« iepriekšējāTurpināt »
The engineering computation sys- Use of Computers in
clay is also made before the end of this tem consists of eight large mainframes CAD/CAM/CAE
year. A cycle typically takes 40 days, an and four supercomputers at head
impossible schedule to maintain if clay quarters plus other mainframes in the Toyota has major activities in this were used as the stylists' working medium United States and at the various plants. area. I was shown demonstrations of and as the source of input data for Recently a transputer system was added body styling CAD, stamping die design, computer models. to do color renderings of car bodies formability analysis of sheet metal parts, Body styling by computer dates to (see below). The administrative com- CAM of stamping dies, engineering 1981 (Figure 6, top), with a complete puting system also has seven mainframes analysis of mechanical parts, process end-to-end system working by 1986 or
. As at Nissan, computation supports planning of machining, and offline robot so (Ref 15). Major efforts were made to most aspects of vehicle design, includ- programming. I did not see anything overcome well-known difficulties with ing CAD/CAM of body parts, exterior comparable to the assembleability designing and joining surface patches and interior design (interior was not as analysis that Nissan showed me, how- described by earlier theories. Methods well developed at Nissan), CAD/CAM
of surface generation and curvature of mechanical parts like suspension and
evaluation were devised that followed power train, structural and aerodynamic Body Styling
the stylists' methods. Control of suranalysis, laboratory automation, stamp
face curvature, its continuity, and its ing die manufacture, NC programming, The objectives of computerized body regularity or uniformity were found to and machining process planning. Toyota styling are stated as
be the most important factors. Primilast made a clay model as primary design
tive shadowing and rendering of highdata input between 3 and 5 years ago. A (1) making higher quality surfaces light lines were possible in 1983. In the good summary of Toyota's computa
last year, extremely realistic color rentional design work is in Reference 14. (2) reducing the required manpower derings have become possible (Ref 16). Toyota makes about three times as and leadtime
The color renderings are computed many cars per year as does Nissan. About
on a parallel computer with 256 transfive new models, plus many minor (3) integrating CAD and CAM puter elements. Computation takes into redesigns, are in the design system at
account such factors as color, type of any time. There are about 200 stylists Higher quality surfaces are smoother, paint, weather conditions, and sun angle and 800 body engineers. No data are the different sections of the body blend at various geographic locations. A new available on how many mechanical, together better, and the final metal caror viewangle can be computed in 30 production, and tooling engineers there realization fits together better. Reduc- minutes, a new color for the same view are. It appears, however, that Toyota tion of leadtime, interestingly, is stated angle in 5 minutes. Among the features has more in-house people per car design as an explicit objective, something Nissan available that imitates the stylists' old project than Nissan has.
would not do. Integration of CAD and methods is representation of reflecNissan was a little better than Toyota CAM is a longstanding goal of every tions from several fluorescent tube at presenting the full picture and giving car maker. Toyota appears to be sev- overhead lights. the flavor and comprehensiveness of eral years ahead of other companies in The styling and rendering system is its long range plans. However, I'm sure realizing these goals.
now used not only to design exteriors that Toyota is ahead in many areas The body styling activity takes the but interiors as well. I was shown photos technically. The scientific depth of its first year of the normal 4-year car design of rough NC-milled clays of dashboards work in surface representations and cycle. During this year, three or four and center consoles (ash tray, shift lever, data structures for holding and manip- complete cycles of styling and evalua- etc.). The design studio has 65 32-inch ulating design data are two of many tion may occur. A cycle consists of diagonal measure flat screen cathode examples. The effort reminds one of making three-view sketches, convert- ray tube (CRT) displays (2000x2000 Nippondenso's commitment to manu- ing them to 3D models and refining pixels) for the purpose of designing facturing equipment excellence as part these, and making a one-fifth scale clay and modifying these surfaces. They run of manufacturing excellence: it is some- model by NC machining from the off a UNISYS 2200 mainframe. thing you cannot achieve by buying computer data. At least one full size things from vendors.
Trim Line :
Press Die Data
Surlace Modellng High-light Lino
Automatic Calculation of Culler Location Complex Surfaces Clearance for the
Another Variation of Cutting
Profile Character Uno
30 Measuring Machine
Figure 6. Body CAD/CAM.
