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#338573 Need some help

Posted by roboman on 30 April 2014 - 03:16 PM in Homemades

Gears is correct. Amazon carries the rails - they're between $7 and $10 or so, and ship free with prime if you have it. The longer mount is for a 9 slot rail, the shorter one is for a 7 slot. If you'd like, I can print you new ones with standard picatinny rails that don't require the MOE rails. The reason those ones are set up the way they are is because I was supplied with the rails beforehand.

Note that I don't currently have black filament and if you want them to match, you'll either have to paint them or wait for me to get black filament when I get back home for summer break in a couple weeks. I can only imagine that the grip and stock plate are painted; I've never printed anything in black except for the rail mounts, and those were on Lucian's printer the night before Apoc. Also, I can replace that stock plate for you, if you'd like. At the time, I didn't realize how low the density was on the Stratasys printer, and now that I have my own, I can make much stronger things that don't take forever to print.

EDIT: Oh hey, my PM inbox was full. Sorry about that, if you were trying to contact me before, you can do it now.



#338351 Homemade 35 mag holster

Posted by roboman on 20 April 2014 - 03:44 PM in Homemades

Very nice. I love seeing the process behind projects like these.

This seems like the kind of thing that would lend itself very well to vacuum forming. MAKE Magazine had an article about doing it at home with an oven and a shop vac a few years ago. I know Lucian tried it with a SS2 shell, but it couldn't hold the detail necessary for a good imprint of the shell. I think a shape like this could work really well, though.



#338313 Homemade 35 mag holster

Posted by roboman on 19 April 2014 - 05:48 PM in Homemades

That is awesome. What did you use to make the form for the fiberglass - did you just alter the broken drum, or what?



#338206 Homemades Picture Thread

Posted by roboman on 12 April 2014 - 07:59 PM in Homemades

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The printing is going well.



#337924 Homemades Picture Thread

Posted by roboman on 31 March 2014 - 04:12 PM in Homemades

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Progress on the new LpLs. I'll edit in pictures of the other two that are bent and ready to go in a bit.



#337798 Any Nerf people here in So Cal?

Posted by roboman on 28 March 2014 - 10:46 AM in General Nerf

This is the more current SoCal Facebook group. We primarily use the group for event invites, as the page didn't allow that at one point. As you can see, it's not terribly active.



#337796 Question about airgun fittings

Posted by roboman on 28 March 2014 - 10:35 AM in General Nerf

Pneuaire has an insanely cheap line of "economy" push connects. Do not apply anything to the tube before you insert it into the connector, or you run the risk of ruining the fitting.

I've used both barbed fittings and push connects, and I vastly prefer push connects if I have space available for them. It's very hard to get a leak-free connection with a barbed fitting if you're not using a tubing clamp of some sort.



#337499 Homemades Picture Thread

Posted by roboman on 14 March 2014 - 11:22 PM in Homemades

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I updated the LpL model so it's MUCH stronger now. The sideplates are a single piece of bent sheet metal that includes a brace at the front to take most of the load off of the front screws and distribute it more evenly through the plates. The rear block also takes advantage of the pockets in the plates and has a series of bosses that engage the pockets to improve the overall strength of the design. The sideplates are now .063" thick 5052-H32 aluminum, and will be either waterjet or plasma cut, and then bent on a brake.

I added two ribs in the catch pocket to lift the catch plate off of the surface and minimize the sliding friction. That should help reduce the trigger pull.



#337080 Plusbow prototype

Posted by roboman on 16 February 2014 - 01:09 AM in Homemades

Yeah, I've got a few that aren't on anything right now. If you want one, PM me or something and we'll work it out there.



#337077 Plusbow prototype

Posted by roboman on 16 February 2014 - 01:03 AM in Homemades

Yeah, it's a 4800 lb CNC mill, and I'm also going to have to have 220V 3 phase run to the other side of my house from the breaker box, so it's gonna be interesting.

I do, it should be in that dropbox folder. Here's the link again if you don't have it. I think it's called "grip.sldprt" or something along those lines.



