Wednesday, February 22, 2017

Six Tips for Effective Optimized Roughing

By Jay Ball - Product Manager, Solid Carbide End Mills

Optimized roughing can be highly effective for machining part features such as pockets with challenging corners as well as any straight walls that require long axial depths of cuts. In fact, this strategy enables you to machine pockets three to four times faster than conventional methods while also dramatically extending the life of your tools. For example, under the right conditions, optimized roughing allows cutting tools to last up to 8 hours when machining titanium, as opposed to 30 minutes of tool life using conventional cutting methods.

However, achieving the best possible results with today’s optimized roughing strategy does require adhering to a few specific guidelines.

1. Adjust radial stepovers
An optimized roughing strategy typically employs multi-flute tools with anywhere from five to nine flutes. As the number of flutes increases, the size of the stepover must decrease to maintain surface finish at faster feed rates as well as accommodate for the decrease in chip spacing. If the stepover is too large, feed rates need to be lowered, which generates more heat due to the larger amount of metal removed in each pass. By decreasing the size of the stepover, you can use faster cutting speeds. More passes are necessary to remove the same amount of material, but the metal removal rates are still higher than at slower speeds due to the increased feed rates. This is the main reason optimized roughing makes tools last longer and heightens thermal stability.

2. Use strong, secure toolholders and fixturing
High-precision holders are crucial in optimized roughing. The holder needs similar specifications to those for hard milling, including less than 0.0004" run out. A precise holder ensures the accuracy of the process, whereas a less secure holder will cause undesirable levels of vibration at optimized roughing’s high feed rates. For the same reason, it’s important to use strong workholding fixtures as well.

3. Make sure your machine is capable of performing optimized roughing
Machine tools used for optimized roughing not only need to be able to achieve extremely high feed rates, but they also need to be able process thousands of lines of code in a matter of seconds. This requires advanced look-ahead capabilities and processing systems found in newer machine tools. Rigidity throughout the machine tool from the spindle bearings all the way through to the ball screws ensures smooth cutting, consistent tool life and unsurpassed part quality.

4. Choose a suitable programming method
It is nearly impossible to program an optimized roughing strategy manually. Many companies provide state-of-the-art programming software, but careful consideration must be made when choosing the right software or software add on. Not all software is created equal. For example, a programing software designed only for complex 3D high speed milling may not be able to perform the complex radial moves inside of tight corners to maintain a consistent angle of engagement, which is one of many keys to successful optimized roughing strategies.

5. Select the right depth of cut
We recommend a cutting depth of 2xD for optimized roughing and taking the full length of the cut in one pass. Smaller radial stepovers make such depths of the cut possible. A larger stepover would increase the amount of heat in the cut, which in-turn, will have a negative effect on tool life and performance, so rpm and feed rates must be reduced. However, a cut that is too deep, over 3xD for instance, creates cutting pressures greater than the tool can bear and causes deflection. Some manufactures add chip splitters in these cases to help reduce cutting pressure which, in-turn, reduces cutter deflection and also helps with chip control.

6. Follow recommended cutting parameters from tooling manufacturers
We frequently see customers encounter problems when they rely on the default cutting data recommendations from programming software suppliers instead of those provided by cutting tool suppliers. Tool manufacturers develop specific recommended cutting parameters after meticulous research and years of firsthand experience. They optimize cutting data for the tool’s design, specifications and for specific material groups.

Optimized roughing is an excellent strategy for achieving quality parts and extending tool life, but requires use of the right equipment and cutting parameters. If you are having problems implementing the approach or want to learn more about how to use the strategy to process a part, contact us.

About the Author
Jay has been with Seco for more than 10 years. As a key member of the product management team, he is responsible for Seco’s solid carbide end mill products in North America. He works closely with global R&D on new innovations to ensure they meet the necessary market requirements. He also provides technical support for high-speed hard milling and micro milling operations, including CAD file review, tooling selections and programming recommendations.

Wednesday, February 15, 2017

Three Reasons to Choose Reaming Over Boring

By Manfred Lenz, Product Manager - Drilling

Holemaking is one of the most common metalworking operations. It’s a critical operation that requires matching the right process with each job to maximize profitability. Boring is often considered the go-to method, but more manufacturers are finding reaming to be a better option in some high volume or high-cost part applications. Here’s why:

1.  Reaming is more consistent.
For some manufacturers – especially those working in exotic materials – consistency is everything. After they have performed numerous operations on an expensive part, the last thing they want is to ruin it on the very last process.

Boring tools and reamers have completely different designs. A boring head is an adjustable tool that consists of a cartridge with an insert. The advantage of this design is that it offers flexibility to use one tool in multiple operations or on different sized parts. This flexibility is often perceived to make the tool more economical, but because the inserts wear – which then leads to inconsistent holes sizes – this type of system can actually result in higher end costs.

A reamer, on the other hand, is a solid tool with a set dimension designed to deliver single digit RAs and micro finishes. It has a lead angle, a diameter, back taper, and a wiper area. On non-adjustable reamers, nothing on a reamer is moving, so it remains consistent and delivers the same hole size throughout the life of the tool. It also does not require replacement of inserts or adjusting by the operator to bring it back to size – which is subject to human error.

Reamers also have an extremely predictive tool life. A machinist using an air gauge to measure parts throughout the manufacturing process can see when it’s nearing time to change the tool and put in a new one before a problem arises. Then, once the reamer is changed, the new reamer will produce a good hole on the very first part.

One of our automotive customers that runs 15 million of the same part per year had been using a boring tool to produce large holes and was frustrated with inconsistency. Holes that were undersized required additional handling to finish bore or hone to size. Holes that were oversized got scrapped. By switching to a reamer, the customer experienced more consistency and eliminated the need for secondary operations and waste.

2.  Reaming reduces scrap.
Reducing scrap becomes especially important when working with very expensive materials. In the aerospace industry, for example, manufacturers often produce lower quantities of parts out of Inconel®, titanium and other high-cost materials. For these manufacturers, using a non-adjustable reaming tool and changing it out more frequently can provide consistent hole sizes throughout the life of the tool and significantly lower scrap ratios.

3.  Reaming can save time.
Unlike a finish boring head, which usually has just one tooth, a reamer will have up to 10 teeth depending on its size. Multiple teeth enable users to use much faster feed rates, and therefore increase productivity over machining with a single tooth tool.

Reaming is also a good choice for materials that cannot withstand high levels of heat and therefore require slower machining and longer cycle times. When it takes four or six times to machine a part out of an exotic as a normal piece of steel, the cost in the part increases exponentially. With that much time invested, it’s important to have a fool proof method in place when the final operation of finishing a hole rolls around.

The bottom line is that reaming offers the big advantage of consistency. Whether you are producing high volumes of parts or small batches of high cost parts, reaming can ensure the process stability and repeatability you need. So, if you have a boring operation that might make sense to switch to reaming, contact us. We can help you decide which process will make you most productive and profitable.

About the Author
Manfred has been with Seco for more than 16 years. In his current role as drilling product manager, he is responsible for every aspect of the company’s drilling products in North America. He works closely with global R&D on new innovations to ensure they meet the market’s tough manufacturing demands. Manfred also supports the Seco sales force by providing them with technical information and cost saving solutions that bring value to customers. In his spare time, he enjoys boating, bowling and golfing.