Every wire EDM machine must have a wire guide system. These wire guide systems serve many purposes that include, guiding the wire to the work piece cut path, providing wire paths during automatic threading, and helping maintain accurate geometry and accuracy throughout cutting operations. These functions make wire guides a critical feature in wire EDM machines, especially in the tight tolerance, micron level accuracies of modern applications
The wire guide system is really a subassembly of the wire transport system. It assures that there will be ideal wire to energizer plate contact for creating a clean current flow through the wire as it cuts. Additionally it also helps keep the wire centered in the wire guides, which is critical, especially in maintaining accuracy through changes in different geometric shapes or patterns. Wire guide systems also guarantees accurate travel movements during the cut, even if you’re cutting in multiple axes at one time.
How it works
A wire guide system consists of presser guides, often made of sapphire, energizer guides that are usually some kind of carbide alloy material, wire guides themselves, which could be ceramic, diamond, or sapphire, and of course the wire and work piece.
The wire is fed out the upper guide, through the workpiece and into the lower guide. The presser guides push the wire and hold it against the energizers to maintain electrical contact for the wire circuit, while the upper and lower heads guide and move the wire through the cut path using servo motors.
There are basically two different kinds of wire guides used today on major EDM machines, round and V-guides. The round guide is the most commonly used due to its peformance in highly accurate taper transition work and auto-threading of small holes (less than 0.025" in diameter), expecially in tight matrices (less than 2 mm).
Split, or V-guides, as on most Makino machines, would be used most often for general purpose EDM work. These are good for cutting tapers up to about 12 degrees and provide advantages of low maintenance and longer life over round guides. A variation of the split guide, known as split-C, provides excellent high taper work of up to 45 degrees. The third and final type of V-guide, known as the variable V-guide, is used by one manufacturer also has somewhat low maintenance and extended life.
Some people ask how V-guides and round-guides differ, and if is one better than another. These wire guides differ greatly, whether one is better than the other really depends on the application. There are four main points where the differences between V-guides and round guides become noticeably apparent.
The V-guide will typically have about a 12,000 hour guide life. It is called a zero-clearance guide, though it’s not really zero clearance otherwise you’d stretch the wire, but the clearance is in actuality about 0.00005” on three sides of the V. The V in this wire guide is about 0.196” long, meaning wire in the precision v-block is about 0.196 in length. V-guides have extremely low maintenance, requiring someone to simply open it up and clean it with a Q-tip dipped in a little light acid.
Round guides typically have about a 2,000 hour life, depending on the type of work it's performing. When using round guides there must be a 0.0002” clearance on each side, allowing the wire to move somewhat liberally. The guide's liberal movement results in high-drag contact between the radius of the wire and the internal radius of the guide when moving the wire. This contact causes wear and tear on the guide leading to its low guide life expectancy. Round guides are also maintenance intensive. They often fall victim to jams resulting from material clogging and guide to wire fusions that require dis-assembly and cleanings that demand ultrasonic cleaners.
Makino’s solution to this dilema in wire guide selection has been to offer multiple systems for the same machine. They support split-precision guides, V-flat split guides, and split-C guides which open up like V-guides which allow water to blast the debris away. These guides are superior for wire feeding, allowing a larger target to shoot the wire through compared to the small hole in the round guide.
PICO Precision Guide System
The PICO precision guide is Makino’s version of what would be referred to as a round-guide and is offered as a hardware option for all Makino SP and UJ wire EDMs. It uses a different upper head and different upper and lower wire guides than the standard V-guide system. Instead of split-C and V-guide opening systems, it is a closed round guide that is targeted towards specific applications. The PICO system does not open and close during auto-wire threading like our split guides would, and is stationary in the head.
Our standard V-guide system is still recommended for about 85 percent of the work performed on Makino EDMs today. These guides open and close during the threading cycles. During re-thread sequences, the waterjet will blast away any debris from the open guides to help prevent clogging. When the guide closes, both the guide and wire in the water thread jet are clean. The large opening allows easier threading than most closed guide systems due to the larger target area to thread the wire through.
Makino has used the split precision and V-guide systems in their machines for years, based upon their easier, more reliable auto-threading systems. Shooting the wire through a split or V-guide system is easier due to the large opening, as well as steady wire handling and it's self-cleaning nature.
