3D Printing

You won't be able to afford a laser scintering (metal) 3D printer. You are talking a million dollars (maybe less for a smaller one though). Plastic ones are 3K or less for cheap ones. You cannot mix metal with plastic. You can make them separate of course.

These parts often have imbedded metal parts, such as a metal

If you want a nut in the plastic part, you can make a slot that allows you to slide the nut in from the side. That would be the easiest way to do it. If you truly want the nut embedded, I suppose you could make the build in two parts, with a pause in between, where you drop the nut into a hexagonal cavity. Then, the 2nd part of the build would cover over the nut.

Jon

I've heard of plastic parts taking 50 hours to make on a 3D printer. Sort of like building a chair out of toothpicks. Maybe machining makes more sense.

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John Larkin         Highland Technology, Inc 

jlarkin att highlandtechnology dott com 
http://www.highlandtechnology.com

It depends.

There has been way too much hype about 3D printing. The hype seems to travel on lack of understanding, or an imagining that what's available today is what will come in the future.

I did see a column somewhere about them, and they guy basically used the example of a table to explain 3D printing, though he said nothing about the time it would take. It was a ridiculous example, since you have to haul all that plastic home first, then wait while the printing melts that raw plastic and puts it into the form of a table, which in this case isn't likely to be ornate, just a block of plastic. Might as well start from scratch with the plastic.

At this point, most of the hype relates to printers that can only do plastic, which limits their value. You can have a nice plastic box that emulates something from the past, but you still won't have a working device, since the printer can't make the insides. Even if it's just plastic gears inside, the printer can only make the plastic pieces, it can't assemble those pieces.

And for the neophyte, it will rely on having a file somewhere that someone else has made so you can get the printer to print it. That's a big stretch from actually building something yourself.

I'm much more likely to need some odd piece of metal, and there are ways of doing that, even before getting a lathe. For plastic, one can salvage old inkjet printers, that seem to all come in a plastic case that can be cut and formed without cracking. When I bought my used HP 4P laser printer a decade ago, I realized on the way home that the cover over the memory expansion area was missing, perhaps that's why it landed at that Rotary Club sale with such a low page count. So I took the cover from some stray inkjet printer I'd dragged home, and cut a piece of plastic to fit that frame on the HP printer. I have to duct tape it in place, but at least there is a cover. That kind of plastic, I think ABS?, is quite workable with tin snips and files.

I did have a need for a piece of plastic a few months ago to try to replace a broken piece, but I'd need the missing piece and skills I don't have to measure it and create a file for the 3D printer. I think in many cases there, people are hoping that the manufacturer will release the files, so you can make your own pieces. I'm not sure that's going to happen.

Some places are started to do 3D printing on demand. I'm not talking about collective workspaces, aka "makerspaces", but libraries and some big box stores, though I can't remember which of those I was reading about last week. You submit the file, they print it, you get the 3D image of the file back, once you pay.

That sort of thing seems to make more sense, a chance to try things out, to get a grasp of what it's all like. And then you can define whether you really need your own printer, or if you'll just have a tiny bit of need for it, and then print endless junk just because you have the printer.

The trick is to see the 3D printers as somewhere in between off the shelf and making from scratch. If you can't yet figure out how to end up with bits of metal embedded in the results, then you need to be thinking in terms of "how can I make this from scratch", which should help to figure out how it would be done with a printer. If you don't have the skills to begin with (knowing how to make a knob is different from making a good looking knob), it's too early to count on the 3D printer to do all the work.

Michael

You would have to be careful, though, that the extruder head doesn't hit the nut as it travels. You would have to have the opening just about closed before you added the metal part.

You may be able to do well enough by putting the nut on the starting board (what do they _call_ it?) and building around it, if you're precise enough.

Or build the knob up with a hexagonal cavity, then epoxy the nut in.

One way or another, the metal part will need to be machined or printed separately.

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Tim Wescott 
Wescott Design Services 
http://www.wescottdesign.com

Before you contemplate investing much money in 3D printing of knobs, check out the surface finish attainable by your intended 3D printer. The ones I've seen all have some sort of pattern left on the part, as an unavoidable consequence of the printing process.

