Not a machine; a system [Video]

To see the LPM as just another machine tool is wrong, although it can be difficult to avoid, both for those delivering the message and for those receiving it. Indeed, anyone looking at it will immediately think VMC, since the 900 by 500 mm table machine is fully guarded, has a vertical spindle served by a toolchanger, with the only oddity being the ProtoTRAK control, rather than a Fanuc or Siemens – they won't see a system or a method of working, which is really the context. A clue to its forte, however, is in its extended name – Lean Production Machine. And you can attach a number of lean principle catch phrases to it – SMED, single minute exchange of dies, which basically means short set-up times; Poke Yoke, that's foolproofing, with this associated with the 12-point, on-screen checklist that avoids any nasty surprises when you press the green button; kaizen, or continuous improvement, because, with cycle time clearly displayed, you can choose to drive that down; paperless manufacturing, because set-up images and notes are held locally at the ProtoTRAK PMX control; while even some 5S principals are here, if you view the included combined tool trolley/presetting station as also a means to keep things tidy and in their place. Key elements supporting the central benefit of short set-up times for the repeat manufacture of small batches, which can be just minutes, are the included tool trolley, equipped with a height gauge for tool length setting; a machine-specific calibrated Z-axis zeroing tool for the presetter; the toolchanger inventory/program requirements comparison list; a pre-bored machine tool table with ball-lock locators at positions known to the machine control – effectively a pre-datumed, built-in 'zero point' workholding system; and quick-change pallets, on which can be secured existing fixtures or vices. On the latter point, tee slots still exist and a datum bar using the prebored holes can be used to butt existing fixtures up against, should companies wish. Image: The LPM is not just a machining system; it's a system LEAN BUT THAT'S NOT ALL Okay, so on its own it is a lean system, but that's not the end of it. The LPM features the ProtoTRAK CNC unit, as popularised by XYZ on both its milling machine and lathe ranges – only XYZ Machine Tools, now owned by ProtoTRAK developer US-headquartered Southwestern Industries, offers ProtoTRAK system in the UK, incidentally. The LPM features a new model, the PMX, which has additional features, as well as background programming (see online feature). ProtoTRAK controls, including the PMX, support the on-machine generation of programs by skilled machinists via a Q&A style procedure, based on machine operations such as PCD drilling, although DXF part geometry can also be imported. They require no G-code knowledge to generate 2 ½D programs (X-Y contouring at Z-axis depths), although can be driven by CAM system-generated G-code programs to support 3 or 4-axis milling. Both the mills and lathes are popular with small companies that manufacture in low volume and, for those companies, LPM offers a distinct further advantage – the ability to boost the productivity of their machinists, with minimal training, through multi-machine manning, where larger, yet still small (short run time) batches are required. What's more, LPM will run existing ProtoTRAK programs straight off. Oh, and like other ProtoTRAK machines, it can be used in manual mode. In companies having existing ProtoTRAK technology, XYZ managing director Nigel Atherton suggests that one man could program, set and run one ProtoTRAK milling machine, for very small volumes or one-offs, while also being able to program, set and run an LPM for the longer batch runs. In fact, he suggests, the LPM represents a continuum of productivity development, supported by ProtoTRAK technology. "If you take the pre-1993 situation of one man and a turret mill, you could calculate that he could earn a company £9/hour profit. Following the introduction of ProtoTRAK, one man could then generate £63 profit per hour with a turret mill fitted with ProtoTRAK. Now, with an LPM, one man can generate £100 profit per hour, but, if he runs a cell of one LPM and one ProtoTRAK turret mill, he can generate profit to the tune of £177." Image: The LPM features the ProtoTRAK control, a PMX version, which means it is an easy step for existing ProtTRAK users to make The figures are based on static labour and component sales values of £15/hour and £20, but see increasing machine hourly rate, while volumes of parts per hour produced increase for each stage, hence the increased profitability. XYZ's applications manager, Mike Corbett, highlights a further advantage; that of avoiding the need to hold stocks of parts to support lower volume call-offs that are uneconomic to manufacture on machining centres, due to high set-up times versus run times. "Apart from the fact that companies have to invest in inventory ahead of invoicing, companies are taking a risk and gambling on the part design remaining unchanged – it doesn't always. I spoke with a company recently at the Subcon exhibition that had experienced just this problem," he underlines. A READY MARKET? With some 13,000 ProtoTRAK mills and lathes in 