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Aeromech

Member Since 19 May 2011
Offline Last Active Sep 04 2017 09:55 PM

Topics I've Started

Frozen Foam 3: Chilled to Perfection

20 September 2016 - 01:14 PM

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Burn off the Christmas cookies and New Year's booze with children's toys and nerdy dudes. This is the third annual installment of the infamous (and only?) winter nerf battle, be sure to dress warm to stave off the frigid Long Island tundra. Note: Must be 13 or older to participate.
 
This is an event where high energy foam blasters, essentially homemade piston mechanisms, are going to be used by participants. There is no supervision of minors, this is not a day care activity. Play at your own risk.
 
When and Where
Saturday January 7th, 2017

10AM - 5PM
Eisenhower Park, Field 2
East Meadow, NY 11554
 
GPS COORDINATES: 40.725080, -73.568716
Eisenhower Park Field 2, In the "crotch" of Hempstead Turnpike and Park Boulevard. It's the South side of the park that borders Hempstead Turnpike, near the Friendly's. I don't know how I can be more clear about this. The park is huge and every year people get lost, so just follow the GPS coordinates.This location is really good especially with a couple of mobstacles, which we will probably have available. There are a couple "lanes" of trees along with ample open field and a good staging area immediately next to the parking lot.
 
Weather Here --> https://weather.com/...ay/l/3966:19:US
Looks like it's going to be 20/30 degrees F and partly cloudy that day, so dress nice and warm.
 
What to Bring
-Eye Protection. I am big on this. Everybody wears eye pro, preferably impact resistant safety glasses/goggles. There are no exceptions to this rule.
-Blasters and darts. This should be obvious. It is a Nerf war. See below.
-Beverages. Bring extra water. There are bathrooms a short walk from the play field, and you'd be surprised how dehydrated you can get even in such cold environments.
-Food. We will provide bagels and coffee for breakfast/lunch/snack. There will be 30 minutes set aside for lunch so bringing a packed lunch would be wise, or there are some fast food joints right on the road.
-Warm Attire. Last year it was relatively warm, like 45 degrees, but FF1 had temperatures sink to like 25 degrees. Hats, scarves, gloves, jackets, waterproof boots, maybe even water resistant pants depending on the levels of snow of the ground. You can always strip off a jacket if it gets too warm but you'd be hard pressed to find someone willing to give up theirs for your cold ass.
-Sportsmanship. If you get tagged out, another game will resume within five minutes. If your blasters are underpowered, tough shit, you adapt. There are enough trees that short range blitz attacks are actually pretty effective when we play objective games. The no-asshattery rule applies here as always.
 
Blasters and Foam Darts
-ABSOLUTELY NO BLACK OR CAMO PAINTED BLASTERS
-Do not count on others to supply you with a homemade if you only brought a single shot pistol. That bring said, we always have people that bring super-stock and you'd be surprised how effective an overhauled Rapidstrike can be against even the most daunting of 4Bs.
-No homemade compressed air powered blasters. All compressed-air powered blasters must have an OPRV. No HPA, this isn't paintball. All other homemade spring powered blasters, and modified or stock store-bought blasters are sweet. Bring extra homemades if you got 'em, expect to be pelted with high energy homemade foam blasters should you attend.
-#6 washer weighed slugs ONLY for homemades. No slingshot weighted darts, no exposed metal darts, no glue-dome darts. This is your only warning. All store-bought darts of any kind are permitted so long as they are not further weighted.
-Bring extra blasters that you are OK with others using. We need as many extra as we can get.
 
 
Other Notes About the Cold
Batteries tend to discharge at a slower rate in the cold, so if you have a battery powered blaster, test it out and make sure it works after you stick it in the freezer for an hour. Dart fit on homemades is also affected due to the low humidity and low temperature, the foam tends to change it's material properties just a bit and likes to shrink just enough to fuck up every perfect fit in your barrel at room temperature.
 
 
Confirmed Attendees
Aeromech +3
Alphatrooper
David
XDevilX
SnoopDoggyDoge
Edmund
DX
EvilBunnyo
Gabe NYDZ
Jax
Nerfgeek
Dusty +?
ASGrocks
Ronald
Blitz
Zackthemack
augamemerald
Borvickos
 
 
Facebook Link: https://www.facebook...19246895097210/


Sear Carbine Writeup

24 July 2016 - 10:34 AM

The idea of using some type of sear to lock a bolt in place has been used on real-steel firearms since the advent of the machine gun, due to the simplicity and self-locking action of the mechanism. In the homemade Nerf market, this is a relatively new field, first being implemented on the ESLT some years ago. This is my attempt to marry SNAP style redneck engineering with the aforementioned locking mechanism.

 

RULES:

-No McMaster/Online ordered parts (Barring a [k25] spring, Good luck finding 11" long springs at a hardware store).

