Thanks for this very clear and informative explanation. It has been decades since I worked in a factory. Back then the Bridgeport milling machines had terrible backlash. They would chatter or jump when using climb milling. Plus, if one was approaching the end of a cut, one wouldn’t know if the tool would grab at that point and pull the work past the past the desired end point. I almost exclusively used conventional milling and couldn’t understand why many people on YT now talk about using climb milling.

High balance end mills are designed to significantly increase performance in highly balanced machining centers capable of elevated RPMs and feed rates. These tools are precision balanced specifically for high velocity machining in aluminum (up to 33,000 RPM).

Facemilling

There are a few coating options available for Aluminum tooling, including the popular gold-colored ZrN (Zirconium Nitride) and the lesser known but highly effective TiB2 (Titanium Diboride). Uncoated tooling can also provide solid machining performance. However, the real key to high performance machining in Aluminum is knowing the proper flute count and helix angle required for your operation.

Traditionally, 2 flute end mills have been the preferred choice for Aluminum. However, 3 flute end mills have proven to be more successful in many finishing operations, and with the right parameters they can also work successfully as roughers. While much of the debate between 2 and 3 flute end mills for Aluminum boils down to personal preference, the operation, rigidity, and desired material removal rates can also have an effect on tool selection.

Hey there, first of all thank you so much for this post and honestly I was searching for the same information from last few days. Keep posting and keep sharing..

With more modern machines now compensating for backlash or utilize backlash eliminators, it has become a much easier strategy to adopt within shops. While we went over some reasons why climb milling is not an effective strategy above, here are some reasons why a machinist may want to explore climb milling:

Plainmilling

Thanks for the question! This would depend on the material grade, speeds and feeds, coolant used, etc., so it’s tough to give one exact temperature. However, the Helical Solutions Zplus coating is great in aluminum and can handle up to 1,110° F. Please give us a call at 866-543-5422 for more information, and one of our tech representatives can learn more about your application!

The helix angle of a tool is measured by the angle formed between the centerline of the tool and a straight line tangent along the cutting edge. Cutting tools for aluminum typically feature higher helix angles than standard end mills. Specialized helix angles for Aluminum are typically either 35°, 40°, or 45°. Variable helix tools are also available and make a great choice for reducing chatter and harmonics while also increasing material removal rates.

Great article. I’ve had to use conventional milling when for example, I’d have my thin unsupported part sticking out of work holding with the tool path contouring around the part (think milling end while cutting a part in a lathe) with the material flexing would cause snapping while climbing because it wants to take a large bite as opposed to ramping the cut in. But yeah, 95% or more is climbing.

If you’re telling me that an endmill with a high helix angle can be fed into the work faster because more cutting edges contact the work per revolution of the spindle, I would agree with you. But If I’m slotting or plunging, I want the chips out of the slot or hole, and I would think a low helix angle would accomplish that better.

In wrought aluminum alloys (i.e. 2024, 6061, 7075), a surface footage of 800-1500 SFM is recommended, with the same calculation being used to find a starting point for RPMs.

End mills for aluminum are often available in either 2 flute or 3 flute styles. With higher flute counts, it would become difficult to evacuate chips effectively at the high speeds at which you can run in aluminum. This is because aluminum alloys leave a large chip, and chip valleys become smaller with each additional flute on an end mill.

As machinists are always trying to find ways to increase efficiency and tool life, climb milling has gotten a lot of recent traction in the space. Less heat is generated within the tool, and friction is more easily mitigated. These two alone lead to longer tool life, allowing for more parts completed per tool, lowering a shops bottom line. Also, climb milling can lead to a better surface finish due to how the chips are formed at the cutting edge.

I like what you said about chip width working. I need a milling machine for some steel. I’ll have to get a dye-cutter that is discounted.

Advantagesanddisadvantages ofup milling and down milling

At its core, HEM is a roughing technique that utilizes a low Radial Depth of Cut (RDOC) and a high Axial Depth of Cut (ADOC) to take full advantage of the cutting edge of the tool. To learn more about how High Efficiency Milling can increase your efficiency, extend your tool life to keep costs down, and get greater performance for aluminum (and other materials), click here to download the HEM Guidebook.

I’m not certain I agree with you. All other factors being equal (spindle speed, motor torque, feed rate and force, etc.), the low helix angle tool would seem to apply more force lifting the chip. (I’m thinking about vectors, but I’ve been out of school for 44 years, and was never good on this stuff.) I don’t have access to a CNC machine. So it’s not like I can run any tests.

Aluminum is one of the most commonly machined materials, as most forms of the material feature excellent machinability, and is thus a commonly used material in manufacturing. Because of this, the competition for aluminum machining can be intense. Understanding the basics behind tool selection, running parameters, and advanced milling techniques for aluminum can help machinists earn a competitive advantage.

Great explanation of the differences between climb milling and conventional milling! I appreciate how you highlighted the advantages of climb milling, especially in reducing tool wear. It’s very informative for someone looking to refine their machining techniques. Thanks for sharing!

Thank you for the question Dustin! We would suggest conventional milling when your material has a rough surface, such as cast iron, or is anodized because when conventional milling your cut is scooping underneath the surface to remove your material making it easier on your tool. Also, you want to conventional mill when using a dovetail cutter that has a weak neck diameter because this will help relieve the pressure on the neck of your tool.

Up and down millingpdf

It depends on your perspective. Are they showing a view looking down at the work piece or looking up from the workpiece.

