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Archive for July, 2016

30
Jul

The Cycle of 3D Life – Thermistors

3D printing, undeniably, has to be one of the most fascinating, frustrating, researched, and misunderstood hobbies of all time. Not that I’ve actually had every hobby known to man to compare this to, but in the ones I have had, 3D printing runs at the top for the aforementioned.

Inevitably it starts with either a 3D printer kit, or a plug and pray…er I mean play printer. At some point, something breaks. Somehow. Quite mysterious in some respects. I’d blame the cat. Except we don’t own a cat.

Generally if you built the printer, fixing it is slightly more straight forward because you usually have a good source for parts and you know, more or less, how it goes together. On the other hand, if you have a ready to go printer, it can be somewhat tasking to find a shop that can or will fix it. Makerspaces are usually good sources for help or information in either event.

The two delta printers at the Wanch here, Rocky & Bullwinkle, have seen their fair share of repairs, mods, tweaks, adjustments and some mayhem that I throw in for good measure. Bullwinkle is the original printer, now 14 months old with 1800+ hours of printing time on it. Rocky is only 5 months and 170 hours.

Within the last couple of months, both printers have broken in the same way. Specifically the hot end thermistor. I suspect some collusion between the two of them for this to have happened but I can’t prove it. I’ll stick with, darn cat. You know, the one I don’t have.

You can find these little thermistors littered all over eBay and are very inexpensive. These are glass bead 100K styled and used to be stuffed inside a piece of brass tubing. There is a set screw on the hot end that tightened on the brass tubing to hold it in place. If you over tightened it, which took a fair bit of force, the glass bead shattered. Bad mojo.

A bigger issue was that companies would crimp the tubing on the end to stop the thermistor from sliding out. They got a little too carried away sometimes and the crimp would cut into the extremely fragile wires from the thermistor and cause a wire to break at that point. That’s what happened to both of mine.

Hot End Type1

At any rate, I suppose a lot of thermistors were getting broken because most of the replacements now are merely the glass bead and you reuse the tubing the thermistor came mounted in. I uncrimped the tubes so there’s some wiggle room.

None the less, now you’ll find a lot of thermistors that look like this:

Hot End Type 2

Or this:

Hot End Type 3

Much more friendly to mount and replace.

Ultimately on a delta because of the motion of the head, there is always some flex in the wiring and, yep, at some point, breakage.

Once I’d replaced the two thermistors, the first thing I noticed was that the heat cycles are different. Both printers seemed to struggle to maintain a nice even temperature. As in hoping all other the place, like +- 9c. That’s a big swing for the printers.

I have a window in the shop as well and if it was open, well, yeah, made things a lot worse.

Just for the heck of it I started looking for solutions and what do you know. Turns out all these thermistors that might look the same are hardly the same. Thus if you replace one, you’re supposed to tune for it. Who knew? I didn’t.

Low and behold, there is already a tuning routine built in the Marlin firmware (I’m using 1.02). Start with a COLD hot end, connect to your printer and send the following GCODE:

M303 E0 S200 C8

Your printer will start a self test cycle to determine the thermistor settings, S200 is the temperature it will use for the cycle. If you normally run your printer hotter or colder, use that for the temp setting.

Here’s a transcript of what the firmware does. Takes about 3 or 4 minutes to complete.

PID Rocky

At the end you get Kp, Ki, and Kd (not to be confused with Kraft Dinner) and you put those values into your Marlin firmware:

PID Configuration

After doing this with both printers, the temp control is FAR superior to what it was.

As an aside, I do notice that one one printer, the hot end temp will always overshoot by 5 or 6c during the initial heating but it settles back down to the correct temp nicely and stays there. Doing a little testing I find out that the heater itself is the culprit. Yeah, they aren’t all made the same either. Who would have guessed…:-)

12
Jul

3D Airprinting Vase Mode

In spite of the fact that I feel I’ve probably made more 3D printing errors than the average person, possibly due to testing to see “what THIS might do” or “cause”, there’s sometimes one of those “ah ha” moments. You know, where the planets align.

Tonight was one of those nights. I’ve printed a fair number of “vases”, single wall designs, to hold pens and stuff and I can usually spot the ones that will print out correctly, and the ones that won’t. But every now and then, one catches me off guard and this is the result.

IMG 1612

Yep. Typical Thingiverse design but it’s coming apart at the “seams”. Now I tried everything I could think of to “fix” some of these, and usually ended up with a big fat fail. Until tonight. Through pure accident.

I am testing out a Cartesian printer (Hobby King Fabrikator), kindly loaned to me by one of the FVMakers (David) and having some fun with it. I was printing some of my torture test prints on it and came to the conclusion that the way the printer is built is good. In this case the bed is the Z movement, the head does the X and Y. I like it.

