Date   

Re: 3D printing challenges etc.

Robert kirkham
 

well, I can't disagree with you Dennis.

To answer the "other software" question, I use two programs - both free - to convert and scale a Sketchup file. So first I export a sketchup file as a 3d model. Then I import the 3d model file into Meshlab, open it and export it as an STL file. Then in Accutrans I open the STL file and scale it. I know there are less clunky ways but I learned this in the early days of Shapeways services, when Rene Gourley was the only one I knew who had tried it. He put me onto these softwares - they were specifically recommended by Shapeways. They work, so I haven't learned a better way - which I know others on this list have done.

Rob

--------------------------------------------------
From: "soolinehistory" <destorzek@mchsi.com>
Sent: Friday, February 08, 2013 7:46 PM
To: <STMFC@yahoogroups.com>
Subject: [STMFC] Re: 3D printing challenges etc.



--- In STMFC@yahoogroups.com, "Rob Kirkham" wrote:

yes - but if using Sketchup to scale the drawing to HO, you can also run
into the 6 decimal place rounding problem if you are not careful. Dividing
most large numbers by 87.1 seldom produces neat 6 (or fewer) digit
quotients. Using other software to scale a full size drawing allows one to
get around that problem. But drawing with the rounding problem in mind
from the get-go is also worth some effort.

Rob Kirkham
I think Rob's problem lies elsewhere.

Let me preface this comment with the confession that I am by no means an expert on Sketchup... In fact, I've never used the software, and all I know I've learned from poking around in their help files and discussion lists, looking for answers to Rob's questions.

That said, the problem lies not in what scale the object is drawn in, or how many decimal places entered points are calculated to. If one were to draw the gusseted end of a hat section brace as a portion of an ellipse, or a NURBS curve, extrude that profile to give it some thickness, lay it over modeled sheathing with V groove edges, and preform the Boolean union operation to attempt to make them one solid, the software is going to preform all kinds of calculations to the limit of its precision, no matter if the original data was entered to three place precision, two place precision, or limited to whole numbers.

The problem is that while software operating with solids as the native environment will either do the operation, or choke right then and there. Sketchup, on the other hand, will happily trim all the surfaces and display them, without any indication that the different surfaces that define what you assume to be a solid do not have concurrent boundaries, and you won't learn that until thousands of operations later, when you try to convert the file to STL format. You end up with something that Sketchup calls "leaky solids", which is basically the software development team's admission that their product can't reliably calculate boundaries with all points within the internal margin of error for concurrent points. It is basically the difference between freeware, and software that will set you back multiple thousands of dollars.



Dennis



------------------------------------

Yahoo! Groups Links




Re: can you id these tank cars?

Richard Hendrickson
 

On Feb 8, 2013, at 6:15 PM, Anthony Thompson <thompson@signaturepress.com> wrote:

Tim O'Connor wrote:
http://www.ebay.com/itm/111007867594
http://www.ebay.com/itm/121060850109
http://www.ebay.com/itm/111007867635
http://www.ebay.com/itm/111007866997
http://www.ebay.com/itm/111007867546
Since bidding has ended, or the item sold, in all five cases, you can no longer click to enlarge. Not many of us can identify much in the little thumbnails provided for buyers to look at.

Well, for some reason I had no trouble enlarging the images, and the tank cars were as follows:

DNCXX 5509 8K gal. AC&F Type 11

TRNX 12001 16K gal. Santa Fe Tk-M built by GATC in 1942

DNCXX 2719 10K gal. Pennsylvania Tank Car Co. built in 1923

MTSX 107 8K gal. Standard Tank Car Co.mid-1920s

ECMX 502 8k Gal. AC&F Type 11


Richard Hendrickson


Re: 3D printing challenges etc.

Scott H. Haycock
 

Thanks for the explanation. It would indeed be frustrating to find out at the end that there is an error(or many) somewhere, and not know where to find it!


Scott Haycock
Modeling Tarheel country in the Land of Enchantm ent

----- Original Message -----








I think Rob's problem lies elsewhere.

