Vacuum Forming Part 2

I am currently working on a new vacuum forming rig.  This rig is going to be different from conventional vacuum forming because it will use female tools instead of male tools and pull the heated plastic into the mold rather than stretching it over the mold.  This is similar to how spar baths are made.  

Because most of the "bucks" I have made so far are male tools, I am making the rig adaptable so I don't have to remake those tools and all new tools will be female form the design phase.    

There are a more than a couple of reasons I am building my rig this way and they are -

1. Time where you have just seconds to evacuate all the air with a vacuum form using positive tools.  Provided there is a good seal, vacuum forming into a female tool means that the need to have the part finished quickly does not apply anymore.   

2. Heat where you have just seconds to get the plastic down and air out before the plastic begins to cool. Pulls made into a female tool can be heated during the process or re-heated if required. 

3. Suction where you must align the plastic to the platen to get a good seal to make vacuum forming work.  In my system, part of the set up will be alignment and a seal tests before any heat is applied.  Once in position, the plastic is not removed for heating.  

4. Part size where the temperature and the plastic types/thickness affects the final part size normally resulting in parts that are slightly over-sized or have paper thin walls.  When making a male tool for vacuum forming, you must take this size increase into consideration. If you want to use thicker plastic to make a thicker part, you lose detail.  With female tooling for vacuum forming, the part is the exact size of the mold very time and no detail is lost, even when using thicker plastic.  It is therefore possible to have sharper lines or use thicker plastic on deeper pulls.  In some cases, parts made using a female mold can look as good as injection molded parts.   

5. Material wastage is reduced.  Generally you need a the sheet of plastic to be at least 40% larger than the footprint of the part you are making a pull from. So you also need a massive platen and heater plus suction to make this work. I believe it is possible to make parts like this from way smaller equipment using female tools on the vacuum forming rig. 

  

Proof Of Concept Test #1

   

The plastic to make the dome in my photo was just 450mm x 450mm x 3mm. If this could be done on a male vacuum form tool, I would suggest that the sheet of plastic would need to be at least 1200mm x 1200mm.  The technical term for what I have done here is Vacuum Assisted Slump Forming as there was not physical tool used apart from the tube of the vacuum chamber.  The dome is 250mm in diameter.       

6. Ease of use. At that size (1200mm x 1200mm), it is now a 2 man job just to set it up, not to mention the energy needed to push the plastic down in the first place (unless you have access to a motorized pro version of that size). With female tooling, once you get a seal, you can start the heating slowly and evenly and get tight edges right to the base. 

7. Fails due to plastic burning are common with DIY vacuum forming because you are on a time line. You need to get as much heat into the plastic as you can to allow the plastic to form properly.  As the plastic heats up, the plastic usually riased toward the heating element before slumping once the critial temperature is achieved.   If the plastic touches the heating elements, the job has failed.  In my system, the plastic can't bow up because it is already under suction.  As soon as it softens, it is pulled down into the tool.   

Sometimes with vacuum forming on a male tool, you won't get enough heat at the edges and as a result, get sloping sides. Look how tight my vacuum form is. The only thing I did wrong with that dome in the first test was I did not use a frame and as the plastic heated and stretched and was pulled down.  It reached a point where it warped and eventually broke the seal. If I had used a good frame and clamping system, I would have been able to have a nice flat surround and I did that in test #2.

Proof Of Concept Test #2

8. Generally, vacuum forming is noisy because most DIY systems use a vacuum cleaner and suction must be on the whole time. I am not using a vacuum cleaner, rather the vacuum pump and chamber I made for degassing resin and silicone.  With my system, once the vacuum is started (and assuming a good seal is made), the pump can be shut off.  It need only be turned back on to increase vacuum as required. 

 The Vacuum System

 

Suction is measured in units of mercury where the weight is based on a cylinder or tube filled with mercury.  In the image above, the amount of suction is shown on the vacuum gauge in both inches and centimeters of mercury.  To put this in perspective, the very best vacuum cleaners will pull about 6"HG.  My system can go to 30"HG which is just over one negative atmosphere.

  

The Heating Unit

The heating unit used here is a fan forced halogen cooking appliance.  What I like about this unit is it has a quick stop mechanism, thermostat and timer.  once I learn the temperature rating required for each type of plastic, I can set the temperature to that and not have to worry about burning plastic.      

