Posts Tagged Improvements
Bird Feeder Unbending
Posted by Ed in Home Ec, Machine Shop, Science on 2018-11-13
At some point in its history, the left rail holding the wood perch on our industrial-strength “squirrel proof” seed feeder took a hit, most likely from being dropped:
Squirrel on bird feeder
I finally got a Round Tuit and un-bent the poor thing:
Bird feeder – rail un-bending
Because the bend happened at the base of the vertical strut holding the shutter, I clamped a Genuine Vise-Grip sheet metal pliers along the straight section. The Craftsman knock-off Vise-Grip then applied torque at the bend, rather than just making things worse, and some two-axis tweakage lined up the rail pretty well.
With the bend taken care of, I clamped the rail in the bench vise with some scrap wood around the strut:
Bird feeder – warped rail
A percussive adjustment jam session flattened the top flange, leaving both sections as flat as they’re gonna get.
While I was at it, I turned a pair of stepped aluminum washers for the new wood rod:
Bird feeder – parting off washer
Which looked about like you’d expect, including a little chatter from the cut off tool:
Bird feeder – perch hardware
Yeah, I drilled the wood rod on the lathe, too; I loves me some simple lathe action.
Reassemble in reverse order and it’s all good:
Bird feeder – perch installed
We’re supposed to bleach the feeder every week to kill off the bacteria causing House Finch Eye Disease and, while I can’t promise a weekly schedule, we’ll (try to) reduce the amount of crud on the feeder this year.
If you’ve got a feeder, sign up for Project Feederwatch and do some citizen science!
Modifying a 2.5 mm Collet Pen Holder for a 3 mm Diamond Engraver
Posted by Ed in Machine Shop on 2018-11-06
Of course, the diamond engraving points have a 3 mm shaft that doesn’t fit in the 2.5 mm Collet Pen Holder, but making a hole bigger isn’t much of a problem …
Start by drilling out the collet closer nut:
Collet Holder – closer nut drilling
The hole didn’t start out on center and I didn’t improve it in the least. A touch of the lathe bit and a little file work eased off the razor edge around the snout.
The knurled ridges at the top are larger than the threaded body, which requires a shim around the threads to fit them into the lathe chuck. Start by cutting a slightly larger ID brass tube to the length of the threaded section:
Collet Holder – brass shim cutoff
I finally got a Round Tuit and ground opposing angles on the cutoff tool ends, so I can choose which side of the cut goes through first. In this case, the left side cuts cleanly and the scrap end carries the thinned slot into the chip tray.
Grab the tube in a pair of machinist vises and hacksaw a slot:
Collet Holder – brass shim slitting
Apply a nibbler to embiggen the slot enough to leave an opening when it’s squashed around the threads:
Collet Holder – brass shim around threads
Put a nut on the collet threads in an attempt to keep them neatly lined up while drilling:
Collet Holder – collet drilling
Drill the hole to a bit over 3 mm in small steps, because it’s not the most stable setup you’ve ever used. Eventually, the diamond point just slips right in:
Collet Holder – 3 mm scribe test fit
Reassemble in reverse order and It Just Works:
Collet Holder – finished
Now, to scratch up some acrylic!
Cheese Slicer Rebuild
Posted by Ed in Home Ec, Machine Shop on 2018-11-05
The cheese slicer frame looked much better after sandblasting with 220 aluminum oxide grit:
Cheese slicer – sandblasted
The flower bed outside the Basement Laboratory door seems a bit dusty, though.
Slathering it with JB Weld steel-filled epoxy went reasonably well:
Cheese slicer – JB Weld curing
JB Weld is much much more viscous than the clear XTC-3D I used last year and the final coating, while smoother than what you see here, has too many sags and dents to say “good job”. I didn’t bother coating the upper tips, because the epoxy will wear off from my morning KP.
The aluminum roller turned on those bare stainless steel screws in the tray, with the threads chewing into the roller bore. While the epoxy was curing, I drilled out the roller to remove most of the ridges:
Cheese slicer – drilling roller
Cut a pair of stainless screws slightly longer than the old screws, then turn the threads off to make a shaft:
Cheese slicer – screw reshaping
The lathe spindle runs in reverse, so the cutting force tends to tighten the screw in the nuts. The big old South Bend lathe had a screw-on chuck and didn’t really like turning backwards.
The new screws won’t win any beauty prizes, but they get the job done:
Cheese slicer – screw shafts
Turn a Delrin rod to a press fit in the drilled-out roller:
Cheese slicer – turning Delrin bearing
Part it off, repeat, ram them into the roller, then drill to a loose fit around the smooth-ish screw shafts:
Cheese slicer – drilling Delrin bearing
Reassemble in reverse order:
Cheese slicer – rebuilt
Looks downright industrial, it does.
Stipulated: this makes no economic sense, apart the simple fact we appreciate utensils that just work.
