Shapeways' HDA - Anybody doing trucks?

[C855B]

It is my perception - correct me if I'm off-base - that Shapeways' High-Definition Acrylate has nearly the detail of FUD/FXD but is much less brittle. If so, would it be a suitable material for locomotive truck sideframe assemblies? There are models on my bench (and several in boxes  ) that suffer from poorly-rendered or incorrect trucks. What I'd like are snap-off/snap-on replacements.

Is anybody doing something like this? Or are there limitations to HDA that I'm not aware of beyond the dimensional fidelity issues with complete shells?

[Lemosteam]

@bbussey tried it on some trucks when it first came out as did I on a horse car roof.

I hope you are not referring to my trucks- lol. 

I find that the support strands that the machine applies are detrimental to the print quality no matter how the print is oriented or designed.  This was evidenced on the bottom of the TP56 shell and walkway frame in that thread.

This is not a criticism of those that use it, I just find it less acceptable than FXD.

Have you tried using an air eraser in the areas around the detail you are trying to improve?

[RAIL N SCALE]

Before Black High-definition Acrylate (B-HDA) went on sale we were participating in a trial with this material.
In theory the details are slightly less than parts printed in Frosted Ultra Detail (FUD). On the positive side is that the surfaces tend to have a smoother appearance that looks more like injection moulded plastics. Although this appears to differ from print to print. Some items showed clear building layers.

We printed some car models and learned that B-HDA is not suitable for mechanical components as it tends to warp quite a bit. As B-HDA requires smart support struts it is sensitive to mis-orientation of those struts. The problem is that only properly located supports will provide good prints. These struts however are not part of the 3D geometry that the designer uploads (because that would require a lot of experience), but is automatically generated. And since Shapeways prints many designs these support struts are not optimized to suit a particular model. We learned that the print orientation and positioning of the struts varied per print which led to differnt printing problems. Another thing is that B-HDA cannot deal very well with thin walls. They tend to bend over or warp. Finally Shapeways manually removes the support struts. And this is not a very precise process. We saw that cutting marks and that sometimes items were cut-off unintentionally.

The advantage of B-HDA over FUD is the far easier post-processing (not necessary to clean the items) although I think the colour choice (black only) is not always nice for painting.

The limitations of B-HDA makes this material suitable for organically shaped parts (like figurines) and other items that do not require a precise dimension. B-HDA is not suitable for geometrical designs and/or designs that feature narrow long shapes. Bigger and more solid designs work best. For this reason we are not offering products in B-HDA.

Kind regards,
Maurice
RAILNSCALE
https://railnscale.com/

[C855B]

I hope you are not referring to my trucks- lol. 

No, no. No.

The immediate interest is in 4-axle ('D') Flexicoils. The current Bach-person DDA40X, of which I have an embarrassing number, has very poor relief detail on the trucks. They may as well be printed flat boxes holding the truck together. I'm also trying to build a fleet of DD35s from James Norris' shells; DD35s have the same basic truck, but without the top-mounted brake cylinders or the brake shoes on the ends. I could carve on the B'mann trucks for the brake rigging discrepancies, but that still doesn't fix the basic relief issues.

I have a semi-local 1:1 Centennial I can take measurements from, and lots of pictures of a truck separated from its mothership. My objective is to produce a snap-on replacement. My concern from a couple of experiences in handling is whether FXD would shatter in this situation, hence my inquiry about HDA.

I think Maurice answered the question. The basic snap-on box has roughly (without looking at one) a 0.030" thickness, to which detail is added, plus I might be subtracting thickness in a couple of places for details. It sounds like this is going to be too thin for HDA.

[peteski]

No, no. No.

The immediate interest is in 4-axle ('D') Flexicoils. The current Bach-person DDA40X, of which I have an embarrassing number, has very poor relief detail on the trucks. They may as well be printed flat boxes holding the truck together.

Funny - this is also my problem. The old Bachmann DDA40X had much better looking truck sideframes. I don't know why they messed them up in the newer version. 
  But the axle spacing between the new and old trucks is slightly different, so I can't just cut off some old sideframes and stick them on the new trucks.

The idea I came up with several years ago (so far only in my mind, although I have all the needed parts and supplies - just no time) is to make a 1-parrt open RTV mold of the original Bachmann DDA40X trucks. Then, since RTV is stretchable, I'll stretch the mold so the axle spacing corresponds to what is used on the new trucks and I'll pout some resin copies using the stretched mold. I'll clean them up and use them as master pattern to make new sideframes with better relief and correct axle spacing. I'll then find a way to attach them to the new trucks.  So without any fancy 3D designs and printing I should end up with usable sideframes with much better relief-details.

[C855B]

... I'll then find a way to attach them to the new trucks. ...

