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ZHESM electric train model

Unique home-made 1:87 model train of first electric train in NL

Since the introduction of the Hobby license we have been happy to welcome many hobbyist DeskProto users. Many of them do in fact achieve absolutely professional results, like in this example of a train model. The model has been made by Dutch hobbyist user Richard (website Digi-Train).

Richard tells about his project:
This train was the first electric train unit in the Netherlands. It was introduced in 1908 on the line from Rotterdam to The Hague and Scheveningen, owned and run by the Zuid Hollandsche Electrische Spoorweg Maatschappij (ZHESM). Of these trains only one motor carriage survived, which can now be seen in the Railway Museum in Utrecht (Netherlands). A model version doesn't seem to exist to my knowledge (more about that on the end of this page). So, after acquiring a (hobby) CNC mill it was a real challenge to build a set of three cars, forming a train unit as normally used in the 1910's and 20's.

The original train, parked in the Railway Museum
The complete design in SketchUp (screenshot)
The last remaining original train, shown in the museum, and Richard's CAD design in SketchUp.

The model has been made scale 1:87 (rail gauge 16.5 mm), making one carriage ca 200 mm long.
Design (CAD) software: Google SketchUp (the free version) with plug-in for DXF and STL file export.
Material: Polystyrene sheet of various thickness (1, 2, 3, 4, 5, and 9 mm) and
polycarbonate sheet (1 and 2 mm).
Manufacturing (CAM) software: DeskProto V.6.
Machine: Colinbus Profiler Pro, control software Colidrive (comes with the machine).

Many parts had to be milled, often two-sided. Many options in DeskProto for strategies, borders, layers, segments, etc. have been used to manufacture all these parts. Special care was taken not to mill too much material at once, thus not over-heating and melting the material.
On this Gallery page the creation of the roof will be shown in detail.

Front part of the roof, in CAD
Center part of the roof, in CAD
Back part of the roof, in CAD
Base part of the roof, in CAD
The four parts of the roof, in 3D CAD.

The roof has been built using 4 separate parts: front, center, back and base.
Front part and back part have been machined in one go, from one 9 mm thick block.
In order to machine this block from two sides it was needed to create two parts in DeskProto. One for milling the bottom side, another (after a 180 degree flip) for the top side and to separate the two parts from the main block.

Roughing the roof ends, bottom, in DP
Finishing the roof ends, bottom, in DP
Roughing the roof ends, top, in DP
Finishing the roof ends, top, in DP
Roughing toolpaths (strategy waterline) and finishing toolpaths (strategy parallel), for the front and back part: both top side and bottom side.

The front part and back part have been exported as separate STL files, to be imported in DeskProto. There for each model a large support block was added in order to clamp the block of material on the machine.

Roughing the center part of the roof
Finishing the center part of the roof
Roughing and finishing the roof's center part.

Next the center part of the roof (with the little 'windows') was made, out of a 5 mm thick sheet.
At first the top-side was shaped with "no extra" for the borders, thus leaving the part attached to the stock material. A simple X-parallel strategy in two roughing steps with a 3 mm flat end mill was used, followed by a one step finishing with a 1 mm flat end mill.

DP screenshot: roughing toolpaths and simulation
DP screenshot: finishing simulation
Roughing and finishing the bottom side of this part (with simulation).

A "trick" with 4 holes on the corners and for positioning pins in the machining table was used to turn (flip) the part to its proper position for milling the bottom side.
The first process was an X-parallel roughing in layers of 1 mm and with "no extra" for the border (again to prevent premature separation of the part from the stock material). Then a finer detailing of only the window styles was done with a one-go X-parallel strategy using a 2 mm flat-end mill. The outside shape was then further detailed with a 1 mm mill and finally the part was cut out with a contouring strategy, using a 3 mm mill in steps of 1 mm.

Sketchup screenshot
Machined model
The roof base: CAD model and result.

The roof base has been machined in a slab of PS, 5 mm thick. Again from two sides, where the top side was machined to max 4 mm deep to keep the part connected to the rest of the material: see the illustration below. Roughing was done with a 3 mm cutter, finishing (a few operations) with a 1 mm cutter (diameter).

The milling machine in action
The roof: four parts assembled
The Colinbus machine, and the four roof parts assembled.

For the bottom side extra operations have been added to exactly machine the ridges (to be used as guides during assembly), and finally a contour toolpath to detach the part.

The resulting train model, two cars
The resulting ZHESM electric train model in action on the track.

After milling the parts still needed to be finished: smoothed with sandpaper and perhaps some filler, sprayed with primer and later in the correct colour, graphic details applied.
Many such parts were needed: this train model has been made including a complete interior !
Richard states":
"With the flexibility that DeskProto offers in strategies, borders, segments, movements and advanced settings all other parts could be manufactured as well, and a fully operational and running model was finally assembled from all these parts."

Picture of the model
 Picture of the real train
The resulting 1:87 model, and the original train.

Many more pictures can be found on Richard's web site (select Projects).

Interesting detail is that Richard later found a second source for a ZEHSM model train, this one made by additive RP technology. This one can be seen at Shapeways, in a shop called SpoorObjecten.
Nice: you now can compare the results of subtractive (CNC) and additive RP !.