-No special tools required (No long-shank countersinks, holesaws, or any of that)

-No 3D printing

-Keep weight as low as possible

 

TOOLS:

-Rat-tail file

-Pocket knife

-Electric Drill with standard bits (no larger that 1/2")

-Woodsaw

-Hacksaw

-Screwdriver

-Sandpaper

SUPER HELPFUL BUT NOT NECESSARY

-Belt sander

-Drill press

-Table saw

-Vice

 

For this Writeup, descriptions will be BELOW the photos they reference.

 

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This was the original idea, using 3D printed components. I wanted to do the same thing without limiting myself to 3DP parts. But this is the idea. Borrow an ESLT/submachinegun catch and use it in place of the fickle SNAP nail and clothespin catch. Insert anecdote of "my SNAP shoots like 150 feet and I've never ever lubed it or replaced anything on it ever" but I have built three and they have ALL failed within 100 shots. Stop trying to convince me. Unless there is some kind of drastic improvement in the design I will not endorse SNAPs as being consistently war worthy. Moving on...

 

The actual catch mech can be seen here. a slot through the body tube and bolt allows a catch finger from the sear to rotate upward and extend into the bolt slot, blocking the bolt from moving forward, when the trigger is pulled, it pivots the sear downwards and the catch finger moves out of the bolt slot, and the bolt flies forward under spring force.

 

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This is the bolt. It is made of 1" PVC, with both ends capped off by cutting board. Get the fat kind, from Walmart, It's $6 and is like 1/2" thick, really great stuff. This bolt is about 7 inches long.

 

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Superlative plunger head screwed into the front. Actually provides a really good seal on this thing.

 

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The back shows a 1/2" dowel sunk into the tube, with the rear cap held on by a screw into the dowel itself. I cut the bolt too short so the cutting board is sticking out, but yours shouldn't stick out.

 

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Pretty standard at this point. Gooped in front bushing, with a slot cut 6.5 inches away from the front, running all the way to the back.

 

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This is an anti-kinking device (1" PVC pipe beveled internally at one end) duct-taped directly to a 1" to 3/4" bushing.

 

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We've all done the thing where we reach into the hardwre store bin without looking and get home with a 3/4" bushing and not a 1/2" bushing. Now is the time to use it.

 

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Now we need to make some decisions. Decide the orientation you want your bolt to stick out. It should probably be at least 45 degrees up from the horizontal. Drill holes all around to lighten it up, but do not drill holes on whatever the "bottom" side is. On the bottom, make a slot about 2 inches long right at the front of the bolt. This is where the catch will lock. Make it wider than it needs to be, it will be much less finicky if this hole is oversized.

 

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Test fitting with the [k25].

 

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Testing with the new handle. I used a 1-1/2" PVC "half piep" (really more like a 2/3 pipe) to snap directly onto the barrel. Note the stylish wooden handle that SNAP users seem to love. You can also just barely make out the hole in the bottom of the body tube; this should match up with the slot that was cut into the bottom of the bolt, so the catch can have access to the bolt slot and lock in place.

 

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This is the guts of the catch, with cutting board sideplates holding everything in. Basically, the trigger is pulled, which rotates the catch itself downwards and out of the way of the bolt. The catch itself is triangular shaped and really just has a piece which pops up into the body tube and locks into that hole in the bolt. Just like an ESLT, make sure you made a slot in the body tube as well that lines up with the bolt slot.

 

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The 3/4" bushing in the rear makes it almost trivially easy to throw on a stock, and the 3/4" pipe is much stronger than the 1/2" pipe. Rubber bands act as the catch restoring mechanism, and create a spring loaded trigger too. The front of the sideplates are held on simply by zip ties.

 

This baby is pretty asymmetrical, but I kind of like it that way. The spring kinks up a little, but the anti kinking mech fixes that without using any guide rods. The spring is not reaching full compression (need to chop another half inch off the back) but has like an inch or so of precompression, gets 5.25 inches of draw with the [k25], and rocks roughly 200 FPS based on just ear-analysis, I want to test it at APOC and get hard numbers.

 

The blaster without a barrel and hopper weighs 1 pound, 15 ounces, so with a barrel and hopper probably around 2.5 pounds, and even that weight can be brought down if you used wooden sideplates or went ham on lightening holes, particularly in the rear where the anti-kinking tube is.

 

Overall, I am mildly impressed with the blaster. A hardware store hitter that can play with the SNAPs with sear reliability and without the need to order anything. Get a pack of springs from spiderbite and you're set.


