R7 Shaping techniques

Posted: October 10, 2010 in Resistant Materials

Initial knowledge 1

Current working knowledge 2.5

I have used various shaping techniques throughout my education these were mainly orientated around wood and sign foam,  my aim for the year is to try to use as many different techniques in as many different materials as possible and to brush up on the ones that I have previous knowledge of.

I have turned wood and foam before using the lathe but it was some  time ago.  I took the opportunity to watch Les demonstrate wood-turning, which I found useful as it certainly jogged my memory as regards technique, the tools to use and health and safety issues.

I remembered that the top variable speed belt must be the same on the corresponding pulley, and that a cap must be placed on the end that you are using.  A centre point then needs to be put in the centre of the piece of wood to be turned using a hide mallet (the driving centre), and the wood is placed on the lathe ensuring that the wood does not touch the tool rest when it spins.

There are different tools that can be used including tool scrapes although they have no cutting edge.  Long and strong gauges, thumb and jandle guage and slim parting tools.

Once you start cutting into the wood its advisable to stop and move the tool rest closer to the wood as it shapes to be able to maintain control of the specific tool you are using.

I have used the wood-turning lathe before and I was quite comfortable in doing so, however there maybe the opportunity to use the technique, perhaps more elaborately in the future.

For ED216  my aim has been  to be taken out of my comfort zone using materials and techniques in shaping that I have not previously used.  For instance my plate storage unit has a plastic interior drainage system, I wanted it to be one solid piece of acrylic in case I wanted to make it removable,  so I had to use the strip heater.  Basically this meant I had to heat the long edges I had marked out and then bend them into position.  Prior to using the heater I ran a small test making a simple toothbrush holder out of the same acrylic.  I included some of the tight angles I needed for my plate rack in order to get an idea of what I was going to do.  I have to be honest and admit that the tooth-brush holder came out fine as it was more an exercise of finding out how the acrylic bends.  The piece aimed at fitting in my plate rack was a much harder task as it was a single piece of acrylic approximately 500mm in length and about 1110 mm in width to get the angles correct.  Because of the way the angles bent in to one another made the task extremely difficult and I had to explore ways of holding the plastic at different angles and wrapping it round anything vertical and straight, even the table leg which probably isn’t the most orthodox way of achieving a 90 degree angle!  The actual shape turned out as well as I had expected although on second glance one side was about 4 mm out and so the lid for my rack would not have been straight.  This led to me re-heating one of the edges and trying to shape it round a piece of wood I’d made to fit which in turn cracked the acrylic slightly, so for my next attempt, I made pieces of fitted wood for the angles and as a result got a much better result.  Hindsight is a wonderful thing and it was a bit of a case of ‘and what have we learned?’  I certainly won’t jump in at the deep end again but I would feel extremely confident shaping plastic in future, and probably not on such a large-scale.  Other experience I have gathered as regards shaping plastic was in the first couple of weeks making the 2 part mould to go with my previous experience in vacuum forming.

My first attempt next to my practice toothbrush holder, also the scale next to the strip heater

My next shaping technique in this process was to make the aluminium shell for the acrylic part of my rack,  so after I had clearly marked out almost a box net shape using pencil, a steel metre rule and an engineers square I had to cut out the shape.  For this I used the large metal guillotine and after re-jigging a couple of the lines to allow space for the blade which leaves around a 3 mm gap in the metal, I set about cutting the sheet.  I was actually surprised at how easy it was, I did not have to apply a lot of pressure and the lines were clean and I certainly obtained my objective of using this piece of equipment with no errors and I would feel comfortable using it again.

My piece of sheet aluminium and my second attempt at the acrylic bending

The next stage and indeed another shaping technique I had not previously used was to actually bend the sheet aluminium into the required box shape.  Although I am aware of the other ways of bending metal such as spinning, the shape and size of my piece of aluminium would not allow to use such methods, and so I required a method using strong steel bar and clamps.  By placing the bar along the line I wanted to bend the metal at and clamping it tightly, I was able to bend the metal vertically to as good a 90 degree angle as I could probably get by hand, and thus move the sides to their required positions.  The trouble came when I wanted to bend the third and largest side as I had already bent the 2 sides into place.  The problem was overcome by cutting a piece of right-angled bar to fit in between the two sides and allow space for the joining flaps, then bending it to meet the other sides.  Overall I found this technique effective and not too difficult, although I am now aware that to bend small widths of materials such as joint flaps is difficult and almost impossible by hand, especially if the width of the piece of metal is very small.  Such as a 10 mm flap which had to be removed completely.  I would be confident to recreate and teach this process although it was a relatively easy shape and my next aim is to shape metal using the lathe.

clamping the aluminium to bend the final side

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