MPCNC: Drag Knife Holder Spring Constant vs. Stiction
Posted by Ed in Machine Shop, Science on 2018-10-26
Sliding a drag knife body in a PETG holder, even after boring the plastic to fit, shows plenty of stiction along 2 mm of travel:
MPCNC – Drag Knife Holder – spring constant
Punching the Z axis downward in 0.5 or 1.0 mm steps produced the lower line at 210 g/mm. Dividing by three springs, each one has a 70 g/mm spring constant, which may come in handy later.
The wavy upper line shows the stiction as the Z axis drops in 0.1 mm steps. The line is eyeballometrically fit to be parallel to the “good” line, but it’s obvious you can’t depend on the Z axis value to put a repeatable force on the knife.
I cranked about a turn onto the three screws to preload the springs and ensure the disk with the knife body settles onto the bottom of the holder:
MPCNC – DW660 adapter drag knife holder – spring loaded
The screws are M4×0.7, so one turn should apply about 140 g of preload force to the pen holder. Re-taking a few data points with a 0.5 mm step and more attention to an accurate zero position puts the intercept at 200 g, so the screws may have been slightly tighter than I expected. Close enough, anyway.
The stiction is exquisitely sensitive to the tightness of the two DW660 mount clamp screws (on the black ring), so the orange plastic disk isn’t a rigid body. No surprise there, either.
Loosening the bored slip fit would allow more lateral motion at the tip. Perhaps top-and-bottom Delrin bushings (in a taller mount) would improve the situation? A full-on linear bearing seems excessive, even to me, particularly because I don’t want to bore out a 16 mm shaft for the blade holder.
It’s certainly Good Enough™ as-is for the purpose, as I can set the cut depth to, say, 0.5 mm to apply around 250-ish g of downforce or 1.0 mm for 350-ish g. The key point is having enough Z axis compliance to soak up small table height variations without needing to scan and apply compensation.
MPCNC: Jogging Keypad for bCNC
Posted by Ed in Machine Shop on 2018-10-18
The bCNC G-Code sender sends jogging commands to GRBL from an ordinary numeric keypad:
MPCNC – Jogging keypad
Unlike the keypads on my streaming radio players, this one requires no configuration at all, because bCNC regards it as just another keyboard input. The catch: you must select any screen element other than a text entry field to have bCNC recognize the keystrokes as “not text”.
You would get the same results from the numeric keys on the right side of a full-size / 104-key plank. I’m using a small “tenkeyless” keyboard, which means I can put the keypad wherever it’s easiest to reach while tweaking the MPCNC.
The ÷10 and ×10 keys along the top row alter the step size by factors of ten, which is pretty much what you need: jog to within a big step of the target, drop to the next lower decade, jog a few more times, maybe drop another decade, jog once, and you’re as close as you need to be with an MPCNC. The -1 and +1 keys aren’t as useful, at least to me: changing from 5 mm to 4 mm or 6 mm doesn’t make much difference.
Jogging to align the spindle (well, a pen or drag knife) with a target using the video camera works really well:
bCNC – Video align
GRBL and bCNC don’t do smooth jogging and the discrete steps aren’t as nifty as the Joggy Thing with LinuxCNC, but it gets the job done.
Dutch Reach
Posted by Ed in Oddities, Recumbent Bicycling on 2018-10-14
I carry a garish scar under my right arm from my collision with a frameless driver door window while commuting from classes at Lehigh U, back in the day, so I’m as bike-aware as any driver you’ll ever meet. After reading several articles describing the Dutch Reach, I put a reminder on the Forester’s driver door handle:
Dutch Reach reminder
The bright yellow block reminds me to peer into the mirror (*) before yanking the handle, regardless of which hand I’m using. Haven’t had any close calls yet, but practice makes perfect.
If you don’t have a label maker, you can hang a tag on the handle.
It’s surprisingly hard to retrain a habit, though …
(*) Update: Yes, I should look over my shoulder, too. At least now I’m aware of the situation and don’t just open the door without thinking. One step at a time.
MPCNC: Modified Drag Knife Adapter Spring Constant
Posted by Ed in Machine Shop, Science on 2018-10-09
The bars on the original MPCNC drag knife / plotter pen adapter had a 100 g/mm spring constant:
MPCNC – Plotter pen force test
Making the bars slightly thicker improved their print-ability:
MPCNC knife adapter mods – OpenSCAD model
The reddish tint marks the new bars, with their location carefully tweaked to be coincident with the stock STL.
Shoving the pen into the scale with 0.1 mm steps produces another unnervingly linear plot:
Modified MPCNC pen adapter – Spring Constant data
Real plotter pens want about 20 g of force, so this isn’t the holder you’re looking for.
A bunch of plots at Z=-1.0 mm turned out well with the ballpoint pen insert, though:
MPCNC Modifed pen adapter – first plots
The globs apparently come from plotting too fast for conditions; reducing the speed to 1500 mm/min works better.
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