The pictures below illustrate the following steps:
A) Preparation of the mould
- take a wooden panel, cut it to size with R = 110 cm and drill the holes for the clamps;
- bolt down a continuous strip that has the negative shape of the profile to the edge of the mould;
- fit 15 wood strips (each with a drill hole to hold a hitch pin) in a starlike shape to the back of the mould;
- put out the chunks with negative profile shape, the chunks for pressing, the wedges, the hitch pins, the clamps and the tension belt.
B) Gluing and bending
this part of the job needs to be carried out speedily, as it needs to take place within the open time of the used adhesive (in this case 2D PVAC glue),
i.e. within about 10-12 minutes , so it is advised to work in pairs.
- fix the mould horizontally onto a stable support and have all tools ready on it;
- apply the glue using a roller and join the 2 halves;
- fix the end of the joined profile to one end of the mould using 2 clamps and start bending from there;
- accurately close the glue joint by pressing the 15 chunks with negative profile shape one by one against the handrail using the chunks for pressing, the hitch pins and the wedges;
- in a final step tighten both ends of the curved handrail axially using a tension belt and position the clamps.
C) After the glue has dried:
take the bent handrail from the mould and sand the glue joints: the optical quality will be identical to the one of a full round handrail!!!!!
After having taken the handrail from the mould the spring-back amounts to about 15% and in this radius the bend will stay:
it will not open up any further, as the glue stabilizes the bend.
The advantages of this glue lamination process are:
1. profiles that are cut in half can be bent to a tighter radius compared to full-size profiles;
2. cheaper profiles with normal joints can be used;
3. the bending radii will stay, i.e. they will not open up any further.