Author Archive
Ink Brush
I tried something new: drawing with India ink and a brush instead of a pen or pencil. I like being able to lay down shadows so fast and loose.
I posted a few others on Instagram, too.
Posted on Tuesday, September 8th, 2015.
Conserving Onshape Document Size
A useful feature of Onshape is revision history, allowing you to inspect or restore any previous state of your design. Reasonably enough, complex revision histories can easily inflate the storage size of your documents – especially if, like me, you learn by making a lot of trial and error modifications to your work-in-progress parts. Although I think the free plan is generous, it does have limits, so document size can become a concern.
For example, here are the sizes of two designs of similar complexity. One is a buckle and the other is a fan plate. The latter is only slightly more intricate than the first (and very simple indeed by professional CAD standards), yet it weighs in at 75 megabytes compared to only 208 kilobytes. That’s useful data for a product or project where the provenance of each change is important, but in this case I know the revision history is mostly junk because it contains hours of doodling before I figured out how to achieve the final design.
So what can do if you want to reduce a document’s size and you know you don’t need all the dust swept under the revision history rug? Barring any overlooked or unimplemented history management features, you can copy a fresh instance of a part studio into a new document. It turns out that doing so discards the revision history and can thus greatly reduce document size. (The feature list steps actually used to create the part are, of course, retained.)
First, right-click the part studio tab in question and select Copy to clipboard. (This is some sort of “cloud” clipboard, not your system clipboard.)
Next, create a new document. Click the new tab button and select Paste Tab. Now you’ve got the same part you started with, minus embarassing memories of mistakes made during its initial design.
Size comparison: the fresh copy of that 75 megabyte design is only 1 megabyte.
Posted on Sunday, September 6th, 2015.
Making Extruded 3D Models of Inkscape Illustrations
So, you have some vector artwork in Inkscape and you want to make it into a stamp or some other sort of 3D-printable gewgaw. Here are two ways to give your paths some depth. One uses Onshape for an interactive approach. The other uses OpenSCAD for a more programmatic approach. Both are parametric, permitting subsequent revision without restarting from scratch.
Posted on Thursday, August 20th, 2015.
Clipboard Case Pannier Hooks
Found this clipboard document case at Staples and turned it into a compact clamshell pannier.
Find the printable STL files for the green hooks as well as a few more photos and details at Thingiverse. Alternatively, fork or view the parametric model at Onshape.
Bonus image: sketching a stronger clasp, using a scanned paper trace of the original as an admittedly not very useful reference:
Posted on Tuesday, August 18th, 2015.
3D Printing a Stamp of a Drawing
Here’s an original marker doodle and the digitized version I made with Adobe Shape CC:
I opened the SVG file in Inkscape and converted the paths to extruded polygons with paths2openscad by Dan Newman. I added a solid base and printed the model as a simple stamp.
It doesn’t work great, but it does work! I’m brushing India ink directly onto the stamp. The printed PLA plastic is not an optimal surface for holding or transferring ink, as it tends to either blot or bead and run off. Here is the best print I was able to make in about a dozen tries:
Posted on Saturday, August 15th, 2015.
The hobo’s guide to exporting vector graphics from Adobe Shape Creative Cloud
Adobe Shape CC is a free mobile app for vectorizing high contrast images. It’s good for generating crisp graphics from sketches. (See my prior post on a similar process using old school tools.) You can export the results as an image directly from the app or retrieve images as free assets from Adobe Creative Cloud. However, to access editable vector versions of your designs, you need a paid Creative Cloud subscription and/or Adobe’s desktop software.
Sort of.