#337075 Plusbow prototype

Posted by roboman on 16 February 2014 - 12:44 AM in Homemades

That bridgeport isn't nearly as nice as any of the Haas stuff, but it'll be nice to have a VMC in my garage when I'm home for vacations.

OnlineMetals is fantastic, and their prices are around half of what McMaster charges. Shipping is pretty reasonable, and their custom cuts are never undersized. They were my main supplier prior to Max Industries, the place I use now. Unfortunately, Max doesn't ship, so I have to have my dad pick it up and mail it to me in a flat rate box, though that's still cheaper for me than any other supplier in existence.

Good luck with that, though. You'll be standing in front of that machine for a long time. Those Mini Mills are pretty sweet, though, and ST-10s are production turning centers. There's one in one of the shops at RPI, along with a Super VF-2, TM-1, TL-1, and ST-10 (and a bunch of other Haas stuff all over campus, including a VF-5 in the physics building for no apparent reason - it's big enough to fit a small sedan on the table). I use 6061-T651/T6511, which is less gummy than normal T6.



#337072 Plusbow prototype

Posted by roboman on 15 February 2014 - 11:13 PM in Homemades

Interesting. My high school had two TM-1s and two TL-1s, though I ran all of my pumpbows on a 1989 Bridgeport Interact 412X with a Fanuc O-Mate control (which I might be buying from the community college within the next year or so at scrap metal prices).

Do yourself a favor and don't buy metal from McMaster. At least use Onlinemetals.com, if not a local supplier. I get my aluminum for about $2/lb after all of the discounts they give me, both because I'm a student and because I got to know them really well over the last year and a half. A few years ago, before I knew about my current supplier or OnlineMetals, I quoted the material cost for an aluminum plusbow on McMaster, and it came out to a little over $100 worth of stuff. 1/8" aluminum sheet is currently about $25/square foot on McMaster, which is absolutely ridiculous. It's about $14/sq ft. on OnlineMetals, and it was $11 for a custom cut sheet that fit 4 sideplates with enough room for my fixturing on the sides at my supplier (somewhere around 14" x 12").

By the way, assuming a $50 material cost per blaster, you're looking at $7.50-$12.50 per hour, which really isn't that much when you consider how much work you're doing.

I really hope you know how to use both that mill and MasterCAM (or whatever CAM package your school uses) very well. It is not a small undertaking to optimize that setup for machining. You're going to need a fixture plate of some sort (or you'll have to pull the vises off, put a spoil plate underneath your sheet, and use strap clamps).



#337069 Plusbow prototype

Posted by roboman on 15 February 2014 - 10:29 PM in Homemades

I see. How long do you expect each blaster to take to build, and where are you getting your materials from? I'm asking mostly because I'm concerned that you haven't completely thought this through. Each of my pumpbows needed about 2 hours of CNC mill time, ~$30 in materials and parts, and many more hours of post-processing (mostly cross-drilling and wire brushing), manual lathe work, and assembly. That's why I'm not making any more after I finish the 16 that were commissioned. In my case, they paid for a trip to Apoc, a 3D printer, and a semester's worth of gas, but I still didn't even come close to making a reasonable hourly wage for the work I did.

And yes, I understand that. What kind of equipment is it (make, model, etc.)?



#337066 Plusbow prototype

Posted by roboman on 15 February 2014 - 10:09 PM in Homemades

The design just doesn't flow well. The lines aren't very clean, and you've got a bunch of different angles that clash with each other when they're stacked, specifically near the grip. Don't let the triangular pockets cut into the outline of the sideplates unless you absolutely have to. I did so on mine to provide clearance for the pump grip.

How do you plan on machining these, and what's your price point?



#337035 Plusbow prototype

Posted by roboman on 14 February 2014 - 10:45 AM in Homemades

I'm not really sure why you put sideplates on this thing, as they don't appear to be doing anything at all. The whole point of using them is to bear the load caused by the plunger head impacting the bushing, since a thinwall polycarbonate tube can't do that very well. It's probably a good thing that those plates aren't under any significant load, though, because you took out an awful lot of material from them, and I'm not inclined to believe that they'd hold up well over time. I'm glad you added the internal radii to the design you posted most recently.



#336781 Help with springs!