Let me preface this comment with the confession that I am by no means an expert on Sketchup... In fact, I've never used the software, and all I know I've learned from poking around in their help files and discussion lists, looking for answers to Rob's questions.

That said, the problem lies not in what scale the object is drawn in, or how many decimal places entered points are calculated to. If one were to draw the gusseted end of a hat section brace as a portion of an ellipse, or a NURBS curve, extrude that profile to give it some thickness, lay it over modeled sheathing with V groove edges, and preform the Boolean union operation to attempt to make them one solid, the software is going to preform all kinds of calculations to the limit of its precision, no matter if the original data was entered to three place precision, two place precision, or limited to whole numbers.

The problem is that while software operating with solids as the native environment will either do the operation, or choke right then and there. Sketchup, on the other hand, will happily trim all the surfaces and display them, without any indication that the different surfaces that define what you assume to be a solid do not have concurrent boundaries, and you won't learn that until thousands of operations later, when you try to convert the file to STL format. You end up with something that Sketchup calls "leaky solids", which is basically the software development team's admission that their product can't reliably calculate boundaries with all points within the internal margin of error for concurrent points. It is basically the difference between freeware, and software that will set you back multiple thousands of dollars.

Dennis


Re: 3D printing challenges etc.

Dennis Storzek
 

--- In STMFC@yahoogroups.com, "Rob Kirkham" wrote:

yes - but if using Sketchup to scale the drawing to HO, you can also run
into the 6 decimal place rounding problem if you are not careful. Dividing
most large numbers by 87.1 seldom produces neat 6 (or fewer) digit
quotients. Using other software to scale a full size drawing allows one to
get around that problem. But drawing with the rounding problem in mind
from the get-go is also worth some effort.

Rob Kirkham
I think Rob's problem lies elsewhere.

Let me preface this comment with the confession that I am by no means an expert on Sketchup... In fact, I've never used the software, and all I know I've learned from poking around in their help files and discussion lists, looking for answers to Rob's questions.

That said, the problem lies not in what scale the object is drawn in, or how many decimal places entered points are calculated to. If one were to draw the gusseted end of a hat section brace as a portion of an ellipse, or a NURBS curve, extrude that profile to give it some thickness, lay it over modeled sheathing with V groove edges, and preform the Boolean union operation to attempt to make them one solid, the software is going to preform all kinds of calculations to the limit of its precision, no matter if the original data was entered to three place precision, two place precision, or limited to whole numbers.

The problem is that while software operating with solids as the native environment will either do the operation, or choke right then and there. Sketchup, on the other hand, will happily trim all the surfaces and display them, without any indication that the different surfaces that define what you assume to be a solid do not have concurrent boundaries, and you won't learn that until thousands of operations later, when you try to convert the file to STL format. You end up with something that Sketchup calls "leaky solids", which is basically the software development team's admission that their product can't reliably calculate boundaries with all points within the internal margin of error for concurrent points. It is basically the difference between freeware, and software that will set you back multiple thousands of dollars.



Dennis


Pacific Electric Boxcar Brakes

super_chief37
 

Hello folks-
I'm currently scratchbuilding a Pacific Electric boxcar based on these examples:

http://www.oerm.org/collection/red-cars-pacific-electric/pe-2731-0
http://www.oerm.org/collection/red-cars-pacific-electric/pe-2721
http://www.oerm.org/collection/red-cars-pacific-electric/pe-2737

Only piece of information I'm missing concerns the brakes. Anyone have a picture showing the arrangement of rods and levers? I did a search here, and someone did post pictures but the links have expired. Also, were the cars equipped with regular KC brakes or split K? Finally, when were they converted to AB brakes as it appears in the pictures? I'm modeling 1941 and I want to know which type is appropriate.

Thanks!
C.I.H.


Re: Box Car Database

Schuyler Larrabee
 

There are a couple of good stories about the [M&StL] box car mentioned above
that should be told sometime.

Gene Green




No time like the present, Gene.