That's my issue. You could sand the detail off the originals and laminate something, but anything more than paper-thin in some areas is going to be "fat", and the shell is already about 8" on the porcine side. I bought a 1st-gen Overland on eBay - entirely too much money for such a crappy mechanism - explicitly to use as a master for doing something like this. I don't recall verifying the wheel spacing, however. I'll take a look tomorrow, I guess, today's dance card is a little full.

[dcutting]

I'm beginning to use small print shops for my parts, they can supply much better detailed and oriented parts because they are in no rush. That also means the walls can get thinner. And I can prevent warping using special jigs whilst the parts are under the light.

I could work on the parts over Christmas break if that helps at all...

David

[SandyEggoJake]

@C855B

Recently had a similar conversation about FUD v B-HDA.  Similar report as Maurice notes here.  Seems the ideal material for 3DP trucks has yet to land at SW.  But for now FUD/FXD may still be slightly better than B-HDA at least in N scale.

Last year I bought some FUD trucks from Eric Cox, Panamint Models via SW.   They look great, but given axle issues, just not runners (yet?  Perhaps I can tune via an N scale reamer, as per the other thread) and I fear they are just too brittle. 

In hopes of building runner worthy trucks, just last week, I got a different design which I hope to try soon.  Matthew Myers, South Boulder Modelworks via SW.  https://www.shapeways.com/product/5JK7RQNJH/n-scale-archbar-tender-truck-frames-detail-part?optionId=63887305&li=marketplace

His solution is just side frames in FXD which are to be laminated over the sides of sanded down commercial POM trucks (in his case, designed to go over Bmann tender trucks).  I don't know if it will work well, but willing to give it a go.  I've yet to "grind & bind", but after I finish some other projects, this will be up soon.  In part as I've yet to determine the best glue for this, but I picked up some Loctite "Hard to bond" plastic glue ...  though have concerns such a system may not be compatible with FUD/FXD.  Kind of curious that these new UV activated glues might also better for this application. 

Of course in prepping to clean the new parts this past weekend, I already crushed 4 of the 8 sideframes just getting them out the packaging ....grrr.     FUUUUUUUUD!

 

[C855B]

... Last year I bought some FUD trucks from Eric Cox, Panamint Models via SW.   They look great, but given axle issues, just not runners (yet?  Perhaps I can tune via an N scale reamer, as per the other thread) and I fear they are just too brittle. ...

Yeah, like I said, I've had just enough issues with FXD brittleness to have concerns about a "snap-on". As to the axles, John's (@Lemosteam) advice is to use the smallest (...I think...) Dremel round burr to touch-up the axle sockets on his UP caboose trucks. It seems to work well... rolls quite a bit better than the brass trucks on the Hallmark and Overland cabeese in the gathering-dust fleet on the workbench.

... I could work on the parts over Christmas break if that helps at all...

I might take you up on that. Sometimes in the next day or so (very busy week) I will take the caliper to a B'mann truck and probe for thicknesses. I'm mulling trying my hand at something more complex than a box , and something that starts with a box might be up my alley. Anyway, whoever does one could stand to make a few cents since this is a common complaint about the model.

[peteski]

I might take you up on that. Sometimes in the next day or so (very busy week) I will take the caliper to a B'mann truck and probe for thicknesses. I'm mulling trying my hand at something more complex than a box , and something that starts with a box might be up my alley. Anyway, whoever does one could stand to make a few cents since this is a common complaint about the model.

If better sideframes were made available (and looked decent) I would buy a set so I wouldn't have to "roll my own". One fewer project on the to-do list.

[C855B]

Some pics for reference. Bachmann:



Overland:



1:1 :





The Bachmann truck sideframe snap-on is essentially an 0.030" box with cutouts for the wheels and gears. While the profile is shallow overall, the biggest problem is the brake shoes and rigging are almost in the same plane as the front of the frame, trying to keep to 0.030" at the bottom of the frame. I think I read where a modeler painted the brake rigging black to give the illusion of depth - not a bad idea. But compare it against the Overland. The Overland has the brake rigging deeper into the frame, plus the better profile and much better relief on the brake cylinders. If there was consideration to use the Overland as a master for a resin sideframe overlay... well, it may not work as an overlay since too much material would have to be removed from the Bachman sideframe. On the other hand, I don't know how important the full frame "box" is insofar as its function as a gear and axle retainer. It may be possible to cut the sides of the box off completely and have it hold since the tabs are on the ends of the mechanism (I should test this). Axle spacing is identical between the two, which is encouraging.

What's interesting is the 1:1 DD35 truck does not have visible brake rigging. I could completely cut off or drill out the brake rigging and grind off the cylinders, and it would be a reasonable representation. A 3DP project for it alone might not be worth the work, but OTOH if you have the DD35 truck, you're 90% on your way to the DDA40X.