You may be able to print a knob and then sand it and polish it, but I don't think you'll be able to just print a nice shiny knob.

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Tim Wescott 
Wescott Design Services 
http://www.wescottdesign.com

The most common (cheapest and easiest to use) material is PLA (polylactic acid), and next is ABS. I think both of those respond well to an acetone vapor soak, which melts the surface a tiny bit so it flows and becomes smooth and shiny. Kind of like fire polishing glass. Also, someone talked about places to get stuff printed, besides the local makerspaces and buying your own printer. One company that prints your files is shapeways.com, charging by the volume of material and what the material is. They also have a storefront where you can sell your printed items. You upload the file, set the selling price, they put it on their web site storefront, when they get an order they print it, ship it, and at the end of the month send you your money minus the printing cost and a handling percentage. Pretty clever business model, I think. Not a customer, just saw their site.

----- Regards, Carl Ijames

Before you contemplate investing much money in 3D printing of knobs, check out the surface finish attainable by your intended 3D printer. The ones I've seen all have some sort of pattern left on the part, as an unavoidable consequence of the printing process.

You may be able to print a knob and then sand it and polish it, but I don't think you'll be able to just print a nice shiny knob.

--

Tim Wescott 
Wescott Design Services 
http://www.wescottdesign.com

From what I've seen demonstrated , the plastic used is seriously non structural, no strength. You would have much stronger structural parts using expanded metal buried along with bushes etc in epoxy, taking a mould off the original part. Probably take about the same amount of time as a 3D printer as well.

Hi Dave,

If you want to get your own 3D printer and make custom parts I can think of 3 things you'll need:

First is a 3D drafting package, something that will make a .stl file (stereo lithography file). I think Google sketchup might work and be free, but haven't used it. Alibre design used to make a reasonable SolidWorks clone for about $100 US that is good. SolidWorks is one of the professional standard tools, but costs a lot.

Second is a program to prepare the .stl file for printing. These programs are commonly called slicers. Makerbot has one for free. There are other free ones available, but they may require tweaks to work with a particular printer. One good one is called Replicator G.

Third is a printer. One decision you need to make is material type. The two main choices for the class of printers you are considering is PLA (a hard, biodegradable, brittle plastic) and ABS. Some printers print only PLA, some print either. Each plastic has its merits. For me, the main benefit of PLA is less part warping during printing and cooling, and the main benefit of ABS is part workability for secondary operations after printing.

There are many types of professional 3D printers. They come closest to turn-key what-you-draw-is-what-you-get operation. There are many services that will print your parts for a fee and have available printers of various capabilities. Materials for these printers cover a wide range from fused plastic powders to stainless steel. Most companies use printing supplies as profit centers and so even after purchasing, printing supplies can cost you. Using a professional service is the surest way to get parts that are exactly as you've drawn the first try.

If you use an inexpensive home printer, prepare to spend a lot of time. You'll need to become an expert in it's operation to produce reasonable results. To my knowledge, there are two main types available. The first, which I've seen but not operated, uses a photo-polymer and a light projection system, and is best for small parts and high resolutions (microns), but the finished material is kind of soft. The second melts a plastic filament to print the part with resolutions down to about 100 um.

For the inexpensive route, here are some of the things you'll need to get right for reasonable results:

- the build plate needs to be flat to within about 50 um. This means you need a machined plate. The plates are typically removable and adjustable, and it's useful to make tools to help you level the plate. Too small a gap means the print nozzle will clog up, too large a gap means the parts will not stick to the build plate. Look at

for .stl files for various tooling. A very inexpensive printer may not include a machined build plate.

- the build plate needs to be heated for using ABS.

- one main problem with this class of printer, and especially with ABS, is that the parts will warp during printing due to differential cooling. The best fix is a heated build chamber. Unfortunately, this is patented and the working parts in a home-class printer are not up to residing inside a heated build chamber anyhow. One thing you can do to help is to enclose the printer to at least avoid cool outside air from circulating. You can also help warping with part design, by minimizing long solid runs of plastic for example, or putting relief slots into the part to break up long runs, and later filling with epoxy. These printers work best for parts with under a 4 inch span.

