CNC router sends production 'through the roof'

Use of a 4-axis CNC router dramatically increases gun stock production - it has more than tripled - since replacing a manual pantograph machine with a 4-axis CNC router.

Made of high-quality hardwoods, Ironwood Designs' products are purchased by individual gun owners, gun dealers and firearms manufacturers to replace the inexpensive plastic or softwood stocks of many imported military guns such as the FN-FAL and the AK-47.

Ironwood Designs also sells a four-piece wooden set that includes the butt stock, pistol grip and an upper and lower hand guard.

* Production bottleneck - as one of the few companies making replacement gun stocks for these weapons, Ironwood Designs has a thriving business.

According to Matt Shuster, Ironwood Designs president, a bottleneck in the production process needed to be eliminated before further growth could occur.

For the first step in making a gun stock, Ironwood Designs used a Zuckerman copy lathe to automatically carve a wood block into the desired 3D profile.

The machine cut the block from an over-sized plastics pattern of the gun stock.

The pattern and the wood block would spin in tandem while the machine's cutter carriage and a sander carriage traversed the block, delivering a clean finished piece in 1 to 3 min.

This part of the production process, which was handled by an Ironwood Designs employee, needed no improvement.

The next step was the problem.

To make the gun stock, Ironwood Designs uses a Zuckerman copy lathe to automatically carve a wood block into the desired 3D profile.

Next, parts are placed on the Techno 4-axis CNC router, which positions and cuts four butt stocks at a time in 3 min.

After parts were cut on the Zuckerman machine, they needed further cutting to carve out the inlets where the stock fits into the rifle and areas where parts, such as the swivel and the butt plate, are later attached to the stock.

After running the parts through the copy lathe, which was located in the company's shop, Shuster took them to his home workshop, where he used a manual pantograph to make these additional cuts.

The pantograph had four spindles so four parts were cut at once.

According to Shuster, it was a back-breaking process that was both slow and inaccurate.

The machine cut with straight flute bits.

So although some parts could be done with one pass of the bit, others required three or four bit changes.

It took an average of 15 min to complete the carving process for four butt stocks.

Error was the other problem.

Using a pantograph involves manually following a pattern with a stylus.

If Shuster's hand slipped, four parts were damaged at once.

He estimates that he had a loss of between 10 and 15% due to carving errors.

Also, as the pattern eventually wore out, edges of the cuts were less sharp, giving them what Shuster calls a 'fuzzy' look.

Templates would also get kinks and other irregularities, all of which were transferred to the finished product.

* Accuracy and speed - Shuster says a desire for a faster, more accurate carving process led him to look at other options, including CNC machinery.

After visiting a woodworking trade show, Shuster purchased a Techno four-axis machine with a 5ft by 6ft table, big enough to handle even the longest butt stocks.

According to Shuster, the Techno CNC router is capable of carving the cutouts in about one-fifth the time it took to do them by hand.

The machine also automatically repositions a part and cuts all sides in one operation, enabling it to run unattended.

Shuster said he required a machine with 4-axis capability because cuts are needed on all sides.

A four-axis machine has dual spindles, one that holds the part and one that holds the cutter.

The cutting program directs the X, Y and Z motions of the cutter as well as the positioning of the part.

After one side has been cut, the part can be rotated, for example, to allow access to the other side.

"With a four-axis machine, repositioning happens automatically, so the cutting goes faster and it's completely unattended," Shuster said.

Using the 4-axis machine, it now takes Ironwood Designs only 3 min to cut four butt stocks, compared to 15 min needed with the pantograph.

The CNC router is located in the shop near the Zuckerman copy lathe; one employee runs both machines.

"We now produce 100 pieces in four hours.

Previously that took us two days," Shuster said.

The quality of the cuts is also improved.

"There is less tearing of the wood because the spindle is spinning at 18,000 rev/min," said Shuster.

"Also, if a cut is off by 0.010in, I can modify the program and easily fix it." He continued: "Now we can produce factory-quality pieces.

You can not distinguish our stocks from the original military production except that we use a higher grade of wood." * New business Opportunities - the combination of higher-quality parts and faster production has led to an increase in business for the company.

After finishing a large, 212 year contract for one gun manufacturer, Shuster has now programmed the CNC machine for a new product, replacement stocks for the Belgian FN-FAL rifle.

Designed in the 1950s, this rifle had been out of production for years.

But surplus versions are being imported and new ones are being manufactured in the United States from old military specifications.

Ironwood Designs now offers replacement parts to manufacturers, who will resell them as accessories.

The parts are also sold to smaller gunsmiths who build FN-FALs for customers, as well as to private owners of the rifle who wish to retrofit it with a nicer wooden stock.

In addition to this new product, for which Shuster anticipates a big demand, Shuster says he plans to use the CNC machine for other projects.

For example, plans call for offering replacement stocks for common guns, such as hunting rifles, which will be easier to install than those currently available.

Most replacement stocks, he explains, come semi-finished, i e, the sides are carved but not sanded, so tool marks are visible.

This requires the gun owner to fit the rifle to the stock, a process than can take hours of filing.

Shuster said he plans to cut these stocks on the CNC machine for a level of accuracy that has been previously unavailable.

"My kits will be innovative because they give you drop-in fit," he said.

"We no longer advertise and yet our volume keeps increasing," said Shuster.

"With the four-axis CNC machine, we're now able to produce replacement stocks for anyone who wants one.".

Back to top