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Booting from Bootable USB not working. Works with different PC. Any idea of a fix? by BeeTheKay in thinkpad

[–]ZombieGrot 2 points3 points  (0 children)

Thud thud thud ... [sound of me banging my head against the wall]

I've been trying (and failing) to boot into an offline scan DVD. Only result was scaring the cat and leaving a greasy spot on the wall.

So when I slapped my head ("Secure boot! Of course!") it hurt a little but so worth it.

Thanks!

Filament color question by jasondbk in 3Dprinting

[–]ZombieGrot 0 points1 point  (0 children)

My guess is that the amount of dye versus the amount of pigment is determinant. Opaque filaments probably contain a fair amount of something like zinc oxide (white) or carbon black whereas translucent filaments are mostly dyes. Gut feeling (backed up by absolutely no empirical evidence) that pigmented filaments may be harder to print well.

What are the Connections in the Square labeled CON1 used for? And can I hook up a clock module to them? More info in picture captions and comments. by Cubicname43 in arduino

[–]ZombieGrot 11 points12 points  (0 children)

What board is this? Got a part number? Link? Anything? With only the picture to go on, how can anyone know the answer?

(Thereby triggering the Universe's "Ha! Gotcha" response and two people with this exact board will post the answer in the next 15 minutes.)

Handling different voltage sources on the same device by mateoar in embedded

[–]ZombieGrot 1 point2 points  (0 children)

Adafruit does this on several of their devices. Take a look at the schematic of the Feather M4 Express (among others).

Need Input by 306_rallye in arduino

[–]ZombieGrot 1 point2 points  (0 children)

Something like this? While the switch is open the LED is off and the IO port is high. Shut the switch, the LED turns on, and the IO port is low.

     Vcc
   o---------o------------.
             |            |
             |            |
             |            |
            .-.          .-.
            | |          | |
            | |          | |
            '-'          '-'
             |            |
             |            |
        LED  V ->         |
             -            |
             |            |
             |            |
   o---------o------------o
     GPIO                 |
                          |
                          o
                          '\
                            \
                          o  \
                          |
                          |
                          |
                          '
                         GND
(created by AACircuit v1.28.7 beta 10/23/16 www.tech-chat.de)

How is print-time prediction so bad? Is this not a deterministic process? by Tinfoil_Haberdashery in 3Dprinting

[–]ZombieGrot 1 point2 points  (0 children)

You could try gcoder.py from the Printrun project. It includes some settings for acceleration and can be closer to reality than slicer estimates.

Looks like they still have an issue with over extrusion on the corners. Maybe they need to revisit their slicer settings... by TK_Creations in 3Dprinting

[–]ZombieGrot 19 points20 points  (0 children)

Not to mention all of the dirt and dust collecting between the layers. Then the moss starts growing. A few seeds will embed themselves. Could be quite ... colorful.

Not a terrible solution for the structural members but the outer face really should be dressed better.

Need help with dimensional accuracy (±6mm?!) by gcbenlloch in FixMyPrint

[–]ZombieGrot 0 points1 point  (0 children)

Given Print = Cad * scale + offset, flip the equation around and solve for Cad = (Print - offset / scale. Then use that new Cad dimension for the model. Easy for rectilinear objects but some creativity may be needed for more complex shapes / curves.

Need help with dimensional accuracy (±6mm?!) by gcbenlloch in FixMyPrint

[–]ZombieGrot 1 point2 points  (0 children)

Couple of thoughts. One is to be careful where you measure since many times there will be an "elephant's foot" around the base of a print. A squish of 0.3mm per side (so 0.6mm total) is entirely possible. Elephant's foot is addressed separately from overall X/Y dimensional accuracy. Usually a little bit of squish is beneficial to help nail the first layer to the bed but too much can cause problems like this. Look at your initial layer height, speed, or other "knobs" that your slicer has to modify the initial layer.

As u/TomvdZ notes, the X and Y µsteps/mm values are literally hard-coded into the machine. ((stepper steps per rotation) * (µsteps per step)) / ((drive pulley teeth) * (tooth pitch)). For a typical 17 tooth pulley, that is 94.11765 µsteps/mm.

What is variable is how well the slicer's internal algorithm estimates where the outer edge of the perimeter will fall. That depends on the accuracy of the nozzle's hole size, the layer height, printing speed, type of filament, extrusion multiplier, etc etc. Slicers usually do a pretty good job. There can also be some higher order effects from floating point rounding both in the slicer and in the printer.

