In the first part, we looked at some of the history of presswork and the various advantages and disadvantages of this method of manufacture.
In this part we investigate a few categories of parts you may be looking to produce and how Bracebridge Engineering would approach them:
A bracket required in high volume
A perfect product for pressing, dependent on complexity tooling prices can start from as little as £2000 and can pay for themselves in a very short space of time. The ideal tooling for this type of product would be what is called a progression tool or follow on tool. Progression tools aim to produce the final part in 1 stroke of the press by combining a number of stages in one tool that progress the part from a coil of metal to its final form. This ensures that the part is made as cost effectively as possible. The downside is a progression tool will normal cost a lot more than single stage tools where several operations are required to get the final part. As a general rule for volumes less than 10,000 a year single stage tooling offers a higher unit cost but is more less costly on the tooling side. So bear this in mind when you are considering the options. If your product is mild steel also ask what surface finish you require as BBE can supply in the following finishes:
Flat plate or 2D product
Some parts such as household window fixings, clamps, electrical boards, Network cable solutions and storage solutions require flat plate pressings with holes or sections cut as shown:
These can be made in high volume in the same was as a bracket however as no large forming is required the product is usually cheaper to produce and tool up for.
Bear in mind with 2D products in low volume, if tolerances are not too critical then these can be laser cut with ease and negates the need for tooling. Laser cutting is the chosen method for parts over 5mm thick. BBE would look to assist you with both methods and are always happy to suggest a method dependant on your needs.
Box shaped products:
If your part formed a rectangular or square box section, then again pressing is a great method of manufacture. The process in which this is done is largely the same as the bracket however in most instances a different process is needed. With some larger parts like car oil sumps a process called deep drawing is used. I’ll expand on that process in the next part type. Box shaped parts can be produced using progression tools however their size tends to be bigger so always check with the manufacturer on this as some presses won’t be large enough.
With regards to press size, the presswork company will do the necessary calculations regarding what size press is required to produce your product. BBE works closely with larger companies if we cannot accommodate a certain part and will always aim to help with any enquiry.
We manufacture the part shown in a number of stages on single stage tooling as this suits the customer and their requirements.
Cans, Pots and circular vessels:
This category of items comes under the ‘drawing’ heading of presswork or stamping. When producing a product such as the one pictured laws apply to the method of production. In most cases you can’t produce in 1 operation as the laws of physics dictate that the material will split if asked to do too much work in one operation. Therefore, they must be done in a series of ‘reductions’ to obtain the final size. Deep drawn pressings refer to a ratio of diameter to height and require expertise to get right. These pressings can be done in a variety of ways. BBE produces many thousands of drawn parts on a weekly basis through a few different methods. Smaller parts are made using progression tooling, however the largest deep drawn parts are done on our hydraulic presses as they offer control and speed adjustment to reduce risk of splitting and deformation. It’s not uncommon to have 5 to 10 operations to get the final dimensions, so bear this in mind when looking to have a part like this made. Some presses called transfer presses have the ability to transfer parts from stage to stage in 1 stroke to produce deep drawn components in high volume. However, bear in mind that typical tooling costs and investment for this type of production is not for the feint hearted!
Points to consider with drawn products:
In the last part we'll look at some common issues that can occur when looking at pressing enquiries and some final thoughts on the topic.