The "Flowing-on" System.

The very latest method of finishing automobiles which have steel bodies is that at present in use by the Ford Motor Co., Ltd., at Trafford Park, Manchester, and elsewhere. The method is a remarkable one not only because of the great saving of time it effects, but by reason of the fact that the "life" of the painted or enamelled surface is prolonged by the improved method.

Stated briefly, the process consists in coating the body with blue-black enamel by means of gravity only; that is to say, the enamel is placed in an elevated tank and discharged on to the work through a flexible pipe and slotted nozzle opened by a lever which is actuated by the thumb of the operator. Thus no spraying is required, while dipping is out of the question, as only the outside of the body is required to be painted.

Each coat takes two minutes to apply to the whole surface of a four-seated Ford motor body! An achievement which justifies our use of the word "remarkable."

But it will be convenient to explain how the present method came into use. Until a few months ago the several undercoats were sprayed on the work in the ordinary manner, but the finishing coat of varnish was flowed on by the gravity apparatus now referred to. Then it was thought that the undercoats might be applied by the same method, and some careful experiments having been made, it was found that by dispensing with the spraying and flowing on the coats a much more satisfactory result was obtained. As the new method caused more paint to adhere to the work than would be put on by the spray under ordinary conditions, one coat, it was found, could be dispensed with altogether. There was also less rubbing down required because of the very smooth coat obtained by flowing on, and, above all, the time of applying the coat was reduced to the extraordinarily short time of two minutes.

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The apparatus employed for this work is of the simplest character. The car body is placed upon a platform mounted upon wheels. This is made of exactly the right size to fit between a V-shaped metal trough which surrounds three sides of the body and is intended to receive the superfluous paint, a considerable quantity of which drips into it from the body as the enamel is applied. This trough, a sketch of which is shown in Fig. 121, is slightly inclined so that the paint which drips off all runs to one point, where it passes through a gauze covered orifice, descends to a small tank beneath, whence it is pumped up to the elevated tank above and is then ready to be used again.

This elevated tank is cylindrical and holds, perhaps, 25 or 30 gallons. It is stationed overhead some 12 or 15 feet high. From this tank descends a flexible metal pipe or hose ending in a slotted nozzle, opened by a lever, which is operated by the thumb of the workman and is closed by a spring. This completes this simple though very effective apparatus.

The body of the car is made of stamped steel which has already received a protective coat of paint of a dull red colour, the body being placed upon the platform or bogie and being placed in position with the V-shaped trough surrounding it on three sides. The first or undercoat is given by rapidly passing the slotted end of the lever valve over the surface, upon which the paint literally pours out. The top part receives attention first and the paint runs down over the surface, which it covers completely, excepting perhaps here and there, where the discharge of paint is directed, and the whole of the outer surface of the car is, as already stated, completely covered in two minutes. This coat dries semi-flat.

In order that the discharge pipe may be kept nearly vertical and be moved around the car as the different sides are dealt with it is provided, at its upper end close to the point where it joins the tank, with a brass swivel union and a horizontal arm which swings around. A stop-cock is also provided.

The undercoat having been applied the body is allowed to rest for a few minutes until the dripping ceases. It is then wheeled on the bogie across the room to an oven, in which it remains for one hour at a temperature of 160° F. This heat is found to be sufficient to bake the paint but is not high enough to injure the woodwork which, of course, forms part of the body. At the expiration of the hour a little stopping of inequalities of the surface is usually found necessary, but in any case the surface is lightly rubbed down with fine glass paper.

The body is now brought underneath a second tank with the V-shaped surrounding trough exactly as before described, and here it receives another coat of enamel or paint, which in this case has a little more body and gloss. After stoving as before and at the same temperature the surface is carefully but rapidly rubbed down with powdered pumice stone and water applied by means of felt pads.

There are a series of four troughs and tanks in all, corresponding in number with the coats to be applied. From the third one the body receives a third coat, is then baked or stoved, rubbed down with powdered pumice and water, thoroughly cleaned off, and from the fourth tank receives the final coat of varnish which completes the operation. This coat of varnish is not stoved but is air-dried. The finish is a blue-black picked out with very dark blue, and it is free from any signs of runs or drips; in fact, no one could tell how the application was made. As already remarked, the coats of paint are somewhat fuller than would be the case if they were applied by spraying, and the durability is thereby increased.

The output from this department is 70 cars a day, a number which would be practically impossible if the work were not so splendidly systemised.