Schuyler


Re: Early Westerfield Dark gray kits

markrossiter67 <Mark.Rossiter@...>
 

--- In STMFC@yahoogroups.com, "Charlie D" wrote:
I have quite a few of the box cars kits from the gray material days that I was able to successfully build without a lot of angst. Much more enjoyable to build than some of the early Sunshine or F&C Urethane kits. The only Westerfield kit that I threw in the towel on was the NYC 70 ton hopper car. Everytime I touched it something else broke. I finally decided that if I ever wanted to model a derailment scene with wrecked cars in it, that car would be the first to go in it.
Mark

I still have several of the dark gray kits running on the layout. His B&A steel boxcar and a couple of the MP 40' automobile cars. I remember using wood floor stock on the interior of the sides to get them straight and it gave me more surface to attach the ends to. The gray resin seemed to eat my drill bits though. I recently finished the GN truss rod boxcar and the NC&StL 36' boxcar in the gray resin. They are a enjoyable build next up is the new RI stock car.

Charlie Duckworth

--- In STMFC@yahoogroups.com, Doug Pillow wrote:

Had two of them from e-bay  a USRA single sheathed and a three bay hopper. Box
car had crackin side I managed to fix. Hopper car I couldn't get together was
warped. Most frustrating kit I ever tried to assemble ended up pitching it in
trash. That material was tough to work with.

                                                                                                          
Doug Pillow

[Non-text portions of this message have been removed]


Re: 3D printing challenges etc.

Tom Madden
 

I wrote:

I design in 1:1 because I work from prototype drawings. When I'm satisfied with the part or assembly I ** an STL file. Also 1:1. I bring that into Netfabb and scale it, and export *that* as another STL file. (I have to use the export function with Netfabb - for some reason I can't get it to ** in that program.)

I find I get a higher quality output if I scale the STL file rather than scaling the design and then creating the STL file. (I tend to lose my curiosity when I find a system that works and will just stick with that.)
Well, that doesn't make a lot of sense! Yahoo dropped two instances of "Save as" enclosed in greater than/less than brackets. They belong where I put the double asterisks above.

Tom M.


Re: Athearn ATSF 34' caboose prototype and roof color question

midrly <midrly@...>
 

Good thing that Rail Alphabet hasn't entered the discussion yet...(grin).

Steve Lucas.

--- In STMFC@yahoogroups.com, Anthony Thompson wrote:

Matthew J. Moellendorf wrote:
Thanks Everbody (especially Tom). Since this caboose will have the older roman lettering, not the later aerial-style . . .
I'm guessing you meant to say "Arial," the Microsoft look-alike of Helvetica, which is indeed more modern looking.

Tony Thompson Editor, Signature Press, Berkeley, CA
2906 Forest Ave., Berkeley, CA 94705 www.signaturepress.com
(510) 540-6538; fax, (510) 540-1937; e-mail, thompson@...
Publishers of books on railroad history


Re: 3D printing challenges etc.

Tom Madden
 

So you would output your final object to another program for scaling? What other programs would you use?

Scott Haycock
Don't know if this will pertain using Sketchup...

I design in 1:1 because I work from prototype drawings. When I'm satisfied with the part or assembly I <Save as> an STL file. Also 1:1. I bring that into Netfabb and scale it, and export *that* as another STL file. (I have to use the export function with Netfabb - for some reason I can't get it to <Save as> in that program.)

I find I get a higher quality output if I scale the STL file rather than scaling the design and then creating the STL file. (I tend to lose my curiosity when I find a system that works and will just stick with that.)

Tom Madden


Re: 3D printing challenges etc.

Scott H. Haycock
 

So you would output your final object to another program for scaling? What other programs would you use?


Scott Haycock
Modeling Tarheel country in the Land of Enchantm ent

----- Original Message -----





Using other software to scale a full size drawing allows one to
get around that problem. But drawing with the rounding problem in mind
from the get-go is also worth some effort.

Rob Kirkham

--------------------------------------------------
From: "Scott H. Haycock " shhaycock@comcast.net >
Sent: Friday, February 08, 2013 6:18 PM
To: STMFC@yahoogroups.com >
Subject: Re: [STMFC] Re: 3D printing challenges etc.





[Non-text portions of this message have been removed]


Re: 3D printing challenges etc.