 I will update this post once the former is made.

More to come soon...

Mark

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Molding And Casting Part 2

The purpose of this blog is a show how to make a 2 part mold.  There are few ways to do this and because the part I am making a mold of is a complex 3D part, I had to change a few things to make it work.  

The part(s) I am molding and casting are soles for the 2015 MAG replicas. These are a 2 part sole with a flat oval part at the front and the 3D part at the rear.  I started by making a new master part where I created an "outrigger" style sole and added "Pyramatic" tread to both parts.  The 3D rear part is complex because it has 'wings' that wrap around the side of the shoe.  Traditional soles are flat and a single part, so an open back mold would be the easiest way to do those.  In fact the front part of this project is done that way.

 

The first step is to ensure your master is as close to perfect as you can get it.  It is best to spend time at this stage rather than correcting each cast part later.  

There are a few materials that can be added to the master for a quick mod.  I used a school grade Plasticine because it does not contain sulfur and therefore does not affect the curing of the silicone being used to make the mold.  

There are also two main types of silicone - condensation curing and additive curing.  I am using the additive type where part A is the silicone and part B is a curing agent.  The product I have used for this project is Vario-40 and it is mixed at 10:1 in weight.   It is translucent and has a shore hardness of A-40.  

DO NOT EVER MIX THE TWO TYPES!  

Unlike some quick set silicones, Vario-40 can be placed in a Vacuum Chamber to degas so you can have bubble free molds and capture greater detail.           

So to start the two part mold, you have to work out where you want the seam lines, fill holes, breath holes and then fill in the parts you don't want silicone to get in during the pour.

In the image above, I filled in the entire inside of the sole with Plasticine and built it up so that only the external surfaces were exposed.  I also shaped the block to have slightly tapered walls so the part would be like a bowl.  I have also added "registration points".  You can make registration points from pretty much anything that won't float away in the silicone.  I have used some glass marbles pushed half way into the Plasticine.  These assist with aligning the 2nd part of the mold so that it "locks into position" later.  

The next step is to build a wall around the part and make sure it is sealed.  The walls can be made from anything including wood, plastic [I've seen Lego being used] and even the clay or Plasticine.  I have used core-flute signs because it is cheap, easy to work and is flexible.  If you need a tighter bend, you slice the outer skin and it will bend right around the part.  I then used a hot melt glue gun to seal the base of the wall and the seams [held in place first with tape].  

When working with additive curing products, ALWAYS use a gram scale and measure the amount to be as close as you can.  I found that I could mix a maximum of 250 grams into a 2 litre ice-cream container and that amount would degas without over flowing into the Vacuum Chamber during the rise and fall.  Fill the mold until you have about 12.5mm or 1/2" covering the part.

    

Once this is cured, you remove all of the fill medium.  Be careful NOT to disturb the or break the seal between the first pour and the master part as you DO NOT want silicone leaking in between these parts during the 2nd pour.  I made my first pour like a bowl so that I would not get any leaks.  The walls extend well past  the highest point on the master.  I have added fill and breath holes at the highest points of the 'wings'.  

Once all the fill medium is removed, you must use a release agent as silicone sticks to itself and you will not be able to get your master part out if this happens.  I have used Vaseline [AKA Petroleum Jelly] as it prevents the silicone from sticking to itself and can be cleaned off with warm soapy water.  

Once prepped, you may then begin to fill the mold.  I let a base line cure first and then placed two small jars inside the hollow which I filled around.  The reason I did this is that the cavities left by the jars act as finger pull holes and  this also saves on silicone.  

 Once this has cured, you can clean up the two parts and you are ready to begin casting.  

The front oval parts are flat with texture on one side only, so I was able to mold these parts using a simple open back mold.   

   

Mark

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Molding and Casting Part 1

Recently I have started learning to mold and cast and so I have invested in a Vacuum Chamber.  After watching many you-tube videos [and with some experimentation], I have learned how to degas resin and pour bubble free castings.  

This blog is about the degassing process.  HERE is a video of the process. 

Air bubbles are trapped in the liquid from mixing.

As the Vacuum increases [pressure decreases], the bubbles begin to expand.

 The bubbles will expand many times their original size.

 Once a full vacuum is achieved [-30" or -76cm], the mix will expand up to 10 times the original volume. 

