3D Printers.

[Colin Leighfield]

You're right Erfolg. I hope that BEB has seen this. With practical home-use 3D printers coming on the market, it would be great to see a review of what's available, their suitability for our needs and examples of what they can do. Some of our fellow forumites like Andy are already realising the benefits of this technology and we have seen examples of pilot figures and other items being produced this way.

Come on RCME, let's see a good feature on this fascinating subject!

[Erfolg]

From the observations of Andy, it would appear that from a structural aspect, that some of the techniques do not result in a truly homogenous structure.

My view is based on his observation that with clear feed stock that between each pass or layer there is some opacity. Normally i would expect that when a polymer is clear, the mers are truly randomly arranged. When there appears to be some opacity, we know there is something different in these regions. From past observations, this has been due to a degree of alignment of the mers. This can sometimes be observed when a plastic bag is stretched in one direction, typically at the handles. Sometimes it can be seen a definite change in colouring as the polymers are preferentially stretched in one direction, creating a general alignment of the the mers.

The banding can be of importance for a number of reasons, it could be aesthetic, optical, or reasons of mechanical properties. These could or may not matter. What matters is a reasonable understanding of what it means at a practical level, dependant on the users needs and wants. For me it is of interest.

The subject has to be interesting.

Come on BEB you are needed.

[Erfolg]

During the night i have had another thought with respect to 3d printers.

Although we recognise that they are capable of creating a facsimile of an object and I also presume from CAD file, we have not commented on such as aspects as to what accuracy and surface finish.

Then there are other issues as to how thick or thin a section is that can be produced in a single pass.

In my opinion there is so much that BEB or some one similar could get there teeth into.

Then my mind went back to the metallurgy issues. It did strike me that some materials would almost certainly benefit or need an inert atmosphere for there effective production, that home usage is almost certainly limited.

Then I thought about my teacher/lectures favourite phrase and concept, that is "Processing History". Although it may be possible to say produce a piece of wire, using Piano wire as the example, not only has the wire a specific metallurgic composition, much of the properties comes from the Processing history. That is heat treatment and the drawing process.

My mind then drifted towards welding, it is a well known phenomena that welding creates a HAZ (heat affected zone). Typically the heat generated results in a changed structure, most frequently grain growth and in some case regularisation of grain geometry. Many will have noted it is often the area to the side of a welded joint that fails, rather than the weld.

Again, it is all of the aspects of production that engineers use to optimise the performance of a item that appear at first sight to be absent etc.

Yet another area of interest, at least to me.

Although nothing to do with 3d printing, RCM&E dealt with the effects of heat treatment, some of the things we modellers do and the detrimental impact these have on the original properties. Again a real example of processing history. I particularly liked the references to the limitations of home heat treatment, using oxide film colours.

[Andy Meade]

Surface finish is generally very good, and can be bettered with post-processing of the part. The more accurate the printer (generally 0.15mm for me, but there are better ones at higher price points of course), the finer layers it can print in, thus you tend not to see the slight steps. It really feels like a wood grain.

I post-process (if I feel it is needed, generally I don't) by one or two of these :

• sanded quickly with medium paper
• put into an acetone vapour bath
• painted with a substance that levels the surface and produces a hard shell (XTC3D being the most common)

Here are two parts "fresh" off the printer that I modelled and printed for my 12th scale B24. The front row of the Wasp rotary, and a ball turret. The turret was the second thing I ever printed, and some sag and irregularities can be seen. Experience on how to design the part for manufacture is quite important when printing, and I'd do this one slightly different if I tried again. But 'tis only a ball turret on the bottom of the plane, and retractable at that, so won't be seen too often.

Edited By Andy Meade on 17/09/2015 12:06:44

[Colin Leighfield]

To me Andy, they look brilliant.

Erfolg, interesting observations, heat affected zones (HAZs) associated with welding are certainly things that we have needed to understand in the industry that I am concerned with. I think we are a long way off producing metal objects to make things like engines in the shed, although one day - - - - . In the meantime there is clearly a great opportunity to make useful bits and pieces from plastic type materials, it's definitely crying out for a feature in the mag.

[Bob Cotsford]

I can confirm what Andy has said above, the cylinders that he produced for me have only a slight linear texture resembling a fine woodgrain. Nothing that will be noticed once in the cowl without bending down for a very close examination.

