Development process example: Grass bag

Case Story Development process example: Grass bag

The iDea 

The market for grass bags is very price sensitive, but has great potential. The base plate is the main cost driver, because for most models, it is manufactured using injection moulding or deep-drawing. A&R Textil has developed an alternative technology to produce cheaper base plates with the same performance: by thermoforming foams.

Preliminary considerations

In order to create the same or even better properties with the new technology, there are a number of conditions to be clarified beforehand: What degree of hardness is required? What thickness is needed? Which shape should the base plate have for optimal stability? What about its load bearing capacity? What kind of designs are possible? Does the EVA foam provide sufficient moisture-protection? What about the durability with regard to soiling, wear and tear and moisture?

Usually, grass bags are made from mesh fabric. We considered whether there were any cheaper alternatives to mesh that met our requirements: withstanding the weather conditions, with the same stability and durability as well as being light and UV resistant.

Is it possible to save additional costs by using alternative options for attaching logos, labels and images?

The Development Process

1. Sketch: The development and construction teams work together and discuss unanswered questions – and develop the first sketch for the thermoform base plate.
2. 3D model: Once everything has been agreed on, the 3D CAD model is created.
3. Prototype tool: The first prototype tool is made from ureol, using a portal milling machine. Ureol is a milling material that is cheaper than aluminium and often used to develop prototypes. At this point, the design can already be changed – for example by milling a logo that is later visible on the edge of the base plate.
4. Finished base plate: The upper and lower tools are installed in the press. An EVA foam plate is thermally heated in the industrial oven, placed in the press and shaped to form the base plate for the grass bag. The completed base plate is punched out at the edges.
5. Indicative tests: Indicative tests are carried out to test the materials used with regard to their durability.
6. Assembly: Once all parts of the prototype have been accepted, the finished base plate is sewn onto the pre-assembled grass bag.