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Armor/AFV
For all ground-operating modelling subjects.
Review
Spectre Scale: Sherman Skink turret
barkingdigger
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ARMORAMA
#013
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Posted: Thursday, March 15, 2018 - 04:21 AM UTC


Tom takes a bead on a new 3D-printed Skink turret!

Read the Review

If you have comments or questions please post them here.

Thanks!
Pave-Hawk
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Western Australia, Australia
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Posted: Thursday, March 15, 2018 - 05:19 AM UTC
Looks like there is still a little warping in the gun barrels, though doesn't appear anywhere near as bad as my hollow originals.
barkingdigger
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ARMORAMA
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Posted: Thursday, March 15, 2018 - 03:49 PM UTC
Possibly, but there's also some camera distortion that exaggerates it - from the naked eye they're not bad at all. (And they are still loose, so may not be perfectly aligned...)
easyco69
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Posted: Thursday, March 15, 2018 - 04:06 PM UTC
kool
easyco69
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Posted: Thursday, March 15, 2018 - 04:10 PM UTC
the question is...what type of plastic is it made of & how does our hobby's glue, paint adhere/react? If I used this I would replace the barrels.IMO
barkingdigger
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ARMORAMA
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Posted: Thursday, March 15, 2018 - 04:12 PM UTC
It isn't plastic - it's printed acrylic resin. You need to use superglue to stick it together.

As for paint, spray on a good coat of primer and then use whatever paint you like. I use acrylics myself - can't stand the stink and tricky clean-up of enamels.
Pave-Hawk
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Posted: Thursday, March 15, 2018 - 04:14 PM UTC
Based on the review, I will be making a few changes to the guns to try and reduce their delicacy, and to strengthen the hatch sprue so hopefully they stay attached.

Also had a request for a 1/48 version so will be adding that too.
barkingdigger
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ARMORAMA
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Posted: Thursday, March 15, 2018 - 07:03 PM UTC
Sounds good Iain. I plan on building mine for the current AA campaign, so expect a build-log starting soon!
Pave-Hawk
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Posted: Saturday, March 17, 2018 - 12:12 PM UTC
Changes are made, so hopefully floors will align and fit a bit better, and the gun assembly won't be quite so delicate. As a rather odd consequence the cost difference between separate and attached floor models is much closer to being the same.

There is also now a version in 1/48 intended to fit Tamiya kits.


Quoted Text

Sounds good Iain. I plan on building mine for the current AA campaign, so expect a build-log starting soon!



I look forward to seeing that.
Cantstopbuyingkits
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Posted: Saturday, March 17, 2018 - 11:30 PM UTC
Why the need for resin, why 3D prints don't have the high costs of injection molds for styrene?
Pave-Hawk
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Posted: Sunday, March 18, 2018 - 04:31 AM UTC
Raw material is relatively cheap for both 3D printing and injection moulding, depending on what material you choose for printing.
Injection moulding requires large outlay to buy the initial moulds, and if you want to do a different model you need another large outlay to create the model and buy different moulds. The moulds also have a limited lifespan.

Commercial 3D printing requires a large outlay for the 3D printer, after which you just pay the cost of model design, and each kit only cost the price of material for the manufacturers. There is no cost to have moulds machined. There may ongoing costs to maintain and service the printer BUT I don't think they would reach the cost to have a full kit mould done.

Having said that, 3D printing isn't cheap, and in my experience parts are more closely priced with cast resin kits if you use similar materials. If you look, full 3D printed kits can get into the hundreds of dollars for even quite small kits. Costs can go up quickly if you choose to print in fancy materials like metals or extra strong plastics.

Through services like shapeways, final cost is affected by how much profit sellers add on top of shapeways costs.
barkingdigger
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Posted: Sunday, March 18, 2018 - 03:53 PM UTC
As Iain says, injection moulding has a high start-up cost because making the steel moulds costs many thousands of pounds. The actual plastic sprues are cheap (pennies, really) but you need to sell lots of them to spread the tooling cost. It also means up-front costs for the tooling, storage of the unsold sprues, and shipping costs to the customer, so is only viable for companies with capital to invest.

3D printing ("rapid prototyping" as it was when it started) uses an expensive machine that can spit out parts from an infinite variety of CAD drawings, so the true cost of the machine is spread over lots of different customers rather than being landed on a single design. The downside is that the printing is not as cheap as I-M, so instead of each shot costing pennies it costs tens of pounds. Since the printers are so expensive, it makes sense to use a print-house like Shapeways - they own the machinery and do all the order-taking, printing, packing, and shipping.

The traditional cast-resin process as used by Verlinden, Resicast, etc requires a "pattern" of the part, and then each casting requires labour that contributes to the cost.

