What is in this article?:
- Design Trends for Automated No-Bake Molding Systems
- New Molding Technologies
Available technologies make productive, affordable, profitable systems possible for any foundry
- Addressing dozens of criteria
- Two types, range of design possibilities
- Universal molding concept
- Dealing with ejection
The basic Palmer UMM rotary molding system is designed to use existing green sand or no-bake tooling to produce molds at a rate of 20 per hour.
When you’re preparing to add an automated no-bake molding system, there are a number of critical decisions to be made that require careful analysis. As with many design projects, the end of the process is often the best starting point. It’s a basic concept to design backwards, at all times keeping in mind the molding process results you expect.
There are dozens of criteria that go into a well designed system, but a few of the main considerations are: mold rate per shift; mold size minimum and maximum; budget available; floor space available; staffing requirements/cost; complexity of coring; resin system; reclamation system requirements; engineering requirements; installation requirements; and time available for installation / commissioning.
Often we’ll ask foundries what their desired mold count is, and we get a one-word answer: “more.” “More” is not a number, but that number must be determined as it is the primary driver for the design of any system. The mold rate must be established at the beginning of the design phase. It can be changed throughout the course of the system design, but a well-defined production rate is a critical decision.
In a typical no-bake jobbing foundry, the work changes constantly. Mold size, complexity, quality, and alloys all change fairly often, which makes designing the molding system a challenge. If all or most of the variables are understood upfront, designing a flexible system is far easier than adjusting a system later.
For some requirements and budgets, a simple mixer/conveyor/mold handler set-up will be sufficient. At the other end of the spectrum, a fully automated system — including sand storage, mixing, molding, cooling, reclamation (both mechanical and thermal), automated casting cleaning, and inspection with first op machining — may be required. There is an extraordinary range of design possibilities between these two types of molding systems.
Parallel Conveyor Systems — Most metalcasters are familiar with the traditional, parallel conveyor loop set-up with transfer cars at each end, but there are a number of modern designs that also deserve consideration. The parallel conveyor system is a well-established process, with various iterations of the basic design installed throughout the world. It is flexible and can accommodate a wide variety of mold sizes and production rates.
Still, this design takes up quite a bit of floor space compared to other designs, and can be more expensive. These designs are fairly complex, too: a fully automated system includes a number of motor starters, proximity sensors and programming requirements.
If a foundry has to carry out a great deal of mold prep work, a conveyor-based system can be a good choice because the prep area/length can be set to whatever the operating conditions require.
Carousel Systems — Carousel based systems are very popular and logical for small to medium-sized molding (up to 60x60x30/30) requirements. Over 90% of the molding systems Palmer has designed in the past 20 years have had some type of carousel design. Significant benefits are the comparatively low capital costs, reduced floor space requirements, and operational simplicity.
With a rollover cycle rate of 90 seconds, a production rate of 20 molds/hour is achievable. Larger molds up to 60x60 require a longer rollover cycle time (approximately 2 minutes), resulting in a mold production rate of 15 molds per hour.
These rates are accomplished with essentially one moving part: the carousel has a gravity roller conveyor on board with high-quality rollers. The empty boxes are rolled off the carousel manually, filled, compacted, struck off, and returned to the carousel in less than the cycle time of the rollover. This is achieved with only one drive and a few proximity switches. Compared to a multi-zone power roller-based system, this is a much simpler system, in terms of operations and maintenance. (Please note that all production rates are for production of copes/drags only, and do not include downstream process such as coating, drying, coring, closing, or clamping.)