Fix for Omni-directional Plunger Rod Binding/False Catching

18 June 2016 - 04:04 AM

So my distaste for omnidirection plunger rods is not unknown to the nerf community, up til now, they seemed to catch less reliably than unidirectional catches, and were overall more fickle. The problem comes down to spring binding issues, particularly with the [k26], and maybe even the [k25]. As the plunger rod is pulled back and the spring compresses, it does not compress perfectly in line with the plunger rod, and tends to "serpentine", getting all wavy and kinky before it reaches it's final stage of compression. During this time, the spring gets caught in the omni-directional catch part of the plunger rod (with the lower rod diameter) and produces either a VERY unpleasant "crunchy" feeling to the prime, and often results in a "false catch" where the spring actually gets caught in that catch region when you pull the plunger rod back. You think the catch has engaged, and as soon as you begin to let go, and the spring is able to exert it's energy, the plunger assembly flies forward. This leads to swearing, sore fingers, questioning your rainbow catch-making abilities, and an overall hopeless feeling knowing that this lifeless piece of plumbing pipe has defeated you. You're better than that mate. Millions of years of evolution have prepared you for this moment. It's time to take on that omnidirectional plunger and make it yo bitch.

 

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The "Before" photo. Here is a pullback with the main tubes "ghosted" out, so the insides are visible but you can still see the outline of the body tube. Typically, the spring binds in the recess near the front of the plunger rod, where it is supposed to engage in the catch.

 

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This is it. This is the easiest solution ever. Cut a piece of 1" PVC Pipe, about 2.5 inches. Make sure it is shorter than the spring at full compression, but not too much shorter. Get it close, but make sure it is still shorter. Take note that the front (left side of the photo) of the tube is beveled on the inside. This is important. Put a few wraps of packaging tape around this so it fits fairly snuggly inside the 1-1/4" PVC plunger tube.

 

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Boom. Throw it in there. Rest this piece against the front of the rainbow catch, with the beveled end facing forward. Sink two screws in there to hold it in place.

 

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This photo provides a little more insight, the anti-binding pipe goes around the spring. When the spring is compressed, it is "guided" to a more "cocentric" position within the body tube. The bevel smoothly pushes any parts of the spring that may bulge out into position, so the spring cannot bend to the point where it would interfere with the catch region of the plunger tube. After installing this into a rainbow pistol/carbine (5 inches of draw, like 1 to 1.5 inches of precompression, 10 inches of [k26] spring)  all false-catches stopped completely. The prime was smoother, and all the problems I was having with the catch vanished. It caught every time, and smoothly. Follow this guide if you're using a [k26] in conjunction with an omnidirectional plunger rod.

 

Make sure it doesn't cover up your speed holes (anti vacuum holes). Once you sink in this piece, just re-drill the speed holes in the main body tube through the anti-binding pipe you just installed. Super easy.


Midsummer Mech-Out 7.16.16

05 June 2016 - 07:21 PM

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Hello once again, friends!

 

The time as come for yet another summer of nerfing. I'm glad to have hosted some successful winter events so far, and I am proud to present my first summer war! Get acclimated to the climate of the hot and humid Northeast before the coming Apocalypse here on Long Island.

 

Where & When
Eisenhower Park
East Meadow, New York 11554
July 16th, 2016
From 10AM to 5PM

 

Precise Coordinates: Field 2 of Eisenhower Park, Here's the GPS link: 40.725879, -73.568206

 

Rough Directions: The closest address to the entrance is 1899 Hempstead Turnpike, East Meadow, NY 11554. Plug that into your GPS and it will take you to the intersection of Hempstead Turnpike and Park Blvd, the main entrance of the Park. Turn onto Park Blvd. If you are taking the LIRR, look to get to the Hicksville Station from Penn Station.

 

NOTE: I am looking into this park and other lower-profile parks as well and seeing if I can book areas out so we can have exclusive access. I will keep you posted here and on the facebooks.

Weather

Here's the linkeroo --> http://www.weather.c...ay/l/11756:4:US

 

Rules
- Must be 13 or older to participate
- EYE PROTECTION IS MANDATORY.
- Absolutely no shooting, pointing blasters at non-players. I will personally escort you out if this rule is broken.
- Be respectful of players and non-players alike. If we need to move, we move.
- No facemasks, camo, or super tactical clothing.
- You WILL dart sweep

- If you are being a jerk/whiner you will be asked to leave. Never had this problem before, let's not start now


What to Bring
-EYE PROTECTION: There's a home depot literally across the street. If you forget it, cough up the $5 and get a pair there.
-Hot weather amenities: A big bottle of water or gatorade, a snack, a towel, sunscreen, maybe a hat.
-At least two primary blasters.
-$5 or so for pizza. May end up getting Domino's pizza. It's sacrilegious for Long Island, but it's cheap.
-Extra Darts.200 is my minimum that I like to carry.

 

Blasters and Foam Darts
-ABSOLUTELY NO BLACK OR CAMO PAINTED BLASTERS
-No homemade compressed air powered blasters. All other homemade spring powered blasters, and modified or stock store-bought blasters are sweet. Bring extra homemades if you got 'em, expect to be pelted with high energy homemade foam blasters should you attend.
-#6 washer weighed slugs ONLY for homemades. All other nonmetal darts are allowed. No slingshot weighted darts, no exposed metal darts, no glue-dome darts. This is your only warning.

