Projectors and 3D Printing

[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...

[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]

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.

[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.

[Marcel Birgelen]

If someone could come up with a design for a 3-D printed worm gear drive for a Hell & Bowell, it would be interesting to see how long that would last.

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.

[Diana Hotka]

The turbine blades inside a jet engine are made by investment casting.

Thank you for your input, I'll check that out for sure!

[Diana Hotka]

I think there is a lot more choice of materials with the resin variety of printers. I'm sure some of them are oil resistant, not sure about UV resistant... but as that is what you typically cure resin prints with, certainly not going to harm them immediately.

And yeah, using 3d prints as a "lost wax" for casting is definitely a thing. But really depends on the parts you are after and in what quantity! Fun for a hobby, but maybe not economical.

You make a good point about the economical aspect. Thank you. Definitely will look into "lost wax" casting

[Diana Hotka]

A consumer liquid resin or filament 3-D printer could likely be used to make parts that don't have to withstand a huge amount of pressure, heat, and in the case of liquid resin printed parts, UV. I've used mine to make a few 9.5mm film cores for a friend (though that raises the question as to whether 3-D printed plastics could potentially produce offgases that would not be friendly to film in archival storage).

If someone could come up with a design for a 3-D printed worm gear drive for a Hell & Bowell, it would be interesting to see how long that would last.

That's really cool that you 3D printed a film core, I'm not sure how 3D printed plastic offgas either, that would be interesting to know. I believe PLA filament is biodegradable and I did find that you can buy polyethylene filament which is one of the archival plastic materials so I'd assume that would be safe for film, https://xtellardirect.com/braskem-pe-filaments.html

I did print with resin one to make a functional prototype and dropped it by accident (aka an accidental stress test) and it shattered, later I learned that resin prints in consumer grade filament is typically used to make pretty objects, not necessarily for function and durability.

On the Van Eck Video Services, they have Bell & Howell worm drives that look 3D printed to me but I could be wrong. https://van-eck.net/en/product-categ...rts-en/page/3/ (in case you need one) I'd definitely be curious how long a personal printed one would last, I'll keep that in mind.

Thank yo for your input!

[Randy Stankey]

The turbine blades inside a jet engine are made by investment casting.

[Ryan Gallagher]

I think there is a lot more choice of materials with the resin variety of printers. I'm sure some of them are oil resistant, not sure about UV resistant... but as that is what you typically cure resin prints with, certainly not going to harm them immediately.

And yeah, using 3d prints as a "lost wax" for casting is definitely a thing. But really depends on the parts you are after and in what quantity! Fun for a hobby, but maybe not economical.

[Leo Enticknap]

A consumer liquid resin or filament 3-D printer could likely be used to make parts that don't have to withstand a huge amount of pressure, heat, and in the case of liquid resin printed parts, UV. I've used mine to make a few 9.5mm film cores for a friend (though that raises the question as to whether 3-D printed plastics could potentially produce offgases that would not be friendly to film in archival storage).

If someone could come up with a design for a 3-D printed worm gear drive for a Hell & Bowell, it would be interesting to see how long that would last.

[Diana Hotka]

Well, parts can also be 3D printed in metal. NASA is working with Rocketdyne to 3D print parts for the RS25, Artemis, engines. Spacex is doing the same. Sections of the rocket stages them selves have already been 3D printed and flown.

Thinking about this makes 16mm projector parts seem pretty insignificent. Plus, there are so many 16mm machines out there, that it's likely cheaper to acquire a replacement projector. Especially with Bell & Howells that have a cracked gear that can take a full day to replace. Those B&H's were pretty hard on film too. The shop labor cost to replace a cracked gear easily exceeds the cost of a good used replacement projector...

There are too few 35 and 70mm projectors left in service for 3D printing to become any more than a boutique service. There are already machine shops that can make one up or more parts.

https://youtube.com/shorts/r0hAO4EEP...dTRsc1lfVROPff

Wow I didn't realize NASA and SpaceX were 3D printing at that level. You make a good point about the cost and time that is needed to be invested into making the replacement part. Additionally knowing about the Bell & Howells is helpful, I wouldn't want to repair a projector only for it to damage a film especially archival film. Thank you for your feedback and sharing the link and video of NASA, really cool stuff.

[Diana Hotka]

You can also print parts with 3-D printing in the normal way then use that as a pattern to cast the part out of metal.

They sell a liquid ceramic dip that hardens in an oven like glass. Then you pack the result in refractory cement and bake it in a kiln. The plastic will melt and burn away, leaving a perfect mold for the part to be cast from.

Once the part is cast in metal, break the mold cool the part then finish by hand or machine, as the case may be.

This is a really fascinating way of processing! Thank you for the suggestion.

[Diana Hotka]

Like with everything else, it really depends on the parts you want to print and with what technology... Many critical projector parts must be able to survive in relatively harsh conditions. Tension stress, constant heat cycles, UV light exposure and potential exposure to lubricants comes to mind. All stuff to factor in when choosing your replacement materials.

Replacing something originally made from metal with 3D printed plastics is usually not a good idea. A good altenrative for 3D printing might be CNC milling, as it produces genuine metal parts with considerable strength and durability.

I didn't think about the UV light exposure and the exposure to lubricants as factors to consider in choosing the materials for replacement parts. I will also look further into CNC milling. Thank you for your feedback!

[Mark Gulbrandsen]

Interesting site...

https://van-eck.net/en/