With tight deadlines what else can you do, but get it done in one tryout – a Japanese Success!
[dropcap]C[/dropcap]hallenged with a ‘short window between receiving orders and shipping the tools or parts’ this blog post details how one AutoForm customer achieved amazing results in die design: with 70% of their tools and parts production declared production-ready in just one tryout loop.
Saitama Shatai Co. Ltd. core business is the production of tools and parts for both cars and motorbikes prototypes. With its high variety of part typology, the company mainly produces fuel tanks, small and medium body parts as well as large doors.
Because of the increasing demand for thin-lightweight parts, the company is ‘forced’ to produce parts in Ultra-HSS and AHSS steels: “we commonly use steel with tensile strength that varies from 590MPa to 780MPa but we also have parts made with AHSS with tensile strength from 980 up to 1200MPa” says Mr. Kitani, manager at Saitama Shatai’s headquarters.
The use of such materials naturally brings issues in terms of springback magnitude and relative tool compensation. When press-forming high/ultra-high strength steels the springback of the part is higher than when forming mild steels, since they deal with higher stress values to produce the same strain.
Figure 1 – Qualitative Tensile Test Diagram
Qualitative depiction for why springback is higher in HHS compared
to mild steel when total deformation applied to both specimen is the same.
Higher springback values make the forming process more complicated since firstly it must be reduced to values that can actually be compensated. What makes the entire process more difficult is the time factor involved: yet effective and successful tool compensation has been achieved quickly at Saitama in line with their timeframe.
“The complex sheet metal forming process starts day zero, on receiving order. Different tasks are involved: tool engineering, tool design, molding, tool machining, tool tryout and production; press-formed steel sheets are measured and checked to ensure dimensional accuracy. During “peak” periods a number of different parts must be produced concurrently. If tool design is delayed the knock-on effect would be disruptive. Therefore reducing the working hours per part / process is extremely valuable” Mr. Kitani said.
Previously at Saitama Shatai the tool geometry was compensated manually directly during tryout. First CAD was used to generate the tool surfaces and through an iterative virtual process was validated (final result would show no splits. Wrinkles etc.. and parts within dimensions tolerance). Once in Tryout, part springback was estimated by long-experienced and particular skilled engineers and the tool geometry was modified accordingly. It really took several loops and consequently long time to finish the tryout of the real tool.
It worked this way until the company introduced the use of AutoForm-Compensatorplus in the tool engineering process.
Group Leader in the Department of Production, Mr. Yasutaka Kumamoto said ‘With increasing use of high tensile steel sheets, and with growing requests from customers to create parts with ever increasingly complex geometries, it was no longer effective to apply the experience and know-how drawn from the “rather-easy-to-form” mild steels. Besides, we have also seen an increase in requests to have even higher accuracy, such as ± 0.5mm from the first lot of the assembly. It has become necessary to have the springback compensation achieved at a far shorter time and with far more accuracy.’
Fast forwards to today; now CAD is used to create the tool model, where AutoForm is next used to run the simulation, calculate the springback and then modify the initial “nominal” tool geometry accordingly to compensate the springback effect. In this way, the company has drastically reduced the man-hours previously required for such tasks.
Mr. Kumamoto recalls that ‘We first had the evaluation software of AutoForm-Compensatorplus for three months, starting in June 2015. What we accomplished during this “3-month trial” period went far beyond our expectations, and so we decided to officially adopt the software in September 2015. Currently, 1 license has been introduced to the headquarter plant in Kawagoe, and it is used by multiple engineers who are in charge of the tryout.’
Nailing it With One Tryout? It Can Be Done.
Daring and most interesting of all; Saitama Shatai has been successful in achieving what they term the ‘one-time tryout,’ meaning – thanks to this solution they achieve parts on the first stamping attempt, totally avoiding the tryout loop.
It’s all done by having data exported from AutoForm-Compensatorplus directly applied for the NC machining to create the tool, so reworking CAD surfaces is not necessary. With this process in place approximately 70% of tools produce parts, made from AHSS, within the tolerance of compensation and therefore they are sent directly to production. The implementation of this software module in the engineering process brings significant reduction in man-hours.
‘About 70% of the tools created for a prototype part are made with our ‘one time tryout’. Yet consider that it is difficult to compensate aluminum, as well as parts that have a lot of flat areas, which account for some failures with our ‘one-time tryout’. The other 30% of the tools requires handwork adjustment (tryout loops). Achieving “one-time tryout” means that we no longer have to re-mill the tool, and even with some of them, we could even cut about 4 working days (32 hours) into the tooling’ stated Mr. Kumamoto.
So how are they doing this? Mr Kumamoto answers ‘On site, the simulation result from AutoForm-Compensatorplus is often used to recreate the surface with 3D CAD, and the surface data is then used for the processing. Our distinct way of using the software is that what is compensated with AutoForm-Compensatorplus is exported as the data for milling the tool. Then the data is transferred to the NC machining to directly process the tool. Such usage is unique to our company, since we deal with a variety of trial products in small batches. This is indeed the case whereby the power of AutoForm-Compensatorplus is fully utilized.’
Great job Saitama Shatai. The AutoForm team congratulates you!