Posted by roboman on 01 February 2014 - 12:10 AM in Homemades

507 Mechanical Movements is a really good resource for that kind of thing. You're gonna wanna go past all of the pulley-based stuff, obviously, unless you want a block and tackle on whatever you end up building. Take a look at the toggle mechanisms for punches, like #140, among other things.

Keep in mind, of course, that whatever you build will have to be beefy enough to stay together under the force of the spring (and the impact when you release it), and your plunger will have to be pretty big to make up for the short stroke.



#336779 Help with springs!

Posted by roboman on 31 January 2014 - 11:49 PM in Homemades

Well, you can figure out the spring constant with F=kx, where k is the spring constant (lbs/inch, in this case), F is the force exerted, and x is the amount of deflection. If you divide 8 lbs by .2", you get 40 lbs per inch, assuming your measurements are accurate. That means that at full compression (3" deflection), the spring load is 120 lbs, which is almost certainly too heavy for you to prime without a system that provides a bunch of mechanical advantage.



#336464 Homemades Picture Thread

Posted by roboman on 12 January 2014 - 03:58 PM in Homemades

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Just a little something I threw together in SolidWorks because I'm waiting for the die casting quote for the 2K tanks...

This is an "afterburner" as people have been calling it. It's got the same size flywheels and spacing as a Stryfe, but with 280 sized motors (way more torque). The motors are custom-spec'd at 25,000 RPM and 12V, though I'd like to see about getting even faster ones. The idea is to have something that someone with absolutely no experience can attach to any N-strike blaster that has the quarter-turn muzzle for accessories. It's got a built in battery tray for 4 AA-sized cells (ideally trustfires or something with a ~3V nominal cell voltage).

It's designed to be 3D printed for now, but I'm going to try to take it further and have it manufactured overseas if there's enough interest, since it seems like the kind of thing that could be incredibly useful for HvZ and other wars that only allow stock darts and/or lightly modded blasters. The CAD is mostly complete, and is just missing the channels for routing the wires, a switch mount, and caps for the back ends of the motors. After I build a prototype of it, I'm going to make a different model that's optimized for injection molding and take it to a company that I found that does low-MOQ molding. I'll probably start a Kickstarter for it at that point, since I obviously can't fund it on my own, and I'd like it to reach as broad of an audience as possible.



#336333 AT2K goo gauge removal

Posted by roboman on 05 January 2014 - 03:18 AM in Modifications

The diaphragm in the 3K goo gauge has much more surface area and is roughly the same thickness, so it takes much less pressure to rupture it. I left the gauge in the 2K primarily out of laziness.

Yep. Whether I go forward with the die casting or not depends on how much they charge me for the first run.



#336331 AT2K goo gauge removal

Posted by roboman on 05 January 2014 - 02:52 AM in Modifications

Honestly, removing the goo gauge isn't really all that necessary, at least in my experience. I was using stock tanks for quite a while, even after I started selling the aluminum ones, mostly because I couldn't keep up with demand and didn't have time to make one for myself. I think I drained one goo gauge out of the ~7 2Ks I've used in the last 5 years or so. Usually, other things tend to break or develop leaks before the goo gauge will, even if you're using it around 7 pumps like I usually do. If you do plug it, a hot glue plug will be more than adequate at 5-6 pumps.

Also, you may be able to get an aluminum tank sooner than I thought, and a better one than the ones I was selling previously, depending on when I get the quote back from the die casting company and how much a run of 100 part sets is. The new ones will have a #10-32 UNF female port on the back cap, so you can use standard tube fittings (like quick connects) instead of hose barbs that have all kinds of problems with leaks if you don't use a hose clamp. If it goes the way I'm hoping it will, I'll be posting in the next week or two with more details about that.



#336218 Homemades Picture Thread

Posted by roboman on 01 January 2014 - 12:32 AM in Homemades

So I did some stuff in the last few days.

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Started on the first 5K tank. My lathe threw and ruined the back cap when I was working on the last step of it, so I decided to quit for the night and haven't had a chance to work on it since.

