In 3D Laser cutting, the part to be cut needs to be positioned and held in the working area of the machine in a repeatable way. One must use some kind a support to achieve this objective. Such supports are known as fixtures, reference fixtures or fixing gauge.
These supports can be fabricated in different ways. They support the workpiece by copying the contour shape of the tridimensional part to be cut. In this way, the part can be easily positioned and fixed for cutting. The fixture also must make sure that the part does not move during the cutting process.
The different types of supports exist not only because of different types of parts that are to be cut but also because of different production volumes to be produced.
A 3D laser cutting fixture installed on the LT-FREE PIECE VALUE configuration’s rotary table. A perfect solution for high production volumes.
Fixtures for high production volume 3D laser cutting
In high production volume sectors like automotive components, the proper designing of support structures for 3D laser cutting becomes extremely important. Only a properly designed fixture will guarantee a reliable cutting process with repeatable results over time.
The fixture must allow unhindered access of the laser cutting head to the cutting areas. By utilizing a precisely customized fixture, the movements of the cutting head, during cutting and also during rapid positioning, can be optimized to have the lowest possible cycle time.
In some cases, it is necessary to use clamps to prevent the part from moving during the cutting process; movements can happen due to the stress-relieved during cutting. Such clamps may have to be placed on the cutting path obstructing the movement of the cutting head and also resulting in incomplete cutting. The solution is to use active clamps which open and move out of the cutting path as the cutting head approaches, allowing the cutting to continue, and close again as the cutting head proceeds on the programmed cutting path.
BLM GROUP customers can choose to design 3D laser cutting fixtures on their own or reply upon the ArtCut software that utilizes BLM GROUP’s vast experience in this field.
Decades of R&D work in 3D laser cutting supported by an extensive number of customers in diverse fields of application and in different parts of the world has enormously enriched BLM GROUP’s knowledge bank. BLM GROUP makes it easy for their customers to make use of this expansive knowledge pool.
Fixtures for low production volume 3D laser cutting
Designing and fabrication of a 3D laser cutting support fixture for very high production volumes may take several weeks. Each sub-component of the fixture would have to be carefully designed to guarantee the same repeatability of positioning and stability after hundreds of thousands of components have been processed; to ensure the first part is the same as the last. Extra care must be taken in their design and manufacturing to ensure the reference surfaces do not erode thereby modifying the stability of the support or the overall structure does not become deformed due to the heat generated during the laser cutting process.
It is clear that design and fabrication of such an elaborate fixture is justified only for high production volume components. When the production volumes are small such complex fixtures cannot be justified in terms of time and cost.
Some sectors are known for small production volumes, for example aerospace, furniture, high power motorcycles, electrical vehicles etc. Even within sectors known for high production volumes, there is always a requirement of low production volumes during the development phase (prototypes) or some special versions. In such situations, how do you design and quickly fabricate a support fixture for 3D laser cutting.
The easiest solution would be to use a CAD/CAM software that automatically designs a support structure for a 3D component that can be easily and quickly fabricated. Only in this way one can satisfy the flexibility requirements of a small series production.
Automatic generation of part supports for 3D laser cutting
ArtCut is an off-line CAM software for programming the LT-FREE and LT360, the 3D laser cutting systems manufactured by BLM GROUP, with a dedicated CAD feature for designing the supports required for part positioning.
This CAD feature automatically designs the support structure made of sheet metal components. If required, the programmer can make modifications to the design to make it lighter or easier to assemble. Once the design is finalized, ArtCut will generate the machine programs for cutting the sheet metal components on all the machines manufactured by BLM GROUP with sheet metal cutting capabilities; LT-FREE, LT360, LS5 and LC5. With a proper post-processor, it can also generate programs for other laser sheet cutting machines.
Whether the part is simple or complex, with ArtCut one can easily and quickly design and manufacture the supports required for 3D laser cut parts.
1. Design in no time
Once the part drawing is imported and the position of the part in space is defined, ArtCut automatically generates the support structure. The programmer can modify several elements including number, shape and thickness or material of the vertical plates making the structure.
ArtCut automatically designs the cutouts to reduce the weight and also adds reinforcement plates where necessary, to make the structure sufficiently rigid.
The programmer can modify the number, thickness or material of vertical plates making the structure and also their shape if desired.
2. Use of commonly available material – Sheetmetal
The support structures generated by ArtCut use only one raw material: Sheet metal which is commonly available in all companies using laser cutting machines. Another advantage is that the sheet metal parts that make up the support structure can be cut on the same machine that would be cutting the 3D parts later in production.
Nesting of the sheet metal parts for a support structure for 3D laser cutting automatically designed by ArtCut.
3. Easy to assemble and position
Automatically generated sheet metal parts of the support structure created by ArtCut include all the necessary cutouts for interlocking these parts with one another
and markings to assist in their proper assembly.
ArtCut also designs the mounting holes at appropriate center distance on the base plate so that fixing the support structure on the table of the 3D laser cutting machine becomes very easy.
ArtCut automatically designs all the necessary cutouts to interlock the sheet metal parts with one another to build the structure easily and quickly.
Support structures for 3D laser cutting of bent tubes
For 3D laser cutting of bent or hydroformed tubes, support structures can be divided into two types, both designed using ArtCut. The first type supports the parts when the laser head can easily access all the areas involved in cutting. The second type is used when the laser cutting head cannot access all the areas involved in cutting and a robot is used as a flexible positioning device to pick up the part from the support structure and present it to the cutting system in multiple cutting positions.
A special feature in ArtCut automatically designs the second type of support structures. It keeps the vertical plates only in the straight portions of the bent tube (away from the bend area) because in the bend area the actual bent tube will not be exactly the same as the theoretical model used for designing the fixture but the straight portions would be. In this way, high positioning repeatability can be assured. ArtCut automatically eliminates non-essential vertical plates and adds reinforcements at the right locations to guarantee the rigidity of the support structure, thus making it lighter.
The two images belowe explain this point. On the left is the support structure for a bent tube that would be designed without this special ArtCut feature for bent tubes (consider the bent tube as a 3D component) and on the right is the support structure for the same bent tube as designed by ArtCut. You can see the difference and appreciate the ease of handling and material saving.
The important advantages of this special feature are summarized as follows:
- High repeatability of positioning
- Hence higher repeatability of cut part
- Lighter support structures without compromising the rigidity
- Hence material savings
On the left, the support structure for a bent tube if designed in the “standard” manner and on the right the support structure for the same tube as designed by ArtCut.
Conclusions
For small batch and prototype production of 3D laser cut parts, ArtCut offers a powerful and versatile software package for designing the part supports. One can easily design, manufacture and assemble such supports quickly using commonly available sheet metal material and the laser cutting machine already present in the shop.