This article does not any. Unsourced material may be challenged. ( January 2013) Direct numerical control ( DNC), also known as distributed numerical control (also DNC), is a common term for networking. On some CNC machine, the available memory is too small to contain the machining program (for example machining complex surfaces), so in this case the program is stored in a separate computer and sent directly to the machine, one block at a time.
DNC Software for CNC program control, drip-feeding programs too large for CNC. Upload via parallel, RS232, RS422 Ethernet, & wireless Ethernet for. NCnet Lite by CADEM- RS232C DNC communications Software Submitted by CNC on Sun, - 23:31 CADEM's NCnet lite is a great little RS232C software program that we have used ourselves in the past and is a free RS232 program.
If the computer is connected to a number of machines it can distribute programs to different machines as required. Usually, the manufacturer of the control provides suitable DNC software. However, if this provision is not possible, some software companies provide DNC applications that fulfill the purpose. DNC networking or DNC communication is always required when programs are to run on some CNC machine control.is also used in place of hard-wired versions.
Controls of this type are very widely used in industries with significant fabrication, such as the, and industries. Contents.History 1950s-1970s Programs had to be walked to NC controls, generally on paper tape. NC controls had paper tape readers precisely for this purpose. Many companies were still punching programs on paper tape well into the 1980s, more than twenty-five years after its elimination in the computer industry.1980s The focus in the 1980s was mainly on reliably transferring NC programs between a host computer and the control. The Host computers would frequently be, or type computers running a variety of CAD/CAM software.
DNC companies offered machine tool links using rugged proprietary terminals and networks. For example, DLog offered an x86 based terminal, and NCPC had one based on the 6809. The host software would be responsible for tracking and authorising NC program modifications. Depending on program size, for the first time operators had the opportunity to modify programs at the DNC terminal.
No time was lost due to broken tapes, and if the software was correctly used, an operator running incorrect or out of date programs became a thing of the past.Older controls frequently had no port capable of receiving programs such as an or connector. In these cases, a device known as a Behind The Reader or BTR card was used. The connection between the control's tape reader and the internal processor was interrupted by a microprocessor based device which emulated the paper tape reader's signals, but which had a serial port connected to the DNC system.
As far as the control was concerned, it was receiving from the paper tape unit as it always had; in fact it was the BTR or Reader Emulation card which was transmitting. A switch was frequently added to permit the paper tape reader to be used as a backup.1990s to present The PC explosion in the late 1980s and early 1990s signalled the end of the road for proprietary DNC terminals. With some exceptions, CNC manufacturers began migrating to PC-based controls running DOS, or which could be linked in to existing networks using standard protocols. Customers began migrating away from expensive minicomputer and workstation based CAD/CAM toward more cost-effective PC-based solutions. Users began to demand more from their DNC systems than secure upload/download and editing. PC-based systems which could accomplish these tasks based on standard networks began to be available at minimal or no cost. In some cases, users no longer needed a DNC 'expert' to implement shop floor networking, and could do it themselves.
However, the task can still be a challenge based on the CNC Control wiring requirements, parameters and NC program format.To remain competitive, therefore, DNC companies moved their offerings upmarket into DNC Networking, Shop Floor Control or SFC,. These terms encompass concepts such as real-time Machine Monitoring, Tool Management, Traveler Management. Instead of merely acting as a repository for programs, DNC systems aim to give operators at the machine an integrated view of all the information (both textual and graphical) they require in order to carry out a manufacturing operation, and give management timely information as to the progress of each step.
DNC systems are frequently directly integrated with corporate CAD/CAM, and CAPP systems.Special protocols A challenge when interfacing into machine tools is that in some cases special protocols are used. Two well-known examples are Mazatrol and 's LSV2 protocol.
Many DNC systems offer support for these protocols. Another protocol is which is found on controls. DNC2 allows advanced interchange of data with the control, such as tooling offsets, tool life information and machine status as well as automated transfer without operator intervention.Machine monitoring One of the issues involved in machine monitoring is whether or not it can be accomplished automatically in a practical way. In the 1980s monitoring was typically done by having a menu on the DNC terminal where the operator had to manually indicate what was being done by selecting from a menu, which has obvious drawbacks. There have been advances in passive monitoring systems where the machine condition can be determined by hardware attached in such a way as not to interfere with machine operations (and potentially void warranties).
Many modern controls allow external applications to query their status using a special protocol. Is one prominent attempt to augment the existing world of proprietary systems with some open-source, industry-standard protocols and and an ecosystem of massively multiplayer app development and (analogous to that with ) so that these long-sought higher levels of manufacturing and can be realized.Alternatives Smaller facilities will typically use a portable PC or laptop to avoid the expense of a fully networked DNC system. In the past and a similar device from Mazak were very popular.Footnotes.