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I got to set up a brand new Haas TM-1P today at the community college that I worked at for the past few summers and christened it with a maximizer bar for NoM, since I managed to leave his in my dorm room when I left for break. It still needs to be cleaned up a bit on the wire wheel, but it turned out pretty nice.



#336177 I reproduced Stampede ECS gears, and "hello"

Posted by roboman on 30 December 2013 - 08:00 PM in Modifications

It'll be interesting to see how they hold up against higher loads. I was looking into having a run of sintered bronze or steel gears done through a manufacturer in China, but if urethane gears work with heavier springs, that would probably be significantly cheaper.

Those are some really nice results, by the way. Did you just use the typical silicone RTV mold?



#336153 3 round burst electric Nerf gun

Posted by roboman on 29 December 2013 - 08:34 PM in Modifications

Roboman is working on something along the lines but running into issues with the nerf wiring controls. Your best bet is to pm him.


I just picked the wrong transistors for the job, and the PCB trace widths are too narrow to handle the current. The boards should still work, but may not be as reliable as I'd like. Expect more progress on that when I get back to school.

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This is the schematic, for reference. It's a 555 configured as a 1-shot timer with 3 selectable delays.



#336152 Questions about batterys and the rapidstrike

Posted by roboman on 29 December 2013 - 08:07 PM in General Nerf

I am using this battery pack My link

That should be fine.



#336150 Questions about batterys and the rapidstrike

Posted by roboman on 29 December 2013 - 07:54 PM in General Nerf

That mostly depends on how fast you want it to shoot. At higher voltages, you'll have a harder time controlling how many darts you shoot when you pull the trigger. The general consensus seems to be that a 3 cell LiPo (11.1V nominal) is right around the point that it is too fast to easily control. If you're running a 2 cell pack (7.4V nominal), you'll probably be fine if you connect the flywheels and pusher motor to the same pack.



#336093 Homemades Picture Thread

Posted by roboman on 27 December 2013 - 03:38 AM in Homemades

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5K tanks are finally happening, for those of you who asked for them long, long ago. If you've asked me for one in the past, the price I quoted at the time is still valid. For any new orders, they will be $80 + shipping, because they're looking to be a royal pain in the ass to make.

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That's 3' of 2" diameter round stock. I've got enough 5K tank stock to make far more tanks than have been ordered, but I don't have the time to make all of them before I go back to school.



#335903 M.O.A.R. N.E.W.T.O,Y.S. SoCal War January 4th in Corona

Posted by roboman on 11 December 2013 - 09:45 PM in Nerf Wars

I may have something on the 28th, but I certainly have stuff on the 4th. I'll do what I can to make it out there, though.



#335674 Modification and Paintjob Pictures

Posted by roboman on 27 November 2013 - 10:51 AM in Modifications

The first three rapidstrike control boards arrived.

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As Azrael brought up to me, some of the current-carrying traces are a bit small, and the SOT-23 transistors may not be able to handle the current consumed by the pusher motor. As such, none of these will be sold - they're just prototypes so I can see what's wrong with things.



#335649 U.G.L.Y. S.W.E.A.T.E.R. Jan 25th

Posted by roboman on 26 November 2013 - 07:14 PM in Nerf Wars

I'm down to go if I can figure out how to get there (basically dependent on how much money I have for a train/bus ticket at that point in time). I would need lodging if you guys are willing to provide it to me.



#335507 Help with springs

Posted by roboman on 17 November 2013 - 12:09 PM in Homemades

What you have to realize is that k changes when you change the free length. The force at full compression of a spring is directly proportional to the ratio between the free length and the active coils. Cutting down a spring doesn't change this ratio, so you get the same max load for all lengths. See this thread I started a while back.

~T


Note that I did actually mention that, and that the second half of my response discussed that. I did not realize that it was directly proportional, though.

EDIT: It has been brought to my attention that OP was looking for power, not force. Power is force over a period of time (or the integral of force with respect to time), so a shortened [k26] will not exert the same amount of power, though it does have the same maximum load when fully compressed. It would not be terribly difficult to find the necessary spring to get the equivalent power of a [k26] with a shorter stroke if you know all of the forces acting in opposition to the spring (friction, inertia, etc.), or the velocity curve of the plunger as it travels through the plunger tube. You would, of course, also need to factor in the reduced air volume produced by a shorter draw, assuming that the plunger tube ID remains the same. So no, to answer one of your actual questions, it's not particularly easy to work that out.