Using a modern desktop browser, right click an asset thumbnail and select Inspect Element to poke around the associated code in the browser’s developer view. Locate and copy the associated background-image URL:
This URL requests a PNG image based on the underlying shape. However, you can edit the URL to retrieve the raw SVG of your artwork. Initially, the URL will look something like this:
https://cc-api-storage.adobe.io/assets/adobe-libraries/[ASSET_ID]/:rendition;size=200;version=0?accept=image/png&api_key=CreativeCloudWeb1&user_token=[USER_ID]
Delete the underlined portions to locate the vector version. You may need to use your browser’s Save As feature if the SVG is displayed instead of downloaded. Be careful to retain the long ID strings and the question mark delimiter (?). Now you can revise the vector artwork you created on the go using a free program like Inkscape.
Here’s a hint to roll your own browser bookmarklet to do this with one click:
Posted on Tuesday, August 11th, 2015.
9000 mile bike check
I recently hit 9000 miles on my bike. I get more fun and function out of it than ever these days. In the spirit of acknowledging good gear, here are a few notes on noteworthy components.
It’s built around a Nashbar aluminum touring frame, which sadly no longer seems to be sold. It was only $99! People ask what makes it a touring frame. Two things, in my experience: first, lots of hardpoints for mounting useful stuff like racks, fenders, and bottle cages, and second, it’s got a slightly longer wheelbase than a “racing” road bike. The stretch is subtle but easiest to see if you look at the gap between the wheels and the seattube/downtube. The extra length provides plenty of clearance for accessories and baggage.
Tires are venerable Schwalbe Marathons in 700c x 32. They’re not cheap but they are bulletproof. These tires have absorbed hits that would burst lesser tires and have chewed up and spit out debris would that perforate lesser tires. I know: the first set of tires I had on this bike lasted less than a thousand miles and suffered constant punctures in city riding. I think I’ve only had four or five flats in the remaining 8000 with these (and some of those were due to valve stem issues).
The wheels are Pure Tour 700s from Bicycle Wheel Warehouse. They are built for durability with 36 spokes and deceptively deep and beefy rims. No broken spokes and still perfectly true.
The saddle receives a lot of comments. It resembles a vintage Brooks but is in fact a Velo Orange Model 3. What’s the deal with leather saddles, you ask? (Many people do.) True, the surface does not feel as soft as the foam coating conventional bike seats, but unlike those seats, there is no rigid platform beneath the surface: the leather is strung like a hammock between the front and back. It fully conforms to your butt and grows increasingly supple over the course of a long ride.
Cockpit levers! Cyclocross-style inline brake levers on the top of the bars maintain control even in relaxed upright riding. Old school friction shifters are not gonna win any drag races but are endlessly adjustable and provide the bicycle equivalent of stick shift street cred (or so I suppose). The one fault with this setup is that the bar-end shifter location is subject to the occasional inadvertent bump. I dig the Gevenalle (née Retroshift) solution of mounting friction shifters on the brake levers – something I still consider for the future of this bike.
Posted on Friday, July 31st, 2015.
Import STL Models to Onshape Part Studios using FreeCAD
Onshape is a sweet new parametric CAD system that runs in your browser. It can import designs from various CAD formats, but it cannot import the ubiquitous STL format popular in the 3D printing world. (Technically, it can indeed import any file type, but only for storage; only select formats can be converted to an editable part studio.)
I don’t know jack about FreeCAD, a cross-platform desktop CAD system, but it can be used to convert STL files to another format (STEP) that can be successfully imported into Onshape.
Posted on Thursday, July 30th, 2015.
Combining Course and Terrain Models with Boolean Modifiers in Blender
I don’t know jack about Blender, the free 3D modeling program, but I have found it useful for combining pieces of my 3D printed landscape models. It performs boolean operations quickly and produces clean output (valid STL files). However, the interface is notoriously intimidating to new users – myself included – so here is a screenshot-illustrated guide to the process I’ve worked out to make a few types of route + landscape models.
This is not a general-purpose tutorial. It is focused on the task of combining an STL terrain model with an STL course model. Both inputs are assumed to exist and to be pre-aligned at the same scale and orientation. (I will explain my process for creating those models in a subsequent tutorial.)
Posted on Thursday, July 30th, 2015.