Identify That Antenna By Sight

It’s a skill that radio amateurs pick up over years but which it sometimes comes as a surprise to find that is not shared by everyone, the ability to casually glance at an antenna on a mast or a rooftop and guess what it might be used for. By which of course I mean not some intuitive ability to mentally decode radio signals from thin air, but most of us can look at a given antenna and immediately glean a lot of information about its frequency and performance. Is this privileged knowledge handed down from the Elmers at the secret ceremony of conferring a radio amateur’s licence upon a baby ham? Not at all, in fact stick around, and I’ll share some of the tricks. Continue reading “Identify That Antenna By Sight”

DeltaPen: Drawing, Painting And Taking Notes Without The Drawing Tablet

Over the decades, a lot of attempts have been made to try and make pens and pencils “smart”. Whether it’s to enable a pen to also digitally record what we’re writing down on paper, to create fully digital drawings with the haptics of inks and paints, or to jot down some notes on a touch screen, past and present uses are legion.

DeltaPen internal components and their function. (Credit: SIP, Guy Luethy et al.)
DeltaPen internal components and their function. (Credit: SIP, Guy Luethy et al.)

Where SIP Lab’s DeltaPen comes in as an attempt at a smart pen that acts more like the pen of a drawing tablet, just minus the tablet.

This project is related to the decidedly more clumsy Flashpen which we featured previously. Due to the use of new flow sensors, the underlying surface (e.g. a desk) can be tracked without needing to be level with it, which allowed for the addition of a pressure-sensitive tip.

In addition the relative motion of the pen is measured, and there is haptic feedback, which allow for it to be used even for more delicate applications such as drawing. The results of trials with volunteers across a range of tasks is described in their presented paper (PDF).

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The Best Threaded Holes For Resin Parts

Threaded inserts are great for melting into FDM prints with a soldering iron. The process isn’t so simple for resin prints, since they don’t generally soften with heat. Off course, you can also print the threads directly, screw a bolt into an un-threaded hole, or tap a hole. Following his usual rigorous testing process, [Stefan] from CNC Kitchen investigated various ways of adding threaded holes to resin prints.

After establishing a pull-out force on PLA using threaded inserts (205 kg) and tapped holes (163 kg), [Stefan] tested parts printed with Prusament Tough Anthracite resin. Un-threaded and tapped holes failed at 44 kg and 55 kg respectively, while printed threads were almost twice as strong, reaching 106 kg before breaking. Stephan also tried gluing inserts into the parts using resin and CA glue. The resin didn’t cure properly in the opaque parts (6 kg) while CA was comparable to plastic threads, failing at 52 kg.

Chart of results
TLDR: Print your threads for best results

[Stefan] also tested regular ELEGOO Translucent resin. The higher hardness of the cured resin allowed the parts to hold on to around 100 kg for un-threaded and tapped holes, while printed threads reached 120 kg. Threaded insert glued with resin did better on the transparent parts thanks to improved UV penetration, but were very inconsistent. Inserts glued with CA performed about the same as on the Prusament parts, failing at 56 kg.

In an attempt to improve the performance of the inserts [Stefan] printed some parts with stepped holes to match the geometry of the inserts, which had the advantage of preventing the insert from falling through during gluing. It only made a marginal difference on the Prusament parts but boosted the strength of CA-glued inserts on the ELEGOO resin to 82 kg. Two-part epoxy was also tried, which matched the un-threaded holes in strength.

So for resin parts you’ll probably be best served by just modeling the threads in CAD and printing them directly. If you need to be able to repeatedly screw and unscrew fasteners in a hole without stripping, threaded holes with CA or epoxy might be a better solution.

Continue reading “The Best Threaded Holes For Resin Parts”