BTRs & DNC Systems Advanced Digital Research, Inc. the leading supplier of DNC (Distributed Numerical Control) hardware and software

DNC Concepts

Eliminating tape with ADRs BTR Hand held terminal makes operating easy EXEC tapes the easy way Cables and settings. Why you need DNC Get control of your shop with AdvancedDNC View the AdvancedDNC slide show Ethernet DNC using FTP Get ADR FTP today How to connect CNCs with Ethernet If you are interested in TCP/IP or FTP see How to Connect CNCs with ETHERNET. Also see the Glossary and FAQ for more information. Topics: Why network machines? What is unique about machines? DNC Implies use of Server Computers Networking Star Networks "Single-drops" Buss Networks "Multi-drops" Wireless DNC Networks Why DNC?: Simply put, you need to connect your shop floor with your engineering and business systems. Or briefly, as manufacturers move from functional structure to Process-oriented structure they "decentralize" to gain flexibility and quality. Originally Distributed Numerical Control (DNC) was used to save time and money over manual methods of loading programs, or using punched tape. Today DNC is an essential element of CIM and production logistics. Networking eliminates errors, and gives all machines a unified way to access files. Network security features keep your files safe. Programs in CNC memory can be saved easily and rapidly, so you will not loose edited files. DNC is constantly improving, and you now have more affordable options than ever. You do not have to buy new machines, or buy an expensive "DNC" options from the machine manufacturers to gain the improvements provided by DNC. Advanced Digital Research Inc. specializes in providing networking for all types/brands of machines. Machines: Factory machines have a specialized computer in them, called the "control", that controls the machines motion in real-time. The machine actions are determined by a program - a command is called a block. Older machines may not have memory and execute blocks fed to them from a tape reader(NC machines). ADR's BTR supports hundreds of different NC/CNC models. We supply cables needed to attach the BTR to the control and have application notes on how to configure our BTR for almost every control. A CNC (computer numerical control) has memory and "devices" (RS232 ports) to move data in and out of its memory. Some CNC can only execute programs from their memory, others can "drip-feed" - execute from an input device, while reading ahead a few blocks. RS232 has been around a long time, and was originally intended as the standard for hooking modems to computers and terminals. A modem allowed connection to the public phone system for long or short distance communication. Now days we "direct connect" CNC to computers using RS232, or use "bridges"(modems) to connect via Ethernet, BlueTooth, USB and other communication "media". DNC Server Computers: The primary role of a DNC server computer is to store programs, and to send and receive data files. A DNC Server Computer in simple terms is any computer running a DNC service program. A network of PC DNC server computers can act like a single large DNC server computer - at a fraction of the cost. A DNC server computer can also be used to create new programs or edit programs, but the activity is usually done on graphic workstations (or PCs) with CAD capability. Computer Aided Design software can be integrated with DNC so that the DNC server files are accessible by both CAD workstations and DNC server. Windows has become very popular in manufacturing, due to its low cost and high performance. Windows Server and Workstations can both support DNC server software. Hardware Evolution PC manufacturers are no longer providing RS232 ports and Parallel printer ports on PCs. So applications supporting serial ports and parallel printers require 3rd party hardware which duplicates the interface capabilities. USB The Universal Serial Bus is intended to connect printers, scanners, keyboards and mice as well as hard drives to the PC. DB9, DB25 serial ports and DB25 printer port connectors are not provided on new PC, because of the popularity of USB. USB is capable of delivering data at a high rate. RS232 ports connected via USB tend to have limitations compared to the serial ports that used to be on the motherboard or provided in a ISA or PCI slot. The problem is that USB is far slower to respond to interrupts, making "Drip-feed" impossible. PCI bus slots PCI Express has displaced the 32bit PCI bus. PCI-E uses a very high speed serial protocol, providing high speed data and low cost due to smaller connectors. Multi-port Serial adapters requiring PCI slots are loosing popularity. Windows Microsoft Windows is the defacto standard in manufacturing. DOS was popular due to its simplicity but it lacks graphics and networking. Windows 2000/XP/VISTA are far superior to earlier versions of Windows, which did not support "Plug and Play" and were much harder to configure. These newer Operating systems are derived from the "NT" kernel, and the serial communications capability starting wiht Windows 2000 has remained virtually