Table For Four...Minivan Table
Service Detail from 3 Dimensional Services
New seating plan option for the Chrysler Town & Country Minivan makes timely production launch thanks in part to diverse rapid prototyping disciplines
Recently it became apparent that, while some automakers were abandoning the minivan platform, Chrysler was energizing its Chrysler Town & Country series of versatile vehicles with sweeping new exterior designs for the new model year. And, upon opening the van's doors, it is just as clear that new interiors and seating arrangements have been introduced, to invigorate the minivans appeal to a broader market. With the launch of the Swivel N Go interior, consisting of two captain-style mid-row seats that can swivel to backward facing positions and a fold away table between these seats and the third row seats, the Town & Country becomes an ideal day traveler for visiting roadside parks and scenic overlooks, tailgating at sporting events and for relaxing breaks on longer trips.
Ah. Comfortable. Relaxing. Calm-except, in most cases, for the teams of designers, engineers and product technicians putting together the various new components, making sure they work right and look good, all in time for the spotlight to shine at the auto show. Plus, at the same time, verify that the components can be mass produced in an efficient, cost-effective meeting all quality and safety specifications.
For the table portion of the Town & Country interior seating project, Chrysler turned to Progressive Moulded Products, headquartered in Concord, Ontario, specialists in injection molding of plastic components, as its Tier One supplier. Progressive quickly had tooled and produced the 2-1/2 x 2 foot polypropylene table top surface and a separate, underside piece for strengthening the table. They also produced a pull handle and latch that would be later assembled between the two table surfaces and used for securing/releasing the table to its support post. Progressive had developed a concept for the remaining table pieces, and looked for assistance in design, engineering and production.
For assistance, Progressive called upon the 3-Dimensional Services Group, a Rochester Hills, MI, based rapid prototyping firm that specialize in the design, engineering and analysis, in-house tool construction, and complete build of first off parts and low to medium volume production runs. Their use of advanced process methods and manufacturing technologies means prototype parts are typically provided up to 70% faster than conventional prototype shops are able to offer.
With deadlines approaching for completing the auto show displays, 3-Dimensional Services began its work on the remaining nine different parts required to finalize the table-to-van installation, plus the assembly process join the table top components.
According to Scott Duffie, sales engineer at 3-Dimensional, the better part of three weeks during the initial stages of the process were needed to analyze and fine tune designs, and review changes with the client. "We had three areas of concern we had to verify," says Duffie, "one was meeting all vehicle safety specifications in that the table had to be strong, sturdy and secure. Two that the table would be easy to setup and take down. And three, that all of the table components were designed for manufacturing intent, that is, high volume production methods could be employed to manufacture the parts efficiently and with the desired quality output."
"Once these initial engineering stages were finalized, the actual working time for us to produce the parts was just two weeks," he continues. "This included a cast part, a stamped bracket, two springs, the tubular support post and reinforcing insert, a machined locking release button and injection molded cap, and even two nylon and Velcro straps for secure storage. This project tested the diversity of our services-requiring stamping processes and fast die making, mold and pattern making, laser cutting, machining, vibration welding, and our own injection molding capabilities, not to mention the engineering team at the outset. We did, however, complete all of the items for the original two sets of tables in time for the show, and have since processed an additional 58 sets of components as S-1 build parts that will be used in field testing."
To illustrate the variety of parts and process used for the Town & Country project, Duffie provides the following descriptions of the components, starting at the bottom. First, a bracket that fits on the underside of the floor panel, providing extra strength to the mounting system. This bracket is a stamped piece of steel, having approximately five draws and contours to nest with the shape of the floor panel, plus six laser cut holes for bolt mounting of the table from the interior of the van. This bracket was E-Coated for corrosion protection.
To quickly make this part, 3-Dimensional Services uses what they call E-Z Cut aluminum alloy for the dies. "We've tested various aluminum alloys and have found this one holds up well for stamping short runs," Duffie remarks. "The speeds at which the aluminum can be cut, however, help reduce machining times by 50% or more as compared to some tool steels. Coupled with today's high speed CNC machining centers, the aluminum tooling allows us to turn out tools, and stamped parts, faster than ever before."