-Bring extra blasters that you are OK with others using. We need as many extra as we can get.


Game Types
-3-15 and 5-0 Team Deathmatch
-Wingman Deathmatch
-Bomberman: A game of my own design; this time with better equipment! [think Luke Skywalker firing proton torpedoes into the Deathstar]
-2 or 3 way Defend the Core
-Super Secret Objective Based Round?!


Food, Downtime, and All Other Rules

We are going to keep rounds moving quickly this time around, with pizza and cold drinks being delivered from Domino's at a pre-determined time, probably around 1PM. Last winter, rounds were a little slower than I would've liked, so this time we'll keep things rocking and then have a solid hour for lunchtime midday.

 

It's gonna be hot. I will have a cooler of stuff and soda will be brought with the pizza. No alcoholic beverages, please, if you want to get some beers afterwards that's fine, but not while we are playing.

 

The don't be a douchebag rule, as always, is in effect.

 

PARENTS OF YOUNGER PERSONS: You are always welcome to play with us, just keep in mind typical participants range from 13 all the way up to ladies and gentlemen in their 40s. We are not a day camp, we are not a nursery. We are under the impression that all participants will act in a mature manner. There is no adult supervision, no liability insurance, and no one who will take responsibility for your child. While injury is unlikely at best, this is an intense sport just like lacrosse or hockey.

 

Attendees: If we get 20 or more that show up, I'll raffle off a free rainbow pistol

RSVP Here, or on the book of faces.

Aeromech

Jesse

Errol

Van

Devil + like 2

Jboynerf

Watch out for DX

Zack the mack

Nerfgeek

Alphatrooper


Definitive Guide to 3D Printing

05 June 2016 - 02:41 PM

FOREWARD

This guide is in response to the several emails per month I receive about 3D printing, and it is easier to throw everything out there once than having to regurgitate the same information a dozen times to as many different souls. People unfamiliar with the art seem to forget that it’s not magic, and it’s not the end all answer to your homemade nerfy engineering problems, so whether you are on the fence about getting your first printer, have some ideas about a new groundbreaking 3D printed blaster, or have your own printer and need some advice in parts design or printer settings, here is a condensed summary of all my experiences to get you started. Please keep in mind the information presented here is nothing new, you can google most of this yourself and find similar results, I've never been able to find a single source with all the information I present here; I am no expert, but I do print a lot and have found a nice set of guidelines I like to follow. So think of this more like a noob’s guide to 3D printing. Chime in with your experiences too, everyone’s mileage is a little different.

 

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1. BEFORE YOU BUY

1.1 Things to Consider

Think about your hobbies outside of nerf, how often you will realistically use your new toy, and what other applications you will (read WILL, not COULD) use the printer on. The printed products are often unsightly in their monotone colors; they will not impress your non-techy significant-other and are not really suited for furniture grade applications, however, I have printed cupboard hinges, light fixtures, and small statues with mine, and myriad other non-stress-critical applications are good places to use a printer in your everyday life.

 

1.2 Types of Printers and their Specifications

These consumer requirements that you have identified will lay the foundations for the specifications of your printer, most notably, the size. There are two figures to keep in mind here. Firstly, the printer dimensions. Self-explanatory, the physical space the printer will occupy on your desk, table, workbench, etc. The second is the print volume. This one is a little bit trickier and will vary based on the type of printer. “Delta” configured Printers will have a print volume that is shaped like a cylinder, and the print bed will be shaped like a circle. Most other types of traditional 3D printers, sometimes called “gantry” or “X-Y” printers will have a print volume that is box-shaped, with a rectangular shaped print bed.

 

1.3 Types of Printer Filament, the “Ink” to your printer

The two main types of print materials are ABS and PLA, sold as rolls of filament. Basically the “ink” to your printer, and each type has its’ own benefits and drawbacks. I print exclusively in ABS, mainly because of the relatively low melting point of PLA, and I am wary of the spooky materials sciences surrounding plastics as they approach glass transition temperatures. PLA transition temps is 70-80 °C, where ABS is 220-240°C. Read: you are probably fine with PLA, but I just prefer to be on the safe side of things, coming from a region of hot, humid summers. So this guide will focus mostly on printing with ABS.

 

This being said, ABS is a pain to keep under control. It likes to be kept very hot and requires the use of a heated bed and adhesive to keep it stuck down while printing, seen below. Most materials, thermoplastics in particular, like to shrink when they cool down. Essentially, as the top layer of ABS cools on top of a layer that is already hardened, the top cooling layer acts like a flexing muscle, and as it shrinks, pulls up the layer underneath it. This phenomena leads to “curling” of the ABS, causing the edges of a printed part to peel off of your hot bed, and may cause delamination between layers, i.e. the separation of the layers mid-print. No bueno for stresses. We’ll get into the engineering a little later. Additionally, ABS carries more odor with it than PLA. Not necessary a bad odor, but one that you’ll have to get used to should you print in an office or something. Below, you can see the ABS on my part curling up from the bed. The glue was 2 weeks old and I forgot to wash and reapply the glue properly. Luckily, this is only a prototype part and it's not going to be going on any blasters long-term.