This scooted me off to see what other Cart’s match this setup. Happened through PRUSA’s site. I started reading some of the blog and then noticed a title that said, “WHAT ARE PERIMETERS GOOD FOR?“. I almost didn’t read it and then I did. And BOY am I glad I did.

The gist of the blog is that perimeters are easy, when your design is a box. It’s when all these angles start to go out or in that crap happens. Normally I use 3 perimeters but when printing vases, I use a single wall. But it fails a lot.

And here’s why: PERIMETERS: 2 vs. PERIMETERS:5 Rising angle: 13°; Layer height: 0.2 mm

Perimeters 3d

Yep. Air Printing. A single wall even at max resolution, well, sits nowhere. Whereas if one has enough perimeters, things will build up nicely. Here’s a snapshot of it, but for a detailed look, here’s the main link to it.

Perimeters curved face

Ah ha. One needs more perimeters and therefore VASE mode in Slic3r is very limited. Then I got thinking that when I looked at some of the samples on Thingiverse people had printed out, they looked like single wall thick. Which is where I got my second nugget.

Apparently Simplify 3D and CURA have the smarts to calculate extra perimeters in these areas and they do. Slic3r on the other hand adhere’s to exactly what you tell it to do. Not what you expect it to do…

Quite a well written blog article and I encourage anyone who has ever suffered these symptoms to read it. Worth your time.

10
Jul

ESP8266 Breakout Programming

Last year I sourced a bunch of ESP8266’s for programming but wasn’t excited about them enough until the Arduino IDE was expanded to support them. Then suddenly all of these inexpensive WiFi things became extremely versatile and useful.

This is the first one I started with, but of course I did some modifications to it. Like rip the battery box off and replace the battery wires with pins.

Esp8266 development board esp 12 er dp8266esp12

The result of the simple modifications was a voltage divider on the RX input because the USB to Serial adapter is tossing out 5V and the ESP8266 is a 3.3V denizen. Two resistors (1K and 2.2K) are used to do the job.

On the PCB’s, the terminals for RX and TX are labeled in reverse. In other words they tell you where the signal is supposed to go on the Serial adapter, not what’s coming out of the 8266.

The second mod was a NC push button on the Vcc line. The 8266 board has its own 5 to 3.3v regulator but in order to program it from the Arduino you need to put it into flash mode in a specific way. If you omit the normally closed push button, just disconnect Vcc at the pin.

ESP8266 Connections

Programming Step 1 – disconnect Vcc at the breakout. Place the jumper on the two pins on the bottom of the breakout.

ESP8266 Step1

Programming Step 2 – Connect Vcc to breakout board. Remove the yellow jumper from the PCB.

Esp8266 Step2

The ESP8266 breakout is now really for you to program it.

Programming Step 3 – in the Arduino IDE the setting for the breakout is the Adafruit Huzzah one. The port will be whatever USB to Serial board you have plugged in.

ESP8266 BreakOut Programming

And that’s it. Open an ESP8266 sketch, compile it and you’ll see the little blue LED on the ESP8266 flashing away like crazy. When it’s done the ESP8266 will automatically start running the code you sent it. It doesn’t reset when you connect the serial monitor to it like the Arduino’s do.

If you have the same breakout board, here’s a sample sketch for you to send to the board. It will sort of simulate the old Knight Rider bar graph and if you cover the photo cell it will change the speed of the cycle.

Knight_Rider

9
Jul

3D Print Fixin’

Sometimes it’s the simplest things, or things that look simple, that will rise up and confound us. At which point all of our accumulated knowledge is about as useful as an umbrella to a fish.

One of the makers at our space was having troubles printing a “Slimer” from Ghost Busters so I suggested he send me the file or link and I’d have a look at it.

First thing was to open the Slimer in Slic3r. And realize in .5 seconds where all the problem areas are.

SLM Step1

For example, there’s the cavernous mouth. 3D printers truly suck at “air printing”. So that throat tonsul is doomed from the get go.

SLM Step2

I won’t mention the second area, the fingers. With the tips of the fingers there’s no firm attachment to the bed and any bump at all and…well…poor old Slimer is going to have some digit problems. And everything there after that connects to it.

SLM Step3

Generating Supports

Slic3r does have built in support generation, but trying to get those supports out from inside Slimer’s mouth would probably qualify you as a budding Orthodontic wannabe.

So off to AutoDesk to find Meshmixer, download, install. Use the IMPORT function in Meshmixer to load in the STL file.

SLM Step4

And BINGO. If we weren’t paying attention, we’d see that Slimer is getting away. The red dot marks the center of the build area in Meshmixer but Slimer is way off that.

