Make Them At Home

The message put out by parts manufacturers and assembly shops in the Far East is that they offer high quality and the lowest labor rates. One is sometimes suspicious of such claims, in view of the multitude of small shops to which the Far Eastern suppliers often give their work to.

Why should one be suspicious?

If you have been to, for example, China or Taiwan, you have seen, in the suburbs and villages, small sub-contract shops spilling out onto the highways. Machinery is highly varied, and you will see 1950s and ’60s cam automatics, capstan and turret lathes, and pillar drills working out in the open.

The better-equipped factories—some are even air-conditioned—will be operating Stars, Citizens, Mori Seikis and the like. These modern factories are the exception rather than the rule.

Why bring up this topic?

Well I was in Leicester, England, recently to visit a family company that had started up a new CNC sliding head automatic shop, based initially on two new Tsugami BS26-IIIs. The shop had successfully won an order to produce the piston and cylinder—by the millions—for a do-it-yourself paint spray gun.

The gun had been assembled in Taiwan, but the European OEM was dissatisfied with the reject rates. Demand for the product was fast increasing, and the Far Eastern supplier could not cope with the volumes required. The OEM also suspected that cam automatics—or even capstan lathes—were being used. Well, we all know that a really skilled capstan operator can produce quality work. Also, that if an operator checks often enough, cam settings on a cam automatic can be “tweaked” to maintain close tolerances—in this case, a 25-mm long cylinder, some 10-mm diameters, and associated 5-mm diameters piston-machined within a few tenths of a thousandth of an inch.

The cylinder, however, is in tough H13 tool steel of 35-40HRC, and the piston is in a sticky Type 440C stainless steel, so manual operators would certainly have to keep on their toes to maintain quality. The reason for such materials is that in service the piston reciprocates at a cool 100 strokes per second.

After carrying out some machining trials on sliding head automatics, the Leicester company tendered successfully for the initial $1.7 million contract and won it. Choice of machine focused on the ability to reliably perform the cross-drilling and deep-hole drilling of the cylinder. Also, a 5-mm wide groove on the piston’s circumference had to be held within 0.001 inch of the faced piston end.

A number of machine tool suppliers expressed doubt at the time that the job could be successfully run under “lights-out” conditions. Key to the success was selecting a machine type with sufficient rigidity and vibration-damping characteristics to cope with the tough tool steel under high volume production conditions. Also, a sliding head automatic is able to produce the cylinder in “one-hit,” whereas two setups would have been required on conventional production lathes.

The job is now being produced 7 days a week on a two-shift, 20-hour basis. It runs unattended during the night. The operator sets up the machines at 6 p.m. and checks them at 9 p.m. Then both machines run unattended through the night until 7 a.m. The company was very careful to establish the very minimum tool life for each cutting tip grade. Solid carbide drills shattered when drilling the tool steel cylinder bore. Tests showed that a cobalt coated high speed steel drill was a more reliable performer, and it drills out 2,000 of these cylinders before a strict tool change is made.

So now the spray gun is being assembled back in Europe, with all parts machined locally. It is an example of how screw machine shops in the “industrialized” Western countries can compete on the basis of using the latest machine tool technology coupled with disciplined tool management systems and stringent quality controls. Skill and machining experience, of course, is crucial.