Everyone wants their prototypes to look exquisite, not weekend afterthoughts that look like 3D sprays. The combination of Delrin and laser cutting machine makes this easy, especially if you learn some trading techniques that can make your assembly functionally and aesthetically popular.
Last time, we delved into the use of Delrin and a typical 40-watt laser cutting machine to make parts, and discussed some of the material constraints. Recently, [Gerrit] let us take a closer look at the material itself. About a year has passed since our first article, but the list of tips is far from complete.
If you are just beginning to get involved in this field, let me introduce you to two classic techniques for laser cutting prototypes: jigsaw stitching and T-nut slotting. Although these techniques are proven, but I hope, fearless readers, they will make you yearn for something cleaner and more refined. If this is the case, please keep reading!
Rivets provide us with a function similar to screws: they are perfect for fixing two boards together. Another benefit of rivets is that their shafts provide a smoother surface for parts that need to be relatively rotated. In terms of quantity, the price of rivets is comparable to that of screws, and they provide different aesthetics, probably because we rarely see them in side projects. The rivets come in various shapes and sizes, but I prefer the standard half-pipe shape variant because their top and bottom only slightly protrude from the mounting material. Using semi-tubular rivets, the exposed bottom mushroom becomes the typical button feature we see on many hinges in clothing and consumer products. As a reminder, specifying the rivet length requires some foresight about the size of the part. For rough calculations, the rivet should protrude about 55% of the rivet diameter of the part before being crushed [PDF].
A word from the wise: Rivets are eternal! Unlike screws, rivets are a one-time operation (except for fancy disassembly equipment). When working with rivets, we must clearly remember the order of operations when assembling the parts together. True story: After riveting two pieces together in the wrong order, I scrapped many parts.
Countersunk holes provide us with two immediate benefits. First, it allows us to put the screws in a design flush with the board. Secondly, it greatly cleans up the look and feel of the parts. Our screws no longer need to poke out weirdly from our parts, it is a pragmatic necessity.
In practical terms, flat head screws allow us to squeeze the gaps between the parts together, saving us space, otherwise the protruding screw heads are so eager to take away from us. In the example on the right, the tight gap between the robot's wheel and the body requires the use of a grub screw solution. In terms of aesthetics, countersinks are not common in laser-cut prototypes. They make our audience think harder about "how did they do it..." instead of jumping guns and shouting "laser cutters!" on our project.
So how to create such a cavity? Fortunately, Delrin uses standard metal tools such as butter. For the vertebrae of the tentacle mechanism shown above, I created this feature using a mini countersunk cage. These tools are specifically designed for the aerospace industry and are used to efficiently rive aircraft together on the factory floor. Pro tip: You can get the same effect as the traditional countersink cutter by properly setting the hard stop nut of the drill press.
Do you need thread features that can withstand heavy loads and repeated tightening and loosening? Then the heat setting blade may be right for you! Like many other self-respecting thermoplastics, Delrin is the prime candidate for these brass blocks.
The heat-set inserts fully meet their requirements: cut any thermoplastic with a hole to a predetermined size, and then put the hot metal insert into the hole. Let the result cool down—puff—the elastic thread feature is now permanently embedded in your part! The supplier sells specific insertion tools, but we found that our soldering iron (up to 250ºC) and a pair of stable hands also work properly.
Sometimes, discovering new tricks is to open our eyes and look at the world around us. Just take a look. Almost every consumer product around us is manufactured in large quantities and requires mass production technology. In order to manufacture these products, designers need repeatable and reliable technology with predictable results. Rivets, countersinks and heating inserts are nothing new. They are borrowed from this world. Pay close attention to the details, and maybe you will find more techniques suitable for laser cutting Delrin. Let us know in the comments! Until then, continue to roll out these prototypes!
Great article! I think you made a little confusion, hot riveting, when you use plastic rods to fix 2 parts, I think this is really not something hobbyists want to do. Your example is the use of metal plug-ins, hobbyists may want to use a lot, because a lens project is widely adopted and plastic lines are affected.
Is it on this page that I recently saw someone using a short-length 3D printer filament and a heat source (soldering iron?) to make the heat pile you described? Not as neat as rivets, but very cheap and easy.
This is smart! I guess it is technically a rivet, because it is a separate fastener (of course, the spirit is exactly the same). I think this is a better "at home" alternative to hot piles. You can cut plastic rivets with a knife and insert new rivets when you need to open the system.
My understanding is that rivets are a kind of compression bonding, and thermal fusion is diffusion bonding, so it can be technically called forming plastic welding. The rivets mentioned in this article look more like blind bolts or screws.
I have also seen hot piles that are not welded. It's like fixing a PCB or a metal part in a plastic case. In that case, it is just a plastic rivet. Therefore, depending on the melting point of the part, both are possible.
You are absolutely correct. I have changed accordingly. Ah, I have to like the flexibility of online writing.
Say someone is allowed to edit his post...
Can anyone recommend a good source of Delrin watches? It is almost twice the cost of acrylic of the same size. I can't find 1/16"x12"x12" sheets for less than $20.
