A Step-by-Step Guide to CNC Automation

In today's global economy where business competition can come from anywhere in the world, many companies are faced with the problem of producing parts with shorter lead times, to a tighter tolerance and at a lower price to remain competitive.  This issue also faces our tooling and mold building shops.  These market demands are forcing large and small companies to determine whether their production capabilities are operating at maximum efficiency and if they are getting the most out of their investment in modern capital equipment.

In addition to the global competition, the American tool and mold builder is faced with the tightest job market that we have experienced in over 30 years. The skilled moldmaker or machinist is a rare commodity today and good ones are hard to find and keep without a quality pay and benefits package.  When qualified personnel are not readily available, companies must turn to the trade schools and to the age-old apprentice program to train from within. The cost to train and keep good quality employees is steadily increasing due to the short supply of skilled workers and the growing demands for technical and computer-oriented job skills.

One way to combat these problems is to increase the utilization of the modern CNC machine tool.  While CNC machine tools of all types are abundant in most shops today, many shops have not extracted the full potential from their equipment. This is because the ideas that are inherent in CNC machining have not been expanded to include the entire shop. A CNC machine tool can quickly process the work without operator intervention, but once the job is finished, the parts may sit in a corner waiting for a bottleneck to clear further down the manufacturing process. Most companies are only able to utilize 1,000 to 3,000 machining hours per year when they have the potential for over 6,000 hours per year of actual billable machining time per machine tool.

Benefits of Automation

There are 8,760 hours in a year. Typically shops can expect to get anywhere from 1,000 to 2,500 hours of attended machining time per year with operators working 1 shift with a 5-day work week. If your machines are not running during the remaining unattended time you can have machine tools that have the potential to run over 6,000 hours per year standing idle more than 50 to 75% of the time!

So how can we get to that magical 6,000+ machining hours per year that every shop owner dreams about? By applying a systematic approach of automation to our shop and CNC machine tools. Even the small shop can reach the high productivity rates once thought only possible with high-volume production work.  A secondary benefit to applying these principles to a job shop is that the shop will become more organized by virtue of the structure required to implement an automated system. Work can be set up and processed without constant human supervision. Changes in the work schedule can be made quickly and easily since provisions for flexibility are at the heart of the automation concept. And the ultimate goal is that the shop capacity to produce work can be increased without large investments in costly manpower. Remember that CNC automation is not something you can purchase, but a process that you apply to your shop!

The 8 Steps to a Successful Implementation of Automation

The process required to implement a successful automation program in a CNC job shop can be refined down to 8 main steps. Each step moves you closer to the ultimate goal of a “lights out” machine shop.  Each step will also help you become more organized and more profitable than you were before. This improvement in profitability helps to finance the future steps required to reach your desired goal.

Each step must be taken in order and be fully implemented into the shop’s day-to-day work habits for the process to be a success. Like the weak link of a chain, a step not taken will quickly develop into a bottleneck that will drain the productivity gains and profits created by other investments in the process.  Even the small shop can afford to make these first steps since they require a relatively small financial investment. The greater investment is in believing in the concept and being willing to follow it through.

1. Standardization of Work

Adding an automated system to the shop does not mean that every part in the shop must fit a particular shape and size or be a production job of 5,000 to 100,000 parts. Standardize the “process” not the workpiece. The first step toward automation, especially in a job shop, is to review the type of work that is done and to look for similarities. This does not mean that you must limit the shop's business to only one type of die or one size of mold, but every shop has inherent standard specifications in place by the nature of the equipment and expertise available.

Once the similarities in the work are recognized, a system for automating the production of these similar parts can begin to take shape. If your shop does 80 to 90% of your work within a 10" x 10" x 6" work envelope and the remaining 10 to 20% varies up to 24" x 36" x 16" in size, it would not make sense to attempt to automate 100% of the work. This would require a tooling system and automation equipment that would be considered serious overkill 80 to 90% of the time.

Instead, the more cost-effective approach would be to automate and improve the throughput of the greatest percentage of your work. More time would then be available to manually attend the larger work on stand-alone equipment outside of the cell. Determining the work envelope for the cell allows the shop management to select the proper tooling system to be used as the “standard interface” between the workpiece and machine tool.

2. Job Planning

Job Planning refers to identifying and documenting the steps required to get a workpiece from the raw material stage to its final finished dimensions and deliver it to the end user. The end user can be an external customer or an internal one like a moldmaker in the final assembly department. This sequence includes the design phase, CNC programming, raw material preparation, presetting, scheduling, machining in the cell, and subsequent finishing operations. This sequence must be adhered to if work is to be processed on the shop floor in an orderly manner. Creating a job plan will also help to predict bottlenecks on the shop floor. Machine tool utilization is more easily optimized when a proper plan is in place for each workpiece.

3. CNC Programming

Over the years most shops have accumulated more than one programming system for their CNC needs. In order to streamline the production of CNC programs a standard programming environment should be selected.

Workstations that will be involved with the programming of the cell should be set up with a competent, integrated CAD/CAM system that provides all of the programming capabilities needed in the foreseeable future. If there is more than one seat of CAD/CAM software being used to program parts for the cell, each system should have the same software release level, with similarly configured hardware.

The CAD/CAM software must also have absolutely clean post-processors that are optimized for the machine tools involved in the cell. These optimizations should include program start, program end, special function assignments, and macros to simplify programming of potentially repetitive features. It can be a major waste of resources if we have a machine tool with special machining functions that we cannot access because our CAM software does not support them.

Adopting a standard programming technique eliminates the need for programmers to interface with the cell operator(s) on the details of every job. The added workload of editing programs on the shop floor after post-processing is not acceptable.

There should also be a documented set of standard programming conventions that each programmer adheres to in order to create programs that every machine operator can understand. These conventions should include standard entry and exit routines, standard cutting directions and cutter offsets, etc.

4. Raw Material Preparation

In order to obtain the greatest efficiency from an automation system, it is important to establish standard guidelines for the production of the raw material blanks to be processed. Considerations should be made at the design level for the mounting of the raw material blanks onto a selected tooling system. It may also be beneficial to build and maintain an inventory of pre-machined workpiece blanks for standard mold or tool components. The cell should never be left idle because the raw material is not available.

Standardized raw material preparation could include items such as:

1. Workpiece blank sizes. (Length x Width x Height or Dia. x Height)
2. Location and size of start holes so that a consistent wire EDM thread position or mill start position can be established and programmed.
3. Machining of reference surfaces on the workpieces to guarantee the accuracy of part registry in the tooling system.
4. Standardized part pickup procedures so the same references can be used across multiple processes.