Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
Tag: Improvements
Making the world a better place, one piece at a time
Although I shouldn’t have used a hardened shaft for the case, the rest of the diamond drag tool holder worked out well enough:
Sherline Diamond Drag Holder – assembled
The dimension doodle shows what’s inside and gives some idea of the sizes:
Sherline Diamond Drag Holder – dimension doodles
From left to right, it’s an M6×1.0 setscrew to adjust the spring preload, a spring harvested from a cheap clicky ballpoint pen, a machined cap, a 3 mm rod (which should be a hardened & ground shaft, but isn’t) surrounded by a pair of LM3UU linear bearings, a machined coupler, and the stub of a diamond engraving tool’s shank.
Tapping 15 mm of M6×1.0 thread inside of the case took an unreasonable amount of grunt. Next time, brass.
The setscrew gets a little boss to hold the spring away from the adjacent threads in the case:
Sherline Diamond Drag Holder – setscrew spring boss
The little machined cap has a somewhat longer spring guide to prevent buckling:
Sherline Diamond Drag Holder – shank cap spring guide
The spring fits snugly on the slightly enlarged section inside the last few coils, with the rest being a loose fit around the guide. When the spring is fully compressed, it’s just slightly longer than the guide and can’t buckle to either side.
The cap gets epoxied onto the 3 mm rod with some attention to proper alignment:
Sherline Diamond Drag Holder – shank cap alignment
The other end of the rod has a 3 mm thread, which would be a serious non-starter on a hardened rod.
The shortened diamond tool shank gets epoxied into the gizmo connecting it to the now-threaded rod, again with some attention paid to having it come out nicely coaxial:
The LM3UU bearings got epoxied into the case, because I don’t have a deep emotional attachment to them.
Unscrew diamond tool, push spring onto cap, drop rod through bearings, crank setscrew more-or-less flush with the end of the case, screw diamond in place with some weak threadlock, add oil to rod, work it a few times to settle the bearings, and it’s all good.
The spring rate works out to 230 g + 33 g/mm for deflections between 1.0 mm (263 g) and 3.5 mm (346 g), so it’s in the same ballpark as the diamond tools on the MPCNC and CNC 3018.
Note: WordPress just “improved” their post editor, which has totally wrecked the image alignment. They’re all set to “centered” and the editor says they are, but they’re not. It’s a free blog and I’m using one of their ancient / obsolete / unsupported themes, so I must update the theme. Bleh.
When programming arcs an error due to rounding can result from using a precision of less than 4 decimal places (0.0000) for inch and less than 3 decimal places (0.000) for millimeters.
A closer look at the coordinates in the lower right part of the spreadsheets (from yesterday) shows the limited accuracy with two decimal digits:
Spreadsheet – GCMC 2 digit – full path – detail
The red blocks mark the first failing arc, where the relative error falls out of tolerance. If GRBL were less fussy (which it should not be), then the next arcs would proceed as shown.
Rounding to three decimal digits pushes the errors into to the third place, with the yellow highlight marking the worst errors:
Spreadsheet – GCMC 3 digit – detail
As you should expect, the smallest arcs have the largest relative errors, although they’re now well within GRBL’s (and LinuxCNC’s, for that matter) limits.
Rounding to four decimal digits makes the errors vanishingly small:
Spreadsheet – GCMC 4 digit – detail
So, by and large, don’t scrimp on the decimal digits … but we knew that already.
I’d been setting GRBL to produce three decimal places, but now I’m using four. Adding a few characters to each G-Code command reduces the number of commands fitting into GRBL’s buffer space, but bCNC normally keeps it around 90% full, so the path planner should remain perfectly happy.
An on-sale pack of yellow Astrobrights card stock tempted me:
Homage Tek CC – Yellow Astrobrights paper
The somewhat wrecked cursor comes from my collection of discards, because I haven’t yet figured out how to mill the outline and engrave the hairline on raw stock.
The paper isn’t quite the same color as my Genuine Pickett Model 110-ES circular slide rule:
Homage Tek CC vs Pickett 110ES colors
Nor, of course, are the ticks and legends nearly as fine as you get with real engraving, but it’s probably Close Enough™ for anybody other than a Real Collector™.
The orange curve is the last surviving (“least dead”) Wasabi battery from the 2017-08 batch and the dark green curve just above it is another DOT-01 from 2019-02. The problem is not so much their reduced capacity, but their grossly reduced voltage-under-load that triggers a premature camera shutdown.