Delrin is a more expensive material. Compared with PS, PVC or ABS, its only real advantage is that it "gives" more and is more flexible. For many of my projects, I prefer ABS or PVC. Hot riveting is not the best process for these because it emits some unpleasant smell (instead of Delrin, which is a nylon), but these two materials The response to glue is much better than Delrin did.
White is cheaper, 5.78 sheets per sheet.
Delrin also has higher chemical resistance to common solvents
Delrin is not nylon; it is polymeric formaldehyde.
The smell it produces is due to its depolymerization and release of formaldehyde. This is also the reason for the almost clear flame when it burns.
Yes, when you discover these facts after a very expensive fire, this makes it annoying and expensive to replace, which may cause the premature death of those involved in the fire fighting without realizing them. Just suck in a large amount of evaporated anticorrosive liquid. It burns very very well.
I suggest anyone find a new material to use. If you insist on using Delrin, you must perform carbon filtration and discharge the smoke outside the work area.
Oh, there must be a material difference. The problem with PVC and ABS is that laser cutting any of them is not safe. Cutting PVC with a laser will generate chlorine gas. It’s not good for optics, and it’s definitely not good for lungs. ABS generates cyanide gas and melts too easily. Polystyrene just doesn't cut well-it melts and emits a lot of smoke.
For many reasons, Delrin is great. Its machining is excellent and it is easy to use cutting tools. It is also very suitable for laser cutting.
If it is cheaper, it will become my first choice for most laser cutting machine projects.
You should know that Delrin is not a nylon. I am not a chemist, but I know that the molecular structure of nylon is very different from Delrin's.
http://www.usplastic.com/catalog/item.aspx?itemid=32866&catid=439 Please note that it is only listed as acetal, not specifically listed as delrin. However, it is half the price you say you can find.
https://www.onlinemetals.com/merchant.cfm?id=209&step=2&top_cat=181
This is a great price! It's time to place an order.
thank you very much. This is the type of article I came here.
agree. So far, Joshua has only written *high-quality articles. There are no Raspberry Pi USB hubs, shell modules, glorious America. Look at my big guns or controversies, click decoy fake articles. Congratulations! Most importantly, his writing respects grammar, is removed from any superlative and "damn, damn" useless words, and never starts with "everyone in the world knows"
In fact, there is only one HaD writer who wears different hats (okay, handles) and styles according to his mood and content. Internet reviewers should be familiar with this game.
Strictly speaking, this is not "him", but a machine.
The quality does not include the food of the North Vietnamese army, because the Nixon War in Vietnam lasted for 10 years. Congratulations. There is hardly any merit here. Please describe in full.
Echo delta...ED...Um...I think it is logical that erectile dysfunction may make someone mentally deranged.
Nixon served as president from January 20, 1969 to August 9, 1974. The Vietnam War from November 1, 1955 to April 30, 1975. How the United States got involved. http://www.history.com/topics/vietnam-war/gulf-of-tonkin-resolution
It has nothing to do with the subject of the post, but have you posted more information about the touch phone system anywhere? It looks like an interesting project.
I just tried to find anything similar to the image and found "nada". Maybe we will see something in the work soon. :)
Isn't it just a bunch of disks stringed on the cable? In my opinion, it actually doesn't look like anything????????
It looks like your standard animatronic tentacle. You pull a rope and the whole string bends in that direction.
Love these! I don't understand why I didn't think about heating the threaded inserts instead of using a hammer or vise to insert them: P
A typical factory installation process uses ultrasonic vibrations of the blades from a tool. Vibration generates very localized heat, just deep enough into the plastic so that the insert can be pushed in.
Countersunk holes also help prevent the screws from loosening. The higher surface helps to lock them.
Be careful what you get when buying countersinks. Most screws are 82 degrees, but there are also 90-degree countersunk holes. 90-degree screws can be found in many airplanes. Also don't buy multi-slot countersinks, they are easy to tremble. To pay for the flute, it is best to use the MA Ford brand.
If it is chattering, you may be spinning too fast.
No, they are just nonsense. If they are strong enough, you can sometimes use them on a milling or drilling machine. You will almost never see a multi-slot countersink in a machine shop.
I'm not sure what store you are visiting. The shops I've been to definitely use multi-slot countersinks. If they chatter, it's probably because their rotation speed doesn't have enough time for the chips to form, break, and clear.
I assert that multi-slot countersinks are more commonly used than single-slot countersinks. Check any cutting tool catalog and compare multiple multi-edged counterbores with a handful of single-edged counterbores. That is not an accident.
Speaking of multi-slots-since you recommended the countersink of the MA Ford brand, I will do the same. The best and least chatterless countersink I have ever used is MA Ford's 6-blade HSS Chatterless Countersink. They are cheap, come in all possible angles and sizes, can be used permanently, and can work at any speed.
This is a good source:
http://www.kbctools.com/products/CUTTING%20TOOLS/COUNTERSINKS/SIX%20FLUTE%20COUNTERSINKS/3432.aspx
I believe that aviation sheet metal is a 100-degree screw. Helicoils requires a 120 degree sink. 90 degrees is what we usually use because people just want the hole to be chamfered or the edge to be broken. Provide better guidelines for screws and pins.
