Another Büssing

[Peter_T1958]

Hi gents
Barneys Büssing conversation led me to the idea to present here, why you hear very little about me in this forum.
Some interesting documents I discovered recently focused my attention on another demanding project. What I would like to try is designing an entire vehicle in 1/25 scale with my CAD program. In the meantime construction is already at an advanced stage. What is all about?

The Büssing MTW 55 is a German heavy prime mover from 1917. There have been few documents and pictures until I discovered a spare parts list full of drawings.


And here the same vehicle in CAD:


Now most CAD work has been done but problems have only just started with the printing of the files. It is frustrating to see what I get different from print services all around the world! Here an example:



So the actual start in the analog modelling adventure is at the moment rather sluggish.
But as soon as I have some results on my work bench I will post an update here.

[Design-HSB]

Hello Peter, thanks for showing, I didn't know the Büssing either. I'm curious how it goes on.

[finescalerr]

Maybe you already spoke to the person who did some 3-D printing for Volker. He is in Germany and apparently very good. -- Russ

[Barney]

Very Unusual - just What I like - please keep us posted with your updates 
Barney

[Peter_T1958]

Thanks for your thoughts!

When I posted this project in another forum, some members there showed some interest to puchase the 3d parts. So I hoped to find a way to print the parts in a good quality in SLA but still attractively-priced. The well known market leader offers very good quality but at a high price – no one would buy it ! Neither I wanted to share my files, this due to bad experience in the past. 

So I tried various suppliers all over the world with the results shown above. It seems, that an own resin printer would be the key to success, the more I could place the supports on appropriate places. Alas this is not an option for me !
Let's see what the future might bring!

Cheers, Peter

 

[Design-HSB]

Hello Peter, in 1:22,5 I would certainly be interested in such a kit, only 1:25 deviates too far.

[Peter_T1958]

Hi Helmuth

The files could easily be scaled to 1/22,5. But I don't know whether printing would be possible in such big dimensions... and imagine the costs
Indeed, that would become a huge model, about 10' (25,5 cm) long ! Mine in 1/25 scale is already big

[Lawrence@NZFinescale]

Hi Peter

As someone with two 3D printers, who prints daily, my comment would be that the files shown are not set up for easy quality printing (on a resin machine at least). That may impact quotes offered.

If the plan is to print then the parts should be prepared with that in mind and consolidated/broken down to suit.  You don't want to sprue them as this generally has no useful function in the print process and limits orientation and support options.  But it's digital so a minor rearrangement is easy to do.

Large scale is also an issue as print time and resin cost will be far greater in 1/25 than they would be in 1/35 or 1/48. It's doable, but development costs are higher.  I've had quite a lot of experience rescaling models and generally speaking upscaling works pretty seamlessly (albeit with higher possible detail).  So it should be feasible to develop the model in a smaller scale to save cost and then upscale when the major issues are all sorted.

[Peter_T1958]

As someone with two 3D printers, who prints daily, my comment would be that the files shown are not set up for easy quality printing. The parts should be prepared with that in mind and consolidated/broken down to suit.

Thanks Lawrence!
That's exactly what I did originally. The model is constructed in 1/35 scale to check printability. Rescaling is easy to do afterwards. The engine for in instance is devided in several parts (engine block, carburettor, exhaust, cooling circuit). Each part leads to several files, as I want to save all important steps in case of a computer crash or annother mishap. In this way I don't have to go back to square one.
Now I discovered, that printing those parts at Shapeways (Fine Detail Plastic) costs much more this way than when I sprued them. I tryed different arrangements until I achieved the best price.
Some other parts were printed in SLA, each in a seperate files. But as I can't control the position of the supports, they are often at the wrong place or (in this example) parts are broken !



And this learning by trial and error is what makes the whole thing so expensive.
Now I am in contact with a manufacturer who showed interest in producing a small batch of my Büssing in SLA technique. If this WOULD be case, I would have to redesign some parts, as he could print much smaller details (which I had to simplify yust to make them printable).
As you have seen, there are a lot of « would » and «could» in the whole thing...