Robert kirkham
 

yes - but if using Sketchup to scale the drawing to HO, you can also run into the 6 decimal place rounding problem if you are not careful. Dividing most large numbers by 87.1 seldom produces neat 6 (or fewer) digit quotients. Using other software to scale a full size drawing allows one to get around that problem. But drawing with the rounding problem in mind from the get-go is also worth some effort.

Rob Kirkham

--------------------------------------------------
From: "Scott H. Haycock " <shhaycock@comcast.net>
Sent: Friday, February 08, 2013 6:18 PM
To: <STMFC@yahoogroups.com>
Subject: Re: [STMFC] Re: 3D printing challenges etc.

Rob
In Sketchup, c an't you draw in full scale then reduce the final result at the end?


Scott Haycock
Modeling Tarheel country in the Land of Enchantm ent
----- Original Message -----


Re: can you id these tank cars?

Anthony Thompson <thompson@...>
 

Rawil Ismail wrote:
Tony, did you try the "See original listing" link? From that linked page, I was able enlarge the photos.
Yes, thanks. I was fooled by all the images "more from this seller" and did not scroll down.

Tony Thompson Editor, Signature Press, Berkeley, CA
2906 Forest Ave., Berkeley, CA 94705 www.signaturepress.com
(510) 540-6538; fax, (510) 540-1937; e-mail, thompson@signaturepress.com
Publishers of books on railroad history


Re: can you id these tank cars?

Pete Ismail
 

Tony, did you try the "See original listing" link? From that linked page, I
was able enlarge the photos.

Pete Ismail
Peyton, CO

On Fri, Feb 8, 2013 at 7:15 PM, Anthony Thompson <
thompson@signaturepress.com> wrote:

**


Tim O'Connor wrote:
http://www.ebay.com/itm/111007867594
http://www.ebay.com/itm/121060850109
http://www.ebay.com/itm/111007867635
http://www.ebay.com/itm/111007866997
http://www.ebay.com/itm/111007867546
Since bidding has ended, or the item sold, in all five cases, you can no
longer click to enlarge. Not many of us can identify much in the little
thumbnails provided for buyers to look at.

Tony Thompson Editor, Signature Press, Berkeley, CA
2906 Forest Ave., Berkeley, CA 94705 www.signaturepress.com
(510) 540-6538; fax, (510) 540-1937; e-mail, thompson@signaturepress.com
Publishers of books on railroad history



[Non-text portions of this message have been removed]


Re: 3D printing challenges etc.

Scott H. Haycock
 

Rob
In Sketchup, c an't you draw in full scale then reduce the final result at the end?


Scott Haycock
Modeling Tarheel country in the Land of Enchantm ent

----- Original Message -----





For example, early on I was using conversions from
prototype dimensions to HO scale dimensions that used all 6 decimal points
available in Sketchup.

Rob Kirkham

--------------------------------------------------
From: "soolinehistory" destorzek@mchsi.com >
Sent: Friday, February 08, 2013 8:46 AM
To: STMFC@yahoogroups.com >
Subject: [STMFC] Re: 3D printing challenges etc.





[Non-text portions of this message have been removed]


Re: can you id these tank cars?

Anthony Thompson <thompson@...>
 

Tim O'Connor wrote:
http://www.ebay.com/itm/111007867594
http://www.ebay.com/itm/121060850109
http://www.ebay.com/itm/111007867635
http://www.ebay.com/itm/111007866997
http://www.ebay.com/itm/111007867546
Since bidding has ended, or the item sold, in all five cases, you can no longer click to enlarge. Not many of us can identify much in the little thumbnails provided for buyers to look at.

Tony Thompson Editor, Signature Press, Berkeley, CA
2906 Forest Ave., Berkeley, CA 94705 www.signaturepress.com
(510) 540-6538; fax, (510) 540-1937; e-mail, thompson@signaturepress.com
Publishers of books on railroad history


Re: 3D printing challenges etc.

Robert kirkham
 

very nice parts Tom! The detail you are able to draw with solid works is impressive.

