them into digital designs in Illustrator/CADtools, we had plans to make the planar components in styrene. (If anybody wants the plans to do this yourself, just PM me and I'll be happy to share.)
The many small curves and fine details of this design meant that cutting the design out by hand would be both tedious and tricky. It was thus the perfect project to try automated laser cutting.
However, having used the Epilog in the past, I knew that none of its existing materials settings would work. The best I could get it to do was to cut out some melted and charred out black figures that vaguely resembled my original design. And in the wrong size no less (more on this and Inkscape later).
However, Brian showed me how to create new materials settings for the Epilog and I began experimenting. The three relevant variables are:
- Vector Speed
- Vector Power
- Vector Frequency
My ultimate approach was systematically to titrate each variable independently and then to make a small test square cut after each change.
Even from the first few test cuts, some things became clear, the main one being that low frequency is probably the most important strategy when it comes to lasering styrene. The concept here is very simple: the frequency controls the number of laser pulses per linear unit of travel of the focal point. A very low frequency would result in a perforated line, whereas a high-frequency line would be continuous. The advantage of low frequency on styrene is that it helps to avoid the material overheating. Lowering the power below anything close to what you would use on acrylic are also important steps toward the same end, but I found that the frequency decreased helped more than anything else and opened up room for me to start experimenting with power and speed (which had more to do with how many passes it took to cut rather than affecting the melting and flaming issues). Another important strategy is multiple passes. You just have to get used to the idea that you're going to have to sit through many repetitive passes when working with styrene. The finer the details of what you're cutting, the lower the power you'll need to use and the more passes, sometimes up to 15 (!) in the case of very narrow walls <1-2mm. I found that too high a speed required far too many passes, so I ended up setting the speed surprisingly low as well as the power.
Here were the settings that worked best for me on 1.5mm styrene. (Interesting, the same held true for 2mm styrene; I just needed to make a few more passes.) Each number is on a scale out of 100.
- power 15
- speed 15
- frequency 50
- 2 passes for score-and-snap, 4 passes for full cut-through
Fine detail cutting
- power 9
- speed 25
- frequency 60
- 15 passes, which should get you almost clear through the material
I found the 15 passes fine-detail cut particularly necessary for the part of the design shown in this video. Those tiny little rounded rectangles have very narrow little filaments of dividers between them, which tended to snap as I was trying to snap out anything but a completely cut-through part. But on the normal power setting (which was already very low for styrene in the first place), these thin walls melted and deformed, while at the same fewer passes meant that the styrene wasn't cut through. With such fine details, trying to snap along scored lines just breaks everything at once, so you really need to cut almost all the way through (you can finish the job with a hobby knife if necessary if the 15 passes don't do the trick (or even do a few more passes, if you have more patience than I do!)
And here is the resulting build test-fit using electrical tape. (The buttons are 3M bumpons, SJ5008, if I remember correctly.)
Now, the problem is that all of the cuts are A LITTLE OFF. The culprit is Inkscape, which is the vector software that the Artisan's Asylum uses for printing to the laser cutter. Let me just say that, like most FOSS, Inkscape is an execrable piece of amateur-hour garbage, and anybody who says it's a plausible alternative to Illustrator for even the most trivial tasks has been dropping acid with Richard Stallman behind a bundle of CAT5 cables in a network wiring closet at MIT. No. No. No.
The issue is that Inkscape just silently throws away the dimensioning units from the files it imports (even when it's formats that accomodate them, such as PDF or AI) and converts everything to screen pixels using 90dpi as its assumption. Illustrator uses 72dpi (an admittedly archaic Adobe quasi-standard). However, in Illustrator's case this doesn't really matter because it actually understands real-world dimensions (dpi only comes into play with Pixel Preview or exporting to raster images), but Inkscape defaults to pixels for its native units (for vector editing software?!). And so all of my drawings get scaled down at a 90:72 ratio, as best as I can tell. And I haven't been able to figure out how to scale them back up at the proper ratio thanks to Inkscape's counter-intuitive interface and horrible documentation. Yes, yes; I know Inkscape can theoretically import DXF, which allows you to set the units. However, that feature is totally broken and ignores half of my vectors. Ugh.
Sorry, I used to work in the open source world and I'm obviously still a little bitter about how ham-fisted most of its tools are.