It should be observed that the varnish is applied in a separate room from that used for the application of colour. This is done in order to exclude dust, and also to maintain the temperature at 90° F.

In considering the essential points of this method of finishing motor bodies, it is clear that the system might be successfully applied in very many other industries to a great variety of goods. The apparatus is so simple in character that no engineer would have the least difficulty in designing a plant suitable for any particular requirement.

It must be admitted that the crux of the whole situation is the kind of paint or enamel used. It must be sufficiently viscid to hold on to the surface to which it is applied, sufficiently liquid to run off freely without leaving runs, tears or "fat edges." And, above all, it must flow out uniformly. All these conditions, however, apply also to a dipping plant, and only require careful consideration on the part of the paint manufacturer who has made a special study of the subject. The varnish applied by this method must also be of a special character so that it may flow out nicely without yielding too thick a coat, which would be likely to lead to blemishes. Ordinary paint, enamel or varnish, then, will not answer for this class of work, but special products must be employed, and when these are obtained, the rest is comparatively easy.

The Floco Process.

This process is in some respects similar to that above mentioned, the difference being that it is intended principally for the application of varnish by flowing over a painted surface done by spray. The essential difference in the apparatus is that the varnish, instead of being discharged by gravity, is pumped up from a tank. It is largely used in America, and is manufactured by the DeVilbiss Manufacturing Company, Toledo, Ohio, U.S.A. It is particularly suitable for automobile bodies and large surfaces generally.

The process flows such materials as varnishes, enamels and japans, when it is impracticable to spray them. It has superseded the inadequate, inefficient flowing systems used in the past, and is also replacing brush and dip methods as practised in many instances.

The equipment of the process comprises a 15-gallon tank, drawn from one sheet of steel and heavily tinned; 1-6 H.P. motor, housed in, driving a rotary pump; regulator; nozzle; electric fittings; flexible fluid hose, and galvanized iron drain trough on rack. All parts, excepting nozzle, hose and trough, are mounted on a castered truck for moving about. The truck is equipped with a rack around which to wind the hose when not in use, and a holder for the nozzle.

The finishing material, such as varnish, to be used is pumped from the bottom of the tank by the electric motor-driven pump, in a continuous stream, through the flexible hose, to the nozzle. The flow of material is adjusted by[Pg 225]
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[Pg 227] the regulator, by means of which a varying amount is not put into use and returned to the tank. In this way the flow from the nozzle is instantly adaptable to any class of work and viscosity of fluid without changing the speed of the motor.

When the nozzle is closed the material pumped is all forced back into the tank through the overflow. This, serves to agitate the material; in fact, is the only agitation necessary with material containing pigment, such as colour varnish.

The body to be flowed is—as shown in Fig. 122—placed over the drain trough. The operator first applies the material all along the top, then flows it copiously over the upper half of the surface. Sufficient material is thus, applied to insure a perfect flow to the bottom. The job is allowed to drain into the trough which carries the material back to the tank—here it is strained and, without the slightest waste, used again.

Only enough material is put into the tank to take care of the work at hand, or to handle the day's production. The maximum amount of material exposed is 15 gallons—the tank's capacity. The nozzle will operate satisfactorily on a gallon of material.

The tank, motor, pump and regulator are—as previously stated—mounted on a truck fitted with casters, permitting of these parts being moved about with the greatest of ease. Another appreciable advantage of this style of arrangement is that an extra truck can be kept on hand and put into immediate use in case of accident.

The cleaning of the parts is simple. The nozzle of the machine is detached and all of the material pumped out of the tank, after which a small quantity of naphtha—or some other similar solvent—is put into the tank and pumped through the machine.

As the motor is only 1-6 H.P., the consumption of power is low. The motor is made for all kinds of current, and can be attached to any light socket.

It may be observed that the pressure tank used in this equipment permits of the use of heavier or more viscid enamels and paints than would be possible where gravity was depended upon. In view, however, of the success which has been met with in the case of the Ford Motor Company, there appears to be no reason why the Floco process should not be used for some of the undercoats, as well as for the finishing.

