Harold Hall

Workshop Processes


In any case, any attempt to be precise will be of little help to viewers as there are likely to be many variables. The maker will have to experiment with the materials and power source he or she chooses to use but fortunately the requirements are not that critical.


The bender

Sk. 1 and Photograph 1 show the unit I made that will bend up to 500mm long but no dimensions are given regarding length as this can be varied to suit the users requirements. It consists of two lengths of white melamine faced board, 150mm wide, and coupled together using a length of softwood screwed to the rear of each but leaving a gap between the two of 15mm.


An M4 csk screw is threaded into the softwood at each end, just using a tapping size drill and forcing the screw in. This makes the screw tight and can be used to adjust the height of the heater in the channel formed by the two boards. The gap between the heater and the plastic sheet placed on top is in the region of 1mm. Use of a countersunk screw ensures the head of the screw is below the top face of the bender, permitting sheets larger than the bender's width to be bent if localised bending only is required. The arrangement is seen in SK. 2 and

Photograph 2.


The method.

With the plastic sheet laying on top of the bender with the bend line coinciding with the heater, the current is switched on. Depending on the heat developed by the heater will be the time taken for the sheet to become hot enough to bend easily.


Preferably, if large, one edge of the sheet should be clamped in position with two small clamps to avoid the sheet moving when being tested. When the outer face becomes too hot to touch, attempt to lift the unclamped edge. Continue doing this until it is found that a bend can easily be formed by lifting the edge up to and past the 90 degree position, assuming a right angle bend is required, switch of the power to the heater.


It will be found that the sheet will attempt to spring back quite a way, but as it cools the bend will become more ridged until the spring back will almost have gone. During this final stage the angle can be finally set. As the sheet cools rapidly after removing from the heat the process of finalising the bend takes only a few seconds.

Plastic Bender, Hot Wire
Plastic Bender, Hot Wire





All pictures can be clicked on to provide a larger view