The next piece of the table was the cast aluminum mounting base. This piece is bolted through the floor panel and attached to the previously described bracket and has a center bore to insert and lock the support post of the table. To complete this part, 3-Dimensional Services used a plaster mold casting process, utilizing a model of the part to first make a negative part, from that negative a rubber positive was formed, which in turn was used to make the final plaster mold. A foundry poured the aluminum casting, then it was back to 3-Dimensional for final machining of holes, central bore and taper, and holes for inserting locking pins.
The next piece up the "table" was the support post, produced from aluminum tubing. The 24" long, 2" diameter support post required it be cut to length, a slight tapering of the OD at one end for easy insertion to the table top, drilled holes for engaging the locking button at the bottom and the upper latch plunger, and a slight extruded outward tapering at the lower end to help with assembly of the steel sleeve. Both the support post and the aluminum casting were mechanically relieved to provide a brushed surface appearance, and then given a clear protective coating to prevent tarnish or oxidation.
The steel sleeve is approximately 3" long and made so that half of its length is press fit inside the support post, the other portion slides into the bore of the cast mounting base. The sleeve has three laser cut slots or channels that align with three pins assembled in the base...when engaged and the post is twisted, the upward angles of the slots pull the post downward for stability and rigidity.
The next feature of the table is the locking button, consisting of two pieces welded together and a decorative cap. The locking button, much like those found in patio umbrellas, is positioned in the support post at the bottom end, and once the post is secured in its mounting by the two lock pins, the button springs out through a hole in the post and into a corresponding hole in the casting, thus preventing the post from turning. The button consists of a small, bull-rounded machined piece, welded to a stamped large 'M' like spring clip, produced by 3-Dimensional. The injection molded plastic cap is assembled over the button. The surfaces of the spring clip, because they would be in contact with the interior metal surface of the support post, were given a 'plastisol' dip, a rubber like coating that would prevent vibration and noise.
At the top of the support post sits the table surface...3-Dimensional Services, though they have the capability to produce coiled springs, found a stock spring that could be used for the top handle latch mechanism. So, they only had to assemble the grip handle, return spring and latch between the two table surfaces, then apply their vibration welding process where high speed motion creates friction and heat, that results in a melting and, under pressure, a joining of the two abutting surfaces.
To disassemble the table, one needs only pull the handle to unlatch the table surface from the support post, and then press the lock button at the bottom and twist out the post to disengage it from the lock pins and from its mounting base. To safely store the table and post, the option comes with two nylon straps riveted to the table's underside-Velcro fastening secures the post to table. Even these nylon straps were made to order by 3-Dimensional, as they were cut and sealed off to prevent fraying as well as having the Velcro materials attached.
"The assembly of the headlamps was an integral part of the prototype process," UPS' Kelly says, "as various options are tried and all of the parameters to efficient assembly are established and documented. These parameters smooth the transition to production. As a matter of fact, we also assembled the pre-production pilot run off as the production supplier geared up his tooling and equipment, thus verifying the assembly process."
"To achieve the level of strength and stability required to meet vehicle safety standards," reports Mr. Duffie, "we held tolerances of the various mechanical features and mating components to + 0.004" so the accumulative effect would be negligible to the overall assembly. But just as critical to the success of this project, were the final appearance and the timing. All three-quality, appearance and delivery-came together to assure the production launch of the new Town & Country was smooth and successful."
And, from Chrysler's point of view? "3-Dimensional Services supplied key engineering and prototyping services during the development of the all new 2008 Chrysler Minivan Removable Table," notes Tom Modick, engineering supervisor at Chrysler Corporation. "Their customer driven approach, high-tech capabilities, and quick turn-around times, allowed us to meet and exceed our objectives."
The 3-Dimensional Services Group consisting of 3-Dimensional Services, Urgent Plastic Services and Urgent Design & Manufacturing, provide prototype services for virtually all process disciplines including laser cutting and welding, machining, stamping, hydroforming and tube bending, injection molding, vibration welding, castings, RIM tooling, rapid modeling, high definition stamping of exotic alloys, and assembly.