5 points to consider when buying a Press brake no.2: Its about the production!

Welcome back to our series of 5 considerations when buying a hydraulic press brake. If you missed part 1, click here to catch up on it. In today’s article we are going to start delving into the thinking around the work that needs to be done with the press brake and how it will affect your choice of machine.

Your bending requirements in terms of your production - part mix and volume.

NC_or_CNC_partsmix.jpg

A crucial part of your decision making concerns the variety of parts you will be bending, how often the variety changes, the volume of each part and how this impacts your ability to meet the demands of your customers or projects.
 
The broader your part mix the more time you will need to spend setting up your hydraulic press brake between production runs. This ‘set up time per job’ component only increases further if the part in question has frequent changes in specification week in and week out, or if new parts are being added at short notice, a common characteristic of the ‘jobbing shop’. 

Conversely, a narrow mix of parts will mean that machine setup is infrequent and typically once off per part, reducing down time between production runs. However, volumes may be high, so a machine with a simple, intuitive operation and fast cycle times will be preferred in this environment.

Now, let's bite size these into the most common scenarios so we can categorise them against the right type of press brake for the job:

1. Low mix-Low change frequency- High volume

A relatively small selection of parts that remain static in their specification, with each being produced in high volumes. New parts are added infrequently.

2. Mid mix - Low change frequency - High volume

A relatively deep library of parts that does not change specification frequently, but are still produced in high volumes. Parts are added on a regular, but predictable basis.

3. High mix - High change frequency - High volume

A high mix of parts and materials with specifications that will change frequently, which are produced in high volumes. Parts are added frequently and with little warning.

Now - the keen eyed amongst you will say that there are many more permutations. For example, what happens when the volumes are low in each case? This can occur and the answer in most cases is to consider this: would you spend money to save time, or spend time to save money? For example, in scenario three with a low volume output, you could spend less money on the machine, longer on set-up and get through a low volume production run in a time frame acceptable to your business. 

So I fit into one of the scenarios - what press brake would suit me?

Hydraulic press brakes have many different configurations in terms of build, delivery of bending force etc. These are discussed in another one of our articles you can find here. For the purposes of this discussion we will focus on Numerical Control versus Computer Numerical Control and how these broad configurations will help you maximise output based on the scenarios. Machines with simple push button pendant controls are still available but have been all but phased out in terms of new machines, so these are not discussed.

NC Hydraulic press brakes - the answer for low mix, high volume.

 The Estun E21 NC provides for simple programmatic control of hydraulic press brakes.

The Estun E21 NC provides for simple programmatic control of hydraulic press brakes.

A NC hydraulic press brake has a control that provides an accurate read-out of the backgauge, referred to as an X axis, and the depth of the beam travel, referred to as a Y axis. These controls feature limited programming capability (watch us programme one here). It is important not to refer to these as true CNC machines, as they do not feature synchronised hydraulics with complex scales, drives and proportional valve systems and are far and away simpler than their true CNC counterparts, and therefore priced far more cheaply and rightly so. They are not ‘bargain basement CNC’ machines (beware the snake oil salesman!). Instead they use a torsion bar for beam parallelism and simple encoders to read screw rotations and move the conventional press brake into the modern era.

An NC hydraulic press brake is good workhorse machine. A popular control, the Estun E21, provides the ability to manage the X and Y axis and programme up to 40 programmes with 25 steps in each, with each step repeatable 99 times. Tooling and material libraries, angle bending, compensation etc. are not available and programming is done at the machine. With a bit of thought and planning, a low mix-high volume environment will benefit greatly from this type of hydraulic press brake, providing excellent value and return on investment. Simple maintenance and over the phone control support will keep the bills low too.

CNC Hydraulic press brakes - the answer for high mix, high volume.

 The Delem DA 66T, a highly functional and advanced CNC hydraulic press brake control.

The Delem DA 66T, a highly functional and advanced CNC hydraulic press brake control.

A CNC machine has a control that not only governs almost every aspect of the synchronised hydraulic press brakes operation, but provides a staggering amount of tools to assist both the operator and draughtsman in extracting maximum performance. Typically these machines have 4 axes consisting of Y1, Y2 (depth of beam travel), X1 (backgauge travel) and R (backgauge finger height). However, more axes can be configured covering the aforementioned as well as Z1 (finger width), Z2 (independent finger width), R1 (independent finger height), X2 (independent finger travel), C (automatic crowning) and more. These machines also feature complex safety systems such as laser finger safety. The high specification drive systems and hydraulic or electrical bending processes are also much faster than even the fastest NC machines.

A CNC hydraulic press brake offers great flexibility and speed. With a tool and material library for reference, the machine will interrogate the part and material parameters (drawn either directly on the control or transferred with USB or network integration) and specify the best tooling for the job. In addition, pressure, crowning, dwell time, spring back rates and more will be determined automatically. The operator can then also carry out a simulation of the bend in 3D whilst checking the machine’s suggested bending sequence. 

The upshot of this is that a well trained operator can set up a CNC machine and begin delivering highly accurate parts in a fraction of the time of NC and conventional hydraulic press brakes. The primary consideration of course is cost. A CNC hydraulic press brake is typically 3-5 times the cost of the equivalent NC machine and will require a more skilled operator and in depth servicing requirements over its useable lifetime.

So now that we really have you thinking, you can look forward to our next article which will cover workflow, material handling and space considerations for your new press brake.

Stay tuned for 3 more insights into choosing the ideal press brake for your business! Missed part 1? Click here.