4,000 companies in the UK, Mr Atherton believes there are many companies that will be able to apply the LPM and associated method of working effectively. But LPM also holds promise for non-ProtoTRAK users faced with the repeat small batch production issue and who are currently making for stock on machining centres. The LPM has been available in the UK since the latter part of last year, although you won't find it in XYZ Machine Tools' current 2011 catalogue. It's a considered strategy, because LPM isn't just another machine tool. Higher visibility promotion is about to commence, but already there are UK companies that are singing the LPM's praises, while there are 150 installed in the US. Here, Plympton, Devon-based PTG Precision Engineers has two LPMs, with a third on order. An established ProtoTRAK CNC/manual milling machine user, the company also has several vertical machining centres. According to Martin Beer, PTG's technical manager, machining centres are not ideally suited to prototype or low volume production – which is why the company has 16 ProtoTRAK CNC/manual milling machines in everyday use and why the new LPM machining system has become an instant success. "With the LPM, we get an extra spindle and great productivity, without needing to employ more people," the technical manager explains. In fact, PTG will soon be running a five-machine cell – comprising three ProtoTRAK LPMs,interspersed with two existing ProtoTRAK VM 4000 bed mills – with just two operators. The skilled operators involved are happy with the new arrangement, not least because, by contributing to PTG's competitive edge, they are also contributing to their own long-term job security. "The natural progression for anyone with a ProtoTRAK CNC/manual machine – and ProtoTRAK is the subcontracting industry's de facto standard – is the LPM, because it provides machining centre capability, without having to learn a new computer language or install an expensive off-line programming system," says Mr Beer. "It is very cost effective and very competitive, as set-up times are extremely quick. It took just 20 minutes from delivery of our first LPM to machining a part, not least because our existing ProtoTRAK programs only need the tool change lines added. "With the LPM, we machine only what is required to fulfil an order, as the time needed to set up for a repeat order is negligible. On that basis, even if I had not been an existing user of a ProtoTRAK machine, I would still have opted for the LPM…not least because, unlike a machining centre, it can be run in manual mode, and this adds still more to its tremendous flexibility." Additional to magazine information from here Setting up an LPM to run can be considered in two parts – first time programming, set-up and run; and subsequent set-up and run. The PMX screen is larger than its predecessor controls, while there's also a separate operator panels with jog wheel and spindle feedrate override controls - manual DRO mode is effected from here. Different too is the incorporation of a new face milling cycle to allow easy skimming of blocks. Programming is almost identical to that of an existing ProtoTRAK milling control, with just a couple of differences. For example, tool diameter and tool type are entered during programming, not in the set-up screen; while coolant is now programmed on or off, not via a switch. Image: DXF files can be imported and programs generated with reference to these Concerns about toolchanger tool position do not arise during programming, tools can be assigned 1,2 3 etc as they are employed in the program, there is a further process later. Having generated a program - which could have been done in background mode, while the LPM was running - the next important step is to run through the Check List, which will make sure all other elements to compete the set-up are attended to, prior to pressing the go button. A red condition means that a check must be made and value entered; amber means it can run, as values are assigned (but could still be incorrect); green means safe to run. Image: The check list is, effectively, the heart of the system The first item asks about reconciling tools in the Master program. This is only required if you are combining two or more program to run within a single master program. This is explained later, but, basically, identical tools in each program must be reconciled to a single tool number, with this single number then assigned (linked) to a toolchanger position where the tool actually resides (see later). The next item on the check list is about Z safety height. Now there is a default value, which is a large figure, measured between table top and tool tip. The check list will show yellow against this item and will allow the machine to run, because you could safely do so without setting a new, lower height. Not so efficient, though. Image: A default safe clearance height is set unless altered Next the programmer is asked to confirm that the tool diameters have been entered correctly in the program section of the tool management screen. This can be done during the course of program creation, but, if not, this prompts for the values. Then comes the toolpath check. This is done by viewing it graphically. Image: Does it look right? A