#335495 Help with springs

Posted by roboman on 17 November 2013 - 12:02 AM in Homemades

Any length of [k26] will produce the same amount of power when fully compressed. 4-5'' of draw requires a 6-7'' [k26].

~T


Nope. Springs follow Hooke's Law, which states F=kx, where F is the force exerted, k is the spring constant, and x is the spring deflection. Full compression on a 6-7" long [k26] will not give you a force of 32 lbs. This thread discusses how to determine the force exerted by a shortened spring (since shortening the spring changes the k constant), using the constant that McMaster gives you (which is not the same as the k constant in Hooke's Law).



#335494 Modification and Paintjob Pictures

Posted by roboman on 16 November 2013 - 11:42 PM in Modifications

PCB layout for the select-fire Rapidstrike controller I'm working on. (I suppose this would be considered a mod)

Top:
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Bottom:
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Note that these are just the prototype versions. On the final ones, the silkscreening will look a lot better, since that's not really very readable. The first three boards have been ordered, and will be showing up sometime in the next 2-3 weeks or so. The boards are .64"x1.02", and can be tucked away pretty much anywhere in the shell. This style will require some soldering, but i'm working on a version that shouldn't, though it will have to be slightly larger to accommodate the connectors. I'm going to be soldering everything in a reflow oven, since it's all surface mount, which should let me produce these pretty quickly. This version will likely be around $20 with free shipping, while the no-solder one will be about $25 + shipping, because the connectors are both expensive and increase the thickness of the packaging. The boards will be that shade of purple, and all contacts will be gold-plated.



#335446 NIC Primary

Posted by roboman on 15 November 2013 - 04:39 PM in General Nerf

Also, in terms of deadspace, how is an RSCB that different from a hopper?


RSCBs have significantly more dead space than hoppers do, because there is more pipe and fittings connecting the outlet of the blaster to the dart tube and barrel. The do tend to feed more reliably, especially with longer darts, but you have to tilt them down between shots. They also work better than hoppers on blasters that have lower air outputs because the dart is seated in the barrel before any air is released, so you don't need a massive volume of air to suck a dart into the barrel. RSCB'd 2Ks work very well, and used to be very popular.



#335311 How to make plungers with perfect seals.

Posted by roboman on 09 November 2013 - 09:50 PM in Homemades

Maybe we should talk about the benefits of Stretch-to-fit shaft seals (aka skirt seals), ucups, and neoprene washers. What are the relative pros and cons of each?

-mike


I've been able to get consistently better performance out of skirts. U-cups have measurably impacted the performance of my springers - Hoongfu and Koree swapped a u-cup out for a skirt on one of the aluminum plusbows I built, and they managed to get a 40 FPS increase out of it. I've never been able to get a neoprene washer to work without massive amounts of friction, though I'm probably doing something wrong and don't really care to fix it, because 1-piece plunger heads make assembly wicked fast.

Skirts seem to have a smaller contact area than u-cups or washers, and they're made of a higher durometer rubber, so they deform less and tend to have less friction. Performance is also very much dependent on the batch of polycarb tube you receive - the listed tolerances are +/- .040" for the ID, which is a huge margin of error. You simply can't expect a homemade to perform well with a plunger tube that's .040" undersized, because nothing is going to work well as a seal without massive amounts of sliding friction. Unfortunately, there's really no way to avoid this if you're using polycarbonate tube from McMaster as a plunger tube, and I'd imagine PVC isn't much better, if it is at all.



#335089 How to make plungers with perfect seals.

Posted by roboman on 30 October 2013 - 01:25 PM in Homemades

Oh thank Roboman. This is quite helpful, I do have access to a lathe. I made a 3D model of your part for reference: http://www.thingiver...om/thing:174234

I have a couple of questions to clarify about this.