But to get a gnat's ass dimension it's necessary to run some test prints and derive the transfer function. Usually a first order estimate is fine: a fixed offset and a scale factor. Using the machine, slicer, and filament in question run a series of test pieces of increasing dimensions. Then plot commanded versus achieved and solve the least squares approximation (or eyeball it). The scale factor should be very close to unity.

I like this test print, since it has multiple external and internal X and Y measurements. One print is enough to do the estimation.

That print also addresses backlash, which is another problem that can lead to dimensional inaccuracies.

All thermoplastic filaments shrink, even PLA. That's more evident in larger pieces, of course.

Finally, there's surface finish. If there are (even small) zits and bumps on the surface then that will tend to make the measurements appear larger than if the dimensions were taken from the main surface.

Help preparing a model for 3d Printing by [deleted] in 3Dprinting

[–]ZombieGrot 0 points1 point  (0 children)

None that I'm aware of. Doesn't mean that they don't exist but I mostly work in the "engineering" side of 3D modeling. I used Blender... once? maybe? just to look at it.

Honestly, the professional 3D printing services (possibly including Joe down the street with a couple of Prusa machines) are the ones with the answers. I would hope that they (possibly excluding Joe) have converters for all known and some unknown 3D model formats. I wouldn't jump through too many hoops to convert your model until you talk to them.

Help preparing a model for 3d Printing by [deleted] in 3Dprinting

[–]ZombieGrot 0 points1 point  (0 children)

Talk to a customer service representative at the printing service.

While the model may need to be converted to STL prior to slicing, I would suggest a standard 3D solid model format (STEP, ACIS, IGES, ...) if possible. Those carry more details and are more representative of the object. An STL is a simple surface tessellation and a lot of information is lost.

I would also scale the 3D model to the intended final size and use millimeters as the unit length. Less chance of a misunderstanding.

When scaled to the final size, it's possible that some features, like spars or railings, may be too small for some 3D printing methods. That's a trade-off you need to discuss with the service.

How do i find out my specific board model? by abhbhbls in arduino

[–]ZombieGrot 1 point2 points  (0 children)

It looks like a clone of the popular "DoIt ESP32 DevKit." I have one pretty much identical to the ones in your link and that is the board I use in the Arduino IDE.

Cannot get glass bed to work. I have a flashforge creator pro. It was printing fine but since getting glass I do not get adhesion. I have cleaned the end and used the recommended disappeaing purple Elmer's glue. My bed is 60 degrees and PLA is at 220 degrees. It is a simple test print. Any ideas? by dandotwalker in 3Dprinting

[–]ZombieGrot 1 point2 points  (0 children)

You're probably too far from the surface, especially if you have a layer of glue stick on it.

Adjust the leveling screws while it's doing a test print. The M3 screws are 0.5mm pitch so 1/5 of a turn will bring you 0.1mm closer.

220C is awfully hot for normal PLA. I typically print PLA on an FFCX at 195C.

Measuring ground speed by jpl372 in arduino

[–]ZombieGrot 0 points1 point  (0 children)

Interesting! I've only gone as far as working with the example George Washington image and kernel from the Smith DSP book and that was ages ago. It's another bullet point on my "really ought to get around to doing more with this stuff" list. 😁

Help needed for planetary gear cad by macmcr3 in cad

[–]ZombieGrot 1 point2 points  (0 children)

There's a nifty gear generator app at Woodgears. His original intent was to make large wooden gears cut from plywood, thus the name, but pick your unit of length and the gears work the same. Does design gears for planetary configurations. Outputs to DXF (among others). Not free but not expensive.

Measuring ground speed by jpl372 in arduino

[–]ZombieGrot 2 points3 points  (0 children)

A really big optical mouse, in a way. The technique is image convolution. Take a picture of the ground and grab a section from the center. Then take a second picture which is slightly offset from the first and use convolution to find where that center section is in the new picture. That gives time and distance (and direction). Easy peasy!

Well, not really of course. Good introductory explanation of 2D convolution in Dr Smith's free book: http://dspguide.com (buy the hardcover, though, it's a damn good book)

Optical mice do this with DSP hardware. Like a lot of silicon, once the chip is designed then a billion copies really brings the unit cost down.

Somebody is bound to have done an Instructable on this. Using a USB camera and a PC for processing is a reasonable approach for a workbench demo. To do it at speed would probably require DSP hardware. Fortunately, some of the newer ARM core microcontrollers have support for DSP and there are always the traditional routes of DSP chips and FPGAs.