V-guide maintenance is quick, easy, and only requires 5-minutes of cleaning about every two weeks, depending on usage. The guide does not need to be removed from the machine to clean them, removing the need for any wire re-alignment after cleaning.
Why develop PICO?
Although V-guides and C-split guides work well for the majority of applications, round or PICO systems are still needed for other applications that feature small holes in tight pitch matrices holes smaller than 0.025" diameter. The PICO process is well suited for assurance in threading of the correct hole, and provides excellent accuracies when cutting variable lands for stamping and fine blanking dies.
Figure 1
Figure 1 above is an example of where the PICO system would be recommended. This application features holes and the scale on top of the die lying closely together. There are 120 slots that need to be machined into this perforating die. The start holes for this job were 0.0118”, and the spacing between these holes is only 0.05”. The diameter to cut these is 0.004”, and the machine needs to perform all 120 automatic wire threads without failure and with no miss-threads of the wrong hole.
Figure 2
Figure 2 is another example of where PICO Precision would be recommended. This was a hexagonal test part that contains 91 separate hexagons. Each cell is 1 mm across, and the hex wall is about 5 mm thick. Start holes are placed on the center of each hex with a 1 mm spacing. All start holes must be threaded with no misses and no miss threads.
Figure 3
In Figure 3 above there's a fine blanking die that was made with PICO Precision guides using an SP43. This part shows the capabilities of PICO guides in helping to maintain accuracy in cutting details like this in a variable shaped contour where specific land heights must be maintained.
This land is 2mm wide, and had to be cut on the contour variance from 15-30 mm thickness of the finished part. There's a 1-degree back-taper that is below this 2 mm land. This part truly shows how PICO has excellent taper control and how it can be put to use in fine blanking.
V-guides versus PICO
The V-guide system is very good at tall threading up to 20” and submerged threading at tall distances. As mentioned earlier, V-guides require low maintenance, especially when using coated wire, and are simple to manually thread with coated wire when the applications demands. The guides ability to open and close allows the water to blast away debris easily. Since some coated wires can be dirtier than plain brass wires, the easy maintenance becomes a helpful feature.
Other advantages include close guide to wire clearance, which allows for accurate control of part geometry. When using a split-C guide system, high angle taper cutting is possible up to 45 degrees. Lastly, one of the top strengths of the V-guide system is its 12,000 hour guaranteed life.
Despite it's many advantages, V-guides do have some limitations. It is possible to miss the lower guide during manual threading operations, especially when the lower head's positioning makes it difficult to see where you’re cutting the wire to the guide. It would be recommended to avoid manual threading when possible. V-guide systems also have difficulty threading holes below 0.025" consistently, especially if those holes are in a close pitch location, like in the prior examples.
Another limitation with this system happens during high-accuracy taper cutting where short-moving taper transitions occur. In other words, there's a hole going through a block and then counter-sunk at the top, but the counter-sink is in the shape of an oval and has to be cut. Often times V-guide systems will leave some wire marks where the oval's large radius transitions to the small radius, creating a need for additional processing after the wire cutting is complete.
Possible difficulties may also be noticed in taper machining over 10 degrees where a fine surface finish is required.
Like the V-guide systems, PICO Precision also has its strengths and weaknesses. It works as an excellent system for threading small holes (less than 0.025" diameter), especially with close pitch (1.5mm or less).
When it comes to manual threading, PICO Precision can guarantee a 100% assurance that the wire will not miss the lower guide, even if you can’t see the lower head. This will also provide easier management of smaller slugs. This type of system eliminates your need to worry about opening up the V-guides and possibly closing on a slug that coudl get hung up on a lower area.
This system can perform high accuracy taper angles up to 12 degrees with ease and provides precise control of land height and taper angle transitions.
PICO is limited however, by lower reliability automatic wire threading, epecially in thicknesses over four inches. In comparison to V-guide systems, PICO is disadvantaged in its submerged threading.
Other issues include lessened reliability with coated wire, which could pose problematic in certain applications.