 After a few minutes, the air is evacuated and the mix will collapse back into itself. 

 Once the air is removed from the mix, the rate at which the bubbles rise and pop slows. 

  As the chamber is re-pressurized, any bubbles still in the mix are crushed by the increase of pressure.

 The mix is now bubble free and can be poured into molds.

  I use both polyester resin [it sets like a really a hard plastic] and elastomer [it is flexible like rubber] and both give superior results when degassed.  The polyester is set off by a catalyst and the elastomer is a two part equal mix compound.  Both need to be mixed properly to unsure proper curing or parts of the cast may remain tacky.  You mix air into the liquids as you stir them together resulting in bubbles through the mix.  If you pour with these bubbles still in the mix, your castings will not be great.  Degassing in a Vacuum Chamber removes the trapped air.    

The next blog will be about making a mold. 

Mark

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Its A Sneaker Thing Part 4 - Modding MAGs

The NIKE MAG was first seen in the 1989 film BACK TO THE FUTURE Part II. The shoe was a Hi-Tech design that [in the film] form fitted to the wearers' feet with "power laces".  The MAG became known as the greatest shoe never made. 

   

In 2011, NIKE released a replica of the shoes with some 'improvements' over the original screen used shoes.  There was 1510 pair made and the shoes were auctioned on eBay with proceeds going to the MJF Foundation.  The average price of these shoes were many thousands of dollars leaving fans of the shoe feeling a little disappointed they missed their chance to own a pair.  

In 2012, a Chinese made replica came available for a fraction of the cost of the genuine article and whilst well made, are not perfect.  The purpose of this blog is to document the modifications I have made to them to make them more screen accurate.  

My Replica MAGs 

 Out Of The Box

The shoes are presented in a yellow box similar to that of the 2011 NIKE MAG release.  Some of these errors with these shoes can be corrected by DIY and some parts just can't be corrected without re-building the entire shoe.  

Upgrading The Ankle Buckle

The factory made Ankle Buckle is quite flat.  The part I have used is a 3D printed [on the right] part that can be found online.  It seems to fit perfectly over the factory part and I had used it to conceal the 3V power supply which provides enough to power the lights in the Sole,  Heel Cup and Ankle Strap.  

Slimming the Toe

One thing that gives the MAG its unique look is the flat clean toe. The original design listed this a "sock type" because there was no toe box used on the screen used shoe.    

Many boots have a clean toe, but they also have the traditional boot shape and these replicas have been made with that boot look [original on right] making them look like "moon boots".  The easiest way to correct this is to heat the toe box up and reshape it.  Size pending, you may get a smooth taper or have to flatten the toe.  I wanted the "sock type" look of the movie shoe, so I flattened mine.    

Lighting the Strap

I cut out the back part out of the factory ankle buckle to allow it to hold 2 AAA batteries.  I have cut out the stamped logo and replaced it with a clear and black version that can be back lit.

Upgrading the Wiring

The original wiring in the shoe is very fragile and parts of mine failed after just a few days wearing.  After removing the soles, I decided to replace both the wire and LEDs.

A New Tongue  

One part that both the 2011 MAG and these replica MAGs have is a short tongue.  I have made a custom replacement part to help make these shoes look closer to those seen in the film.  The factory replica tongue is made from a stretchy fabric where the 2011 and the screen used MAG features a leatherette part.  My new tongue is made a from leather look vinyl with a stitched ribbon edge.  The top part is about 20% longer than the original.    

OUT RIGGER SOLES    

The original sole features translucent parts that are made from a tough rubber.  Unfortunately, it seem this rubber is not UV stabilized and the rubber turns yellow rapidly.  The shape is also not correct with a vertical outside edge.  I wanted to correct this to be closer to the shape of the proper outrigger soles the real shoes have.    

To do this, I have created a new master part that I have been able to mold and cast. The new part is cast in clear elastomer and features the correct pyramid tread on the base and the correct "waffle" pattern on the sides.  The photos [above 3] show my prototype in water clear elastomer along with the base of the master part that I used to make the molds. 

Glow In The Dark

After a few electrics fails, I decided to remove all the wiring and go with a Glow In The Dark additive for mixing into clear elastomer.  I dub these 'solar powered" as they only need to be exposed to bright light for a short time to glow.  The image above was taken with a phone camera in a fairly bright room after exposure to sunlight for less than 1 minute.   