SLM Step5

So like the most dismal words ever heard by an Amway salesperson, “No Soap”. We have to fix this first, and thus, we bail out of Meshmixer for the moment.

STL Repair

The best piece of software for “fixing” bad STL’s is netFabb (free)…Go find, download, install, get running….then head to the project menu to open the troubled Slimer.STL file.

SLM Step6

netFabb will display Slimer, usually in a glorious green colour, but we’re going to “fix” him so who cares.

Look for the + sign (think of the red cross) and click on it.

SLM Step7

Good. Unfortunately that didn’t really fix anything, just started the process. We need to continue so head down to the bottom right corner of the display and look for “Automatic Repair”…and click on it.

SLM Step8

A dialog will show up with two options. Default repair and Simple repair. I used to use Default, but found that Simple repair works 100% of the time (better too)… so click on Simple Repair and then the Execute button…(don’t worry about executing Slimer; he won’t mind).

SLM Step9

You’ll notice the display sort of changed for a split second and what has happened is you have TWO Slimers. The original and the new one. We need to get rid of the first one (original) leaving only the repaired one.

Bottom of the main display look for the Apply repair button, click it.

SLM Step10

You’ll get a dialog asking what you want to do with the two parts. We want to remove the OLD part, thereby leaving the new part.

SLM Step11

So WooHoo, we’re done right? Yeah, not so much sparky. We have to SAVE the repaired design. Like this (a CONTROL CLICK for the Mac guys):

SLM Step12

Now the STL is repaired. And this is how you’ll repair any STL file that has issues. It works way better than the auto repair in Slic3r so it will pay you to learn how to do this.

Back to Supports

Remember when we last opened Slimer in Meshmixer he didn’t center on the print area? News flash for you. He still doesn’t. netFabb doesn’t auto centre, it assumes we know what we’re doing. And in some cases, that’s a good assumption. In this case, ah, no.

So how do we center it? Easy. Open the repaired STL file in Slic3r. Then use the EXPORT STL button in Slic3r to save the centered STL

SLM Step13

Exit Slic3r and get Meshmixer going again. Now, before you complain that you didn’t need to “fix” Slimer with netFabb at all and you just wasted your time, the point was to show you HOW to fix if need be, so you learned something (you did pay attention didn’t you?) so, your time was not wasted and in the future you may even thank me. Silently. Under your breath. Begrudgingly. Or not.

Importing Slimer repaired and centered in Meshmixer now looks correct. The red dot is close to where the good Lord split him so he’s in the center. If you catch my drift.

SLM Step14

On the left side of Meshmixer is a bunch of icons. Because someone failed their GUI design phase I think, but, well, an icon is worth 1000 words, hence click on the Analysis and then Overhangs.

SLM Step15

A dialog will display where you can make custom overhang settings or just use the defaults, as most of us do. The button labeled Generate Support is the one we want. Click on it.

SLM Step16

You’ll see a progress bar, some messages (or many in this case) about “nodes” and “pruning”. In a period of time Slimer will appear with supports. These are not permanent at this point. If you want to delete one or many, hold the CMD key down and click the support to make it go away. If you make a mistake (and how else would you have gotten to this blog in the first place eh?), CMD Z will UnDo and put the support(s) back.

SLM Step17

If you notice areas on the design are in RED, those are the areas that are going to have printing problems. Due to the angle of the printing (less than 45 degrees for example) and that’s where support(s) will be of benefit.

When you have the supports left you want, click the DONE button and then use the File Export item to save the supported STL file.

SLM Step18

Supports Complete

When we reopen the STL problem slime ball in Slic3r, he’ll look a lot different. Like he has grown way more teeth. Really those are just supports.

SLM Step19

Those small supports will break off quite easily when the printing is done, yet they do provide more that adequate support during the printing phase.

Summary

This lesson has been brought to you by the … oh wait, wrong program… hopefully you’ve gained some insight as to how netFabb repair and Meshmixer support works and you’ll be able to easily use them both when you need to. And yes, both programs do a LOT more, but just having a good understanding of how to fix things is a huge leap. Forward. Up. Okay, maybe just a bit of a wiggle then.

Having gone through all of the gyrations of fixing this design, to print, as you see it, there are other ways to do it as well. On Thingiverse, search for Minions. You’ll notice that they are printed in two halves and glued together. There is no reason why Slimer couldn’t benefit from the same procedure.

A simple task in Tinkercad to split, save the halves, perhaps fixing in netFabb (Tinkercad can screw up when generating the STL file) and then printing. My thought is it would be a lot easier printing. Or not. Honestly, I haven’t tried it, that’s an exercise for the reader. And yeah, you might miss this nugget if you just looked at the pretty pictures…