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Useful Articles
What to consider when buying castings
SELECTING THE FOUNDRY
There are many ways to select foundry suppliers: names taken from a
buyers guide, from the visitors' book, advertising material, magazines,
and recommendations from other buyers and engineering staff. Buyers
should actively seek more reliable information about sources of supply
and try to match foundry capacity to their purchasing needs. This can be
achieved by issuing a questionnaire to prospective suppliers. The
answers provide the buyer with data concerning his potential suppliers.
Foundries may be reluctant to answer some of these questions; however,
the buyer should insist this is done as a prerequisite to consideration
for future business.
Replies should be studied with care because they will reduce the scope for error and provide the guidelines for future purchasing policy. For example, the buyer will know whether the supplier can produce the grade of material required in sufficient quantity. Attitudes on quality can be assessed from the percentage of total production and quality control personnel directly involved in the quality control program. The buyer should recognize that a foundry's strong emphasis on quality control indicates they are probably producing very high grade castings. Their price structure will reflect this whether or not castings to exceptionally high standards are required.
If it is intended to buy heavily cored castings, look for the supplier who produces this type of casting. Discuss capacity to avoid disappointment after the order is placed. Failure to make delivery schedules may be the result of coremaking capacity. Generally speaking, buyers would do well to make buying decisions on the realities of the situation: the price, quality/inspection standards required for any given set of physical and mechanical properties. From the answers to the questionnaire, the buyer may ascertain whether or not transportation will be a problem and the prospects which may exist for further development of business with the supplier. Perhaps the most important point, when all other conditions have been satisfied, is to look at the foundry's current pattern of production. Is it high volume, small castings, or jobbing and what are their standard flask sizes? Flask size can have an effect on prices and quality of castings. If possible, when designing castings, keep in mind the flask size, so as to maximize the number of patterns on a plate. This will be a significant step in the process of cost reduction. Always allow sufficient space around the casting for the coreprints (the projections needed to provide adequate support for the core). Consult the foundry supplier if in doubt on this point.
THE FOUNDRY AS AN EXTENSION OF THE BUYER'S MANUFACTURING
CAPABILITY
After the selection of a source of supply, both the buyer and the
seller should regard their relationship as that of partners. Plan to use
your gray iron supplier as an extension of your business. If the buyer
builds a close relationship with the foundry, it is important to have a
policy of using few suppliers and not send inquiries to every foundry
that solicits business. There may be cost savings from new sources and
the buyer should keep in mind that changing circumstances can affect
purchasing decisions. There are hidden costs and hazards in changing
sources. The cost of expediting and monitoring quality can increase in
direct proportion to the number of suppliers. It is better, if the
existing supplier is a good one, to negotiate and increase bargaining
strength by concentrating on the cost of a few, rather than many
sources.
In cases where the buyer's company is forced to accept "penalty clauses" or is dependent on prompt delivery, there is perhaps an alternative to visits or telephone calls.
First, obtain the supplier's agreement that delivery is part of the contract - that is, in return for certain consideration (price) the supplier undertakes to supply good quality castings at the agreed date.
The advantage of this type of arrangement is that the top management
at the foundry have a convenient means of measuring their delivery
performance.
Some attempt should also be made to establish the cost of quality
problems. In all probability, the cost of a rejection over a very broad
spectrum of castings procurement is as much as five times the original
price. Thus, if a batch of castings costing $1 each has a reject rate of
5%, the true cost of that batch is: five at $5 each plus 94 at $1 each,
a total of $120 for $1.20 each, an increase of 20%. The actual cost of
quality or late delivery is an important consideration, the fact is that
these costs may be significant and emphasize the need for better
understanding between buyer and supplier.
FOUNDRY COSTS
Because of the many types of foundries, the range of metals cast, and
the wide range of casting processes, it is difficult to offer guidance
on the subject. There are a few considerations which may be helpful.
Irrespective of the type of foundry, costs will break down into three
main categories: materials, direct labor, and expenses. Materials may be
subdivided into raw materials - pig iron, scrap and alloying
constituents - and process materials - coke, sand, molding materials,
bonding agents, shot, paint, etc. Increasing mechanization and
automation have made some impact on the foundry industry, but labor
remains a high percentage of costs. Expenses are extremely variable
depending on the facilities of the foundry and the method of costing.
There is no magic formula which can be universally applied to foundry
costs, it is usually possible to obtain some indication of the
percentage ratio of pig iron, scrap, etc. in a typical melt charge.