The Batmax batteries measure better than the craptastic Wasabi batteries, worse than the STK batteries, and should survive the next year of riding. As before, I have zero belief that Amazon would send me a “genuine” Sony NP-BX1 battery, even at six times the nominal price, nor that it would perform six times better.
Batmax is one of many randomly named Amazon Marketplace sellers offering seemingly identical NP-BX1 batteries: Newmowa, Miady, Powerextra, Pickle Power, LP, Enegon, and so forth. Mysteriously, it’s always cheaper to get a handful of batteries and a charger, rather than just the batteries, so I now have a two-socket USB charger:
Batmax NP-BX1 – USB dual charger
Despite the “5 V 2 A – 10 W” and “4.2 V 0.6 A – 5 W” label on the back, charging a pair of batteries after a ride started at 700 mA from a USB 3.0 port. The charger makes no claims about USB 3 compliance, so I’d expect it to top out around 1 A from a generously specified port.
Eight minutes later, we’re turning onto the Dutchess County Rail Trail:
Losing the Battery Bag – flight – 2019-02-25
And then it’s gone:
Losing the Battery Bag – gone – 2019-02-25
Mary drove past there on her way to a distant meeting, but the little red bag was not to be found anywhere. Maybe it’ll reappear on a fence post or taped to the bulletin board; I’ve tried to return things I’ve found that way.
I expect somebody got a nice present and, if naught else, it’s good to drop happiness into the world.
There’s another reader and a quartet of batteries on their way.
After sliding the HON Lateral File Cabinet shelf into place and installing the bumpers, it seemed rather loose and floppy. Comparing the situation with the other file cabinet showed it had a missing glide button in the rear and two missing slides at the front.
A replacement button emerged from the end of a Delrin rod:
HON Lateral File – shelf button – parting off
The original buttons had an expanding stem, which is easy to do with an injection-molded part. I opted for simple adhesive, with enough of a blob underneath the shelf to (presumably) lock it in place forevermore:
HON Lateral File – shelf button – installed
The slides required an iterative design technique (pronounced “fumbling around”), because nothing on either side remained square / plumb / true / unbent. I hacked the first version from scrap acrylic, broke off anything that didn’t fit, and got better measurements from what remained:
HON Lateral File – shelf front guide – size test
With those measurements in hand, the second version used a pair of weird flat-head shoulder screws (probably from a hard drive) to anchor 3D printed angle brackets into the frame:
HON Lateral File – shelf slides – version 2
Those worked reasonably well, but PETG doesn’t produce a nice sliding surface, so the final version has flat-head Delrin studs in slightly tweaked brackets:
HON Lateral File – shelf slides – version 3
As with the buttons in the back, the original slides had expanding studs holding them in place, but glue works fine here, too:
HON Lateral File – shelf slides – version 3 – installed
The button isn’t quite square to the surface and the slide isn’t quite flush with the bent metal in the frame, but it’s Good Enough™ for a shelf that won’t get lots of mileage.
For reference, the brackets should print vertically to wrap the plastic threads around the upright for better strength:
HON Lateral File Shelf Slide – Slic3r
If you did it the obvious way, the upright side would break right off at the first insult from the hulking shelf, although they’re basically a solid chip of plastic, with a little infill inside the bottom slab.
While I was at it, I pulled the springs to make them a bit longer, so they touch the back of the frame when the shelf is half an inch behind the front face of the drawers. A firm push and those Delrin contact points let the shelf pop out an inch or so, with plenty of room for fingers underneath the front edge.
Some drawer slide stops near the back needed attention, too:
HON Lateral File – slide stop bumper – bent
I cannot imagine how hard somebody slammed the drawers, because bending the stops back to a right angle required a Vise-Grip and some muttering:
HON Lateral File – slide stop bumper
Oddly, the cushiony hollow side faces away from the drawer, toward the back of the frame, because putting it forward holds the drawer front proud of the front frame face. Maybe HON cost-reduced the steel slides by making them just slightly shorter and using the same bumpers?
The drawers have begun filling up from boxes scattered around the house:
HON Lateral File – fabric stash
That’s the “orange” part of Mary’s collection, now with plenty of room to grow!
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The Smell of Molten Projects in the Morning 