I'm still searching for a workaround for the Inkscape scaling issue. An inspection of the relevant listservs isn't helping. I have a few ideas for workarounds:
- See about hooking my own Microsoft Surface up to the laser printer directly and printing to it from Illustrator (if the AA folks will let me and the drivers are available publicly)
- Try printing from a PDF viewer in Linux, which hopefully would respect the PDF format's native understanding of real-world units
- Try getting Inkscape to scale the artwork to compensate for its distortion factor
- Try figuring out if there is any export/import format that Inkscape will actually understand properly
Slowly but surely I'm figuring out this styrene pwpw thing though!
Like I said before, that is one sexy-looking test build my friend Gawd, I want one of these, lol.
Thanks for sharing all that info pertaining to the process, btw!
I have no skill, experience or software for that sort of thing, so your post was very comprehensive and informative.
Last edited by Eric Ardros; Jan 28, 2015 at 11:58 PM.
Nothing terribly exciting tonight. I milled out a pocket for the holo-imager button. The body is now almost ready for casting.
And painted the first round of my Geordi PADD (for the six hundred and twelfth time), in what is probably a controversial color. I'll probably end up doing a second darker round after I see what it looks like when dry, but I am definitely going for a fairly light purplish pink color. What can I say? This is how it often looks to me on screen. But I probably overdid the lightness here. I feel like the lighting environment at the Artisan's Asylum is weird. I might start mixing paints here at home, where I also have access to a color calibration monitor. I tend to mix colors off of references on my Surface at the workshop, and they end up looking quite different. Oh well.
(It's one bottle of Golden High Flow pearl white paint with 40 drops of Alzarin Crimson Hue and 23 drop of Transparent Dioxazine Purple.)
Last edited by norbauer; Jan 29, 2015 at 3:42 AM.
Wow. That Inkscape issue would drive me 100% bat$h|t. At Techshop we have a different laser cutter and we just print straight from Illustrator. I save all my work to my Dropbox, so I can just download it right there at the laser station, set up the print in the printer settings, and off we go. Any changes I make I just save and upload back to my Dropbox. We have Inkscape on the machines there, but now that I've read your post, I'm just not going to bother. Illustrator's worked for me for almost 20 years.
Same idea at the Makerbot, though because they're not hooked up to computers, there's a little SD card-based sneakernet to be dealt with. But I can make my part in Blender, pull it into the Makerbot software on my Mac, slice it, and save it to the SD card, all here at home.
I'm never more frustrated than when I have to fight bad software to get something done. I make stuff to lower my stress...
sorry, double post...
Nice depth of field!
Oh yeah, the prop is very nice too.
One thing I realized when I started getting into this prop stuff more seriously late last year was that one of the most important tools I would need would be a macro lens. I love the one I ended up getting: a Nikon 105mm/f2.8.
I think I'm about to finally invest in a DSLR. Photography on the brain lately.
The polish on that is amazing! Did you use the simichrome on the resin too? Or a different compound?
The best investment in photographic equipment I've ever made is a subscription to Lynda.com, by the way. There is so much excellent material on there. I can especially recommend the courses on photography fundamentals by Ben Long (from courses on exposure basics choosing specialty lenses).
- - - Updated - - -
Yup! Turns out that it works really well on all kinds of stuff. I have used it to hand-polish and buff out scratches on plastic very well in the past.
The only downside over polishing compound is that it really isn't viscous enough to be used on a wheel, so it flies all over the place when you use the buff. But that's why I rent workspace outside of my apartment.
Last edited by norbauer; Jan 30, 2015 at 10:57 PM. Reason: added quote
Last edited by norbauer; Feb 4, 2015 at 6:14 PM.
Those look very beautiful!
Sorry for the few updates lately, but in Boston we've been in the middle of the largest amount of snow in a two-week period we've seen in recorded history. As a result, getting to the workshop has been difficult to impossible, depending on the day.
A few little random updates:
I got hardware and aluminum stock from McMaster for making the ratcheting door for my TNG later-seasons medkit. My aspiration is to make the most accurate replica ever made (most people make the door out of plastic).
Did some minor prop work on my VOY desktop viewer
And I got in the mail the components for a VOY Pathfinder desktop viewer—also used in DS9, I believe, but I prefer not to acknowledge non-canon material
I don't have pics, but most of my time lately has been spent polishing up aluminum on TMP scanners. I have also decided a final step will be a protective layer of carnauba wax to forestall oxidation.
I also got in molds for the Kurlan Naiskos.
I cast two of them up just an hour or ago ago and they came out pretty well. After I get them cleaned up, I'll post photos, probably tomorrow. I was astonished by how much resin this thing takes: about $100 worth per casting. I found out that the small figures that go inside were made a little too large (due I think to an error in an auction listing I was using for the dimensions), so I'm going to have to commission the sculptor to make me a smaller one so that all twelve can fit inside.