PICO is also troubled with higher maintenance and lower life than V-guides, especially when using coated wires. Users should be concerned about higher maintenance due to the difficult to clean closed structure of the guide itself. The round-guide system also tends to force the wire into one area repeatedly, wearing down certain areas quickly. It will also have a limitation in high precision machining of corner accuracy due to its guide to wire clearance. There's also a limit in high-angle taper cutting over 12 degrees. The shape and structure of machines featuring round wire guides will not permit inclusion Makino's H.E.A.T. technology either.
Good results are still achievable using round guides, but you will have to work harder to achieve the same results you’d get with a V-guide.
Which is best for you?
The first thing you have to do is evaluate the EDM work you do. If you work on a lot of general applications work, do a lot of job shop work, refrain from a lot of critical taper angles or land transitions for fine blanking, or you don’t do a lot of perforated die work on a small scale as far as structure of the dies, then you will probably do well with a V-guide type system.
If you do small hole, tight-pitch threading, then you’ll want to go with a PICO system. When you're evaluating high-accuracy taper angles, the type of angle and specific accuracies will determine the wire guide system best suited for your applications.
It's also important to evaluate your shop maintenance practices. If you know your shop isn’t very good at keeping up with the maintenance that’s recommended, you probably want to go with a split-guide type system that is easier to take care of and has lower maintenance that’s required. If you keep up with maintenance, you can really choose any of the systems and not expect problems.
Availability of PICO
PICO is available on Makino SP and UJ machines with the MGW-S generator. They can be ordered as an option from the factory, and can be retrofitted on an existing machine that has the standard V-guide system.
Either PICO or V-guide system must be chosen when the machine is ordered, as they are not interchangeable systems. So you’ll have to make the decision what kind of work you do and hat system would work best for you when you place a machine order.
PICO can also be added to an existing machine originally made with a V-guide system. If you make this choice before any use of the machine, you can change the system out without any cost. Once you use the machine, it’s an additional cost to purchase the PICO system. Pricing is available from Makino.
Makino's new DUO wire EDM series increases your options, providing hybrid wire EDM technology that lets you choose between PICO and V-Guides in a single machine. Other features of the DUO series include, Dual Spark Generators, Dual Filter Tanks, Dual Flush Pumps, and more. For more information on the DUO wire EDM visit www.makino.com/library and view the webinar entitled "Improving Wire EDM Performance, The New DUO Series," or check out the webinar of this article entitled "Choosing A Wire Guide System."
The wire guide system is really a subassembly of the wire transport system. It assures that there will be ideal wire to energizer plate contact for creating a clean current flow through the wire as it cuts. Additionally it also helps keep the wire centered in the wire guides, which is critical, especially in maintaining accuracy through changes in different geometric shapes or patterns. Wire guide systems also guarantees accurate travel movements during the cut, even if you’re cutting in multiple axes at one time.
How it works
A wire guide system consists of presser guides, often made of sapphire, energizer guides that are usually some kind of carbide alloy material, wire guides themselves, which could be ceramic, diamond, or sapphire, and of course the wire and work piece.
The wire is fed out the upper guide, through the workpiece and into the lower guide. The presser guides push the wire and hold it against the energizers to maintain electrical contact for the wire circuit, while the upper and lower heads guide and move the wire through the cut path using servo motors.
There are basically two different kinds of wire guides used today on major EDM machines, round and V-guides. The round guide is the most commonly used due to its peformance in highly accurate taper transition work and auto-threading of small holes (less than 0.025" in diameter), expecially in tight matrices (less than 2 mm).
Split, or V-guides, as on most Makino machines, would be used most often for general purpose EDM work. These are good for cutting tapers up to about 12 degrees and provide advantages of low maintenance and longer life over round guides. A variation of the split guide, known as split-C, provides excellent high taper work of up to 45 degrees. The third and final type of V-guide, known as the variable V-guide, is used by one manufacturer also has somewhat low maintenance and extended life.
Some people ask how V-guides and round-guides differ, and if is one better than another. These wire guides differ greatly, whether one is better than the other really depends on the application. There are four main points where the differences between V-guides and round guides become noticeably apparent.
The V-guide will typically have about a 12,000 hour guide life. It is called a zero-clearance guide, though it’s not really zero clearance otherwise you’d stretch the wire, but the clearance is in actuality about 0.00005” on three sides of the V. The V in this wire guide is about 0.196” long, meaning wire in the precision v-block is about 0.196 in length. V-guides have extremely low maintenance, requiring someone to simply open it up and clean it with a Q-tip dipped in a little light acid.
