View source for Cast Aluminium Plaquette

[[File:DTlogo2.png|400px|right]]
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===== What to Make: =====

Design and Make a small plaque based on a number, logo or initials.
* The number, logo or initials should be limited to 3 characters and the area of the final plaquette should not exceed 15,000mm<small><sup>2</sup></small>.
* The plaque should be cast as an aluminium relief and backgrounds either painted or filled with coloured resin.


=====What to Use:=====

* Make the [https://en.wikipedia.org/wiki/Pattern_(casting) '''Pattern'''] by cutting out a design from 3mm thick '''[[Manufactured Board|MDF]]''' or '''[[Manufactured Board|Hardboard]]''' and glue to a 6mm thick backing ''(or machine from solid 9mm stock)''.
* Paint to a good finish using the paint to create a small [https://en.wikipedia.org/wiki/Fillet_(mechanics) '''Fillet'''].
* LM4 aluminium casting [https://en.wikipedia.org/wiki/Ingot '''Ingot'''] or equivalent.
* Exterior metal primer, undercoat and paint; alternatively coloured [https://en.wikipedia.org/wiki/Polyester_resin '''Polyester'''] or [https://en.wikipedia.org/wiki/Epoxy '''Epoxy'''] resin.


=====Things to find out and think about:=====

* Find out about the process of '''[[Sand Casting]]''' ''(but note differences in '''Runner''' design described below)''.
* Ensure a bold, simple design with good spaces between design elements - remember the mould will be made of sand and the [https://en.wikipedia.org/wiki/Pattern_(casting) '''Pattern'''] will need to be withdrawn without crumbling or damaging the mould cavity.
* Think about the chosen [https://en.wikipedia.org/wiki/Font '''Font'''] style and size - if a door number, will it be seen from the edge of the property?
* Are there any traditional logos which could be used - e.g. [https://en.wikipedia.org/wiki/Astrological_sign '''Zodiac or Astrological Signs'''] or [https://en.wikipedia.org/wiki/Hieroglyph '''Heiroglyphs''']?
* How can you calculate the weight of cast aluminium required to ensure there is enough melted before pouring into the mould?
* How will the finished plaquette be fixed or mounted in place?


=====Some ideas:=====

* '''Uses''' - door numbers, club signs or logos, paper weight, box lid insert, medallion, garden markers ''(e.g. for vegetable rows)'', a 'branding iron' to scorch logos or patterns on to wooden structures and products.
* '''Shapes''' - square, rectangular, circular, . . . etc. . . raised or recessed, with or without a border or edge?
* '''Fixing''' - on wall, post, floor, . . . by screws, nuts & bolts or glued . . . loose ''(i.e. no fixing)''? 


=====Ways of Making:=====

Make the [https://en.wikipedia.org/wiki/Pattern_(casting) '''Pattern'''] using '''[[CAD|Computer Graphics]]''' to generate a full size design and print-out to use as a template. Glue to 3mm  '''[[Manufactured Board|MDF]]''' or '''[[Manufactured Board|Hardboard]]''' and cut out with a '''[[Coping Saw]]''' or '''[[Scroll Saw]]'''. Alternatively cut out directly using a '''[[:Category:Computer Controlled Equipment|CNC Laser]]''' or machine from solid 9mm material using a '''[[:Category:Computer Controlled Equipment|CNC Router]]'''.


Make a '''[[Sand Casting|Green Sand Mould]]''' from the  [https://en.wikipedia.org/wiki/Pattern_(casting) '''Pattern'''] as follows:

{|
|-
| Place the '''Pattern''' on a '''Moulding Board''' and cover with the '''Drag''' joint side down as shown.


Dust, or sprinkle and brush, '''Parting Sand''' over the '''Pattern''' to help stop sand sticking to it and to ensure it withdraws more easily from the mould afterwards.


Proceed to fill the '''Drag ''' with '''Moulding Sand''' using finer grained '''Facing Sand''' nearest the pattern if available.


| [[File:CastPlaquette1.png|400px|right]]

|-
| Fill the '''Drag ''' with '''Moulding Sand''' and compact it by using a '''Rammer''' in decreasing circles starting from the outside of the frame.


Once filled, level off the surface of the sand to the edge of the frame using a '''Strickle'''.
----
<span style="color: green">'''Note:'''
A short length of 25mm dowel makes a suitable '''Rammer''' and a '''Strickle''' can simply be a straight length of rectangular bar or wood strip.
</span>
----
| [[File:CastPlaquette2.png|400px|right]]

|-
| Turn over the '''Drag''' and add the '''Cope'''.