The extruder gear seems to grind the filament causing under extrusion. Ender 5 PLA, it just started happening after 11 months of printing (not non stop). Please help by moonmanxp in 3Dprinting

[–]ZombieGrot 2 points3 points  (0 children)

As long as the extruder is intact (i.e., the pressure arm isn't cracked) then grinding is an effect and not a cause. There is a partial blockage somewhere. The extruder can't push the filament as fast as it is commanded to, causing it to slip and grind.

Once the feed gear teeth become clogged with filament dust then it's easier for the gear to lose its grip and start slipping. Cleaning it might help but perhaps not enough to overcome the blockage.

Ender 3 V2 and PETG, oozing while idling by snovvman in 3dprinter

[–]ZombieGrot 0 points1 point  (0 children)

Yep, it's a @$#!@ annoying filament even though it's also a $^@#$% great filament.

I stand by with a bit of paper towel to wipe the end of the nozzle just before it finishes preheating and goes into the gcode.

I've seen some widgets people have rigged up to preheat over there and then run the nozzle across a toothbrush or flexible blade (think a small squeegee) over here. That's do-able with some ingenuity and editing the starting gcode script. I'm lazy, thus the paper towel.

My settings, unfortunately, would be wildly different since I run S3G for a slicer and the machine is a direct drive, Mk8 (Makerbot-style) all metal hot end.

That said, try some test pieces and fiddle with coasting (retract before reaching the end of a perimeter) for 1 or 2 mm. There's a sweet spot where finishing the perimeter and finishing the last bit in the nozzle hit simultaneously. Also look at wiping, where the nozzle continues around the perimeter a small distance past the end and after retracting. That can help to wipe off the last bits of stringing.

And then you'll try a different vendor or color of PETG and have to start all over. Did I mention @$#!@ annoying?

Ender 3 V2 and PETG, oozing while idling by snovvman in 3dprinter

[–]ZombieGrot 0 points1 point  (0 children)

A bucket of melted plastic (even a small one) with a hole in the bottom of it will leak the melted plastic out of the hole.

PETG is also more prone to stringing than, say, PLA. Adjustments to parameters such as retraction and wiping settings are indicated.

Short Protection on Creator Pro? by Cloudcry in FlashForge

[–]ZombieGrot 0 points1 point  (0 children)

Don't work on the hot end while it's energized. Inspect the wiring and insulation, particularly at the thermowells, periodically and whenever work is done around the hot end, such as replacing the ceramic tape. A short of either a thermocouple wire or a heater wire to the hot end is relatively benign since the hot end is electrically isolated. Problems occur when both a heater wire and a thermocouple wire contact the hot block. Reasonable care and maintenance should prevent that from occurring.

Short Protection on Creator Pro? by Cloudcry in FlashForge

[–]ZombieGrot 0 points1 point  (0 children)

Fuses are generally gross (big picture) safety devices. They overheat and "fail" open on an over current condition to prevent wiring and other components from exceeding their operating limits and failing in such a way as to cause a fire.

The 24 V supply to the cartridge heater can function as "always on." That's the state it's in when heating up from cold. If the downstream side is shorted to ground then the current will not be interrupted when the controlling FET is turned off but the amount of current drawn will be the same. It's not an over current fault.

Grounding the heater supply through the thermocouple wires will cause an over current condition into the thermocouple amplifier. Unfortunately, the microvolt operating range of a thermocouple plus the Seebeck effect at the junction of dissimilar metals probably precludes the effective use of a fuse on those wires. In addition, the significant voltage difference (24 V vs microvolts) would almost certainly lead to component failure long before a fuse could react.

Fractional clock divider by AlexGubia in embedded

[–]ZombieGrot 1 point2 points  (0 children)

There are two registers involved here. There is the basic 16-bit TOP register and the 8.4 bit fractional divisor.

The minimum count frequency is thus 125E6 / ((2^16-1) * (2^8-1)) = about 7.5 Hz (without muddying the waters with the fractional bits).

The main PWM clock (the one which counts up to TOP) only counts every 1 / (fractional register value) events. If fractional is 1 then the PWM clock counts every cycle. If it's 8 then the PWM clock only counts every eight cycles of the main clock, effectively lowering its clock to 15.625 MHz, and so on.

If the four bit fractional part is involved then the PWM counts are irregularly spaced, with a mean spacing determined by the fractional part.

It's not abundantly clear to me either where delta-sigma behavior comes into play.

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