Rob

--------------------------------------------------
From: "pullmanboss" <pullmanboss@yahoo.com>
Sent: Friday, February 08, 2013 12:50 PM
To: <STMFC@yahoogroups.com>
Subject: [STMFC] Re: 3D printing challenges etc.

Mick Storzek wrote:

It all goes back to the mantra I've been chanting...

I can't get no
RESOLUTION,
I can't get no
RESOLUTION,
But I try, and I try, and I try...

Until the process can reliably yield .003" steps on the surface, and reliably construct smooth vertical walls, I just don't see much use for it. I keep seeing people singing the praises, but I'm not seeing any photos of the actual models, just overall photos of frosty white blobs.
OK, here's some photos of that parts plate I mentioned yesterday. It was designed 1:1 in SolidWorks 2012 and saved as an STL file. The STL file was scaled to 1:87.1 and validated in Netfabb, a free viewer available through Shapeways, and sent to ADC manufacturing. ADC created the part using 3D Systems Projet process in 29 micron layers at 750 x 750 DPI resolution. (Shapeways calls it their FUD process.) No white blobs because I hit it with a light coat of gray primer so I could make a mold. Photographed in direct sunlight to accentuate every detail, defect and dust particle. These two photos show the whole plate from two different angles:
http://pullmanproject.com/Plate1.jpg
http://pullmanproject.com/Plate2.jpg

Here's the center portion in extreme closeup:
http://pullmanproject.com/PlateCloseup.jpg

In this photo you can see a heavy wax track below the drain valve housing on the bottom of the left unit. You can also see the general roughness of the vertical surfaces. But that sheelmetal flange running the length of the middle unit is 1/2" thick - 0.006" in HO, and perfectly defined. (It projects 1".) Likewise the rivets at the top edge of that unit are 1/2" in diameter and nicely defined. But most impressive is the lack of stairstepping on the angled faces of all three housings.

I did nothing but clean and prime that plate. I polished out the wax tracks and cleaned up the first generation castings, and those will be my production masters.

Tom Madden


Watch Your Step decals

George Courtney
 

Anyone know of any HO or N scale decals that contain a Watch Your Step warning in white? I had a set of old Walthers with this for a caboose but naturally ruined one of the decals. Many of the decal providers don't have photos.

Thanks,
George Courtney


Re: 3D printing challenges etc.

Robert kirkham
 

Dennis has basically nailed the source of my difficulties. Better software is the obvious solution, but for now I'm getting sufficiently good results with free software (Sketchup) that I am instead working to improve my drawing skills. For example, early on I was using conversions from prototype dimensions to HO scale dimensions that used all 6 decimal points available in Sketchup. "Wow - can I draw with precision" I thought. Dumb beginner mistake. As a result, the software couldn't handle dividing a space in two equal parts as it would require the 7th decimal place. Seems self-evident now, but I didn't catch that in my early on line learning efforts. Given the resolution of the printed product, nothing was being achieved with 6 decimal places that couldn't usually be achieved in 3 (and sometimes 2) places.

Rob Kirkham

--------------------------------------------------
From: "soolinehistory" <destorzek@mchsi.com>
Sent: Friday, February 08, 2013 8:46 AM
To: <STMFC@yahoogroups.com>
Subject: [STMFC] Re: 3D printing challenges etc.



--- In STMFC@yahoogroups.com, Richard Brennan wrote:

At 09:57 PM 2/7/2013, Rob Kirkham wrote:

That too is too subtle with 3d printing.

So I've drawn and re-drawn it - and each time come to a leaky dead end.
When I get the interest back, I'm going to start from scratch and do it again.
I suspect the issue is NOT your drawing...
but the specific 3D print process/technology you are using.

Question - Were you expecting finished models to be:
1st generation: 3D print each car + paint + lettering?
2nd generation: 3D print master car car + resin-cast copies + paint +
lettering?

If the latter... then the need for 3D print quality trumps the desire
for a low cost print,
and you can find a print service that will do the resolution you
need. They do exist!

Just a thought...

--------------------
Richard Brennan - San Leandro CA
It all goes back to the mantra I've been chanting...

I can't get no
RESOLUTION,
I can't get no
RESOLUTION,
But I try, and I try, and I try...

