Projectors and 3D Printing

[Diana Hotka]

I also have a resin 3D printer and although those prints are very detailed, even the harder ABS-style plastics aren't good for high mechanical loads. Most resins I've used are far too abrasive for extensive use. It's fine for some small prototypes, but nothing like a high-stresss worm gear.

As for UV-light resistance: The interesting thing is that this resin is usually cured using UV light. Many resin formulas start to become brittle after extended UV exposure, much like many plastics, especially the flexible ones. I guess the UV light causes the softeners in those plastics either to evaporate or to react in such way that they don't perform their work anymore.

That being said, I've seen some nylon SLS 3D prints that are very heavy duty and perform very well under high mechanical stresses. Those prints can also be ordered from 3D printing services. Those same services also often offer metal SLS prints, usually at far higher costs though. Keep in mind though that a CNC milled component will almost always outperform a 3D SLS printed component on strength and flexibility.

PS: I own a Lamy 2000 fountain pen dating back to the early 1970s, which apparently used one of the first metal sintering "3D prints" ever in an industrial production run. Many of those concepts have been around for a while, apparently.

As for metal casting in wax:
It's something I want to try someday. The problem here is obviously heating the metal and confidently working with it.

Wow that fountain pen is pretty cool, hopefully its still in functioning. You've given me a lot to think about which I appreciate. I have heard that SLS printing particularly with nylon or carbon fiber produce high strength components, my concern is always the small amount of dust from the finished model that is near impossible to remove completely from my experience, this dust getting into the the mechanisms or gears that would interfere with the overall function of the machine. It really does seem that CNC is way more ideal. Thank you again for your input.

[Randy Stankey]

While CNC is good, I wouldn't rely on it for traditionally-made machine parts.

I the old days, machine parts were made and checked by hand to ensure proper form, fit and function. Today, people rely, too much, on computers to do the fine work for them. Even if you make parts by CNC, you might, still, have to finish them by hand.

In such a case, I'd suggest learning how to machine parts, yourself, or finding somebody who can do it for you.

Even if you follow my suggestion of 3-D printing and investment casting, you'll still have to finish by hand or by milling and lathing to proper dimension.

You can't always take finished parts out of the machine they were made on then, immediately, put them to use. There is always, at least, a little finish work to be done.

[Marcel Birgelen]

No matter what production technology you choose, you'll always need to finish the parts to some extend. For additive 3D printing you often need to remove supports, wash off uncured resin or sand it to get rid of printing lines. Sintered parts should also get a good ultrasound cleaning to get rid of all the non-sintered stuff that remains on the object. Depending on what you need the part for, it may require a coating, paint job, etc. If you order those parts at a maker shop, you often also can ask for a post-processing job to be applied.

But to be honest, when it comes down to metal parts, I'd rather rely on a professional, computer milled part than some shoddy "self-assembled" part nowadays. Metal working has become an art form and doing it proper requires quite some skills, those skills have become increasingly rare. I love seeing some Japanese metal workers with hundreds of years of tradition at work, but I wouldn't trust the metal shop around the corner coming anywhere near close. I'd rather have them push the buttons on the CNC machine. I do, unfortunately, have some experience. Last time I ordered a bunch of metal parts that simply had to be cut from metal sheets, bent at 90 degree angles and welded together, I ended up with each part being its unique design... as in, nothing fit together...

Keep in mind that tons of low quantity high-performance metal parts nowadays come out of a CNC machine, as casting is only viable at a certain volume and milling can be done cold: Easier to handle, faster turn-around times and you don't need to account for shrinkage. Also, casting comes with challenges like stresses building up inside the casted parts, due to irregular cooling. Getting rid of those stresses requires at least another heating cycle.

PS: My Lamy 2000 fountain pen is doing fine and I still regularly use it. It's one of the best pens I've ever had and still writes beautifully. It was clearly made at a time when German engineering still stood for real quality and ingenuity. The "3D printed part" is the front of the pen, which holds the nib. It also has a distinctive sintered look to it. You can still buy those pens today and the model they sell today is almost identical to the one from the 1970s.

[Randy Stankey]

Metal working has become an art form and doing it proper requires quite some skills, those skills have become increasingly rare.

I remember an "old guy" who used to hang around in the bar. I was a teenager at the time.

Jim was a machinist in the tool room at a local manufacturing company. He wore a cowboy hat, smoked cigars and had a handlebar mustache. There wasn't anything about machining he didn't know, so to speak. He was one of those guys who could machine parts to half a thou every day and, if he needed, he could make them to a tenth... and he could do all the math in his head.

Long gone are the likes of he...