1) It looks like this is one whole piece. It doesn't come apart does it? If so I guess you can't adjust how much the seal is being clamped down. 0.325 height compared to 0.375 height on the seal is squishing it a little bit. Did you play with that height to improve the seal or does it not matter?
2) I assume you just stretch the seal over the head and to put it on, right?
3) Why is there so much distance behind the seal's backstop? You have half of an inch behind it. Is this to keep it stable and concentric with the plunger rod?
4) What is the diameter of the cone's widest part? I couldn't figure that out. Is it documented in there? I just guess 0.9*1.25

-mike


1) You don't need to clamp down on the seal with single piece plunger heads. You will get a perfect seal if you make it correctly. The thickness of the parts of the seal that actually touch the plungerhead is .325". There should be no squishing involved.
2) Yes.
3) It gives you more area to attach the plunger head to the rod. I like to cross-drill it and press a .125" stainless roll pin through the head and rod. It's permanent and the pin has a shear strength of something like 1200 lbs, so the plunger rod or head will fail long before that pin does.
4) 1.125". I guess I missed that dimension.



#335082 How to make plungers with perfect seals.

Posted by roboman on 29 October 2013 - 09:21 PM in Homemades

Also, NOM's aluminum plunger heads are made by roboman on his precision metal lathe.


They are indeed. You can't really make one without a lathe, which I'm assuming you don't have. If you do have one, they're not terribly difficult to make, and take about 30 minutes once you get good at it.
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Here's a drawing that isn't to any particular standard but should be good enough for anyone's purposes here.



#334972 Homemades Picture Thread

Posted by roboman on 24 October 2013 - 09:31 PM in Homemades

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New L+L design for a commission for Psyk.

The catch "block" is entirely 3D printed and makes up a majority of the blaster's structure, replacing all structural standoffs. The grip is a modified version of the design I used for the pumpbows, and is also 3D printed. All flat aluminum parts will either be waterjetted or CNC milled and subsequently sandblasted for a satin finish. The sideplates, catch plate, and catch cover plate are laser cut UHMW or ABS sheet. The top rail is designed to the MIL-1913 standard, and accepts all picatinny rail-compatible accessories.

STLs for those of you who want to try printing the parts yourselves will be up after I build the first one. A number of people have asked if I will be selling these, and I'll consider it if there's enough interest. This is simple enough that I should be able to build them very quickly, and I'd estimate that they'd wind up being around $80 + shipping.



#334759 Homemades Picture Thread

Posted by roboman on 13 October 2013 - 07:01 PM in Homemades

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Fairly certain I haven't posted this before. Tornadobow priming handle for ACNerfshop from a commission in early July. I don't really intend to make any more of these, other than for the two tornadobows that I'm building for Korned.

http://www.youtube.com/watch?v=g3QpOjrN_TA

Found some video on my phone of the machining process (second operation) and threw it on Youtube earlier today.



#334749 Any one intrested in 3D printed parts

Posted by roboman on 13 October 2013 - 01:27 PM in Homemades

I think that if you wanted to sell any 3d printed stuff that requires a seal, you should look into vapor polishing. Blasterparts.de sells a 3d printed centurion kit with a new barrel and mag adaptor that I think are vapor polished to make the seal with the dart. Just figure out a way to make a smooth surface like vapor polishing, or as you already mentioned, smash brass in the barrels, to get that seal.


Keep in mind, of course, that vapor polishing requires you to use ABS or a similar thermoplastic that's soluble in acetone. PLA is not, and you cannot get good results with ABS without a heated print bed.



#334745 Any one intrested in 3D printed parts

Posted by roboman on 13 October 2013 - 11:13 AM in Homemades

If you have a design file then it would be fairly cheap as I said I am not trying to make money. But I sometimes use my friends printer which is a Zcorp Z650 and is very expensive and much nicer than mine if you want it to be stronger, so he has to charge me when I use it.


You do know that ZCorp printers print in plaster, and that the parts that come out of them are not intended to be functional models at all, right? They're designed to print a full-color scale model of something you designed, not a part that can be used in a mechanical device with any sort of strength or durability requirements. They are really cool machines in their own right (basically inkjet printers that deposit ink into the plaster to bind it locally), but plaster models would not last very long at all for nerf purposes.