When planning how to space your tools and stretch your material, common questions you may ask yourself include: How close should I space a single tool within the forming aperture? How close should I space similar multiple tools to each other and the forming aperture? How do I stretch my material with a printed grid pattern?
Here is some advice from Formech:
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Tool Spacing
When it comes to spacing a single tool within the forming aperture (assuming the tool is a simple block with uniform height), you will want to space the tool from the edge of the aperture between 0.3 to 1.0 x the height of the tool. 50mm (2”) x 0.5 = 25mm (1″) space.
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When spacing similar multiple tools to each other and the forming aperture you want to avoid webbing between the tools.
The material stretch between the tools and the stretch between the tool and edge of the aperture can vary, especially when you are looking to keep the plastic sheet size to the minimum to keep costs down.
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Wall Thickness
Typical wall thickness depends on several factors (e.g. pre-stretch, plug assist and tool design). It’s important to remember that a simple block of uniform height will typically thin down by 50% on the near vertical side faces.
Material Stretching
You can enlist several different methods to control material stretching, including:
- Heat – too much heat and the material can be over-stretched on the sides as the tool rises.
- Vacuum- applying vacuum earlier and controlling the speed can help
- Shapes – additional blocks can force the material to stretch in other directions
- Wires and masking strips between tools can restrict the material movement
- Pre- stretch can help to achieve a more uniform wall thickness
- Table up speed – too fast and this can cause the material to blow a bubble as the tool rises.
- Plug assist to hold the material as the tool rises into the sheet
- Tool temperature – a cold tool can restrict material flow
- Tool corner detail – sharp corners on tools can also stop the material from flowing over the tool
- Clamp frame/reducing window frame height will influence material heating