 

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For PLA, a hot bed is not absolutely necessary (but still recommended), and because of its’ low melting temperature, is less likely to curl up on you, and produces less odor than ABS, but I’ve heard it is more likely to jam up in your printer, so maybe a little bit more of a maintenance hog. It is also more environmentally friendly than ABS, as it is made from plant based oils. I have far less experience with PLA, so someone else that uses it is free to chime in.

 

1.4 The Shit Nobody Talks About

There are so many drawbacks and inconveniences to 3D printers, and I will mention a few here and go into depth several of them in this novella. For one, TIME! I am printing a receiver for Nerf magazines for a PCSR variant, I’m only making it as a prototype, yet this 4 x 4 x 3 part is going to take 12 hours to print and it’s only a prototype part 4 layers thick! Damn, there is almost always a better way to do things than 3D printing unless your geometry is incredibly complex.

 

SMELL! ABS smells up your room. SOUND! I need headphones/earplugs to be able to sleep at night any more if I make any overnight prints. TEMPERATURE! If your print room is cooler than like 80 degrees, your prints will tend to delaminate and peel off the bed. TROUBLESHOOTING! DIY printers means DIY fixing. If parts break, you have to take the initiative and reverse engineer some of the parts/ go back into the manual and figure out what’s wrong. This experience was a crash course in electronics, mechanics, and stress application. Luckily the Rostock has a great instruction manual. LIGHT! If printing at night, the display is backlit and I have yet to modify my code to turn it off. SAFETY! We’ll get to that in a minute.

 

1.5 Pricing

All of these factors, maximum temperatures of the hot-end, type of printer, size of printer, the inclusion of a heated bed, will all affect the cost of your printer. I have seen some for as cheap as $200. Some are as expensive as $3000 for consumer models. Some are pre-built, other have some assembly required or come as kits, and hell, if you are good enough you can literally build your own from zero (Read: You probably aren’t good enough to build your own from zero.) I chose the Rostock Max V2, a kit-build, with everything included in the box, just nothing put together. The wiring, mechanical assembly, soldering, tuning, and troubleshooting, and troubleshooting, and troubleshooting was all left to me. If you want a fun project, and are confident in your building/tinkering skills, I say go for it. If you just want to get printing already and can’t be bothered with the VERY likely screw-ups of DIY, then a pre-built one might be the way to go. Market price for my printer is $1,000 for the kit, but because I put it together myself, I have the print volume of a printer twice as expensive.

 

Being builders of homemade blasters, most of us reading this are probably very mechanically minded individuals. If electronics and software aren’t your thing, I’d say don’t worry too much. If you have a kit build, read through the instructions and jot down any questions you have, find community resources, reach out to the company, google how to make proper connections, etc. I had no problems with my Rostock instructions, they were very thorough. As for software, it is my understanding that most kit builds operate on software that can be downloaded from a community site. For my printer, I didn’t write a single line of code! It was downloaded from an open source webpage for 3D printers.  This will probably be the case with almost any other kit or pre-built printer you come across.

 

One last thing to consider is the community of people surrounding your printer. Is the company reliable and trustworthy? What do the reviews say about this printer? Are experiences generally positive? What do these guys use theirs for? Feel out the market for something you like.

 

It’s all very specific to each person and is a decision that is ultimately your own to make. This is where I cannot help you. Research the shit out of printers and find one that you like. Hell, go on craigslist and see if you can get a used one for cheap. Fixing a broken printer or building it from a kit really gives you an idea of the things’ personality. It’s hard to explain. But it feels right.

 

 

2. THE GOOD STUFF

2.1 Terminology

I guess now would be a good time to introduce some of the common vernacular we use round these parts, if things weren't technical enough for you yet.

 

Below is a half-finished part that I hang on my wall to demonstrate some of the physical phenomena of 3D printing. I have referred to "layers thick" a few times already, and this is precisely what I am referring to, more correctly called "perimeters". Generally, the more perimeters you have around the outside of your part, the sturdier it will be. You can actually count the number of perimeters I have here, This one is 6 layers/perimeters thick. When I say "layers thick" this is what I mean, as opposed to "layers tall" or how many individual, horizontal layers make up your part (the number of cards stacked up in your deck).

 

The second quality to note is all the cross hatching hexitriangular nonsense you see in between the perimeters. This is called "infill" and basically allows for the print to be completed faster than if it was a completely solid part, and still keep the finished product relatively strong and lightweight. The infill basically forms many little "tubes" that follow the layers vertically upward, the view you see below is a "top" view, so the print bed was originally on the underside of this part. Not much to say here, except I like to keep my infill about 40%. This means 40% of the inside volume is occupied by the infill filament, and the remaining 60% is air. You can go anywhere from 0 to 100% infill, but at some point diminishing returns kicks in, and I supposed if you wanted to make a totally hollow part that's how you could do it.

