Jump to content

Model Monkey P-51D 3D-Printed Exhausts


Recommended Posts

That's a great question!


The material in which the product is created is not the same kind of resin we are accustomed to.  It has some unusual properties and so has to be prepared a bit differently than typical modeling resins.  I'll explain, please bear with me, the explanation may help you avoid some headaches.


The exhausts are created from an acrylic plastic called "Frosted Detail".  For some products, it comes as either "Frosted Ultra Detail" ("FUD") or "Frosted Extreme Detail" ("FXD").  These exhausts are printed in FXD, the better detailed and smoother of the two.  FUD/FXD behaves differently than does injection-molded polystyrene or chemically-cured resins normally used to create other superb aftermarket products for models. FUD/FXD is chemically related to Plexiglas.


FUD/FXD is not the same material you see used by the kind of 3D printer used by hobbyists at home or in schools.  Those printers often extrude a material that is chemically related to nylon and looks and behaves like nylon.  That is not what these exhausts are made from.  The 3D printer that produces these exhausts costs a whopping $70,000-90,000 USD.  That is no garage printer.


Compared to resin products cast in a mold, there is no casting block to remove. Bonus.


The acrylic resin here is made using a liquid acrylic resin that is cured by exposure to ultraviolet light.  There are actually two materials laid down by the printer when the model is made, the acrylic plastic itself, and a waxy material that supports overhanging features during printing.  (The wax is later melted away in a low-temperature oven at the factory before it is packaged and shipped to you, leaving you with just the acrylic parts.)


The nature of the acrylic resin in its liquid state causes it to naturally harden quite quickly, nearly instantly. But it must remain in a liquid state in order to be extruded from a 3D printer. So, a chemical inhibitor is introduced to the formulation that prevents the resin liquid from hardening. It is ultraviolet (UV) light that destroys the inhibitor permitting the resin to naturally, nearly instantly, harden. The 3D printer lays down a layer of liquid acrylic, flashes it with UV light hardening it.  Then the next layer is laid down on top and flashed with UV light, layer by layer, creating the model.


The presence of any microscopic bits of intact inhibitor trapped within the resin can keep enamel paint from hardening.  This is why I strongly advise customers to expose their products to direct sunlight for several hours before painting.  The sun's UV light will destroy any remaining inhibitor permitting the use of enamels.   Called "post-curing", sunlight exposure is critical to painting success with enamels.


Generally, acrylic paints are not affected.  There are some exceptions, so post-cure your parts even if you intend to use acrylic paint.


Sometimes, tiny bits of wax remain, too.  A good soaking in common liquid dishwashing detergent ("Dawn", "Fairy", "Simple Green", etc.) can remove those stubborn bits.


Please be advised that FUD and FXD can be harmed by strong chemicals like acetone.  Acetone can melt FUD/FXD.  Some modelers like to use acetone, acetate (found in acetone-free nail polish remover) and Bestine (heptane) to clean FUD/FXD. Some designers recommend it. I do not. Too many of my customers have reported that acetone, acetate or Bestine damaged the acrylic. I recommend only mild, water-based detergents like Dawn, Fairy, baby shampoo (no conditioner) or Simple Green in warm water to clean FUD/FXD. Those products have never caused me any problems personally nor have I received any reports that they caused problems for customers.


General rule of thumb: if you wouldn't use a cleaning product to clean Plexiglas, don't use it to clean FUD/FXD.


Some plastic modelers are accustomed to using methyl ethyl ketone (MEK) as thinner for airbrushing enamels on injection-molded polystyrene models. Don't use MEK with FUD/FXD. One of my customers used MEK on a large product printed in FUD. He discovered and reported that a white powdery residue formed on the surface of the paint some time later. There was no harm to the product, but it was a nuisance to remove the residue, requiring a second cleaning. Based on his experience, I advise against using MEK as a paint thinner on FUD/FXD.

Hope this helps!

Edited by Model_Monkey
Link to comment
Share on other sites

  • 2 weeks later...

Great review!    I wonder how they compare in size/shape/texture to the Eduard/Brassin exhausts. 


I have two sets of the Eduard/brassin exhausts. Perfect casting as usual, but they are VERY skinny. Definitely too skinny, i can even say anemic.

I then drilled the kit exhaust, and they look nice, too, but lack the detail of the resin, and are also pretty skinny compared to what i see on the pictures.


So yesterday i ordered two of these 3D printed exhaust. They look better in proportion.

Link to comment
Share on other sites

Guest Maxim

I used many of Model_Monkeys parts in the past on ships models and his parts are really nice in Extreme detail. Just be careful that it is brittle so if you think about drilling anything 3D printed be very careful. Also good advise to expose the part to UV light for an hour or so. I have used mostly acrylic lacquer paints and had no problems with paint not adhering. I've used MRP, Mr Color, Tamiya lacquer sprays without problems.

Edited by Maxim
Link to comment
Share on other sites

  • 2 weeks later...

Thanks for the compliments!


Regarding the intake plates, due to present 3D-printing requirements, the plates would have to be designed unrealistically thick if 3D-printed.  IMHO, photo-etch remains the more realistic material for the perforated plates.


Eduard makes a basic photo-etch set that includes the perforated plates (please click here).  There may be other sets available, too.


Hope this helps and thanks again!

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

  • Recently Browsing   0 members

    • No registered users viewing this page.
  • Create New...