Colour Chart 1

The colour of the light is CYAN which is made from equal amount of GREEN and BLUE.

As mentioned, there are a few things that can not be corrected on these shoes. I have listed all the things that CAN NOT be improved and they are -

CUFF:  This is stitched directly to the collar and can not be corrected without making new uppers.

PULL HOLES:  These are cut wrong and sewn around.  Like the cuffs, these can't be corrected without making new uppers.

SWOOSH:  This part is incorrect in shape and slightly too large. Because it is recessed, it can not simply be removed and replaced.

SEAMS: The real MAG has only two seems, one up the back of the shoe and other on the inside of the side centered between the 4 laces.  On these replicas, the side seam is too far forward being between the 1st and 2nd [from the toe] laces.  The back seam should go all the way up to the cuff.  On the replica, there is a 3rd seam where the top of the collar is joined.  Although this seam is hidden by the Ankle Strap it should not be there.       

LACES: These are too wide although, I actually prefer these over the width of the laces on the real shoe.

A Detailed Look At The Changes 

HEEL CUP and MIDSOLE were originally listed here as parts that could not be upgraded.  The Heel Cup is a good part, just slightly undersized.  Both the heel Cup and Mid-Sole are made from a grey rubber that is too dark.  One of the more controversial mods I have done is to pop the Heel Cup out of its slot on the inside of the Mid-Sole and attach it to the outside of the Mid-Sole.  I then built it up with layers or rubber to make it larger.  Both the Heel Cup and Mid-Sole were then coated in a light grey rubber.  I also re-did the splatter and made larger MAG letters using an Aqua rubber.  Unlike paint, these will not crack, peel or scrape off.  

 Colour Chart 2

Mark

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Movie Props

As I have always been a fan of the movies.  Recently I decided to start a replica prop collection.  My first replica props was acquired back when I was just 18 [RAMBO III knife].  So whilst my collection is small, it is growing and the purpose of this blog is to share some of the items I've collected so far.

STAR WARS

A NEW HOPE TK 1:1 Stormtrooper 'buckets'.  These were a work in progress at the time of the image capture but are all finished now.  As I am a member of the 501st [31138] I will eventually buy the entire armour kit. These are an 'AP' [Authenty Props] '2 piece' helmet apparently made from the original forms used in 1976.  One of the buckets belongs to my wife who has lovingly hand painted the 'frown' and 'decoder' and is part way through doing the ears.  

She is also a member of the 501st [TK41138] has already purchased her full armour.  Together over 4 months we built her a fully wearable Stormtrooper suit.    

  

 A mini ATST [All Terrain Scout Transort] from the film RETURN OF THE JEDI.  This is a Hasbro vintage release based on the original Kenner toy line, just way more detailed.  i also have the AT-AT from THE EMPIRE STRIKES BACK.  

I have several miniature space craft from the 6 SW films as well as these action figures.  I wanted the original 12 and found these more detailed versions and decided not to get the vintage figures.  

    

BACK TO THE FUTURE Part II

BACK TO THE FUTURE II was a fun film that took product placement to a whole new level.  There are so many props based on real brands in that film's future sequence including NIKE, Pizza Hut, Pepsi and Matel.  

I wanted to get a MATTEL Hover Board to display these shoes on and found one on eBay for $99.00.
  
The NIKE AIR MAG was probably the shoe responsible for the whole Hi-Top craze in the late 80's/early 90's.  These are a replica of those shoes and have now been severely modified to be morescreen accurate.  

  

Dehydrated Pizza

The dehydrated Pizza was something I made because it was one prop in that film at stood out as a cool collectible item.

RAMBO

The top image is of all the knives released from the four films.  Above is the famed 'mission' knife with a Jade Budda.  There are several modifications needed to make this collection screen accurate.    

LORD OF THE RINGS

These are items that came with the DVD [statues of the Kings] and Blu-ray box sets [the ONE RING] of the films.  

I, ROBOT

This is my latest addition.  Sonny, the special prototype NS5 created to set things right.  He is quite detailed with a removable rear head cover and has a special disc storage section.  

PREDATOR

This was released with the 3D version of the classic 80's film PREDATOR.  It is not 100% accurate and is only 75% of the proper size, but it is pretty cool.  The Bio lifts off to reveal the creature underneath.    

More to come...

Mark

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