Towards the end of last year I shared with you my designs for a Baldwin RT-624 for the Pennsylvania Railroad, you can find the post here.  In the post I said that the RT-624 would be the first of my kits to be available in the XHD material.  In this post I want to show you how some of the XHD parts came out.

XHD stands for Extreme High Definition and is a term 3D Systems use for their 16 micron layer thickness setting on their Projet 3D printers. The majority of my 3D printed parts are printed by Shapeways in their Frosted Ultra Detail material.  FUD is also printed on a Projet machine at a 29 micron layer thickness, 3D Systems call this UHD or Ultra High Definition.  With 3D printing layer thickness, the lower the number the better the quality of the print.  But that does come at a price, with a smaller layer thickness the 3D model will take longer to print.

My first order of XHD prints was for four RT-624 kits as shown below.  The shell in the middle is a Shapeways print in their FUD material and the shell on the left has a set of  brass Additions train phone antenna test fitted in the roof.  The four XHD shells are shown here as delivered from the printers.

The first thing you notice is that the XHD prints are blue, whereas up untill now all my prints have been white. They are not blue because they were printed at a 16 micron layer thickness but because they were printed in a different material.  Shapeways use 3D Systems’ VisiJet^® M3 Crystal material for the FUD prints but my 3D printer in London uses 3D Systems’ VisiJet® M3 Procast material.  The main difference, apart from being blue, is that the Procast is designed for lost wax jewelry casting and is perfect for very small details.  It is still as permanent as the Crystal but it has a slightly lower tensile strength and higher tensile modulus, which means that it is just that little bit more flexible and therefore less brittle.

The main question is how much better is the 16 micron layer thickness compared to the 29 micron?  I must point out that the FUD shell used for this comparison has not been cleaned as thoroughly as normal; it still needs some of the powdery residue cleaning off.  Below are the kits in both layer thickness. Initially they look pretty much the same.  The Shapeways FUD model has all the detail, everything fits perfectly and it has been used to make some fantastic models, please see the RT-624 Gallery here.

It’s only when you get very close that you can start to see any differences. Looking at the two images below the roof of the locomotive is curved and in the FUD the curve is not quite as smooth as in the XHD.

Orientation also plays a big part in how well a 3D print comes out.  The top of the print will always be the best finish and any area that comes into contact with the support material also runs the risk of a slightly rougher finish.  These XHD prints were printed as if they were sat on the locomotive chassis.  This is the most expensive way of doing it because, just as if you were printing an upside down bath tub, the whole of the locomotive shell had to be filled with support material to print the top.  The benefit of this is that all the detail on the top comes out very clearly.  In the photo below you can see the lifting brackets and bolts around the exhaust stack are crisply printed. The details are still printed on the FUD model and are just as visible but they are just a little bit fuzzy. Don’t forget these details are tiny, the lifting ring is only about 1mm (0.039″) wide.

With smaller parts such as the fuel tanks, as you can see in the image below, it is very hard to see the difference between the FUD and the XHD prints.

With the trucks the two differences I could see were firstly that the XHD had a better definition on the tiny springs cast into the frame, and secondly the FUD has a better overall look. Both printers have heads that move over the print and the higher the definition, the more any offset calibration will show up in the print as vertical lines. So although the XHD print has better detail, the lower definition FUD print doesn’t show these vertical lines. Both prints show the horizontal lines made by layering the material as they print and the XHD layers are much smaller, but it has the added vertical lines from the moving print head.

Again with details like the cab interiors and horns it is very hard to tell the difference between XHD and FUD as you can see below.

Another advantage with specifying the XHD orientation is the quality around the sides is uniform, that is to say it is the same on all four sides.  Sometimes with the FUD prints one side can be rougher than all the others if it was on the bottom next to the print tray.

As with the FUD prints the XHD has to be cleaned to remove the waxy material left over from the print process.  Below is a shot showing a FUD print, an XHD print in the middle and a cleaned XHD print on the left.

The cleaning process has taken some of the blue colour out of the print, here are some more shots of the model after it has been cleaned.

As you can see in the photo above the XHD can still suffer from roughness under overhanging details, and as with the FUD this area will need a little scrub.  I find a toothbrush does this nicely.

So all in all is the XHD print better than the FUD? Well, I think it comes down to personal preference as well as your budget.  Currently the XHD prints are about three to three and a half times the price of the FUD prints. The really fine detail is sharper on the XHD but once painted the difference may not be so clear.  The XHD has the advantage of having a uniform finish on the sides but it can still suffer from rough areas which come into contact with support material and under overhangs. The calibration of the particular print machine can affect the quality of the 16 micron print head, causing vertical lines.  It may also depend what you want to use the 3D printed shell for; on smaller, more personal layouts where you are closer to your trains it is important to have as much crisp detail as possible, whereas on larger layouts when you are at least a few feet away from the trains such small detail may not really be visible. 

I think the detail on the XHD prints is superb, and I’m really excited that 3D printing is able to offer such high definition, particularly for us N-scale modelers. However, in my particular layout the cost of these prints is a little high compared to the FUD which is still a very good print. I anticipate that this level of XHD printing will become more viable to mid-budget modelers like myself in the future. If you have the budget, I would recommend these XHD prints.

If you would like any of my products printed in XHD please contact me through the contacts page and I can give a quote.

In next week’s post I will be sharing with you the finished O scale UP excursion train tenders and letting you know how to get them.