Dust, or sprinkle and brush, '''Parting Sand''' over the surface to stop the two halves of the '''Moulding Flask''' sticking together.


Fill with '''Moulding Sand''' and ram to compact it then '''Strickle Off''' as for the '''Drag'''. 
----
<span style="color: green">'''Note:'''
When casting in aluminium, '''DT Online''' has found it easier to omit '''Sprue Pins''' at this stage and cut them later with a length of 25mm diameter thin-walled metal tube. 
</span>
----
| [[File:CastPlaquette3.png|400px|right]]

|-
| Lift off the '''Cope''', put to one side and turn over the '''Drag''' on to the '''Moulding Board'''.


Cut a '''Runner Sprue''' through the compacted sand of the '''Drag''' to one side of the '''Pattern''' using thin-walled metal tube and pierce.small vent holes down to the '''Pattern''' using a thin wire ''(e.g. welding rod)''.


Turn over the '''Drag''' again to expose the '''Pattern''' and use the tube also to cut a '''Runner Gate''' between the '''Runner Sprue''' and the '''Pattern'''.

----
<span style="color: green">'''Note:'''
This is different from a traditional '''[[Sand Casting]]''' technique. '''DT Online''' advises that aluminium casts well if the mould cavity is located in the top box and a single parallel '''Runner Sprue''' feeds down to it and no '''Riser Sprue'''. To achieve this, the '''Moulding Box''' will be used later such that the '''Drag''' is on top.  
</span>
----
| [[File:CastPlaquette4.png|400px|right]]

|-
| Screw a large woodscrew or screw eye into the back of the '''Pattern''' - this will be known as a '''Rapping Pin'''.


Take a short length of metal bar or strip, hold on to the '''Rapping Pin''' and rap the pattern from side to side to loosen it - the bar will be known as a '''Rapping Iron'''.


Continue to vibrate the '''Pattern''' by rapping as you gently withdraw it from the sand to leave the mould cavity. 


Blow out any loose sand and repair any damage with '''Moulding Tools''' if available ''(small spatulas and teaspoons can be modified to make these sufficient for school use)''.  
| [[File:CastPlaquette5.png|400px|right]]

|-
| Replace the '''Cope''' and turn the re-assembled '''Moulding Flask''' over such that the '''Drag''' is now on top.


Use a short length of a larger diameter metal tube ''(e.g. 75mm - 100mm)'' and form a '''Runner Cup''' by packing with '''Moulding Sand''', shape a pouring basin, cut a '''Sprue''' as before and place on the '''Drag''' on top of the previously cut '''Runner Sprue'''.


Place the completed '''Moulding Flask''' in a sand covered '''Moulding Tray''' at ground level and add weights to prevent leakages though the joint between '''Cope''' and '''Drag''' as the melt is poured.  
----
<span style="color: red">'''Safety Point!'''
'''Pouring molten metal is extremely dangerous!'''
* <span style="color: red">Ensure there are no trip hazards between the furnace and the moulding tray containing the flask.</span>
* <span style="color: red">Make sure that any tools introduced into the melt ''(e.g. to remove '''Dross''')'' are pre-heated and dry.</span>
* <span style="color: red">Wear full face shield, leather gauntlets and apron.</span>
* <span style="color: red">Use purpose made '''Crucible Tongs''' and '''Carriers''' to carry the [https://en.wikipedia.org/wiki/Crucible '''Crucible'''] to the moulding tray and pour.
</span>
----
| [[File:CastPlaquette6.png|400px|right]]

|}

=====Testing:=====


* Did the [https://en.wikipedia.org/wiki/Pattern_(casting) '''Pattern'''] withdraw from the sand mould satisfactorily and, if not, how could the design be improved?
* Did the casting show any signs of sinking as a result of contraction on cooling? If so, can [https://en.wikipedia.org/wiki/Chill_(casting) '''Chills'''] be introduced across the top of the pattern when it is placed on the '''Moulding Board''' at the start and rammed up to be part of the mould such that they force the metal to start cooling from the top of the mould?


=====Further Work:=====
 

* How would you design a series of interlocking plaquettes to enable different numbers or longer names to be used? 


[[Category:Secondary]]
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[[Category:Manufacturing Projects]]
[[Category:Casting]]