Round guides typically have about a 2,000 hour life, depending on the type of work it's performing. When using round guides there must be a 0.0002” clearance on each side, allowing the wire to move somewhat liberally. The guide's liberal movement results in high-drag contact between the radius of the wire and the internal radius of the guide when moving the wire. This contact causes wear and tear on the guide leading to its low guide life expectancy. Round guides are also maintenance intensive. They often fall victim to jams resulting from material clogging and guide to wire fusions that require dis-assembly and cleanings that demand ultrasonic cleaners.
Makino’s solution to this dilema in wire guide selection has been to offer multiple systems for the same machine. They support split-precision guides, V-flat split guides, and split-C guides which open up like V-guides which allow water to blast the debris away. These guides are superior for wire feeding, allowing a larger target to shoot the wire through compared to the small hole in the round guide.
PICO Precision Guide System
The PICO precision guide is Makino’s version of what would be referred to as a round-guide and is offered as a hardware option for all Makino SP and UJ wire EDMs. It uses a different upper head and different upper and lower wire guides than the standard V-guide system. Instead of split-C and V-guide opening systems, it is a closed round guide that is targeted towards specific applications. The PICO system does not open and close during auto-wire threading like our split guides would, and is stationary in the head.
Our standard V-guide system is still recommended for about 85 percent of the work performed on Makino EDMs today. These guides open and close during the threading cycles. During re-thread sequences, the waterjet will blast away any debris from the open guides to help prevent clogging. When the guide closes, both the guide and wire in the water thread jet are clean. The large opening allows easier threading than most closed guide systems due to the larger target area to thread the wire through.
Makino has used the split precision and V-guide systems in their machines for years, based upon their easier, more reliable auto-threading systems. Shooting the wire through a split or V-guide system is easier due to the large opening, as well as steady wire handling and it's self-cleaning nature.
V-guide maintenance is quick, easy, and only requires 5-minutes of cleaning about every two weeks, depending on usage. The guide does not need to be removed from the machine to clean them, removing the need for any wire re-alignment after cleaning.
Why develop PICO?
Although V-guides and C-split guides work well for the majority of applications, round or PICO systems are still needed for other applications that feature small holes in tight pitch matrices holes smaller than 0.025" diameter. The PICO process is well suited for assurance in threading of the correct hole, and provides excellent accuracies when cutting variable lands for stamping and fine blanking dies.
Figure 1 above is an example of where the PICO system would be recommended. This application features holes and the scale on top of the die lying closely together. There are 120 slots that need to be machined into this perforating die. The start holes for this job were 0.0118”, and the spacing between these holes is only 0.05”. The diameter to cut these is 0.004”, and the machine needs to perform all 120 automatic wire threads without failure and with no miss-threads of the wrong hole.
Figure 2 is another example of where PICO Precision would be recommended. This was a hexagonal test part that contains 91 separate hexagons. Each cell is 1 mm across, and the hex wall is about 5 mm thick. Start holes are placed on the center of each hex with a 1 mm spacing. All start holes must be threaded with no misses and no miss threads.
In Figure 3 above there's a fine blanking die that was made with PICO Precision guides using an SP43. This part shows the capabilities of PICO guides in helping to maintain accuracy in cutting details like this in a variable shaped contour where specific land heights must be maintained.
This land is 2mm wide, and had to be cut on the contour variance from 15-30 mm thickness of the finished part. There's a 1-degree back-taper that is below this 2 mm land. This part truly shows how PICO has excellent taper control and how it can be put to use in fine blanking.
V-guides versus PICO
The V-guide system is very good at tall threading up to 20” and submerged threading at tall distances. As mentioned earlier, V-guides require low maintenance, especially when using coated wire, and are simple to manually thread with coated wire when the applications demands. The guides ability to open and close allows the water to blast away debris easily. Since some coated wires can be dirtier than plain brass wires, the easy maintenance becomes a helpful feature.
Other advantages include close guide to wire clearance, which allows for accurate control of part geometry. When using a split-C guide system, high angle taper cutting is possible up to 45 degrees. Lastly, one of the top strengths of the V-guide system is its 12,000 hour guaranteed life.