- The home-class additive printers (melted plastic) can't print much of an overhang reliably (around 45 degrees or so). You need to take this into account when designing your parts.

You mentioned embedding metal into the parts. Brass inserts are available in various sizes and can be melted into holes in ABS parts using a soldering iron (one you don't love anyhow). Printing ABS with embedded metal parts, while not impossible, is IMHO, impractical in most situations. JB weld epoxy has been useful for modifying parts after printing.

To sum up, I think these printers can be a useful tool for prototyping, making jigs and even for short run production, especially for internal brackets that don't need the strength of metal and where surface finish is not important. The home-class machines require a large investment of time but not a lot of cash. The professional printing services are the best bet if you need only a very occasional part or if you have a reasonable budget for parts. I might compare using the home-class machines to making pcbs at home vs using a professional service, say 20 years ago.

ChesterW

Though The Motley Fool feels otherwise, I don't think 3D printing will have the success //among consumers// people are predicting. At the moment, it's basically a "toy" product -- and will probably remain so for at least a decade. HP has been wise not to rush into the market.

What I'd like to see is a system of "manufacturing on demand", especially if were possible to improve on the item being replaced. For example...

I have two classic Sony radios, the TFM-825 and TFM-117WB, whose paper-cone speakers were okay-sounding 50 years ago, but would sound a lot better with plastic or plastic-doped cones. Wouldn't it be nice if I could order a "modern" version for $10 or $20? (Ditto for the classic KLH full-range driver.)

This is difficult, though not impossible. The problem isn't //making// the speaker so much as it is //analyzing// existing samples so the printer can duplicate the frame, the cone, etc. The cost for a single copy would be beyond unreasonable.

Thanks for your input, Chester I'm well aware of the software and 3D modeling requirements in order to even begin to make a 3D printer work. I've a number of years experience using and supporting CAD modeling systems, although it's been several years ago. And I know that the parts produced aren't perfect, but they can make parts that would otherwise be very to duplicate by other means. As you infer, learning more about the types of plastics that these things can handle is very necessary.

I'd like to see one in action, and get more info on what they can (and can't) do. Right now, as I said in my original post, it's an interest, not something that I have my heart set on doing. Other types of manufacturing have been proven to be cost-effective for hobbyists, such as vacuum forming, and machining, but each process has its own set of pros and cons, as does 3D printing. I think my next move is going to be to find a company that will make parts for me. I didn't know that these these services exist. Do you have any recommendations?

Many thanks for all the input from the others who have responded.

Dave M

I'm not familiar enough with the printers to know how they actually build a part (the "starting board" is called a "build table"). How close to the table and previously deposited layers does the extruder nozzle have to be? Would that distance negate the ability to "print" around another object? I guess that would be the critical factor.

A new question just came to me... Can a printer build upon a previously finished part? IOW, can I build half of a part, imbed a metal part inside a cavity, then put the part back on the table and have the printer build the rest of the part on top of it?

Maybe I should be asking these questions to the 3D printer marketers? Anyway, thanks for the suggestions,

Dave M

I think the nozzle is nearly touching the part so anything higher than the ~0.1mm layer thickness would interfer

I don't see why not, as long as you keep everything aligned

-Lasse

I've watched videos of people doing the vapor soak to alter the surface finish. I've yet to see one that did a good job without a loss of detail. Knobs typically have ridges around the perimeter as a grip surface. Such a vapor polish would likely cause the ridges to erode away along with any markings that might be on the knob. But look at some of the videos and decide for yourself.

Rick

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Rick

I cant imagine it being too expensive to rotate the sample while scanning it with a laser to build up a 3d file of it. Has it been done?

NT

Yes, and if the logic "it's shaped like the thing, it must be the thing" works for you, then you're home free.

There's a lot more to manufacturing a successful product than getting a bunch of pieces made out of random materials that are more or less the right shape.

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Tim Wescott 
Wescott Design Services 
http://www.wescottdesign.com

So it has been done. I can't imagine why someone would use random materials.

NT