Having established an approximate cost per ton of foundry output, based
on the average cost per pound of a range of castings purchased, it is
possible to arrive at a rough idea of the range of costs of the various
materials, expressed as a percentage of total costs. An idea of labor
costs as a percentage of total cost can be calculated using average cost
per ton of output related to the numbers of direct and indirect
personnel and the assumed labor rate. By multiplying the number of
impressions on a pattern by the unit price for the casting, it is
possible to estimate the return per flask expected by the foundry. Care
must be taken to differentiate between cored and uncored casting, grade
of material, molding method, and flask size when using this method of
calculation.
Assuming castings represent a sufficiently large area of expenditure,
the buyer would be advised to analyze casting prices by foundry process,
grade of metal, size/weight, cored or uncored, molding flask size, and
molding machine used. This is useful in comparing sources of supply and,
related to quality statistics, provides a helpful guide to policy making
and a useful tool in the negotiating process.
COST REDUCTION AND MUTUAL PROSPERITY
This is the basis of good casting procurement. There is no point in
buying low cost castings if the supplier goes out of business. There has
been a tremendous reduction in the number of foundries in the U.S. There
are many reasons: environmental controls, the need for more investment,
overseas competition from lower wage countries, etc. If buyers wish to
continue purchasing in the U.S. and retain this important basic
industry, there must be more professionalism, less secrecy, and more
honesty regarding capability on the part of the foundry and a general
recognition that mutual prosperity is essential.
Some actions on this subject which may influence buying policy
include:
- Action by Foundries
- Increasing specialization
- Refusal to produce unsuitable/uneconomic castings
- Mergers into large groups
- Development of own machining facilities
- Improved technical liaison
- Assistance with preferred material specifications
- Improved production control arrangements
- Action by Buyers
- Design to use supplier flask sizes
- Encourage foundries to provide a design advisory service
- Better designs - more consultation
- Careful choice of process
- Closer quality monitoring and feedback
- Action by Both
- Use of optimum batch quantities
- Closer cooperation between buyer and seller
- Better planning - more reliable deliveries to achieve lower
investment in inventories - Long-term customer commitments to encourage investment
on special plan - Capacity planning - advance notice from buyer
- Steady load to optimize manufacturing costs
- Cooperation between buyer and seller to deal with monopoly suppliers with regard to scrap prices, availability, etc., and with representatives of government departments concerning licensing, regulations, etc.
- Introduction of computers for costing, production planning, and all administration.
THE QUOTATION
The buyer is best served by the concentration of expenditure on a few
rather than many sources. Using available information, the buyer should
request quotations from those foundries with whom he is prepared to do
business in the event to their submitting the most attractive bid (i.e.,
best offer in terms of price, quality or delivery, or any combination of
these and other factors which may influence the purchasing decision.)
Inviting quotations from poorly equipped low cost producers, whose ability to meet required standards may be in doubt, and setting their prices against those sources known to observe higher standards as a negotiating ploy, leads only to disaster. The buyer must beware of the foundry which, as a short-term expedient, is prepared to undercut all competition. Such foundries, in the final analysis, discard unattractive items, usually at times inconvenient to the buyer, and what appears to be a saving becomes a significant loss.
To attract the best quotation the information given to potential sources must be comprehensive and should include the following details.
- Part number.
- Drawing number, and the number of copies of drawings required.
- Description.
- Material specification, U.S. standard or equivalent.
- Annual requirement broken down into a monthly or weekly schedule.
- Batch quantities required and commencing date.
- Pattern equipment - if existing give details, if new pattern required, request prices and details, state for prototype or production use.
- Actual or estimated casting weight.
- Special features required such as:
- Finish
- Cleaning
- Heat treatment
- Nondestructive tests
- Fin tolerance
- Clearances for a jointing component
- Service conditions:
- Abrasion
- Corrosion
- Temperature
The drawing accompanying the quotation should indicate the following standard material specification or mechanical properties desired:
- Tensile
- Hardness
- Dimensional tolerances
- Maximum/minimum temperature characteristics
- Pressure tightness (if important)
- Machining data
- Location of part numbers, trade marks, machine locators
- Gaging points (if applicable)
- Require separate prices for castings and pattern equipment. Drawings used for quotations should be marked "for quotation purposes only."
Note
Having provided the potential suppliers with comprehensive details of
the requirement, insist that quotations are complete and do not produce
more questions than answers.
If the requirement is for intricate castings, the quotation should specify those features which cannot be achieved in the "as-cast" condition. Quotations should be accompanied by a marked drawing showing the precise form of supply and identifying any special machining allowances. Ambiguities regarding price, quality, material specification, delivery, non-destructive testing, terms of payment, etc., should be identified and eliminated before any quotation is considered.
