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FAQ – Frequently asked questions

Here you will find answers concerning BRUDERER products:

Question 1

When installing punching tools, BRUDERER recommends clamping the lower section of the tool first followed by the upper section, and screwing the clamping plates tight one after the other. Why is this? Would it be inadvisable to clamp the tool the other way round (starting with the top followed by the bottom)?

Yes. We do not recommend clamping the tool the other way round. The position of the tool must be defined/set by the lower section, as the ram may tilt slightly above the strip level. In order to avoid warps in the tool or machine guides, we strongly recommend proceeding as described.

 

Question 2

What is the purpose of strip lifting? Is punching not possible without strip lifting?

The strip lifting device prevents erroneous variations in dimensions, thereby preventing variations in dimensions accumulating from one stroke to the next. Precise positioning of the stock with the pin stop is made possible by enabling the strip on every stroke, with the result that variations in dimensions are corrected to zero on every stroke.

 

Question 3

How often does the oil in the lubricant circuit on a BSTA 50E need to be changed? Does the oil filter also have to be changed when the oil is changed?

See the Maintenance Intervals section in the Operating Instructions.

 

Question 4

Our punching tools often remain on punching presses for a long time (3-4 weeks). When removing the tools we always find evidence of corrosion on the tool clamping plates as well as on the lower and upper faces of the punching tools. What is causing this? Is there something specific (e.g. a spray) that we could use to prevent corrosion of this nature?

The corrosion on the clamping surfaces is being caused by the tool and clamping plate sliding against one another under high load. To prevent this, we recommend clamping the entire tool surface as tightly as possible. In this respect, it is also advantageous to clamp in the lower section of the tool as tightly as possible but leave the upper section looser (only tighten it as much as you need) so that the upper section of the tool can flex as required in relation to the ram.

 

Question 5

At the start of the early shift we forever have to realign the punching strip and relocate the position of the punching strips in the tool. We work on the basis of a two-shift pattern and the punching presses are shut down overnight (ram in TDC). This rules out the punching strip being stopped by the strip feed unit. Would leaving the punching presses closed (in BDC) overnight cause problems for the tool and/or machine? This would mean that we would no longer have to spend so much time realigning at the start of each day.

No, there is no reason in principle not to do this, as long as it is permitted by the tool.

 

Question 6

How precisely and using what as reference (e.g. following the upper clamping plate) should punching presses be aligned? What do we need to be aware of?

Alignment accuracy is determined by the punching process. The reference for aligning punching presses is always the strip level and strip feed direction. You need to be aware of the tool sequence (lower section and upper section) (see Question 1).

 

Question 7

We are using a punching press with manual stroke adjustment. On changing strokes we have on occasion "lost" the stroke. Having to relocate the old stroke often takes a lot of time and patience. Have you any tips for relocating lost strokes?

If a stroke has been lost, you need to engage the shaft in the nearest lock, turn the stroke manually and check it at the same time. You'll soon be able to identify where you are in respect of the stroke.

 

Question 8

Our company uses its own BRUDERER BSTA 25 and BSTA 500 punching presses, amongst others, to produce high-precision electrical contacts for the automotive industry. These multistage punching tools feature stamping stations, for example for crimping and stripping. We optimise each punching tool during setup at low speed (250 spm) before accelerating the machines to the operating speed of 850 spm. When we measure the stampings on each punched part again, we find that they are several hundredths of a millimetre deeper than they were previously during setup. This means that we have to correct the ram height by 0.10 mm once operating speed is reached. What are the reasons for this variation? Can our punching presses be retrofitted with an automatic feature to correct the ram height?

The reason for this variation is that the acceleration in the scenario you describe is increasing twelvefold between a tool being set up and operating speed being reached. Variable centrifugal forces arising as a result of acceleration have the effect of pulling BDC down. To counter this, BSTA 500 presses, for example, support ram adjustment whilst the machine is running. This flexible ram adjustment feature cannot be retrofitted to older machines. Please contact us for more detailed information.

 

Question 9

Our tools are fitted with spring-loaded blankholder plates and centring pins. Despite setting the feed length precisely, we are finding that the carrier foil hole pattern is slightly oval in shape. There is also evidence of flash formation on these centring holes, even though the punch and sleeve have only just been ground. What can be causing this? Is the feed inaccurate?

If the strip is not lifted by the feed in time, the strip stock may not be centred precisely. However, as the stock is aligned in the tool, the pin stop will look for another way when the tool closes and punch a new hole reflecting its conical shape or at least distort the existing hole.

 

Question 10

As a component supplier to the automotive industry, the products we manufacture include plug contacts for ABS. Some contact parts of the strip stock (CuZn) are gilded. During the punching process, we are forever finding evidence of abrasion of the gold during feeding (BBV 202), and some of this adheres to the upper feed roller. The results range from marks on the strip to mispitching. We have already tried all possible options (reducing the contact pressure to a minimum, polishing the feed rollers, etc.) but without noticeable improvement. Can you suggest a way of avoiding this abrasion of the strip stock?

To avoid stock abrasion, we recommend that you start by trying feed rollers with a variety of coatings. Should this not reduce the abrasion, we recommend that you use a BRUDERER gripper feed unit instead of standard BRUDERER BBV feed rollers. Abrasion can also be reduced/avoided by applying a thin layer of oil to the surface of the punch strip just before feeding. This should prove particularly successful if you are using aluminium strips.

 

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