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My Rostock is a delta style of printer, so these next parts may not look exactly like they do on other printers, but the principles and functions are identical. Below is a photo of the hot-end printing a part, now using green filament. The "hot end" is the general name for the entire assembly that heats up the solid plastic filament to a hot and sticky goo. That whole big thing. The nozzle is the tiny little brass thing at the very bottom making contact with that part that lays down the next layer. Those wires you see are hooked up to two heating resistors buried inside the hot end that heat the whole thing to 235 °C. If you've ever hooked up a resistor to a battery, you know it gets hot. Same idea here. All that orange cellophane looking stuff is actually a special heat resistant tape called Kapton. Keeps everything in place and doesn't melt until like 400 °C or something ridiculous like that. 

 

IMG_20160607_124941_zpscdlof2lw.jpg

 

2.2 Design of Parts

So you have your printer and now it’s time to design your own parts. This step is optional, if you just want to spit out pre-made parts there’s nothing wrong with that, but this is my hobby and I’ll cry if I want to. Good parts design is crucial to having printable components. I use Autodesk Inventor and save parts as their solid parts, as well as .stl, this seems to be the format that 3D printers like.

 

Remember that 3D printing is really just like stacking a deck of cards, one by one. Each card is only a few thousandths of an inch “tall”, but several inches long and wide. One card placed on a table is almost two dimensional. Stack 52 cards on top of each other, and look at that, you have a tangible 3D rectangular prism shape! Think of each card as a “layer” of the print; it may not be a rectangular shape, but you get the analogy.

 

Each layer is supported by the layer underneath it, or at least that’s what we are shooting for with parts design. I’m going to give you some examples of good and bad parts right here.

 

Let’s say I want to make this bracket shown below, measuring 3 inches tall, 3 inches wide, and only 1 inch deep. Is this a good orientation to print it? I.e. should the face currently on the bottom be what’s touching the hot bed?

 

bracket1_zpsu4pcpnfm.jpg

 

No. mostly certainly not. The Top-Left arm is not supported by anything underneath it. Remember the deck of cards analogy, now imagine each card is not rigid, but rather made of jelly. Each card is supported by the layer beneath it. With nothing to hold up that first layer of the bottom of the arm, the hot filament will fall right to the ground as it exits the hot-end. It doesn’t cure instantly, in fact the filament takes several seconds to fully cure/harden/cool. Like squirting elmers’ glue out of the bottle, it becomes a solid eventually, but it takes some time to get there first. Our “glue” dries faster, but it is still essentially a liquid when it’s squirted out, all the same. My rule is that every “arm” like this must have a lower face that is at least 25° away from horizontal. I think Kane’s rule is 45°, like I mentioned, everyone’s is different.

 

So we have two options here: Fix the part by applying the rule I mentioned above, or change the orientation of the part so another face is touching the hot bed. I will opt for the second one this time around…. So is this part “printable”?

 

bracket2_zpsaslxqnsz.jpg

 

Hmmmm, I’d say it’s better but still not ideal. The channel on the bottom left part is left unsupported again, and will probably sag or produce a sloppy couple of layers. The circular holes shown typically aren’t as problematic because even though they are technically unsupported from directly below, they sort of build up to that point of being unsupported, and much like an arch bridge, provide enough support while it’s being printed to be not of major concern until the diameter exceeds maybe 2 or 3 inches.

 

So what do we do here? There are two options: Either change the orientation again or allow the use of support material on you printer software. I don’t like support material mainly because it seems to promote the use of poorly designed parts rather than making parts that are honestly better and stronger to begin with. Plus, it adds more steps to the end process of finishing off the parts, and leaves jagged or pointy bits that are uncomfortable and unsightly.

 

On this next orientation change, again we are left with some options. Either rotate the part again, so the channel is vertical, (which would work because it’s now essentially a circular hole on the top that will be supported well enough as previously mentioned,) or turn it on its’ side. This second option is probably the better one. Why? Well if each layer is only 0.2mm thick, the general rule is that it will always take longer to print vertically than horizontally. So if you can keep your parts short, keep your parts short. Let’s turn it on its’ side….

 

bracket3_zpsge3uk8ry.jpg

 

This is probably the best way to print this part, with one last little change I want to make. The first layer of your print is the most important, as a good bottom “bed” layer will ensure the best adhesion to the bed for the duration of the print. Small little details are not usually good for this, as they are likely to get knocked off during that crucial first layer of print. What I usually do for complex pieces is make a “raft” for the part that covers all the holes and smooths out the bottom face of the part. Below, all I’ve done is drawn a square bottom to the part and extruded it 0.030 inches, or about 4 layers. This is easy enough to remove with a knife or drill bit for the holes, and makes sure there is good contact with the hot bed. It adds some time to the print, but it helps with adhesion and therefore final quality in my experience. In short, the first layer of your print should always be kept SIMPLE. No holes, no weird wavy or jagged geometries. Keep it simple. A square, a circle, a rectangle.