saving program reminder comes next. Next the ball-lock location – A, B or C – must be entered. This tells the machine which location hole the pallet is datumed from. Each location is visually identified on the machine. There is no default value, this must always be set, as the same program may be run in different positions. Image: The ball-lock position is a datum position within the machine. The control 'knows' where this is, physically Next, the machine knows where the pallet is, but within that, X, Y and Z offsets from the ball-lock hole are required to give the part datum, often the centre of the job. These are found by using standard measuring equipment. They could also be set by 'touching', for example, the top surface using a tool or wobble bar, in the case of the Z-offset. Next, if a company wanted to run multiple parts, then a location offset has to be entered to shift the program. Only one location offset value is allowed. This envisages parts made from a single strip or block. This value is entered on the above screen, too. Now the tools used in the program must be assigned to tools in the toolchanger. So, tool 1 in the program (or reconciled master program) might actually be at location 8 in the toolchanger. The link is made here. Image: Is tool 1 in the program tool 1 in the toolchanger? Probably not, so the two must be linked You can see that, although the LMP has a 16-position toolchanger, there are a further 5 virtual positions. These support manual toolchanging for high value boring bars that you don't want to keep in a machine or large tools that exceed toolchanger pocket capacity, for example. Tool length offsets are entered next. For a new tool, values will be zero and this will give a red flag. Tool length is measured by use of the tool trolley's height gauge – a zeroing tool is used to datum the gauge, with this zeroing tool supplied with the machine, having been calibrated for use with it. Existing ProtoTRAK users would be likely set tool length on the machine. Image: If a tool is already in the magazine, then a value is already set, but if not, a value must be entered The last two stages are about removing and adding tools from the toolchanger. Obviously, tools used in the program that are not in the toolchanger must be added, and this is indicated on tool management screen. In fact, tool removal comes first, in case space needs to be created to allow for the addition of a different tool. In such a case, the screen will show two tools at the same toolchanger position prior to removal. The relevant tool is highlighted in each case. Tools for removal are moved by the machine into the spindle; are then manually removed from the machine spindle, with the new tool then manually loaded to the spindle, which the machine then places in the toolchanger. Image: It's all very clear - the screen highlights what's to be added Once all is set, part run time is displayed prominently on the screen, with a count-down function operating as the machine runs. For repeat runs, the program already exists. It is possible to combine up to four individual programs and to run them from a master programme. The option to run tool-by-tool, to minimise tool changes is possible, otherwise it can be part-by-part. Associated with each program can be images of set-up, as well as notes related to past experience or 'watch out' notes that may relate, say, to the prescribed use of tooling from a specific supplier. The PMX has USB ports, allowing transfer of images from a camera and the plugging in of a USB keyboard. Parts, fixed on pallets (in fixtures or a vice), can then be located on the table. For vices, there's a special vice pallet that features a vertical datum wall plus distance bar that allows a block of material to be set in the right position, relevant to the ball-lock position, on the machine very quickly. Image: Making it easy - the pallet locates in the ball-lock locations and the vice-held workpiece is set by using the distance bar and datum wall The operator then runs through the check list again. For some items, the status is always red, or 'don't run', until these have been checked and cleared. Included here are the specification of ball-lock position and assigning of tools to toolchanger positions. If a master program had been created, then item 1, reconcile tools in master program, would be red. Other items may be red. For example, tool length offsets, which will be red if the tool is not in the toolchanger and has to be added. After that, the LPM is ready to run. Repeat set-up times can be measured in minutes, assuming all the preparation work has been done, with parts and tools ready to load, as they should be to get maximum benefit. But even first time out including programming, the process is quick, lean and under full control. And all this is why XYZ Machine Tools' LPM is not a machine; it's a system. Box item 1 LPM specification in brief The XYZ ProtoTRAK LPM is a solid cast iron construction, 15 hp/8,000 rpm, BT 40 vertical spindle machine. It has a 900 by 500 mm table and axis travels in X, Y and Z of 785, 470 and 530 mm, respectively. It also has linear guides, a 16-station carousel tool changer and rapid feed in all three axes of 20 m/min. First published in Machinery, July 2011