jhovel
6th Apr 2016, 03:31 PM
This is barely metalwork related, I'm afraid, but the machine I built is made from metals :)
As some of you know, I restore old motorcycles. Once in a while, an issue with supplies of spare parts makes it worthwhile to set up tooling to make replicas of parts for a whole community of enthusiasts.
This was the case recently with the coolant overflow bottles for 1978 to 1983 models Honda CX500 and 650 bikes (including the turbo versions). None of the 4 types used over those years are availalbe any longer new (for the past 10 years or more) and they are all getting brittle and unreliable now.
Originally made by blow moulding of polyethylene, which is faaaar to expensive to set up for small runs. A quote by a friend was in the order of $12,000 :oo:
So I read myself into the various plastics manufacturing methods of hollow items and eventually landed on rotational casting for this purpose.
In priciple, a thin flexible mould is made from silicone (called a ''glove mould'), supported by a hard shell made around the outside of it. The hard shell is arranged to be split and separated from the silicon glove. Once the original part - in effect the pattern - is removed for the arrangement and the mould reassembled, a quanity of liquid polyurethane is poured into the mould, the opening plugged and the whole assembly rotated in two axes to distribute the liquid plastic all around the walls of the mould. This is continued until the plastic sets (from minutes to hours, depending on the material properties).
The usual arrangement is a rotation machine with a timer.
So I set out to survey my scrap and useful spaces, and came up with a collection of materials that could be recycled into such a machine.
The result may be of interest to others, so here is a picture and a video of it running (empty). The mould is fastened inside the inner rotating frame with rubber bands or metal straps or tape.
One of the bottle shapes:
361908
The machine:
361909
A video:
https://youtu.be/Trj0D3h6ioQ
As some of you know, I restore old motorcycles. Once in a while, an issue with supplies of spare parts makes it worthwhile to set up tooling to make replicas of parts for a whole community of enthusiasts.
This was the case recently with the coolant overflow bottles for 1978 to 1983 models Honda CX500 and 650 bikes (including the turbo versions). None of the 4 types used over those years are availalbe any longer new (for the past 10 years or more) and they are all getting brittle and unreliable now.
Originally made by blow moulding of polyethylene, which is faaaar to expensive to set up for small runs. A quote by a friend was in the order of $12,000 :oo:
So I read myself into the various plastics manufacturing methods of hollow items and eventually landed on rotational casting for this purpose.
In priciple, a thin flexible mould is made from silicone (called a ''glove mould'), supported by a hard shell made around the outside of it. The hard shell is arranged to be split and separated from the silicon glove. Once the original part - in effect the pattern - is removed for the arrangement and the mould reassembled, a quanity of liquid polyurethane is poured into the mould, the opening plugged and the whole assembly rotated in two axes to distribute the liquid plastic all around the walls of the mould. This is continued until the plastic sets (from minutes to hours, depending on the material properties).
The usual arrangement is a rotation machine with a timer.
So I set out to survey my scrap and useful spaces, and came up with a collection of materials that could be recycled into such a machine.
The result may be of interest to others, so here is a picture and a video of it running (empty). The mould is fastened inside the inner rotating frame with rubber bands or metal straps or tape.
One of the bottle shapes:
361908
The machine:
361909
A video:
https://youtu.be/Trj0D3h6ioQ