Financing

Having become assured that the foregoing conditions have been fully met let us proceed with the train of thought. It is necessary to lay out a certain sum for plastic injection molds plant equipment and operating expenses. The amount needed will be governed entirely by the size of plastic injection molds plant required to produce the items previously determined. Of course, the major part of this capital investment will go into injection molding machine equipment, boiler, high and low pressure pumps, an accumulator and a compressed air system, but some of the smaller necessities such as piping, valves, finishing machines, furniture and fixtures, must not be omitted from the calculations.

If selfcontained injection molding machine are going to be used there will be no need for the machine auxiliary equipment. Whether the funds for procurement of this machinery shall be placed at $10,000 or $100, 000 is contingent also upon the size of plant to be built. An other factor which enters into the determination of this figure is the type of machinery purchased. Returning to the capital required, however, it should be kept in mind that the source of this money is of utmost importance.

All enterprises of whatever nature in business are founded on either money or credit and the terms of financing have a great deal to do with the fixed capital charges under which this enterprise must labor. It is essential then that any such terms be distinctly and thoroughly understood before any papers are signed. A misunderstanding in this direction may prove to be a hazard too difficult to overcome at a later date and very often failure may become obvious even before the project is far under way. Terms of financing should be such that provision is made for any exigencies that might arise during the course of the first few years.

It is a fairly simple matter to prognosticate certain conditions, but many times sufficient allowances are not made. An engineer when designing a bridge has to figure live and dead loads, stresses, and strains in every strut. After he has completed his calculations he then applies what is known as a “factor of safety”—which is actually nothing more than a ratio. He first theoretically calculates safe beam sizes and then multiplies by a certain constant to take into account the unknown hazards, such as possibly a record breaking snowfall or some other unusual happening.

In business, there are unfortunately a great many more hidden hazards than there are in the safe construction of a bridge, but after taking into account everything that can possibly happen it is always a sensible idea to apply a factor of safety of at least 2 to 1. This, of course, should not be interpreted too literally and does not mean that if $100,000 was decided upon as the amount necessary for fixed investment and operating expenses, the figure should be doubled. It does mean, however, that if fifty percent were set aside for operating expenses that an additional $50,000 would be adequate insurance for all contingencies.

So many enthusiastic enterprisers subconsciously deceive themselves and awaken only too suddenly (and usually too late), to find that they had been too optimistic at the outset. The application of a definite factor of safety should positively be made and will, in many instances, be the means of sustaining a business otherwise doomed to failure through lack of sufficient funds for continuance.

Oil Hardening Tool Steel for Auto Car Trim Mould Making

The oil hardening tool steels are probably used in plastics auto car door mould manufacture as extensively as are all of the other mold steels together. This includes carburizing steels, hobbing steels, water and air hardening steels.

Next to the air hardening steels, those which may be hardened by quenching in oil have the lowest distortion characteristics of all of the tool steels. The distortion of oil hardening tool steels upon heat treatment is less than the tolerance limits for some plastics mold applications, and this advantage, coupled with favorable machinability, accounts principally for their wide use. When the accuracy limits for finished mold parts are closer than the expected distortion, it is often possible to make allowances for distortion, and thus still hold the required accuracy with an oil hardening tool steel.

Hardness control, from extremely hard to fairly soft surfaces, is possible when oil hardening tool steels are used. Brightly polished surfaces, having good abrasion and crushing resistance, may be produced on car bumper mould cavity parts made of these steels. Guide pins, bushings, cams, cutting tools, and other mold parts which require high strength and hardness are usually made of oil hardening tool steels for best all around results.

The analyses of ten typical oil hardening steels which are used extensively for plastics molds are tabulated in Fig. below

Thales Directory

Hobbing Steels

Hobbing steels are in a highly specialized class of materials. Many China mold makers prefer to use a practically pure iron for hobbing mold cavities. It is the softest and easiest to work of all of the hobbing steels, although it must not be subjected to high crushing loads because the soft center core metal below the case hard-high speed steels require a considerable amount of heating time. In such cases, the advantage of minimum time in the furnace is not always clear cut.

Some bumper mold making tooling applications require the use of tool steels because carburizing steels are not applicable. Hobs, for example, must be extremely hard at the surface, and the hardness should extend rather deeply into the center in order to make the hob resistant to the severe crushing which it must stand, and to have high tensile strength, as well. Hobs may be made of air hardening, water hardening, or oil hardening tool steels. Oil hardening is usually preferred, with water hardening steelthe least used, and then generally only for small, simple pieces not critically subject to cracking in heat treatment, nor subject to heavy hobbing pressures.

Pre-Hardened Steel

Tool steels are furnished normalized, annealed, or hardened to the limit of machinability. Often, it is satisfactory to have a mold part made of a pre-hardened steel and omit heat treating it after machining. This is a practice which must be pursued carefully, however, and the steelmaker’s recommendation should be sought before proceeding. Usually not much depth of machining should be made on a pre-hardened block of steel if it is thick, because of possible non uniformity of the steel structure due to the thickness. Pre-hardened steels are useful in small plastic mold company which do not have proper hardening facilities, and they are useful when mold parts must be made quickly, without risking possible spoilage in heat treating. If long life and severe service conditions are factors in the use of a mold, pre-hardened steels are usually not satisfactory, because they cannot be hardened enough to stand the service conditions without becoming non machinable.

Hot rolled tool steels are available in rounds, flats, and squares, in sizes from Vk” to 8” diameter, from x to x 10″ or 12”，and from V₄ⁿ to 6″ square. Larger sizes may be obtained as forgings. Specially finished tool steels are also available. Drill rod is accurately polished to fractional, decimal, number, and letter drill sizes. It is obtainable as plain carbon, water hardening steel, or

as high speed steel. Ground flat tool steel, plain carbon, is available. This material is used for gages, shims, templates, retainers, parallels, gibs, and for many other applications which may conveniently use a stock which is finished all over.