unchanged. This means new and old application can continue to use RS232 serial ports. Networking Machines: DNC means connecting the company database with machines. You might dedicate a personnel computer to each machine in your shop, or you might support all of your machines from one central computer. ADR can provide you with software and hardware applicable to both of these choices. When many machines are attached to one PC there are two common network topologies commonly used: star and bus. You must choose a network topology and then wire your shop, we are here to help you do it right. Drip-FeedWhen the NC program is too large to fit into the CNCs memory, it can still be run, by the PC feeding the data to the CNC as it needs it. Not all CNC can do this. The problem is to keep the CNCs buffer full of data without ever going empty, because if the CNC is "starved for data" the part being machined could be ruined. Care must be taken to insure that, no corrupted data is ever processed by the CNC, or data is lost. The PC must remain "ON-LINE" during the execution of the program, turning the PC off, or "Suspending" to save power would be a disaster. DNC Wired Star Networks use Single Drop Connections radiating from a central point: Data transfers can be directed from the DNC server computer, or remotely requested at the machine. A popular form of Star network is the RS232 DNC system. Since most machines support RS232 they can be directly attached to inexpensive multi-port communication board in the DNC server computer. This type network is described as master-slave because the server manages the network. Unfortunately each machine maker developed their own procedures for accessing an RS232 DNC server, making the design of generic DNC software complex. Another popular Star network is based on 10BaseT Ethernet. An Ethernet Hub (switch) is used as the central point and twisted pair wires carry data at 10Mbit/sec. Some machines can directly attach to Ethernet others require adapters. Ethernet is referred to as a peer-to-peer protocol because there is no dedicated network manager. FTP (based on TCP/IP) is standard procedure for accessing DNC server files. ADR's LanTap Ethernet adapter handles the DNC procedures required by the CNC. DNC Wired Bus Networks use Multi Drop Connections This network configuration uses bus wiring to network the machines. Since most machines only support RS232, Adapters must be attached to the machine to give it the capability to access the bus network. The adapter makes each machine addressable by the DNC server computer. The DNC server computer uses a protocol to share the bus. Data is protected via error correcting protocol procedures performed by the computer and adapter - data will not get lost or corrupted on its way to the machine. Two common Bus networks are RS422 and thin wire coax Ethernet. Wireless Ethernet DNC Networks Wireless DNC is gaining popularity. Wireless Ethernet can be used to connect a wired Ethernet system to wireless nodes via "Access Points". The Access points translates the Ethernet packets into radio signals, bridging the gap between the wired subnets. The benefits of eliminating the wires gets offset somewhat by new problems related to interference of the radio signals. Care must be taken to prevent blocking the radio signals with metal, or operating RF devices such as microwave ovens. Wireless DNC operates by the "line of sight" rule, the sender must "see" the receiver in order to work. Wireless DNC signals can bounce off metal or walls, a condition called "multi-pathing", which can stop communication. Data security is also an important consideration, because of the "broadcasting" of data. Nearby wireless notebook computers/PDAs could be listening in or joining your network. Blue Tooth - An alternate to Ethernet wireless is "BlueTooth" wireless. Blue Tooth is intended as a means to connect computer components such as mice, keyboards, printers and SERIAL PORTs to a PC. Notebook computers are popular in manufacturing due to the ability to freely move about. With BlueTooth serial ports at the CNC the operator does not have to phyiscally connect a wire from the CNC to the notebook, eliminating grounding problems and tripping on the cable. The distance limitation of 100 meter, means this technology requires PCs near to the CNC. Bluetooth is a frequency hopping Spread Spectrum radio, operating at 2.4GHz. Bluetooth was designed specifically for replacing wires of all kinds; Ethernet was designed as a datalink protocol for computer networks. Bluetooth makes your PC software "think" you are using wired COM ports, so your DNC software works with Bluetooth without any change. Behind the scenes, Bluetooth Generic Access Profile (GAP) handles discovery and establishment of links between devices that are unconnected, and Bluetooth Serial Port Profile (SPP) defines how to set-up Virtual Serial Ports and connect two Bluetooth enabled devices. 1813 East Dyer Road, Suite 412, Santa Ana CA 92705. Tel (949)252-1055   Fax (949)252-1490 Copyright 2007 Advanced Digital Research, Inc. - all rights reserved.    Revised Jan 21, 2007.