Posts Tagged Thing-O-Matic
That’s a 0.035 inch = 35 mil hex wrench, of which Eks reminds me “Any time your design requires a tiny [obscene gerund] wrench, you’re doing it wrong”.
The sequence goes like this:
- Loosen that tiny setscrew
- Unscrew & remove the mirror boom
- Remove brass screw & azimuth pivot
- Tighten screw in elevation pivot
- Tighten tiny setscrew on elevation arc
- Reinstall & tighten azimuth pivot
- Reinstall mirror boom
- Tighten tiny setscrew
Going strong after seven years!
But, as the saying goes, that’s not a herringbone gear. This is a herringbone gear:
We always read the signage:
They’re parked in front of the National Museum of Industrial History in Bethlehem, PA.
Ex post facto notes from the third Squidwrench Electronics Workshop.
Exhibit various 50 Ω resistors, including my all-time favorite, a 600 W 3 GHz dummy load:
… down to a 1/8 Ω metal film resistor.
The dummy load’s N connector triggered a regrettable digression into RF, belatedly squelched because I wasn’t prepared to extemporize on AC concepts like reactance which we haven’t covered yet.
Discussion of resistor applications, power handling, power derating with temperature, etc:
Why you generally won’t find 50 Ω load resistors in Raspberry Pi circuits. Cartridge heaters for 3D printers, not aluminum power resistors, although everyone agrees they look great:
Discussion of voltage vs. current sources, why voltage sources want low internal resistances and current sources want high resistances. Bungled discussion of current sources by putting diodes in parallel; they should go in series to show how added voltage doesn’t change current (much!) in sources driven from higher voltages through higher resistances:
Use Siglent SDM3045X DMM in diode test mode to measure forward drop of power / signal / colored LEDs, discuss voltage variation with color / photon energy. Measure 1.000 mA test current for all forward voltages.
Compute series resistor (500 Ω) to convert adjustable power supply (the digital tattoo box, a lesson in itself) into reasonable current source; roughly 10 V → 20 mA. Find suitable resistor (560 Ω) in SqWr
junk box parts assortment, digression into color band reading.
Wire circuit with meters to measure diode current (series!) and voltage (parallel!), measure same hulking power diode (after discovering insulating washers now in full effect) as before in 1 mA steps to 10 mA, then 15 and 20 mA, tabulate & plot results:
Discover warm resistor, compute power at 20 mA, introduce cautionary tales.
Lesson learned about never returning parts to inventory, with 560 Ω resistor appearing in diode drawer. Cautionary tales about having benchtop can of used parts as front-end cache for inventory backing store.
Another intense day of bench work!
Over the course of those six years I’ve ridden about 6 × 2500 = 15000 miles, maybe more, maybe less. I can ride at 15 mph for a while, but 12 mph seems a more reasonable overall estimate, making for a bit over 1000 hours. Figure the bike spends that much time sitting outdoors at the far end of the ride and you’re looking at what 2000+ hours of sunlight does to ABS.
In addition to discoloration, the plates have become brittle, as shown in the chips in third one down, and permanently deformed due to the pressure of the nylon bolts compressing the black foam against the fairing.
A closer look at the top plate:
My 3D print quality has improved a lot since then.
New plates of a different design are, as NASA puts it, “in work”.
The pix come from the new LiDE 120 scanner. It does a good job with the color, but has (for good reason) an essentially zero depth of field: if it’s not on the glass, it’s out of focus.
The Zire would power on whenever the switches clicked or that little joystick moved, which happened regularly enough to be annoying.
Mary made a small case that matched the other pouches I carry around:
She made the case to fit an HP48 calculator, but it was close enough for the Zire.
Time passed, the Zire died, I started carrying a Kindle Fire in another pocket, but the ABS slab provided a convenient stiffener between some Geek Scratch Paper and the various pencils / pens / markers / screwdrivers / flashlight filling the available space.
Unfortunately, minus the backup of an electronic slab, the protector finally failed along an obvious stress riser:
I cut a similar rectangle from a sheet of unknown flexy plastic, rounded the corners, clipped the pencils & whatnot to it, and maybe it’ll survive for a while.
The final installment of musings about building a large-format 3D printer …
(Continued from yesterday)
Perhaps they saw your blog post?
The old-old (original) high-resistance Kysan motor costs something like $45 and, apart from minor cosmetic differences, looks /exactly/ the same as the old-new low-resistance motor. If you were picking motors and didn’t quite understand why you needed a low-resistance winding, which would you pick? Hence, my insistence on knowing the requirements before plunking down your money.