 

bracketfinal1_zpslq4ejog7.jpg

 

Another thing to keep in mind is the size of the part, or thicknesses of peninsulas on each layer. For example, the part shown below has a crack about midway up the far wall, because it is only about 1/4 inch thick at that point. Thin walls have the same tendency to curl up, but don't have the interlayer surface area to hold the top layer down like thicker layers. Something to keep in mind while designing, and just another reason 3D parts often look blocky or bulky. Also, a crack is visible on the close wall, right at the transition from angled to vertical where the magazine will eventually sit. This is due to a sharp angle transition, even one that small leads to a big stress concentration. This is why it's a good idea to make "prototype parts" first, that will print faster than the final part, and will reveal weaknesses in the design that may not have been apparent initially.

 

20160605_182541_zpsuowg1fmq.jpg

 

2.3 Principles of Engineering

Good parts design is essential to parts that aren’t going to fail in the field. I can tell you firsthand that just making the part a few layers thicker isn’t always going to solve your problems. The first generation of pullbacks were embarrassingly not up to the task of full on outdoor nerf wars. That being said, these failures have taught me a good deal about the weaknesses of 3D printing, and the amount of working around you will actually need to do to make a sturdy and robust part.

 

The first thing to remember is that these are literally individual layers that are sort-of-not-really adhered together. The filament extruding from the hot end never gets to a truly molten state, and rather just reaches a sort of glass transition temperature. The filament while being extruded gets squishy and sticky, but the layer beneath it is still fairly cool. A chemical bond is never actually formed between the layers, and the rule of thumb is that the 3D printed strength of an item is 30 percent that of an extruded/ injection molded part. Yeah. Less than a third of the strength. This is where people seem to have issue. 3D printing is not the golden goose egg to homemade blasters. Like a drill press, or a scroll saw, or a belt sander, it’s just another tool, and you don’t NEED any of them to make a banging Christina Hendricks (or Chris Hemworth, depending on your mood) homemade. Don’t forget that. You can’t just print anything you want willy-nilly. Go ahead, try to print a sentinel shell or something. It will literally fall apart. This is why the printed blaster parts we are familiar with are often thick or goofy looking. They NEED to be that way to even be a fraction the strength of their counterparts.

 

Morever, think of the stresses on the part. The interlayer surface planes will always be the weakest link in the part. Pulling apart the layers is pretty easy for example (tensile stress), but the parts handle COMPRESSION stresses very well. I’ve actually printed a set of longboard risers which are holding up with no problems because they are sandwiched between the metal trucks and the wooden deck, and are always in a state of compression. The PCSR catch shown below holds up well because the interlayer forces are largely compressive with a bit of shear. Reason out the stresses. Draw a free body diagram if you need to to visualize the forces. FEEL the stresses in your parts. An extra five minutes on paper will save you like seven hours on the print.

 

20160103_111138_zpsejgghqlz.jpg

 

Think about the bearing stresses too. The force that occurs when a screw or bolt or rod is put through a hole in your part. It’s going to want to split your layers apart, whether pushing apart the layers like an axe, or prying them apart like a crow bar. Distribute these stresses wisely. Think 4 screws are good enough? Use 6 or 8. Be generous with your factor of safety. If your stresses are directly in line with tensile forces, there is a good chance that your part will be overstressed. If you have high stress components, either print the layers at an angle to the forces (to mix shear and tensile stresses) and ensure all your sharp corners are rounded out. Filet everything you can get away with. Sharp corners are particularly pronounced in 3D printed parts. Layers will almost always separate on a sharp transition. That first example we did REALLY should have a quarter inch filet on that inside corner….

 

bracketfinal2_zpsi3nkvxku.jpg

 

That’s better. Additionally, below is a comparison of the original pullback handles, with the mk V and up handles, with gradual filets on the inside corners, and a completely redesigned shape, with layers printed 8 degrees offset from the normal of the applied forces. Left is old, right is new.

 

handle%20comparison_zpsaqwmasc8.jpg

 

 

3. PRINTER SETTINGS AND SUGGESTIONS

3.1 Technical Stuff

To reiterate, I use a Rostock Max V2 Delta style printer. My hotbed is borosilicate glass coated with 1-2 layers of purple glue stick glue, applied when the bed is cold. Wash this off with glass cleaner and replace with new glue every 6-8 prints, or whenever the ABS starts to peel from the bed. This hot bed is typically set at 108. Anything below this seems to peel off the bed too easily during printing. My hot end is a 0.5mm nozzle set to 235. Anything below 225 seems to result in delamination, or peeling, between individual layers, something that is highly unwanted in stress bearing components. EDITTED 9/26 for better results.