The following article by M. C. Hillick appeared in "The Painters' Magazine," of New York, and will doubtless be read with interest:—

The Willys-Overland automobile factory has recently been installed with sixteen large enamelling furnaces or ovens having a volume of 48,000 cubic feet and a capacity of 140 tons of enamelled product every ten hours. These ovens have been electrified and they require approximately 5,500 horse-power. For some months past the Overland Company has been testing one of these electrically-heated ovens, and the results have, in every way, measured up to expectations. Formerly the company, in common with practically all other companies using enamelling or baking ovens, employed gas as the treating medium. The ovens now electrified are almost entirely automatic in operation. When the oven is loaded the closing of its doors automatically throws a switch which turns on the current. A pyrometer which can be adjusted to operate at any desired temperature rings a bell when the proper degree of heat is reached, thus notifying the attendant, and also automatically turning off the current. The electrically heated oven does away with all flue gases and with their attendant dirt and spots. It also reduces the required volume of ventilation to the minimum, thereby eliminating air currents and the dust which, in greater or less degree, usually accompany them. The electrification of the ovens does away with explosions, banishes danger from fire, and gives an assured "safety first" to the workmen. The heat is said to be non-oxidizing and, therefore, cannot scald the operator. The working quarters are rendered comfortable and a higher grade of work is made possible.

While for the custom shop painter it is a long way to such equipment, the fact that these facilities are gradually being acquired leads to the assumption that, in the course of a few years at most, some portion of the work coming to the shop for painting repairs will be handled through the baking oven. In connection with this subject of enamelling and oven baking, the various costs of paint and varnish, it is to be noted that the excessive temperature employed in baking is being criticised as detrimental to the finish. Recent tests are said to have been made which show that baking paint and varnish at the maximum temperature shortens the life of the finish. Mr. J. W. Lawrie, of the Chemical Works of Milwaukee, Wis., has stated that, as a rule, the lower the temperature and the longer the time[Pg 229]
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[Pg 231] the paint and varnish is baked, the finer the appearance, service and durability of the finish and the greater its capacity for resisting moisture. The finish will have more elasticity and deeper lustre. Mr. Lawrie is of the opinion that twelve hours at 180 degrees are better than five hours at 280 degrees.

In some motor car shops, within the past two years, by the use of baking ovens cars were painted and finished, all coats being baked, and made ready for service in three days. However, we are not commending or recommending this practice. For the custom shop painter, especially, it is entirely unsuited. Nor would we recommend the baking process for surfaces other than metal. The same disadvantages marshalled in opposition to baking paint and varnish upon wood surfaces fifteen years ago, or longer, still remain in evidence. For aluminium, sheet steel or other metal panels or metal surfaces in general, the baking process offers an opportunity for finishing work under conditions more uniform than any which may be expected to prevail outside the oven. An other advantage is noted in favour of oven baking. It permits the use of more elastic materials without the aid of artificial oxidizing agents. As compared to the present air-drying system, the oven baking method, operated upon a conservative basis, permits the car to be thoroughly painted and finished in six or eight days. The use of more elastic materials—paints, colours and varnishes—has been mentioned as a part of the oven baking method. Upon steel surfaces this is perhaps more necessary than upon aluminium, and possibly iron. Steel has a linear expansion double that of wood. As a matter of fact, experts in these matters employed by the Pennsylvania Railroad assert that the contraction and expansion of steel surfaces is much more pronounced than the same action in wood. Materials of greater elasticity as compared to those used in natural air-drying practice are urged.

Primers and surfacers, and the general class of foundation coats, will require an average of three hours' baking at 200 degrees F. While some colours require higher degrees of heat than others, 170 degrees F. baked for, say, six hours will dry the average colour, excluding white. The latter pigment, baked at a temperature varying from 85 to 110 degrees F., will dry properly in the course of a few hours, and retain its natural purity of colour, whereas at a higher degree of heat the white takes on an objectionable yellowish cast. Black, at the opposite end of the colour pole, can be safely baked for six hours, at something like 200 degrees F. Finishing varnishes, taking them as they run, will bake at from 110 to 150 degrees F. for five or six hours. In all baking practice the personal equation figures largely. Reason, good judgment, the capacity for taking pains—all these are items of importance.