[Stuart]

Well, it still looks impressive to me.

Stuart

[Lawrence@NZFinescale]

Well I meant to say Peter, it's looking very nice.

Welcome to the world of 3D prints by the way - your experience here is typical.  There is CAD, there is printing and then there is model production - The latter being the optimal fusion of the two. 'Optimal' being somewhat subjective and machine/resin dependent.

Shapeways FD is a different technology to the common LCD resin printer, and different constraints apply.  These days I would rate the print quality as poor for our needs compared to a decent resin printer, but it does have some advantages.

Using the resin printer for producing models is generally quite cost-effective.  The cost for one offs being in the work up rather than production per se. My two images attached sum this up!!

In terms of support placement, you should be able to discuss this with your printer.  However you do need supports, so it's often a balance between print quality and part clean up.  Understanding the printer constraints helps in part design as the worst issues can often be avoided.  Bear in mind that any technology has its limitations and it may be easier to spend 5 minutes filling and sanding rather than chasing absolutely perfect prints.

[Peter_T1958]

Hi Lawrence

I noticed the quality differences too. Although I was very pleased when I received my first SLA printed wheel, while sanding and filling the few imperfections parts broke apart. When I realised at the end that there was more a pile of rubble then clean work I threw the whole thing frustrated into the bucket.



So I went back to Shapeways and their Fine Detail Plastic which is not the leading edge of technology but a solid basis. Of course you have to clean it up and to sand it.



But you are right : With a resin printer, much more would be possible... I just have to find THE right provider !

[Lawrence@NZFinescale]

I'm a fan of your stuff.

Resins vary a lot in their strength, impact resistance, detail, hardness etc, etc.  I use two for the most part.  The first has good performance properties but is a bit translucent so does not look great unpainted (fine with a coat of primer though).  The second is somewhat softer and has great detail, ideal for figures and things without large thin sections.  There is also the possibility of a castable resin with transfer through to bronze. The latter is a good option for small fragile parts.

I do offer 3D printing to modellers on a commercial basis.  Being a modeller myself I'm generally able to determine what's going to make the customer happy in regard to support placement and so on.  I'm in New Zealand, so not really optimal for helping you, but I'm happy to chat about approaches if you wish.

[Peter_T1958]

Thanks for the very kind offer! In the meantime I played around with Chitubox which seems rather quick to learn and I am looking forward to have first results from a regional provider soon.

What made me unsettled is that I don't know what approach promises the greatest success. I took a quick look on your homepage and discovered this breathtaking item :



Caption : A finely detailed one piece resin print representing the firebox and cab fittings of the NZR K class 4-8-4, in 1:64.

Obviously You are able to print such complicated items in one go; all parts as one file ! So this should be able with my parts too and I do not have to dissect everything just to arrange it in Chitubox (or similar programs) or do I understand that incorrectly?

[Lawrence@NZFinescale]

Thanks Peter

Understanding print setup will really help you get the best results.  It's probably best to let your supplier do the actual set up though as resins and machines vary in their performance.

With resin printers it comes down to the arrangement of parts.  Something like a tree with upwardly angled branches needs no support at all.  A tree with a weeping habit is almost impossible to print as every branch needs support - at the thin tip.  So with the boiler backhead, many of the elements can be unsupported if printed in the correct orientation and so it is not quite so difficult as it might seem.  In Chitu (which I do not use) you'll be able to search for 'islands' (=unsupported regions).  In simple terms, any arrangement of parts that eliminates or minimises islands in need of support is likely to produce a better print.

Spoked wheels can be quite problematic.  If printed vertically most spokes can be unsupported but any close to horizontal will need support and almost inevitably look slightly different to the rest in the print.  Printed flat the front of the wheel comes out really well, but the rear face does not. For cast loco drivers this is fine as the rear face will be turned up anyway.

So for your wheels I would look at dividing them into the tread + outside spokes + 'hubcap' and separately inside spokes + rim + hub, or something along those lines.

In terms of drawing practicality, leave all of your parts separate.  Only combine them when producing the print file, leaving the source as separate parts. It will just make your life far easier.