CHIP-BREAKING ON LATHES IS HIGHLY FUNCTIONAL - Citizen Machinery

Josh Watkins, director of Welsh subcontractor Harlech Engineering, has recently bought two lathes from Citizen Machinery, a Miyano fixed-head model installed in mid-2023 and a sliding-head Cincom one year later. Both benefit from the manufacturer’s LFV chip-breaking software in the operating system of the Mitsubishi control, which he says has transformed turning efficiency and productivity in his Swansea factory.

The twin-spindle, double Y-axis-turret Miyano ANX-42SYYLFV turning centre fitted with a three-metre bar magazine replaced a slower, single-turret lathe of a different make. It resulted in significantly higher productivity, both through faster cycle times and fewer operations, usually producing components in one hit. It was, however, the LFV software that set the machine apart from a couple of similarly specified lathes on the market that Mr Watkins was also considering.

Before taking the decision to purchase, he asked Citizen Machinery’s applications department in Bushey to carry out time trials on a couple of brass components he machines for the automotive industry. One was a dial assembly bracket that sits behind a car fascia.

It was taking 8 minutes to produce on a sliding-head lathe on which the spindle power and driven tool capability were limited, so further time on a vertical machining centre was needed to produce two tapped holes – and the part had to be handled and reset for the second operation. The same component comes off the Miyano complete in 4.5 minutes. There are four other brackets in the same family that similarly benefit from faster production.

A second type of shorter bracket that used to be produced in one hit on a sliding-head lathe was also programmed and proved out on an ANX in Bushey. It likewise is being produced faster on the fixed-head machine in Swansea, with the added benefit that Mr Watkins has been able to free up the slider for other, more appropriate work.

Free-cutting brass does not require any special attention in regard to chip-breaking, but other materials do, such as 316 stainless steel, which accounts for more than three quarters of the work going through Harlech’s shop floor.

Mr Watkins commented, “Historically we have used two other types of chip-breaking software on sliding-head lathes, but Citizen’s LFV is more effective than either.

“The function is easy to incorporate into a cycle, as it simply requires a single line of G-code to switch it on or off.

“Moreover, the starting parameters suggested in Citizen’s off-line Alkart Wizard software are normally nearly perfect, so there is little trial and error involved.”

Harlech also uses LFV when producing copper studs for an outdoor furniture manufacturer. This malleable material is notorious for generating stringy swarf that wraps around the tool and workpiece, risking damage to both. With the Citizen chip-breaking software switched on, the ribbons are reduced to shorter chips that can be evacuated as easily as those produced when cutting brass.

The studs are turned longitudinally and undergo a lot of face turning to produce a dome shape and face grooves. It is a long-running contract that in the past has been fulfilled on both fixed- and sliding-head lathes having ineffective or no chip breaking software. Cycle time is approximately two minutes and after every 10 parts it was previously necessary to stop the machine to clear the working area of copper ribbons. Now the job runs unattended into or even through the night on the ANX.

Mr Watkins advised, “This is a big help, as the studs are required in batches of 1,500. The microsecond intervals of air cutting that breaks the swarf into fine chips lengthen this exclusively LFV cycle slightly, but on the plus side we are able to take deeper cuts, so there is little difference overall. Best of all it just works, without any fuss or tweaking of parameters.”

On other materials that tend to string, LFV is switched off for up to 80% of the time to maximise productivity. For example, it is typically on for rough turning the outside diameter (OD) of a stainless steel part but off for finish turning, on again for drilling and especially for internal boring, and off again for parting. The versatility of being able to engage and disengage the function so easily is paramount.

By mid-2024 it was apparent that, with business holding up strongly, more sliding-head lathe capacity was required in the Swansea facility. A 32 mm bar machine was needed to fulfil the largest possible range of work. As Citizen’s Cincom L32-XLFV also benefits from the chip-breaking software, it was the obvious choice to bring the subcontractor’s tally of sliding-head lathes to eight, the other seven being of a different brand.

Mr Watkins says the chip-breaking software is equally effective on the slider, working perfectly when turning internally or externally, drilling, or milling at either spindle. A good example of its effectiveness is when producing a black acetal, shaft-type component for the veterinary industry. Plastics are also known to generate long, stringy swarf when being turned. Following comprehensive training at Citizen’s Brierley Hill centre and afterwards on site in Swansea, Harlech engineers were able to program an efficient cycle to produce the 165 mm long part from 30 mm diameter bar without any problems due to entangled swarf.

In the main spindle, it is faced and deep hole drilled to two-thirds of its length, bored and internally threaded, the latter operation without LFV. The software is switched on again for OD turning, after which longitudinal slots are milled without LFV using a ball nose cutter. After parting off and transfer to the synchronous sub spindle, the remainder of the through-hole is drilled, followed by boring and thread cutting, with the chip breaking function either on or off as for the front-end machining.

The other facet of the Cincom L32 that Mr Watkins likes is the modular tooling layout, in particular the manually-rotatable B-axis tool post that allows live cutters to face forward for axial work or to be turned through 90 degrees for work on the outside diameter. In addition, it can be positioned anywhere between 0 and 90 degrees, facilitating angular machining by up to three tools. This provides considerable flexibility when programming the machine in Alkart Wizard and it is easy to key into the control the angle at which the tool post has been set and clamped.

Mr Watkins concluded, “We have been a family-run business since 1990. Toolmaking and press working used to account for a majority of our turnover, but subcontract turning and milling is more than two-thirds of our business now. We mainly serve the medical, automotive, domestic appliance, electronics and rail industries.

“We have been investing heavily over the past eight years in modern, multi-axis CNC plant to become ever more efficient. I must say, however, that the latest two Citizen lathes with LFV have taken our productivity to a whole new level.”