Despite it's many advantages, V-guides do have some limitations. It is possible to miss the lower guide during manual threading operations, especially when the lower head's positioning makes it difficult to see where you’re cutting the wire to the guide. It would be recommended to avoid manual threading when possible. V-guide systems also have difficulty threading holes below 0.025" consistently, especially if those holes are in a close pitch location, like in the prior examples.
Another limitation with this system happens during high-accuracy taper cutting where short-moving taper transitions occur. In other words, there's a hole going through a block and then counter-sunk at the top, but the counter-sink is in the shape of an oval and has to be cut. Often times V-guide systems will leave some wire marks where the oval's large radius transitions to the small radius, creating a need for additional processing after the wire cutting is complete.
Possible difficulties may also be noticed in taper machining over 10 degrees where a fine surface finish is required.
Like the V-guide systems, PICO Precision also has its strengths and weaknesses. It works as an excellent system for threading small holes (less than 0.025" diameter), especially with close pitch (1.5mm or less).
When it comes to manual threading, PICO Precision can guarantee a 100% assurance that the wire will not miss the lower guide, even if you can’t see the lower head. This will also provide easier management of smaller slugs. This type of system eliminates your need to worry about opening up the V-guides and possibly closing on a slug that coudl get hung up on a lower area.
This system can perform high accuracy taper angles up to 12 degrees with ease and provides precise control of land height and taper angle transitions.
PICO is limited however, by lower reliability automatic wire threading, epecially in thicknesses over four inches. In comparison to V-guide systems, PICO is disadvantaged in its submerged threading.
Other issues include lessened reliability with coated wire, which could pose problematic in certain applications.
PICO is also troubled with higher maintenance and lower life than V-guides, especially when using coated wires. Users should be concerned about higher maintenance due to the difficult to clean closed structure of the guide itself. The round-guide system also tends to force the wire into one area repeatedly, wearing down certain areas quickly. It will also have a limitation in high precision machining of corner accuracy due to its guide to wire clearance. There's also a limit in high-angle taper cutting over 12 degrees. The shape and structure of machines featuring round wire guides will not permit inclusion Makino's H.E.A.T. technology either.
Good results are still achievable using round guides, but you will have to work harder to achieve the same results you’d get with a V-guide.
Which is best for you?
The first thing you have to do is evaluate the EDM work you do. If you work on a lot of general applications work, do a lot of job shop work, refrain from a lot of critical taper angles or land transitions for fine blanking, or you don’t do a lot of perforated die work on a small scale as far as structure of the dies, then you will probably do well with a V-guide type system.
If you do small hole, tight-pitch threading, then you’ll want to go with a PICO system. When you're evaluating high-accuracy taper angles, the type of angle and specific accuracies will determine the wire guide system best suited for your applications.
It's also important to evaluate your shop maintenance practices. If you know your shop isn’t very good at keeping up with the maintenance that’s recommended, you probably want to go with a split-guide type system that is easier to take care of and has lower maintenance that’s required. If you keep up with maintenance, you can really choose any of the systems and not expect problems.
Availability of PICO
PICO is available on Makino SP and UJ machines with the MGW-S generator. They can be ordered as an option from the factory, and can be retrofitted on an existing machine that has the standard V-guide system.
Either PICO or V-guide system must be chosen when the machine is ordered, as they are not interchangeable systems. So you’ll have to make the decision what kind of work you do and hat system would work best for you when you place a machine order.
PICO can also be added to an existing machine originally made with a V-guide system. If you make this choice before any use of the machine, you can change the system out without any cost. Once you use the machine, it’s an additional cost to purchase the PICO system. Pricing is available from Makino.
Makino's new DUO wire EDM series increases your options, providing hybrid wire EDM technology that lets you choose between PICO and V-Guides in a single machine. Other features of the DUO series include, Dual Spark Generators, Dual Filter Tanks, Dual Flush Pumps, and more. For more information on the DUO wire EDM visit www.makino.com/library and view the webinar entitled "Improving Wire EDM Performance, The New DUO Series," or check out the webinar of this article entitled "Choosing A Wire Guide System."
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