Very rarely, does a press brake operator get the luxury of running the same part week after week with custom metal fabrication.
Twenty enclosure brackets can be in a morning batch. The next order might be four stainless covers, then an aluminum prototype order, which was made three months ago, and a repeat order. The material, flange position and bend sequence / tooling requirement is different in each drawing.
When it comes to this work, custom metal parts manufacturers don’t necessarily need the highest capability per hour when it comes to press brake machines, but rather the ability to get to the next correct part as soon as possible.
It is for this reason that a flexible press brake should be considered in all aspects of job changeover, programming, positioning and repeatability, as well as tonnage.
Before there is a bending problem there is a setup problem at custom fabrication.
It can be as easy as a 90° turn and last only seconds.
It can take a lot longer to prepare for that bend to be executed properly.
The operator may have to read a new drawing, identify materials, identify thicknesses, select tooling, move the backgauge, figure out the sequence of bends, run a test part and make adjustments as necessary. If the order only has 5 or 10 pieces, these set-up minutes can be a large part of the order.
This is the cost associated with fabrication that is of high mix-low volume.
The machine must thus be able to allow frequent changeovers. Operator memory previously used to decide on ram positioning is now converted into repeatable production settings with the help of CNC-controlled ram positioning, programmable backgauges and stored job data.
For a shop that does work that frequently changes, a customized hydraulic press brake can also be designed for work length, tonnage, control and part complexity and not just put all jobs through a single configuration.
| Job Change Activity | What Should Be Defined | Production Risk If Undefined |
| Drawing Review | Bend sequence and references | Wrong bend order |
| Material Setup | Grade and actual thickness | Incorrect force or correction |
| Tool Selection | Punch and die combination | Radius or interference problems |
| Positioning | Backgauge reference points | Flange dimension variation |
| First-Part Check | Angle and critical dimensions | Scrap carried into the batch |
| Repeat Job | Stored program and setup record | Repeating previous setup work |
The Drawing to be a Bend Sequence, before any metal is at the machine.
One reason for the failure of custom parts is that the individual bends are treated one by one.
This is not six separate bending operations in a six bend enclosure! The geometry of a workpiece can be altered by each bend and potentially impact if the subsequent flange can reach the tooling without collision.
Before the first cut, good CNC preparations pose a number of questions:
Which of the bends would you do first?
Is there an existing flange to interfere with the punch/machine frame?
In which place does the operator need to refer to the work piece?
Does the part need to be repositioned during the bending process?
Are multiple tooling setups required to perform multiple operations?
The modern CNC press brake machine for sheet metal bending has a control over the ram movement and feedback of the machine, which can make the repeatability of the machine between strokes better. APEX also calls CNC programming as a method of minimizing the repeated bend-measure-adjust operations which are prevalent in conventional setup.
The true benefit of automation for custom work is more than just automation. It’s having the ability to transform an intricate drawing into a managed series prior to any unneeded material is utilized.
The more unpredictable the part mix, the more important backgauge flexibility is.
With simple backgauge positioning, simple parts can be produced.
It shows the limits quicker with custom components.
Changes in flange depth can occur on either side of a part and there can be several reference points or asymmetric geometry. Then the operator has to spend more time to manually adjust the sheet or check the dimension between bends.
More of this positioning work can be automated by use of a multi-axis backgauge configuration. Further X, R and Z-axis options can achieve more complex positioning of work pieces and minimise manual repositioning in multi-bend workpieces, adds APEX.
This means that for a custom fabrication shop, there is a helpful guideline to follow when purchasing:
Never mention the backgauge around the simplest piece of work that you create. State it at the parts which now require a lot of time for setup and measurement.
That should make it easier to see if any more axes will add any value.
While the tonnage is still important for custom parts, it’s not the case that every job requires maximum tonnage.
There are a variety of different types of materials, thicknesses and bend lengths when using custom fabrication.
This can be tempting to purchase much more capacity than is needed for most jobs. The rated tonnage is just part of the bending process, however.