The method of converting stylists' This system is well described in but is delayed because many of the sketches to 3D model data demonstrates Reference 17 and is credited with component analyses are approximate. a widely felt problem, namely, that 3D shortening die design time by 50%, die Toyota obviously decided not to wait modelers are too hard to use. Toyota manufacturing by 30%, and die tryout until perfect analyses were available employs specially trained computer by 30%. A major point made by this and went ahead to tackle the problems technicians who convert the sketches paper is that the program does not use of integrating the existing tools into into a first model which the stylist and finite element method (FEM) for stress one system. This decision has put Toyota the technician correct together. The and formability analyses. Instead, rather on a higher plateau, since integration is technician interprets the shading in the basic analyses are used. These include a new learning opportunity. sketch to obtain an impression of the local elongation ratio, speed of deforintended shape, then produces that mation in local regions, shape change Process Planning for shape in a surface model. The stylist of grid lines, and other functions that Machining “Box-Type" can view the realistic renderings, an can be computed either from geometry Metal Parts orthographic line drawing, or a cross alone or from basic stress analysis. The section. Curves can be modified in ways goal was not a perfect system but one This system helps designers to choose very similar to those available in that would help designers find good the necessary machines and tools for Macintosh drawing programs, the most solutions using methods they could making complex parts. An example is a familiar being adjustment of endpoint understand and interact with. complex aluminum cylinder head with tangent vector lengths and orientations. Figures 7 and 8 contain a nice exam- pockets and holes for cam shafts, valves,
These technicians are obviously ple. Here the use of the mean section valve springs, and so on. It is assumed rather special people since they must length ratio is shown. Along a particu- that the part will be made on an existhave both an artistic sense and com- lar feature line, different segments are ing set of NC machines with a continuputer skills. They must also provide an defined (sections) and their length before
ous parts conveyor. Parts can circulate important part of the human interface and after forming is calculated. The on this conveyor and visit any machine between the stylists and the computer. maximum ratio before and after and in any sequence. Thus transportation
the rate of change of this ratio along capability does not limit process planDie Face Design and
the feature line are cross plotted. Data ning. Formability Analysis
of this type for 10 past designs were The part is divided up into regions
collected and correlated with the die in two ways: by type of feature (hole, Dies cannot be the same shape as tryout time for each. Excessive tryout flat) and direction of machining (front, the desired final metal part due to the times (over 900 hours) lie above the back, perpendicular, oblique). I believe
. I springback of the sheet metal and fric- diagonalline, providing designers with
diagonalline, providing designers with that the software finds the features itself, tion between it and the die face. It used rapid feedback on potential problems but I am not sure about this. The machinto take about 3 weeks to design a sim- months in advance. Another feature of ing system is divided into zones conple die but now with the computer this type of analysis is that the designers taining machines capable of dealing system it takes only 1 week. The func- can put in their own experience, giving with one or more feature types and tions supported include direct data them a feeling of ownership and confi- directions. transfer from the styling database, dence in the program and allowing data The software makes two types of addition of shape details for the final to be accumulated for future use or calculations: finding the right zone for part (lightening holes, folds from front training of new designers.
a group of features and planning the to back, locations for fasteners) and It is said that in some U.S. car cutting conditions for each feature. details to permit forming (flanges where companies methods like this cannot be When several zones are capable of the die grips the perimeter of the piece), used effectively because the stylists will making a feature set, the designer plus formability analyses. These analy- not modify their designs. In one com- chooses one. He does this apparently ses permit the die designer to predict pany, the stylists report to the chair- without any consideration of workload possible forming problems and redesign man of the board whereas the engi- in the zone from other parts. Each hole the stamping process (or occasionally neers report to the president. In another feature is classified by a group technolask the stylist to change the part) to company, a similar integrated body ogy technique using such characterisavoid them.
engineering system is being pursued tics as number of steps, tolerance on
diameter, need for threads and cham- The process plan for the valve cover shown. The problem is to program the fers, and so on. From these characteris
took 5 days versus a month before the robot to move the spray gun over the tics, the cutting time is estimated and system was used.
car's surface. In the past this has been compared with the cycle time capabil
done on the factory floor by human ity of the zone. The designer can alter Robot Offline Programming teachers who physically grasp the end the plan to correct cutting time imbal
of the robot and move it while a tape ances among machines or he can try a I was shown a color 3D wireframe recorder records the moves for later different zone. The system then calcu- simulation of robots spray painting car playback. The number of robots now lates the details of the plan such as bodies and parts. Both stationary parts has grown to the point where there are cutter path and tool number.
and continuously moving cars were not enough teachers.
Figure 8. Criteria of surface deflection in quarter panel by the mean section length ratio. The pillar base of a
quarter panel for a notch-back style car is in the shape of a saddle, which results in nonuniform forming. Therefore, surface deflection tends to occur at this portion. It is vital to check on the mean section length ratio as well as the spreading behavior of the punch contact area to avoid the surface deflection. The figure shows processed data of the formability evaluation according to mean section length ratio in 10 kinds of quarter panels of recent models. Maximum values of this ratio are plotted against gradient of this ratio and a line is drawn to separate the good designs from the bad ones according to the die tryout time.