Machine deburrs sheet metal automatically

Automatic sheet metal deburring machine has been operating for three months with the best availability levels, without any down time, in three-shift operation at a truck frame manufacturer.

The giant German MAN Company has installed a LISSMAC SBM deburring machine to bring the quality of their sheet metal products up to the latest standards.

MAN Gustavsburg is an independent business unit within the production network of MAN Nutzfahrzeuge group which with 34,094 employees constitutes the largest company in the MAN Group, which operates all over the world.

The Gustavsburg plant, which was established as long ago as 1859 is now, thanks to many years of experience in the manufacture of systems and machines the leading European supplier of pressed parts and components for the commercial vehicles and private car market.

In accordance with the increasing demands from customers for product quality and cost reductions, the company invested in a steel brushing machine and an automatic de-stacking unit made by Lissmac.

This is where the sheet metal parts cut out by a laser cutter receive the last 'grind' for the immersion painting which follows.

* Economic manufacture of lorry frame reinforcements - to obtain an optimal ratio between the load-bearing capacity of a lorry frame and its laden weight, the slim-line frame carriers are reinforced at specific, precisely identified points.

The exact dimensioning of such reinforcement panels usually results in unconventional forms.

The batch size decides which procedure functions economically.

Panels of this type can be pressed or thermally cut out.

"Whilst we use the highly productive pressing process for the mass production of such reinforcement panels, for smaller production batches we have installed a Bystronic laser cutting centre," explains planning engineer Roland Menk, and he continues: "With this laser equipment, we can fulfil special requirements from clients at short notice".

"This laser equipment operates very flexibly and can be controlled directly via production engineering.

Apart from being able to carry out urgent orders rapidly, we value the outstanding repeatability for best-quality laser-cut sheet metal parts.

The laser equipment cuts out all pre-set recesses and contours without any problems, and also executes bores in the sheet metal." As a rule, the sheets are 4 to 12mm thick, but they can be up to 20mm thick.

The cut-out sheets have a maximum length of four metres and a maximum width of 700mm.

"In order to combine the laser equipment's high flexibility with high productivity we cut with a mixture of oxygen," explains Menk, and he goes on: "This oxygen certainly causes oxydation and a build-up of slag in the vicinity of the cut edges.

This oxide layer not only prevents any stable bond from forming between the sheet and corrosion-preventing lacquer coatings, but even with powder coating or galvanising the material bonds fall below the usual standard.

And then we found a reference to a steel brushing machine from Lissmac in the specialist press.

In order to test for the necessary process reliability," continues Roland Menk, "We initially accepted a tender from Lissmac to brush our laser-cut sheet metal parts with a test machine.

We lacquered these brushed sheets in our cathodic immersion painting equipment and passed them on to our test laboratory.

It turned out that the sheet metal was now forming a permanent bond with the paint, even on the laser-cut edges.

Then we investigated the availability of the steel brushing machine.

We specified a solid format which was well suited to our three-shift working.

And so a positive decision was made to invest in an SMB 1000/2A steel brushing machine." * Steel brushing machine - at the centre of the ergonomically constructed brushing centre stands the Lissmac 'SMB 1000/2-A' steel brushing machine.

It operates using an efficient brushing process - contra-rotating brush belt elements with brushes positioned at an angle provide for optimal processing of the cut edges.

The sheets to be processed run through the machine automatically and are brushed on all sides simultaneously by four brush belt elements positioned opposite one another but offset in just one pass.

This generates suitable surfaces for coating on both the external and internal edges.

The steel sheets to be processed may have a maximum thickness of 20 millimetres.

At the same time, the brushes slightly round off the cut edges which are often sharp.

This should very definitely contribute to the avoidance of accidents during manual handling.

The maximum width which can be machined by the steel brushing machine illustrated is 1000mm.

1500mm wide steel brushing machines of this type also exist.

There are absolutely no operating problems.

The thickness of the sheet to be processed is centrally set, using a hand wheel.

A separate scale gives the operator a reliable indication of the current operating range set.

The feed is likewise infinitely variable and can be selected freely over a range of 0 to 10m/min.

A stacker transfers the sheets to be brushed onto the lifting table, which is installed in front of the brushing machine, on a special pallet.

Sufficient space is available for the operator between the brushing machine and the lifting table.

The operator manually pushes the long sheets from the lifting table into the brushing machine, which then feeds them on further.

For this stage of the operation, the pick-up level must coincide with the working height of the steel brushing machine.

To bring this about, the operator moves the lifting table to the required level, using a pedal switch.

The brushing machine pushes each individual sheet onto a roller conveyor.

This roller conveyor takes the brushed sheet metal part up to a stop, the position of which is infinitely variable.

For really long sheets, this stop is at the end of the roller conveyor.

With the help of a light barrier, which is installed at the start of the roller conveyor, it can be ensured that only one individual sheet is on this conveyor at any one time.

This regulation guarantees a reliable transition for automatic stacking.

The grid-shaped pick-up unit, the fingers of which wait for the item to be transferred between the rollers of the roller conveyor, must in fact take only one individual sheet on each occasion for safety reasons.

* Pick-up unit - driven through a chassis and lifting gear, which operate on an area portal, the pick-up unit raises the sheet metal part until it is securely conveyed over the stop bars of the drag bar on the stacking table.

When the pick-up unit has cleared this hurdle, it locates itself and draws back.

The brushed sheet metal parts therefore accumulate, little by little, into a stack which is up to 500mm high.

To ensure that the pick-up unit can also safely take sheet metal parts which are up to 4m long, it is just as long as the roller conveyor.

So the portal needs only the X and Z axes.

The stack height is monitored by another light barrier.

When the stack reaches the pre-set stack height, the equipment stops operating and the operator receives a signal to empty the stacker table.

In order to guarantee the maintenance of all industrial health and safety standards, the automatic stacker device has a protective grid and a light-grille barrier on the open access side.

If anyone enters this protected area, the entire system switches off.

There is also an emergency cut-out key on the operating panel, which likewise immediately puts the equipment out of operation.

Small-format sheet metal parts are supplied in a box pallet and unloaded onto the lifting table.

This is now lowered until the operator can comfortably reach into the box pallet to transfer the small sheet metal parts to the brushing machine.

After brushing, these small components fall into a pre-positioned box pallet.

So that the box pallet can be positioned on the exit side of the brushing machine, the roller conveyor and the stacker table must first be moved back about 1.5m.

This can easily be done manually, since both the roller conveyor and the stacker table are mounted on wheels which run on rails.

Once they have been moved back, the roller conveyor and the stacker table are stopped and electronically locked.

The effect of this is that the pick-up unit can not move and the operator can move in the area, the other machinery in which is not locked, and the steel brushing machine can operate.

"This machine," Menk emphasises again, "Has been operating for three months with the best availability levels, without any down time, in three-shift operation.

Another convincing technological feature is the long brush tool life of two months, during which the brushes have certainly been subjected to a lot of stress while in three-shift working.".

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