Material strength, actual thickness, bending length, V-die opening, punch radius and bending method are all factors which affect the required force. The press brake tonnage calculation guide further focuses upon the actual bending length to be used, instead of taking the full working length of the press brake.
A more preferable method is to examine the actual part mix of the shop.
Consider the thickness and the most frequent recurring material, the length of the common bend, the smallest required flange, and any special operations which may be required like hemming, or offset bending. If occasional extreme jobs can be accomplished another way, don’t automatically let this dictate the machine specification.
A custom shop requires available capacity on numerous jobs, not just great capacity that is idle.
Repeat Orders Are Where Stored Process Knowledge Starts Paying Back.
It is with repeat orders that stored process knowledge begins to pay off.
The initial order for a made-to-order part could take some research.
The second should not be a new-beginning.
It is important that once a part has been successfully produced the shop preserves the CNC program with the material, tooling, backgauge references, and verified corrections. On re-ordering the same component, the customer’s data is added to the production asset.
This is important because many “custom” parts are not a one-off-part. About weeks or months later they come back, sometimes in different batch sizes.
The ability to store proven settings in a CNC system decreases reliance on the person who originally ran the job. It also aids in getting the 2nd production run to the approved first piece condition.
Knowing the working principle of a press brake isn’t enough, though. When manufacturing certain items, the bigger issue is whether or not the machine can reliably replicate a previously proven setup should the job come back.
Take a look at the Machine judging by the Difficult Jobs Between Production Runs.
But an optimized press brake can be used to manufacture one family of parts in a high volume factory.
Usually a custom fabrication shop doesn’t have that luxury.
Gather a set of real drawings that includes: a simple part, a multi-bend enclosure, a short batch, a challenging flange geometry and a repeat order. Discuss the tooling, axes, working length, CNC functions and necessary tonnage with the supplier using those drawings.
This gives a much better feel for real-world restrictions than can be gleaned from the specifications alone.
Buyers don’t always choose the best press brake machine for custom metal parts based on the tonnage or number of optional axes.
It is the machine that enables the shop to alter drawings, materials and batch sizes without having to pay the same set up cost over and over again.
| Representative Part | What to Test on the Press Brake |
| Simple Bracket | Basic setup speed |
| Multi-Bend Enclosure | Bend sequence and interference |
| Asymmetric Part | Backgauge positioning |
| Short Custom Batch | First-piece setup efficiency |
| Long Flange Part | Angle consistency across length |
| Repeat Order | Program retrieval and setup reproduction |
Final Shop Check
Before choosing a press brake for custom production, check out the work that’s currently holding up the bending department.
Is the problem on the computer program? Tool changes? Manual positioning? First-piece correction? Complex bend sequences? Or trouble copying a previous work?
After that it’s fairly straightforward to configure the machine.
When flexibility can be managed, custom fabrication can be profitable. The press brake should enable variety to be a production capability, not a time sink every day.
FAQ
Q1. So, is it correct to say that a CNC press brake is perfect for small batch custom metal parts?
Yes. It is especially beneficial when jobs change often or when jobs repeat after a lengthy time period, CNC programming and stored settings are invaluable. They minimize the creation of setup knowledge that needs to be re-established manually.
Q2. What Press Brake Features are Important for Complex Custom Parts?
CNC control, appropriate tooling, programmable backgauges and adequate axis flexibility is important. The specific setup can vary based on the parts being manufactured and their geometry and positioning requirements.
Q3. What press brake tonnage to use for custom fabrication?
Determine the size of the force based on material strength, thickness, length of the bend, the tooling and the bending technique used. Don’t select capacity from just the thickest material description or total machine bed length.
Q4. Do multi-axis backgauges make sense for all of the custom shops?
Not at all, as basic components often don’t warrant it. They are more useful in situations where components have multiple flange depths, or the flange is positioned asymmetrically or the flange is manually repositioned regularly between bends.
Q5. What data to provide a press brake supplier?
Submit a number of typical drawings plus materials, tolerances, and batch sizes, and thickness range etc. Real parts provide the supplier with a significantly improved platform for machine and tooling suggestions.