Learning how to drip feed a CNC machine is necessary if you want the system to work the way you want it. Even though CNC machines have different specifications, the drop feeding process is generally the same. In this article we’ll take a detailed look at drip feeding and what it’s about.What is Drip Feeding?Drip feeding is a technique of uploading a program into a CNC machine with as few commands as possible. The method includes a handshake process so the sender is aware when to halt sending and when to transmit additional data. Drip feeding is most effective when you’re trying to run a program on a CNC machine with limited memory.How to Drip FeedYou have to put the CNC machine in DNC mode. DNC (direct numerical control) is a command used to transmit programs in a CNC machine.
The DNC is used to send programs in the system, and it can also be used to drip feed a program if machine memory is insufficient. DNC may also refer to modern CNC machines with a hard disk or USB port.Once you have set the CNC machine in DNC mode, you can send it instructions. A CNC machine has a FIFO (first in first out) buffer that stores some CNC codes, and the buffer uses a handshake signal to inform the sender to stop. Due to delays in communication between the CNC and the sender, the buffer capacity is not filled up.The DNC SystemThe DNC system manufactures a CNC communications network, providing you with the means to manage CNC machines and programs. These systems provide a vast array of CNC communications protocols which are used for uploading, downloading and drip feeding NC code.These DNC protocols are also capable of obtaining DPRINT data off the CNC, allowing you to integrate machine tool monitoring in the CNC machine.
A typical DNC system is comprised of Ethernet connected serial hubs or a 32 bit serial card, depending on the model. Control devices are usually the most effective for DNC systems, and some machines also work with wireless CNC machines for greater flexibility.Features of a Quality DNC SystemA quality DNC system is necessary for efficient drip feeding. Drip feeding can take hours if the program is large, and if the last stage a problem occurs, it could lead to system errors or force you to start over again.Features of a good DNC system include:Effortless sending, receiving and drip feeding of the NC code. This should be easy to do regardless of the machine you send it to.The DNC system should also make it easy to drip feed, receive and send G code programs off the controls without the need to use your computer.A well-designed CNC program also allows for superior revision control because you’re able to retrieve programs from a central spot.A high quality DNC program also lets you save programs without the need for the user to intervene. This is also a useful feature to prevent accidental overwriting.A DNC system allows the operator to control the CNC machine from any personal computer on your network.
More importantly, it eliminates the need to buy extra memory for your system, increasing production and reducing the number of processes.How to Optimize CNC Drip FeedingThe secret to getting the most out of drip feeding is to purchase the right DNC software. With the right program you’ll be able to coordinate the DNC systems as well as manage the CNC parameters, programs, offsets and settings.For optimum results, look for software that has extensive CNC communications support. The needs of users vary, but at the very least there should be support for wireless Ethernet, RS-422 Ethernet, RS-232 and parallel.Aside from networking your CNC machine and better drip feeding, you also get support for multiple CNC machines, part markers, PLCs and other components. If you’ve got a shop, a well-designed DNC system allows you to simultaneously drip feed, upload, download, send and receive DNC programs.One of the problems with running multiple CNC machines is they become difficult to organize and keep track of.
With the right DNC software you will have the chance to group them accordingly. Depending on the program, there could even be unlimited CNC support, perfect if you have plans for expansion.Why Drip Feeding DNC Systems MatterApart from the factors mentioned above, the DNC enhances workflow. If you’ve got a shop, a well-run CNC machine with a capable DNC system eliminates the need for switch boxes and other hardware that takes up valuable space and cost money. If the DNC runs properly, drip feeding will proceed smoothly.You’ll also have a complete network solution for your CNC machines. Drip feeding is essentially about maximizing production, getting powerful programs to run even if your system has limited memory. However today’s DNC software can do more than that.
When set up, you’re assured only the latest programs on the server are activated and any changes are safely stored.Tips for BuyersIf you want drip feeding simplified, look for DNC software that is feature packed but easy to use. Fortunately there are a lot of DNC programs designed to work with PCs and have a user interface similar to PC programs. This means the programs have cut, copy, paste, drag and drop and toolbars so it looks familiar with a light learning curve.Aside from the features, you should also check the price, quality and the feedback it gets from users. With the Internet this should not be too difficult to do, and the time you spend researching their background will be worth it.ConclusionDrip feeding is an important part of any CNC operation, but it’s not hard to figure out how it works.
As it is, CNC machines have become easier than ever to use, and there are software available which simplify the drip feeding process even more.Source:via Table Sawz.