 

To combat delamination, I recommend the use of an enclosure. This can be as simple as a box made of wood or plastic, or a large storage container retrofitted with a small window and door. For enclosure heating, I have used incandescent light bulbs that I scrapped from an old desk lamp, and integrated these into the enclosure. There are certainly better heating options, but incandescent bulbs are cheap and can be found almost anywhere, and provide enough heat for my purposes. The enclosure doubles not only as a means of keeping heat in, but keeping the cold out. It suppresses the noise of the printer somewhat, and blocks the cool air of a fan or air conditioner or an open window which may provide inconsistent or accelerated cooling of your print layers.

 

I use Matter Control as my printing program. I print a MINIMUM of 8 layers thick on all components using the aforementioned 0.5mm nozzle, with an infill of 40%. For stress bearing components such as the Pullback under stock pull-bar, I use 10-12 layers thickness, and for rainbow catches, I print at 100 layers thick, to make sure that there is total fill on each layer. Speaking of, my layer height is 0.20mm. Smaller print layer heights have the problem of curling up on overhanging geometry, such as the back end of pistol grips, but once again, everyone’s experience is different. It’s always better to print a few more layers and wait a little longer, than rush the print job and have parts break on you in the middle of a war. Printing more layers will make your parts stronger, but if your part is poorly designed, it will merely be a bandaid on the problem.

 

For components with screw-holes, invest in a tap wrench with appropriate tapping bit. Tap the first ⅔ of the hole and let the screw tap the rest itself. This gives you a good adhesion to your part while preventing the part from splitting. If your part begins to delaminate or split, and you cannot be bothered to print another, I’ve found it best to apply some superglue or epoxy to the damaged area.

 

3.2 Community Input

Meaker suggests not to run PLA and ABS through the same nozzle or printer. This makes sense. If PLA melts roughly 150 °C lower than ABS, any ABS chunks left in a nozzle from previous prints would remain solid, and block up the printer.

 

Draconis recommends using ABS pipe weld to repair ABS parts. I've never tested this before but this really seems like a good idea. I just hope the results don't mimic those of acetone. Again, everybody has a different experience with this stuff, and I'm only here to point you in the right direction if I can.

 

3.3 Safety

You're working with really hot things. Should be obvious but don't touch the hot end or the bed. Even if you turned it off, it stays hot for a couple of minutes. Don't be an idiot.

 

Everything I have read suggests that 3D printing is overall safe. I understand tiny nanoparticles are produced, as well as a negligible amount of hydrogen cyanide. As it stands now, I largely ignore these issues, but you shouldn’t. A good idea is to print in a well ventilated area, in a relatively large room, windows open, that kind of thing. My eventual goal is to have several printers running in tandem in a large closet or enclosure with a proper ventilation system, ducts with fans directing air out of a window would not be something difficult to accomplish, and would be rather modular when I get my first apartment that would not take kindly to me tearing out walls. When I have a proper workshop, ventilation will be a real thing.

 

Fire safety is the real big deal. Google 3D printer fires and things get not-so-pretty. Again, my ideal long term setup is to have a simple Arduino controlled CO2 fire combat system within said enclosure to starve the fire. If you are not a mad scientist by the light of a full moon, there is another product for mortals to invest in that already exists on the market. I have yet to test it out, but it seems like a good idea. It’s called smoke signal; I’ve linked it at the end of this article, and I will make a review once I have it properly installed. It only shuts off printer power, and doesn’t actually put out a fire, but it does prevent the spread of an electrical fire. In conjunction with a CO2 flood from the aforementioned system, this could be a very effective tool in fire prevention.

 

All this being said, do not leave an active printer unattended! Always be within earshot of your printer, and if nothing else, stick a 5 dollar smoke alarm to the top of your printer! It may just save more than your new toy.

 

 

4. THE END

Have more to add? Leave a comment and I’ll add it in. If I ever receive a nooby 3D printer question I will respectfully refer you to this article to read in it's entirety. Think some advice is faulty or inconsistent with your own experiences? Write it in a comment. Think this article sucks? Roflcopter spend 6 hours of your weekend and write a better one. Anyway, thanks for the read and putting up with my dry humor.

 

Nerf on you beautiful technologists and engineers and tinkerers and athletes and artists. I hope this helps you in some small way.

 

20160226_225738_zpsz53z1aib.jpg

 

-Aeromech

 

Additional Information Provided by:

Meaker

Draconis

 

Resources

ABS vs. PLA

http://www.protopara...r-3d-printing/]

 

ABS tips

https://www.matterha...inting-with-abs

 

Rostock Max 3D printer Instructions

http://download.seem...-2ndEdition.pdf

 

3D Printer Fire Prevention Device

https://3dprint.com/...-3d-print-fire/