Until the process can reliably yield .003" steps on the surface, and reliably construct smooth vertical walls, I just don't see much use for it. I keep seeing people singing the praises, but I'm not seeing any photos of the actual models, just overall photos of frosty white blobs. I'm sure one of the various additive processes will eventually yield good, usable parts... but whether we will be able to afford them is another issue.

Rob's file problems seem to trace back to the fact that Sketchup is not a solid modeler, it's a SURFACE modeler, that defines a solid by its boundary surfaces, It will therefore draw surfaces that appear to enclose a volume, but really don't. Since the STL files used by most of the "3-D printers" are extracted from solids, if the Sketchup surfaces don't actually enclose the volume, then the solid isn't there, and won't be converted. This isn't a slight of Rob's CAD abilities, the problems most likely derive from rounding errors in Sketchup's calculations as it attempts to trim the various surfaces to each other. For the web animation purposes Sketchup seems to be aimed at, these errors are insignificant; not so for our purpose. I suspect that a step up to industrial grade software would solve the problem, but not cheaply.

Here is a link to a web discussion that has several links to software plug-ins that help identify problem areas in a Sketchup model:

http://sketchucation.com/forums/viewtopic.php?f=79&;p=276399

Of course, finding the problem is one thing, fixing it is a whole 'nother issue.

Dennis




------------------------------------

Yahoo! Groups Links




Re: 3d printing challenges etc.

Robert kirkham
 

I can see this discussion went on while I've been at work, so I'm coming back to it late. Anyhow . . .

The purpose of my efforts with 3d printing have been mixed. Some of the parts are one-offs and I'll use the printed version. But most of them are freight cars, and my intent is to get good masters for casting etc. The ADC product has been very satisfying in that respect, and does produce usable models.

The problems I've encountered with the CPR automobile boxcar are unique and reflect my learning curve. Having since completed a number of other drawings without problems, I know the problem is my own. I think somewhere along the line I started out with a careless minute error; without going into a lot of detail, Sketchup has the unhappy tendency of making such errors very hard to detect if you are not on the lookout for them while drawing.

For example, imagine a polygon of 24 sides - what Sketchup would call a circle. Imaging other shapes in the mode you are drawing result in lines that connect at tangent to the circle. Very often this will occur without any trickiness, and the lines will go where you draw them. But if a junction/end point between lines occurs so close to another junction/end point that it is within Sketchup's minimum, the machine will round them to a common point when in fact they should be two discrete very close points. If you know this problem, you can draw around it and avoid it. But even then one can occasionally fail to notice when it happens. So one starts to be more careful about these problems. And that will mostly allow you to avoid them. Dennis Storzek got me onto the problem of rounding errors - which is essentially what I am describing. Ever since I received his advice, I've managed to draw without too much trouble. But old drawings with lurking problems are very hard to fix.

Starting afresh and just re-drawing the car sides from scratch will result in good sides. I just have to want to do it - and I got to the point where I didn't want to for a while (although this discussion is bringing the desire back). For the time being I'm having a lot of fun doing a steam loco frame and cylinders . . . .

Rob Kirkham

--------------------------------------------------
From: "Richard Brennan" <brennan8@earthlink.net>
Sent: Friday, February 08, 2013 7:42 AM
To: <STMFC@yahoogroups.com>
Subject: Re: [STMFC] 3D printing challenges etc.

At 09:57 PM 2/7/2013, Rob Kirkham wrote:
<snip>
That too is too subtle with 3d printing.

So I've drawn and re-drawn it - and each time come to a leaky dead end.
When I get the interest back, I'm going to start from scratch and do it again.
I suspect the issue is NOT your drawing...
but the specific 3D print process/technology you are using.

Question - Were you expecting finished models to be:
1st generation: 3D print each car + paint + lettering?
2nd generation: 3D print master car car + resin-cast copies + paint +
lettering?

If the latter... then the need for 3D print quality trumps the desire
for a low cost print,
and you can find a print service that will do the resolution you
need. They do exist!

Just a thought...

--------------------
Richard Brennan - San Leandro CA
--------------------



------------------------------------

Yahoo! Groups Links



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