A good read for some who have not seen it

http://www.ipnews.com/archives/general_editorials/oct05/AmTTech.htm

Daewoo’s Puma 2500 LSY Opens Door for Productive In-House Manufacturing

Airgun makers are not large companies, and AirForce Airguns makes America’s only line of precision adult air rifles with a minimum amount of staff and equipment. Owner John McCaslin designed his rifles to be easy to produce, and now, with the help of Daewoo’s new Puma 2500 LSY CNC lathe, he can make all of his machined parts in-house.

The Fort Worth manufacturer is candid in his praise for his company’s latest mill/turn lathe. “Our frames are 22″ long and are complex parts to make. Though made from an aluminum extrusion, every function of the gun is based on the frame and it must be right. We used to outsource frame production to a local company that made them on vertical milling centers. They had to be re-fixtured three times to finish all six sides, whereas my new Puma 2500 needs to be fixtured just once,” said Mr. McCaslin.

John McCaslin, owner of AirForce Airguns shows the air gun manufactured on the new Daewoo Puma 2500 LSY.

“When I began talks with my Doosan – Daewoo salesman, he suggested I look at a small CNC mill with a rotary indexer, because I wanted to feed the extrusion-like bar stock and have complete parts drop onto a conveyor. We decided a Puma 2500 LSY could do the job with some minor sheet metal work to eject the 22″ long completed part. With a modified SMW barfeeder we can feed the odd shaped extrusion through the machine’s 3″ spindle hole and completely mill it out with live tooling on the turret. The part is finished completely except for minor deburr and can be ejected onto the parts conveyor through a lengthened ejection port with a modified parts catcher. Though each gun frame takes several minutes to complete, there is no human intervention during the process. This saves us time and improves accuracy. After running the frames, we change out the machine to run the lathe parts that make up most of the machined components for the guns.”

“By having the machine in our plant,” Mr. McCaslin continued, “we can do things in economical batch sizes, rather than being forced to meet minimum order quantities. Also, we are no longer held hostage to the production schedules and quality standards of our former vendors. If we need 500 of something right now, we simply set the machine up and make it. Since the machine automatically feeds in material and ejects completed parts, the operator can do other things while occasionally checking tolerances of the parts and loading the bar magazine. We feel that we now have a machine working for us, instead of the feeling that we are working for the machine because of the need to have an operator’s constant attention.”

“We are still finding things for the Daewoo Puma 2500 LSY to do, since we have this powerful manufacturing capability we can design new components and accessories around its specific capabilities,” Mr. Caslin said.

Jack Butts, president of AmTTech had the following to say: “When John McCaslin of AirForce Airguns first came to us with this project he had already spoken to several area machine tool dealers and builders as well. From visiting with John, I assumed everyone (including AmTTech) who had reviewed his requirements regarding the manufacture of the AirForce Airguns’ frames had substantially made the same recommendations for a suitable part process. This process entailed the use of rotary indexer supplied with a horizontal tombstone to catch multiple sides of this extrusion in one fixturing on a small vertical machining center.”

“John’s vision was to make this an unmanned or lights-out operation if at all possible,” Mr. Butts continued. “Taking into account McCaslin’s desire for automation we then weighed the option of interfacing a pick and place robot to a Daewoo 3016 VMC. His annual lot requirements for frames were small enough that it made it virtually impossible to justify this expense. In addition to the frame, there are a host of small turned parts in this precision air rifle, which necessitated the need for a CNC turning center equipped with a parts catcher and barfeed. A few of these components have the occasional cross hole which might suggest the need for a 3-axis (mill/drill) option on the lathe, but once again the justification was weak considering the small lot sizes and the need for a VMC had already been established.”

McCaslin’s idea was to move up a couple of frame sizes on the selection of a CNC turning center in order to gain enough bar capacity to potentially barfeed or pull the rifles extruded frame. With the addition of Y axis and a Sub Spindle John felt he could run the frame complete on a turning center using the barfeed to address his wish for automation. To meet this specification AmTTech proposed Daewoo’s Puma 2500 LSY, a 30 HP, 3″ bar capacity, Y-axis turning center. “To us at AmTTech this concept seemed quite clever, however many obstacles needed to be addressed to make this a viable manufacturing solution,” said Mr. Butts. “First of all, this frame has no turned diameters. This in itself was not an obstacle but it is a little unusual that we would be using the lathe spindles for rotary indexing only.”

The challenges here were as follows: barfeeding (with a magazine type feed) an irregular shaped extrusion, offsetting the extrusion in the machine spindle to facilitate chucking on the barrel diameter and discharging a 22″ long part via parts catcher/conveyor which was designed for a maximum part length of only 5″.

AmTTech began addressing these issues by sending sample extrusions to every viable supplier of barfeeds distributed in the United States. SMW Systems was willing to make the required modifications to their standard Spacesaver 2100 Servo Barfeed and guarantee successful loading of this odd shaped extrusion. Additionally, Trusty-Cook was selected as the supplier for the spindle liner due to the ease of handling the irregular shaped part with their design of molded polyurethane spindle liners. Here the part was offset to position the rifle barrel on centerline with the machine spindle. The only modification needed was the addition of a wear plate to the end of the liner in order to eliminate premature liner wear on the initial bar load. Royal Products was selected to supply the dead length collet chucks and blank collet pads, which would be machined via EDM to accommodate the shape.

“In my eyes the biggest problem we faced at this point was unloading the part with a modified parts catcher,” said Mr. Butts. “In order to eliminate expense McCaslin agreed to modify the parts catcher arm and bucket himself if AmTTech would facilitate the required sheet metal modifications to the machine enclosure and aid in perfecting the system. This was agreeable to all.”

“From AmTTech’s viewpoint this process seemed viable even though we all felt a small CNC turning center and VMC might be a better approach, especially for first time CNC user with a limited amount of machining and programming experience. To aid AirForce Air Guns with the implementation of this system we contractually agreed to 100 hours of additional engineering and applications support. This time was spent by AmTTech’s applications specialist in training AirForce Airguns’ employees and also programming and perfecting the machining process for the Airgun’s frame as well as over 30 additional turned components.”

Butts further stated, “I must admit I was a little concerned with selling a first time user a multitasking machining concept. It has, however been quite successful due primarily to John McCaslin’s ingenuity and determination. My feeling is that AirForce Airguns is a company on the move with a really cool product. Everyone should take a look at this Airgun.”