Oven baking methods are being successfully employed in some of the large city repainting establishments. A firm near New York, for example, using what is known as the radio process, paints and finishes a car in three days. The cleaning of the cars is accomplished by the use of a steam jet, a treatment which is said to cut away the grease like magic. All surface defects following the cleaning of the car are touched up and faced over with the necessary filling and surfacing materials. Then these patched-up parts are rubbed down with water and rubbing brick, and the general surface of the car is lightly rubbed with pulverized pumice stone and water. All colour, and varnish colour, coats are applied with a paint atomizer. This atomizer is a pistol-shaped device operated with a trigger, the material being sprayed from the muzzle of the barrel. The varnish colour is baked for three hours at a temperature of from 110 to 120 degrees. From 90 to 100 degrees of humidity are provided for the oven, and by means of an exhaust fan a fresh supply of air is furnished every three minutes. In the oven where the varnish colour coats are baked a thermostat is installed, which regulates the temperature. All the air entering the oven is washed and purified by running it through a water tank before it enters the oven. This water-washed air is forced into the oven by a fan blower, and contact with a radiator superheats it.

In practice, the high humidity here referred to, and the water-washed air, are mediums which serve to keep the outer surface of the drying coat moist while the inner surface is drying, in this manner furnishing in due time a paint film dried uniformly from top to bottom.

The finishing varnish is dried in an oven having a maintained temperature of from 90 to 100 degrees, the humidity being regulated at from 60 to 70 percent. This humidity is likewise found to assist a varnish film to dry uniformly throughout.

The treatment of the car chassis in the establishment here referred to is quite similar to that given the body of the car. A steam treated potash bath is provided into[Pg 233]
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[Pg 235] which fenders and other removed parts are immersed, removing all grease and foreign substances, and even the paint, from such parts. These parts, after cleaning, are then dropped into tanks containing the required paints, varnish colour, etc., after which they are taken out and drained and then consigned to an oven maintained at a uniform degree of heat.

Other establishments having ovens installed are employing methods designed to secure equally quick results without sacrificing any measure of durability or appearance.

In the absence of ovens, not a few car and carriage painters are practising the so-called hot-air method as far as possible. Successful results are reported in many instances, the work being turned out quicker, with an increase in lustre advised in some cases. This method is very simple and requires no previous experience or special training. Anyone capable of providing the necessary degree of heat—85 to 95 degrees F.—and maintaining it for eight or ten consecutive hours, can have the benefit, in full measure, of the hot-air system. Coats of paint, colour, varnish colour and varnish dry rapidly in a temperature at the above degree, where the ventilation is good and a fair volume of pure, fresh air can be constantly brought into the drying room.

Notes on the Construction of Stoves.

The construction of stoves for use in connection with enamelling and baking japans generally does not properly form part of this treatise, but a few remarks on the subject may be of service. It is to be regretted that in only too many cases the stoves employed are very inadequate. In some cases they are heated by gas, and the jets cause a certain amount of discoloration. This is objectionable even when the work is black, but if it is coloured it may lead to serious disadvantages. In Fig. 126 is shown a sketch of what is known as the "Perkins System of Heating." It is largely adopted in many trades for enamelling cycle frames and parts, lamps and motor horns, etc. It is this system which is used by Messrs. Lucas, Limited, of Birmingham, a description of whose plant is given elsewhere. In the "Perkins" system water is heated under pressure, and the comparatively high temperatures required for drying and other similar purposes are obtained in a simple but efficient manner.

The apparatus consists of circulations of hydraulic tubing, certain proportions of which are formed into a coil and placed in a furnace situated in any convenient position outside and below the drying chamber. The apparatus is hermetically sealed and self-contained, the heating water circulating from the furnace through the heating pipes or coils and back again to the furnace without any loss through evaporation. No pumps or moving parts of any description are required, so that unskilled attention only is needed.

The illustration shows a simple application of the apparatus, which is the type often employed for cycle and motor parts, bedstead frames, electric apparatus parts, etc. The arrangement of the pipes, of course, depends upon the class of work which has to be dealt with.

In Fig. 127 is shown a type of stove manufactured by Goodyear and Sons, Churchfield Works, Dudley. The construction is a great improvement on the old-fashioned type of enamelling stoves, which through faulty design were responsible for great loss through radiation and combustion. The work done in such stoves is necessarily inferior. The firm named are among those from whom may be purchased up-to-date stoves heated by gas (ordinary lighting or producer), steam, superheated water, and oil, either single, double, or treble cased suitable for purposes which a few years back were hardly dreamt of, and which may be said to range from hairpins to bedsteads, and include munitions of war, such as stoves for shell drying and varnishing. A very important part of the process of stoving is the rack and trolley system of transport in and out of the stove, which in effect means that no article is too heavy for such process. In the production of stoves for enamelling certain firms have made a special study of the requirements, including those above mentioned.

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