Each method has its uses, but the designer must balance the costs with potential sales and the effort of churning out & selling the product.
Cantstopbuyingkits
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Posted: Monday, March 26, 2018 - 11:15 PM UTC
Of course, that why I couldn't understand why Iain wanted to have this conversion in resin, which has the need for CA glue and avoidance of the toxic dust plus the lack of flexibility for thinner parts mentioned in the review, over plastic.
Pave-Hawk
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Posted: Tuesday, March 27, 2018 - 08:01 AM UTC

Quoted Text

Of course, that why I couldn't understand why Iain wanted to have this conversion in resin, which has the need for CA glue and avoidance of the toxic dust plus the lack of flexibility for thinner parts mentioned in the review, over plastic.



Cost.

Based on my estimates, I could make resin versions that I could sell for about $AU25-35 (not including postage which might kill from Australia depending where it went) and still cover the cost of resin with a small profit.

That's bit cheaper than a shapeways print, and I would have control over the quality of the final product.

Selling through shapeways is more expensive for the buyer, and I have no visibility over the finished product until someone tells me if it's good or bad. Very much Caveat Emptor, no matter how much work I do. Plus I am not the best 3D modeller around, so my work is close, but very much NOT exact, whereas I could get a physical model closer to the real thing.

The advantage of shapeways is that I can make fast changes based on feedback, and produce different scales to suit different kits at effectively zero cost, so that the next purchaser can get an "improved" version, but again, I have to wait for feedback to ensure I didn't stuff something up during my changes.

Ultimately, the reason I went with shapeways for this despite my preference for doing resin, is simply that real life prevents me from being able to spend the time that I would need to finish the master, produce a mould and get kits made up.

So now I am slowly working on my next piece, an Australian 6x6 Land Rover chassis to replace the fantasy part that Black Dog produced.
Cantstopbuyingkits
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Posted: Tuesday, March 27, 2018 - 03:47 PM UTC
Ah, so Shapeways only offers resin, not plastic printing, right?
Pave-Hawk
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Posted: Tuesday, March 27, 2018 - 04:27 PM UTC
Shapeways has a variety of different materials and different printing processes to suit each material.

Each material has different levels of detail that it can reproduce. The higher detail materials tend to cost more than the basic plastics, and the metals are even more expensive.

barkingdigger
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ARMORAMA
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Posted: Tuesday, March 27, 2018 - 04:31 PM UTC

Quoted Text

Ah, so Shapeways only offers resin, not plastic printing, right?



Yes, although they often refer to their acrylic resin as "plastic" in the generic sense of a mouldable material. Technically the "plastic" we see in kits is styrene, an oil-based product which is heated to a liquid and squirted into a metal mould to form shapes. Shapeways uses an acrylic resin "plastic" that can be printed droplet-by-droplet onto a build tray to make the parts - kinda like cutting out the shapes from layers of paper in a stack. I don't know anyone that offers 3D-printable styrene - it may not be possible to do it at all.

And to make matters confusing, the traditional cast resin we see in aftermarket parts from Verlinden, Formations, etc is different to the acrylic resin printed at Shapeways!

If anyone develops the technology to 3D-print styrene plastic parts, they'd make a fortune!
Pave-Hawk
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Posted: Tuesday, March 27, 2018 - 04:57 PM UTC

Quoted Text


Quoted Text

Ah, so Shapeways only offers resin, not plastic printing,

I don't know anyone that offers 3D-printable styrene - it may not be possible to do it at all...

...If anyone develops the technology to 3D-print styrene plastic parts, they'd make a fortune!



Styrene covers a whole family of plastic including HIPS and ABS. ABS is is one of the more common 3D printing plastics available and is compatible with the styrene used in model kits. I believe Plastruct brand materials are also ABS.
barkingdigger
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ARMORAMA
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England - East Anglia, United Kingdom
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Posted: Thursday, March 29, 2018 - 02:06 PM UTC

Quoted Text


Quoted Text


Quoted Text

Ah, so Shapeways only offers resin, not plastic printing,

I don't know anyone that offers 3D-printable styrene - it may not be possible to do it at all...

...If anyone develops the technology to 3D-print styrene plastic parts, they'd make a fortune!



Styrene covers a whole family of plastic including HIPS and ABS. ABS is is one of the more common 3D printing plastics available and is compatible with the styrene used in model kits. I believe Plastruct brand materials are also ABS.



True - I should have said pure "polystyrene" for kit plastic! ABS is a styrene-based mix, but it doesn't react with the mild glues we use on PS kit parts. (I have fond memories of trying to get Plastruct girders to bond onto my plastic conversions as a kid...) And as far as I know, the use in 3D printing is mostly limited to the low-end machines that heat and melt a thread of ABS to fuse it onto the model as it builds up - these are different from the polyjet printers that make parts suitable for our modelling hobby. I'm not sure if something in the rubbery component of ABS might make it unsuitable for polyjet printing?

But I still think the Holy Grail of 3D printing would be a polyjet machine using pure polystyrene! Just think of the possibilities...
Pave-Hawk
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Posted: Monday, September 09, 2019 - 06:13 PM UTC
Raising a bit of dead thread, but I wanted to add that due to requests, the skink turret is now also available in, 1/48, 1/32, and 1/16 scales.