Inefficency - the enemy within
Seiki Systems has declared war on CNC machine tool downtime for small batch production. MARTIN OAKHAM reconnoitres Seiki's new offensive, born of DNC, but delivering much, much more than just NC program transfer.

Manufacturing used to be very different. Once upon a time there were lots of people doing hidden jobs to help keep production moving. Nowadays most of them have disappeared, in the grand scheme of improving efficiency. This leaves fewer people to handle day to day housekeeping - keeping track of fixture details, tool-ing lists and drawings etc. Many companies have invested heavily in dedicated DNC systems, CNC machine tools and software packages such as scheduling and CAD/CAM - believing that they would solve more problems than they do; but practices have in fact remained much the same.

I'm not disputing that most changes are for the better; a CAD station is clearly more flexible than a drawing board and a DNC link is more efficient than having operators wandering around with floppy discs. But these systems were not developed with the day to day problems of running a job shop' in mind machine operators still struggle to find tool setters when they need them and managers still struggle to meet the production efficiency expected of them. This leads to frustration for machine operators and production managers, excessive overtime and, dare I say it, the 'tweaking' of figures.

HOW PRODUCTIVE ARE YOUR MACHINES?
Seiki Systems is addressing this with a series of innovative Windows-based modules, under the broad heading of DNC, aimed primarily at refining the processes between an MRP system and the shop floor. These include a direct DNC system/NC editor; an advanced networked DNC system including a configurable interface for integration with any EDM/PDM data management system; a comprehensive 'Manufacturing Data System', to store, manage and allocate status control for all manufac-turing data needed per job, including text files and drawings; and a very advanced tool management system. This is a bit different to your average DNC system - which simply downloads post processed data to a machine at the request of the operator.

According to Seiki Systems, stand-alone CNC machines used for small batch production work can be as little as 30% productive - not the 70% productive so often quoted (ask some production managers - I did, and they agreed). To back this, Seiki Systems has identified four areas responsible. The first is a total lack of DNC, but this in itself only accounts for 10%. More important is the lack of adequate technical data for operators, which accounts for 15%, and poor organisation, planning and maintenance, which accounts for 20%. The remaining 25% is due to poor tool setting strategies.

Let's look at some typical situations. The company MRP system outputs a request for 30 'left hand floggle toggles' by Tuesday and 12 'widgets' by Wednesday. That's fine, but it doesn't say what order it wants them in - just when they have to be done by. If the jobs are in brass, then steel, then brass again, many companies would manually re-structure the list to do all the brass components first, to minimise setups. Fine again, but this takes considerable time and thought. If you cannot locate the toollist or setting notes for the jobs, or the setter has gone off to look for lost tooling - you're wasting time. Worse still, if the only person who knows how to do a job goes off sick, who do you get to take over? Does it matter anyway, if none of the other operators know what to do? Do you need a crane? Did Joe still need to do a slight offset on that recess, or was the program updated? The latest CAD/CAM systems can't do much to help you here; you need something to help the new operator do the job - eg toollists, setup details, notes or even some video footage.

Those already familiar with Seiki Systems' products are probably thinking that its MDS system (covered in MWP April96) solved all these problems. This is true, but as Seiki Systems' general manager David Trowell, points out, the step was too big for most companies, many of which had no hint of a DNC system. By offering our customers a range of modules we can give them a system that they will make a hundred percent use of. We offer the freedom to use whichever EDM, PDM, and CAD/CAM system they like, and if customers require an upgrade, at any point, we will only charge them the difference between the module they have and the module they are upgrading to. We develop a best fit system for our customers, help them find a suitable module and give them future advice. We don't try and replace everything either. If the company is already using an open PC network, we make use of it.' So, what are the options? If you have no DNC capability whatsoever, you can start with NC Program Manager - a low cost DNC solution using a PC or lap-top. This is a Windows-based CNC editor developed to create and compare NC programs and has a configurable RS232 communication facility. You can save setups for as many machines as you want. NC Programs can be transferred either to and from the Editor or to and from the Windows File Manager. In each case the machine tool is selected from the menu (created in the Communication Configuration Module) together with the required file to be transferred. The complete requested transfer is then graphically represented on the screen for the operator to confirm the transaction.

If the Windows File Manager is con-figured to have a proven and 'returned' directory for each machine tool, the programs can be transferred via these, and the NC Text Editor can be used to compare the differences prior to acceptance of returned pro-grams. Robot loading programs can also be handled in this way.

Direct DNC System eliminates the need for any shop floor DNC terminals. It comprises a host (centralised) PC equipped with the number of RS232 ports/cables needed to link up all the machine tools on the shop floor; up to 32 can be supported from any one PC. All NC programs are filed on the host PC within a directory set up for each machine tool, in exactly the same way as files are handled in the standard Microsoft Windows File Manager.

A 'Transfer' program is stored in each machine tool, which can be used to directly transfer the required program from the PC to the machine tool. In order to effect the transfer the machine tool operator enters the required program name in the 'Transfer' program on the CNC and then selects 'output' followed by 'input'. The required program is then transferred to the machine tool.

Direct DNC System can be used to call programs to the machine tool, return machine tool edited programs and transfer other files, eg, unproved pro-grams, tool offsets, etc from other direc-tories by password access if required. The facility to view the contents of a host directory on the CNC screen is also included. A log book is automatically generated in order to log the time and date of each transfer, the file size and last modified date.

