Instrument Room Requirements

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A tool loom should be incorporated into every injection molding operation. There are a wide range of capabilities in such departments, ranging from ejector pin replacement to welding and rewiring parting lines.

Molding facilities should also consider building their own molds rather than purchasing them from a vendor for many reasons. In each of these situations, particular equipment is required in order to complete the associated tasks. Funding, space, and personnel become more important as the activity becomes more complex.

In determining which tool room is best suited for a given application, factors such as the local talent pool and experience, the amount of funding available, the desired degree of control, and the amount of molds involved should be considered.

The goal of molders should be to fully satisfy the needs of their customers, but it is more cost-effective to use external sources for molding and internal sources for mold maintenance and repair. A full-service vendor is defined as one who assumes full responsibility for the mold, regardless of where the mold was made.

The tool room equipment for large molds is large. By contrast, small molds require smaller equipment. In general, larger equipment requires more space and money, while smaller equipment requires less.

Currently, tool room capacity depends on the availability of staff. It is common for a tool loom to be built at a molding facility only to be found lacking in personnel when the loom is operating. It is becoming increasingly hard to find newcomers to the toolmaking and moldmaking professions. Therefore, many tool rooms throughout the industry are understaffed, or even empty. A tool room requires enormous capital, space, and time, so it is wise to check if there is talent available. It is important to air-condition the tool repair department to protect repair equipment from temperature and humidity.


The molding shop should have a mild mold repair department on site, unless it is lucky enough to have a tool shop right next door. Molds are cleaned, inspected, and stored in this department after production runs are completed. Furthermore, this department analyzes any damage discovered during the inspection process, determines whether it can be fixed inhouse, and makes the relevant arrangements.

Depending on the equipment and the available personnel, a list of repairs that can be considered “minor” could be small or long. Replace damaged or malfunctioning ejector pins, clean and polish mold and cavity surfaces, remove vent stains, replace damaged sprue bushings, replace O-ring seals, add vents and change cavity inserts for interchangeable molds and family molds. It is recommended that the department has several tools available to do this work, including a small lathe, small horizontal milling machine, small surface grinder, drill press, and hand tools,both manual and powered.

Also necessary are measuring tools and a surface plate. To work with the maximum-sized mold, a table and a hoist must be able to support its weight. Decorative items and scraps such as drills, taps, ejector pins, polishing media, etc., should also be included in Additionally, miscellaneous tools are needed, such as a bench grinder and a shop vacuum.nd shop v acuum. It takes at least 100m2 of space to house a small repair department.


In addition to performing all of the work listed for a minor repair facility, a major repair facility should also be able to perform additional work. As part of the additional work, mold surfaces will be repaired, waterlines will be added, parting lines will be refurbished, cracks and dents in the mold and cavity walls will be repaired and surface changes resulting from minor engineering changes will be performed. Additional equipment would be needed including larger milling and turning machines, surface grinders, drill presses, a horizontal, metalcutting band saw, arc and TiG welding devices, as well as hand tools including hand grinders and high-speed rotary tools.

Obviously, major repairs will require an additional 2,500 square feet (232 m2), or more, due to the increased size and number of the required equipment. Adding a tyout press to the department can increase that requirement substantially.


The majority of shops are unable to afford to keep an in-house moldmaking department. Designing and creating molds requires different levels of skill, but true moldmakers are at the top of the list. The number of moldmakers is dwindling as I mentioned earlier. Molds are built by two to five toolmakers and/or machinists for every moldmaker working in the shop. It takes at least 1,000 hours to build even the simplest mold. Over the course of a year, it quickly becomes evident that a three-person team cannot build many molds. Molds are increasingly needed, therefore more people are required.

Moldmaking at an in-house facility typically takes place over one shift and employs several moldmakers, with the rest, including support staff, working three shifts (for comparison, a job-shop moldshop can employ three shifts). The average mold maker works between 50 and 60 hours a week and requires limited equipment. In addition to everything mentioned earlier, this equipment includes two or three plunge-style EDM machines, a wire EDM, a heat-treating furnace for small items (larger items are sent out for heat treating), a large air compressor for air-operated equipment, a multi-axis machining center, one or two centerless grinders, a large lathe, and additional surface grinders and horizontal mills.

In most businesses, the company does not supply hand tools. The toolmaker, the machinist, and the mold maker are expected to furnish these tools. For better mold handling, the moldmaking facility should have overhead cranes, forklifts, and chain falls for its own use. Ship- ping docks and receiving docks must be easily accessible from the building. An adequate tool crib is required.
Moldmaking facilities require more space than repair facilities due to the additional equipment and requirements. Depending on how many and what size molds are expected, this space requirement might exceed 500m2.


Molds must be handled and stored effectively and prudently regardless of the type of mold restoration or mold building done. A mold is an expensive investment, and these costs are usually borne by the customer, but the molder is responsible for keeping that mold in good working order while it is in the molder’s possession. A mold’s annual maintenance cost averages about 5% of its initial price. Mold construction has a higher level of quality that is the responsibility of the mold maker, and mold design has a higher level of performance.

For molds that have been damaged during storage or use, certain repairs will be warranted. During use or storage, the item will be damaged more often. Examples of that are wearing of gtae areas, broken core pins, peened parting lines, etc. Storage is often plagued with rust damage, which is common.

If you keep any production run with the mold in storage, you should save the “last shot.”. These provide a visual representation of the last part the mold produced. By inspecting the parts, a repair person can determine the condition of the parting line, the surface of the cavity, the position of the ejector pin, and other pertinent information.