Without stock-feeding capabilities, CNC lathes cannot automate part production. The solution is bar pullers, which advance parts along the production line. The way it works is simple. The puller presses onto the remaining stock after the part is finished and a powered chuck moves it along. The chuck is then secured, and the bar puller removed from the stock, which can be turned. Rinse, repeat.
Trouble is, bar pullers are aftermarket parts, and the most well-engineered parts are expensive. You’re talking over $1,000 for an aluminium or tool steel bar puller, and that’s for an off-the-shelf part. If you need a custom job, double that figure. Also, off-the-shelf parts have limited range, by which we mean they cannot accept every stock. It means one puller may not be suitable for the next run.
Fabricating custom bar pullers
bmi CAD Services, an electromechanical job shop, uses CNC lathes to manufacture parts and bar pullers to automate their production line. However, the high cost of bar pullers made them look elsewhere for a solution to automating the production line, which is when they came across 3D printing.
They now use custom, 3D printed bar pullers to automate stock feeding into their CNC lathes, unlocking higher productivity.
Whereas off-the-shelf bar pullers would cost the company over $1,000, they 3D print theirs for around $13 a time. This is a huge saving of 195%, with a difference of $987 and that’s for a part that costs $1,000. Most bar pullers cost even more.
Incredible strength and durability
To fabricate their bar pullers, bmi CAD Services use the Markforged Mark Two 3D printer, which is capable of 3D printing Onyx (a nylon and carbon fibre blend), Carbon Fibre, Fibreglass, Nylon, Kevlar and High Temp Fibreglass. Bmi use Onyx and continuous Fiberglass filament to reinforce parts even more, which results in bar pullers which match or exceed the strength of solid tool steel parts.
A non-marring Onyx surface prevents damage to stock material, while Fiberglass reinforcement adds affordable high strength and stiffness. This is the perfect combination for strength, durability and cost.
Perhaps the biggest benefit to 3D printing bmi has witnessed is the flexibility it offers them to cater for unique stock. They can 3D print a new bar puller in around 8-hours, which means a new production run can be fulfilled the next day. The team can also prototype parts quickly, sending CAD designs to print within just a few days. This enables them to design bar pullers specifically for stock requirements and meet customer’s needs.
With 3D printing, bmi has dramatically improved the productivity of their CNC lathes and unlocked huge cost savings to boot.
3D Printer: Mark Two (Enterprise).