If an operator modifies a program; he/she will not override the original program; this is the responsibility of the production manager. The manager sees the number of edits made on his/her PC and can compare them with the original file(s) before deciding whether to commit them or not. When the operator reloads the program, at a later date, a comment will be displayed stating if the modification(s) were accepted or not. I cannot stress enough just how useful it would be to an operator to be able to look at any/all the files in the directory (0-listing) without moving from the machine tool, edit them, state what jobs have been completed and send the programs back. It would be like seeing the light at the end of the tunnel for the first time.

SIMPLER SOLUTIONS
The next module up the DNC ladder is Networked DNC System. This is in effect an electronic plastic wallet containing all the files and programs an operator could possibly request. The host PC system can simultaneously feed up to eight machines and has a configurable interface enabling integration with any EDM/PDM data management system. Edited NC programs can be returned to the host PC for comparison with the original in the same way as the Direct DNC system. In addition to NC programs, tool lists, drawings, setting information, notes, photos and video footage, the operator can access material sizes and verification programs such as CG Tech's Vericut. If the operator is not authorised to edit a program he/she can identify the problem on screen using a light pen - the equivalent of scribbling notes all over a program printout.

Companies looking to install this level of system are likely to be using a PDM or EDM data management system, meaning that all the files in the machine folders will have been installed on a giant central database kept somewhere in the company vaults! To those not familiar with PDM, it allows a design change to be filtered right through to the NC program in an associative way. There are generally two problems with these systems according to Trowell: you need a degree in computer science to get a grasp on what is going on; and most top management don't know what a DNC system really is.

Seiki Systems has come up with a simple solution. The operator logs onto his/her shopfloor PC/controller which simulates an EDM/PDM environment. All communication with the central database is done using a question and answer screen. This automatically downloads a copy of every file recalled and puts it in a temporary directory. The machine tool 'points' to this copied data, maintaining the integrity of the EDM/PDM data. As with all networked systems, the EDM/PDM system can be anywhere in the world, and is not limited to the company vaults. The production manager is generally responsible for setting up where the information is coming from. For the operator it's simple - you put in the job ID the job number and press 'start'. If you want to view the job you press 'view' - simple. How many companies can you go into and ask what is the next job, what does the drawing look like and how do you set it up? Not man, and this system will give you the answer in seconds.

If this is not comprehensive enough for you, there's always MDS (Manufacturing Data System), which gives you everything the Networked DNC system has to offer and much more. The addition is the ability to record setup times and cut times etc so that the information sent by the MRP system can be optimised. The MDS allows you to do things like draw a graph of the progress made on each job, for each machine. If a job is finished early, the computer will pull all the other jobs in the queue back; an urgent job can be slotted in and the computer will show you what effect this has made on all the other scheduled jobs for that machine or resource. You're really cooking with gas now!

The factory manager can look at the screen and immediately see the status of every machine on the system: for example if it's waiting for apart, if the operator is waiting for a first off inspection clear-ance, if the machine is being set, undergoing maintenance - or in production. In fact there are 84 user definable areas that can be monitored. The production efficiency for each machine tool can be interrogated over any period you like, one day, one week or over a year. By looking at these trends you can identify where problems lie. You might even find that you don't need a new machine at all to remain competitive, just to sort out your setting and inspection efficiency. You can see where Seiki Systems got those figures from now, can't you?

BASED ON EXPERIENCE

The final module left to discuss is ToolMan. This Windows-based tool management system provides rapid access to tooling information with the aim of reducing inventory growth, minimising the total quantity of tools set and minimising tool changing between each job. It relates individual tooling elements to tool assemblies, and tooling assemblies to a specific job.

Additionally, tooling assemblies can be assigned to a machine tool (eg, permanent tooling at a machine). ToolMan includes the facility to compare (optimise) new tooling assemblies for new jobs with existing tooling on the machine to minimise the total quantity of tools set. If new tooling is required you can go straight to third party data-bases such as Sandvik's, and look at their tooling data.

ToolMan also allows you to list every job that can be done on a given machine tool setup and to give you a list of the tools used in the order of frequency. A CAM programmer can then look at this list and develop new programs around the most commonly used tooling. For example, rather than ordering a new 120mm diameter shell mill, the programmer can opt to use another tool already used in the carousel, say an 80mm shell mill, and take two passes rather than one.

In use, you can drag in a job list, look at the total tools used, analyse the list and remove any duplicates. This might save the setting of 17 tools. Then you can take the tools left and compare these with the fixed tooling left in the carousel. The resulting list can then be compared with the variable tooling. You might find that you only need to set three tools and can remove 14 tools. These can be added to your fixed tooling if required. This is how you get your 25% savings. You are not querying what the most used tools are - you know what they are. You can also tie the graphics for the tools up with your CAM system so that the tooling data does not have to be duplicated. You can even put in comments about tool graphic data in your tool list. The data is passed to the CAM system, complete with graphics.

This 'open' modular suite of Windows based programs is truly impressive. Each module offers seamless integration with other software systems, is extremely straightforward and comprehensive, being designed to suit both small job shops and large blue chip companies alike. I was so impressed by what I saw, and I believe it is only a matter of time before every 'go ahead' company in the UK has implemented such a system. It's what we need if we are going to stay competitive as an engineering nation.

The entire project was conducted in response to real shop floor situations, and as David Trowell of Seiki Systems says, 'we couldn't have done this without the support of Hitachi Seiki and their customers who supplied us with the information about the problems they were experiencing.'