To be fair, I didn’t understand that problem until the Thing-O-Matic rubbed my nose in it. With all four motors. Vigorously.
So, yeah, I think I had a part in that.
comes back to the same numbers over and over
The new-new leadscrews have something like half the pitch of the old-new and old-old threads; I don’t recall the number offhand. In any event, that gives you twice the number of motor steps per millimeter of motion and roughly twice the lifting force. This is pretty much all good, even though it may reduce the maximum Z axis speed (depends on your settings & suchlike).
When it moves upward by, say, 5 mm and downward by 5 mm, you’re measuring position repeatability. That level of repeatability is pretty much a given (for the M2, anyhow), but it doesn’t involve stiction & suchlike.
Can you move the platform up by 0.01 mm, then down by 0.01 mm, and measure 0.01 mm change after each motion?
Do larger increments track equally well in both directions?
Move upward a few millimeters, then step downward by 0.01 mm per step. Does the measurement increase by 0.01 mm after each step?
Repeat that by moving downward, then upward in 0.01 mm increments.
If the platform moves without backlash & stiction in both directions with those increments, it’s a definite improvement.
I wish I knew more
everything you learned is burned into your head forever
The way to learn more is exactly what you’re doing.
Two things I learned a long time ago:
1. Whenever you have two numbers, divide them and ask whether the ratio makes sense.
2. Whenever you don’t understand a problem, do any part of it you do understand, then look at it again.
Also, write everything down. When you come back later, you won’t remember quite how you got those results.
Which is precisely why I have a blog. I search with Google (site:softsolder.com microstepping) and /wham/ I get a quick refresher on what I was thinking. That’s why I keep link-whoring URLs: that’s my memory out there!
You’ll sometimes find scans of my scrawled notes & doodles. They won’t mean anything to you, but they remind me what I do to get the answers in that blog post.
modern controllers utilize much higher voltage and current bursts
More or less. Microstepping drivers apply a relatively high voltage, far in excess of what the winding can tolerate as a DC voltage, then regulate the current to a value that produces the appropriate waveform.
This may be helpful:
The mass of the bed APPEARS to be cancelling out any magnetic or mechanical stiction.
That can’t be true in both directions: the gravity vector points downward and the results aren’t symmetric. I think you’re reading noise. If the sequences of motions I described don’t produce the results I described, then you’re /definitely/ measuring noise.
From back in the Thing-O-Matic days:
E3D hot end setups vs MakerGear’s?
I’d want that groovemount post in an all-metal socket, though, rather than the traditional plastic, to get solid positioning and tolerance control. Makergear has the right idea with the aluminum V4 heater block mount.
Continued musings about building a large-format 3D printer …
(Continued from yesterday)
taking your challenge and am starting by cloning the M2
That gives you an existence theorem: you know exactly what you want to end up with.
AFAICT, few of the M2’s parts bear standardized numbers you can simply order from a reputable seller. Makergear knows what it’s buying (obviously!), but they’re under no obligation to help out: you must reverse engineer the requirements, find a suitable part, find a supplier, then buy one item.
Let me know how that works out for cost & performance; “cost” should include a nonzero value for your time and “performance” should have numbers you can verify. I (obviously) think the build will be a dead loss on both counts (*), but good data will be interesting.
(*) Albeit useful for educational purposes, which I’ve used to justify many absurd projectst!
How the heck do you read out the current (estimated, obviously) X Y Z position absolute to the machine coordinates?
Perhaps M114 or M117?
My overall list may be helpful, although the RepRap Marlin reference has more detail on their command set:
The LinuxCNC (and, perhaps, Machinekit) G-Code languages give you access to built-in variables and extend G-Code into a true scripting language. Marlin evolved differently and doesn’t support that sort of thing.
G-Code is pretty much a write-only language, but you can do some interesting things:
I use the gcmc compiler whenever I can for actual CNC machining:
Works for me, anyhow, although I don’t do much CNC these days.
move my nozzle up .01 at a time
Stiction / microstep errors / command resolution prevent that:
The only way to measure the nozzle position is to measure a finished part with a known height, because any variation comes from the first layer offset. That’s if you have Z=0 at the platform, of course, rather than whatever offset you get by defining Z=0 at some random height based on jamming business cards / feeler gages / special Japanese rolling papers under the snout. [ptui & similar remarks]
You need numbers. Lots of numbers. [grin]
strip basic tools out of the control interface
Yet another reason I don’t use S3D: that “Simplify” thing gets in the way of my obsessive need for control.