Design of a Tube Forming Machine

In a short time, we managed to move from theoretical assumptions into practice and manufacture a device for forming aluminium tubes. Even when testing with already aged tubes (T6), they achieved very good results. Scrap was initially within the anticipated ** range of 4 %.** However, the tube manufacturer also had to make an effort to supply us with all semi-finished products within comparable parameters.

Solution and Method

In a short time, we managed to move from theoretical assumptions into practice and manufacture a device for forming aluminium tubes. The device fully meets their wishes and expectations. In some respects, they even exceeded them.

Above all, with pressing speeds they are several percentage points better than the initial assumptions. Quality and repeatability are very good.

Results

Even when testing with already aged tubes (T6), they achieved very good results. Scrap was initially within the anticipated range of 4 %. However, the tube manufacturer also had to make an effort to supply us with all semi-finished products within comparable parameters. There were some difficulties with ensuring perpendicularity of tube cutting, and somewhat more with ensuring equal quality across different batches of semi-finished products.

Through testing and monitoring all parameters, they corrected the quality in several shipments to such an extent that scrap was also reduced below 2 %. Our only more serious problem is breakage of plastic guides, which frequently occurs when the tube tears during forming. The fault lies in the material and partly also in insufficient lubrication.

According to the feedback they received, it does not happen that cracks appear on the product that has undergone cold expansion. With their process, we managed to eliminate poorly manufactured tubes, which they otherwise eliminated in subsequent phases of processing and inspection, during ** turning or X-ray inspection**. All the objectives they set at the beginning have thus been fulfilled; there is only the hope that the business will last long enough and they will manage to create some accumulation for future projects.

They confirmed all hypotheses; the conditions for successful work are also given. However, there is a real danger that the customer might steal the idea. In development, they perhaps approached them with too open cards. Cold pressing, which they used in their case, proved to be suitable.

With this, they reduced material consumption as anticipated. According to customer data, the processing of their products by turning is also faster and of higher quality. Since tubes with microscopic porosity were eliminated on the press, these did not end up on the lathes and did not cause tool breakage there either.

With the manufacture of this device, they also indicated the direction in which we can operate in small companies, where we do not have the resources and knowledge for large scientific research. However, we do have ideas and solutions that, within the framework of existing knowledge, enable us to achieve technological progress. The approach that enables us to manufacture as much as possible at home proved to be cheaper and above all faster.

Changes they thought of during the manufacturing itself were also implemented on the go without difficulty. By choosing a bolted instead of welded construction, we did not significantly lose rigidity, but individual frame components could be manufactured precisely and thus ensured parallelism of the upper and lower crossbar and the coaxial position of the workpiece and tool. Initial tests showed that a clamping device is not necessary.

Moreover, if they had manufactured it, they would have firmly clamped the workpiece with it, thereby preventing the workpiece itself from axially adjusting to the tool. Accuracy would have been impaired, and wear of components, tools and cylinder would have been much greater. The simple implementation of mandrel extraction proved to be effective.

When adapting to possible other product dimensions, it will be necessary to adapt or manufacture a new fixture for extraction. The need to change the control method from relay to controller implementation has not been detected so far. However, they detected slightly increased heating of hydraulic oil during prolonged use and at slightly higher ambient temperatures.

Constant oil temperature is important for ensuring constant conditions and maximum repeatability. In future, it would be good to add a cooling device to the unit. They completely misjudged the assumption that we detect the lower position of the pressing tool using a limit switch.

The length of raw materials deviates too much to be able to ensure repeatability of pressing depth. Fortunately, they already anticipated an adjustable delay after reaching the lower position in the initial phase. They now used this to ensure pressing time, and manufactured the limiter mechanically on the pressing tool.

Thus, the tool always penetrates to the same depth into the workpiece, and after the set time has elapsed, the device automatically switches to tool extraction movement. Such a solution could be a second or two slower, but regardless of raw material length, it ensures equal pressing depth. This is also an important customer requirement, as it simplifies the next processing phase.