Indexable Drilling: An Interesting Alternative
This post looks a bit deeper into a high volume CNC lathe operation for a production level screw machine parts manufacturer in Western New York. Our focus today will be on indexable drills. We will briefly discuss what these tools are, how they’re different from regular solid body drills, and how they can make a difference in productivity.
Application Overview: Why Indexable Drilling?
The part is an automotive part. It is a coupling and the material is a mild steel, a “medium carbon” steel. This post will not give exact part dimensions or exact depths of cuts. But we can assume that this coupling is 1.5” long and 1.5” diameter and requires a through hole of 27mm. The production volume is 30,000 pieces per year.
Given the size parameters and the high volume, the parts manufacturer runs this job on a CNC lathe. This post talks about the drilling process, but the complete operation is (1) drilling and (2) cut off; it is a production feed part. Given the existing machine set ups, in this operation the part is rotating and the cutting tool remains stationary.
The Cutting Tool Specialist looked at the material, the operation, the machine tool availability, and what was required of the finished part. The first thing to note is that this is a 27mm hole and is a through hole just over an inch diameter. The part is 1.5” long so the drill should be 2xD. 2xD means that this is a tool designed to drill at a depth of cut about two times the width of the hole. Ex: drilling a hole 0.5” with a depth of 2.0” would be 4xD.
The pain point for the parts manufacturer is cycle time. Some quick math:
- If we need to manufacture 30,000 parts a year, and we have <50 days of available machine time on the production schedule
- We need to plan on 700 parts per day, on average
- 700 parts per day translates to about 100 parts per hour, on average
- 100 parts per hour means we need a cycle time of less than a minute
- Target cycle time was 0:35 (35 seconds)
- Keep in mind, the cycle time also needs to account for the cut-off operation in addition to the drilling operation
Both the Cutting Tool Specialist and the parts manufacturer agreed that the actual removal rate of material in 35 seconds is quite aggressive. But doable. We just needed the right tool.
Indexable Drilling: Flexibility + Range of Options
The cutting tool being used is a Pramet series 802 indexable drill, 2xD. When we discuss 802 series drills in CNC applications, keep in mind that the drill can be used as a rotary or stationary tool. So, the tool will work for us in that regard. Remember, 2xD means that this is a tool designed to drill at a depth of cut about two times the width of the hole.
Now would be a good time to actually see an indexable drill in action. This video does a good job illustrating the cutting tool properties and applications.
The hole diameter is 27mm and indexable drills (802 series drills) offer some flexibility in this regard. The drills are single edge and may also work off the outside axis. The drilled hole dimension can be adjusted to within +.008″ to -.020″ using an off centered tool. Learn more about this flexibility here. You can also find a technical breakdown sheet of drill bodies and insert geometries here.
- Every square drilling insert offers 4 cutting edges, letting you achieve maximum usage from each piece.
- Internal inserts, which must cut in the middle of the drill at zero cutting speeds, are made of durable grades with a very strong chipbreaker.
- External inserts are wear-resistant and enable the user to increase cutting speeds at the periphery of the tool, up to double the speed of comparable solid drills.
The right choice of the peripheral insert grade ensures high productivity and long life of the tool. A Horizon Solutions Cutting Tool Specialist can help you make the right choice.
Cutting Tools that Outperform Expectations!
Our team tested the proposed cutting tool. It performed very well and exceeded the user expectations. Remember how we did a quick analysis of cycle time? The initial target was less than 35 seconds. This system is drilling the hole in 6 seconds, helping the parts manufacturer exceed their desired cycle time. This post will not give exact machining parameters, but there is a speed and feed rate at 2100 RPM that hit a perfect point of material removal for this application. The tool being used could actually be run even faster, up to 2800 RPM. Everyone from the machine operator to production manager was impressed with the efficiency and reliability of the operation.
In addition to the previously mentioned pain point of cycle time, an additional pain point raised by the user was that previous competitive tooling configurations resulted in breaking and chipping of inserts. The 802 drills provide stability and reliability under unstable conditions or interrupted cut. There is less breaking and chipping of inserts which results in an overall holistic improvement in cycle time. There is less machine down time.
Overall, this is a nice win. The new cutting tools are producing parts quicker and of a higher quality than the previous system.
Not only that, but the new cutting tool components are actually less expensive piece by piece that the previous system as well.
Success is when we deliver a cutting tool solution that outperforms your expectations.
Have you tried indexable drills? How were you using them – did you rotate the cutting tool or did you rotate the workpiece? What types of grades or chipbreakers have you had success with?