[Colin Leighfield]

Sounds good to me!

[Erfolg]

The information that Andy has provided, is informative, yet is almost a tip-bit to tempt us to want to know much more.

The use of 3d printer to produce dummy engines, might be obvious, once you have seen that they can be done. Again there is more information required, for those of us who no nothing of the production method.

Typically this would be, can hollow objects be produced, particularly where weight is to be saved. The photos do suggest yes. Yet there is much, much more to understand.

For dummy engines, could differing colours be conveniently be incorporated, which could be for such features as perhaps black crankcases, silver Barrels on cylinders, perhaps red plug leads etc.

Perhaps the most obvious question, is how much would a commercial product cost as a one off.

I envisage two extremes which range from cosmetic products through to structural items. What does this mean for us the customer.

It really does appear to be an exciting technique as Colin suggests, yet until we all know more and understand the opportunities and limitations, 3d printing will remain a magical process, rather than an every day appropriate process, for some items.

[Andy Meade]

Hi Erf,

Always happy to answer questions! Once I have a 3D model from CAD, and it is imported to the printer software, I can decide what happens with the interior :

• Shell. The part is printed just as an exterior shell, one layer (approx .2mm) thick. This would be very fragile and not really recommended.
• Solid. No voids at all internally - the heaviest and I don't use this very often. Perhaps when printing a small bellcrank it would be good.
• 3 levels of "fill". Now 3D print files (STL files) are just surface data, so the printer software creates a honeycomb interior, if neither of the above options are selected. These levels of fill then can be tight, standard, or wide. Generally I use wide, as it makes a very suitable, stable piece.

Different colours (and sometimes, mediums) can be used if you have a multi-print head. I have one nozzle on mine! Again, pay more for more features, but I can retro-fit if need be. So different colours in different areas and layers is fine, and as hinted, different mediums. There is a water-soluble filament available that can be used and later dissolved from the inside of parts once complete, or of course these can be used to created male molds for sand casting.

Filament price is charged per kilo on a reel, and can vary from £10 to £80 per kilo - so prices are typically based on printed weight plus CAD time if required.

[Olly P]

I have used industrial 3D printers for proto ping, and unfortunately never did print anything hobby wise.

If any of the 3D printer manufacturers want me to review the machine then please do send me one.... I am also happy to do a write up for the mag, but it may be some time before I have the time to do so!

[kevin b]

Interesting topic.

I have seen a news article which says that a French economist correctly predicted what would happen to the recorded music industry, back in the 1970's-80's. He also now says that international manufacturing will go the same way due to 3D printing.

**LINK**

Interesting times, as the Chinese say !

[Colin Leighfield]

Just imagine drawing up your new car, switching your 3D printer on and finding the car standing ready to drive the following morning. I fancy making a working moon-rocket, just like Wallace and Grommet did!

[Andy48]

Just think of all the little plastic bits we use in modelling, most of which cost an arm and a leg and are always just a bit too small or just a bit too large. Download an appropriate file, scale it, print it.. hey presto!

Going a stage further, how about fus formers, wing ribs, spats (now an endless supply of those really appeals), all those neat little scale parts etc.

Christmas wish list!

[Philflyer]

I have an NGH 9cc petrol engine. This was not a good start with ‘gassers’ due to the very poor carburettor but was made to run with a Just Engines glow carb. It is now very reliable but the stability of the fuel metering could be improved by thermal isolation from the crankcase. All the makers of model petrol engines now fit a spacer between the crankcase and the carb that is made from some sort of plastic. I think one could be made with a 3d printer. Does anyone know if materials are available for use in a 3d printer that can withstand the temperatures that are likely to occur? I imagine it must be up to 300 degs C.

[Martin Harris - Moderator]

I don't think it's likely that a home printer would be able to cope with any thermo-plastic material (if one is available) capable of withstanding 300 degrees - the filament material would need to melt at considerably above this and I don't think any normal printer head could reach such a temperature...

[Erfolg]

There was an interesting article in the IMechE mag, on the subject of 3d or additive manufacturing.

Rather than there being the one technique and materials, there are a range of production methods. It seems the use of the term of 3d printing, tells you as much about the production method or process as saying, the item was "machined". Accurate in general terms, vague in the specific.

Non the less, in many respects it saddens me that I am now retired, as i would have very much pushed to be involved in the use and understanding of the processes in Engineering.