Yes, I think your view of 100 degrees is correct. Suitable for shallow taper of thinner metals.
82° for imperial screw size 90° for metric 100° for aerospace (larger clamping area and reduced metal plate depth) 120° for Helicoil
I used something similar to the so-called hot riveting in the article. A 3D printed part in which the hexagonal hole is too small to fit a nut, so I use a soldering iron to gently melt it into place. It is very sturdy and does not require any special inserts.
Just to throw it out as a subtle change, I used a hot air rework station to soften/almost melted the nut trap before inserting the nut with great success. Or pass the screw through, start on the nut, and then apply hot air while tightening the screw. Helps to stay consistent. (This is not to say that the described soldering iron technique also does not work properly.)
When dealing with 3D printed PLA parts, hot air stations are usually good because you can selectively soften and reshape parts that are not printed correctly. (Probably you can use other plastics to achieve the same effect, but I just stick to PLA.)
Oh my god... first sentence... snarky, how much? Or is this just elitism? I hope it comes from the comments, not the post itself.
Maybe you shouldn't be so sensitive?
"Not a weekend afterthought that looks like a 3D spray" That's not all?????????????????? For a long time, we have always been happy to be able to spray 3D parts Crazy. Why are you back? ? ? ? ? ? ? day…
...We made the printer with the Erector Set and Mecanno and the hot glue gun!
One of my pet projects that is progressing very slowly is a CNC, which is used to process various aluminum (aluminum) extrusions into Meccano-type parts.
Sadly, today’s young people don’t have the fun and educational stuff as our more or less toys.
The only strange thing about this CNC is that one axis will be the extrusion itself. It can be said that the CNC will climb along it. This will minimize the size of the CNC, while also reducing costs by a small amount.
So I'm not entirely sure why you mentioned that the rivets are permanent, and mentioned that you throw away the parts because you riveted them together in the wrong order.
Every rivet I have used can be easily removed by carefully drilling the center of the rivet. And since rivets are usually in the range of a few cents, drilling out the rivets and reassembling the project is much cheaper than throwing away the manufactured parts!
For new parts, you need new rivets anyway. :-) But sometimes the heat of the drilling will soften the plastic enough to rotate the rivet instead of drilling it out correctly.
It can be shown that the insertion of the brass insert fits perfectly with the soldering iron, in Delrin and many other plastics. In addition, it greatly increases the strength and reduces the possibility of breaking at thin materials (<3 mm). Great article, please more :)
If you don't care about the 100% perfect fit between the underside of the screw head and the countersunk hole, if this does not happen to you, you can usually use the tip of an oversized ordinary drill bit instead of a special countersunk hole cutter on hand.
Just ?????????????????? Be careful not to let it grab and pass through your workpiece. Been there and done that thing more often than I want to remember.
A small, smooth tube cut to the right length and fixed with some blutack is great for avoiding this problem and also makes multiple holes faster and easier (so the blutack or tube will fall off after each hole)
Ah, great idea! I tried drill stoppers (metal rings with fixing screws), but they don't like to be firmly fixed to the groove part of the drill bit. Of course you need to be very close to the end for this.
Regarding countersinking with a laser cutting machine, it is a bit possible. On our Epilog Legend 75 watts, we used the color mapping function to etch a set of rings embedded in each other. Each ring toward the center uses a higher power setting, and the result is a deeper Delrin etch for each ring. This results in a stepped tapered etch pattern that works relatively well as a countersink. In order to obtain a smooth surface, a second pass with a lower power range will help reduce ridges. It is suitable for MDF and 8-32 screws because the steps are almost inconspicuous. We have considered trying to use Delrin countersink drilling when the laser is out of focus to help "mix" the steps more.
This sounds like an article that might be worth HaD. :) Well resolved the limitations of the tool.
This takes much longer than the anti-sinking with a drill, and the result is much worse.
As mentioned above, for example, making a grating on acrylic will create a cavity for the screw. Just need to exert strength and speed to the required depth
So you got the 3d stl file from this tutorial? This has also completed all the coding?
http://www.instructables.com/id/Animatronic-Tentacles-with-Arduino/?ALLSTEPS
This is a zip containing all the arduino code and the 3d file that created it.
Knowing that this project looks very similar to what I saw a few years ago.
No, this is native, although the design is inspired by Richard Langdon's two-stage tentacles from the Stan Winston tutorial series.
I posted more information about building these here: http://hackaday.com/2016/09/13/the-bootup-guide-to-homebrew-two-stage-tentacle-mechanisms/
Any tips on where to find the plastic material hole design for heat setting inserts? I am using McMaster https://www.mcmaster.com/94180a504, but their only design dimensions are taper angle and drill size. Where should you place the bottom of the cone, or close enough?
If you use a laser to cut these holes, you can completely ignore the taper angle and just take a picture of the drill size. The laser "notch" has the same effect as the cone angle because it holds the part in place before melting it with a soldering iron.
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