However, though Climb Milling is often the current preferred way to machine parts, there are times when Conventional Milling is the necessary milling style. One such example is if your machine does not counteract backlash. In this case, Conventional Milling should be implemented. Without accounting for backlash, breakage can occur due to the forces within the machine during tool engagement.

Unfortunately, there is no easy way to calculate the axial pull force on a tool during HEM roughing applications. We are currently working on a way to calculate this but there are a lot of different variables that go into this. If you are worried about any application you may be performing and a possible tool pull out, I am more than happy to get you in touch with one of our application engineers who have had countless years of experience and will be able to tell you if you will have any issues.

The article claims that a higher helix angle (45 degrees), makes for more aggressive cutting. If you look at the pictures you show of three endmills with 35, 40, and 45 degree helix’s, the one that would lift the chip further with each rotation of the cutter, is the tool with the 35 degree helix. So why wouldn’t that be considered a more aggressive attack on aluminum, and more suitable for high efficiency work?

I have a requirement from my customer that the swarf be less than 0.5 mm on my supplied components. What is the standard for measuring swarf?

Helical Solutions offers high balance tooling in standard 2 flute styles, as well as coolant-through 3 flute styles for reduced heat, enhanced chip evacuation, and increased material removal rates. These tools, like the chipbreakers, are also an excellent choice for High Efficiency Milling toolpaths.

When it comes to a lower helix removing chips faster, we tend to disagree. As a helix becomes shallower, the vertical forces on each chip become less and are therefore unable to lift chips as quickly. As a helix becomes less and less, there is less lifting force on the chips and they are moved vertically at a far slower rate. A higher helix will actually lift chips more than a lower helix.

There are two distinct ways to cut materials when CNC milling: Conventional Milling (Up) and Climb Milling (Down). The difference between these two techniques is the relationship of the rotation of the cutter to the direction of feed. In Conventional Milling, the cutter rotates against the direction of the feed. During Climb Milling, the cutter rotates with the feed.

In my experience, roughing style corncob type endmills will get you the highest MMR’s with your available hp at the spindle. I’ve been machining a job constantly on the search for a better roughing tool to increase the MMR. I’ve found HEM’s efficiency is entirely dependent on the part geometry that you are applying the toolpaths too. If your part dictates that there are substantial retracts/entries/exits from cutting, you may find that your sexy super fast feed rates end up with longer cycle times as you spend more time cutting air. I’ve spend countless hours on this, and even with the roughing tool I’m currently having major success with, it’s taken time to dial in the most efficient Spindle speeds and feeds. It’s not just about firing up the machine to the highest RPM and having at it. You need to find the sweet spot in the spindles torque curve. Once you’ve found where that is, then you can start jacking up feed rates and playing with axial and radial DOC’s

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Finally, to provide more clarity on your point that chips must be lifted up through the flutes to be evacuated, this is correct for drills as there is nowhere else for the chips to go. For end mills, especially in low radial engagement situations such as with HEM, chips are ejected radially and are not really getting the chance to move up through the flutes. That small amount of vertical motion will actually be more with a higher helix.

Climbmilling

These tools are excellent for more advanced toolpaths like High Efficiency Milling, which is another important tool for a successful aluminum machining experience.

I think you’re both right. you get more lifting force with a shallower incline, because of mechanical advantage, but it’s slower. Think of distance travelled along the Z axis per revolution.

A 60 year old worn out manual Bridgeport is all I have to work with. (It is in better shape than my 65 year old worn out body.) I rarely climb mill anything, specially not steel. But if the cut is really light, and I want a good finish, I climb mill. , I apply some drag with the table lock screw, and that seems to eliminate the chatter.

Cast Aluminum has less tensile strength but with a higher flexibility. It costs less, and has higher percentages of outside elements (silicon, magnesium, etc.) in its alloys, making it more abrasive than Wrought.

“Conventional Milling should be… utilized on casting, forgings” In my head, I logically organize castings as least processed, forgings as most processed, and everything else (hot rolled, cold rolled, extruded) somewhere in between. So to me, that part seems to say ‘use conventional milling for everything’, which is obviously not right. Could you show me where I went wrong,? More specific examples, like case hardening, why a particular direction of cut is preferred for a chunk of metal with unknown provenance.

While there are many factors that go into the parameters for every job, there are some general guidelines to follow when machining aluminum. For cast aluminum alloys (i.e. 308, 356, 380), a surface footage of 500-1000 SFM is recommended, with RPMs varying based on cutter diameter. The basic calculation to find a starting point for RPMs would be (3.82 x SFM) / Diameter.

One of the most important things to consider when machining aluminum (and many other materials) is effective chip evacuation. Standard 2-3 flute end mills running at recommended speeds and feeds and proper chip loads can evacuate chips fairly well. However, 3 flute chipbreaker tooling can run at increased speed and feed rates for even better performance. The unique offset chip breaker geometry creates smaller chips for optimal evacuation while still leaving a semi-finished surface.

Up milling and down millingwhich is better

High Efficiency Milling, commonly known as HEM, is a strategy that is rapidly gaining popularity in the manufacturing industry. Many CAM programs are now including HEM toolpaths, and while virtually any machine can perform HEM, the CNC controller must feature a fast processor to keep up with the additional lines of code. A great example of High Efficiency Milling toolpaths in Aluminum can be seen below.

This is one of those left hand cutters! How about turning the tool, and cutter the correct direction. G41 climb cutting on the right side. G42 or conventional cutting on the left. Sorry I couldn’t help myself.

Climb Milling is generally the best way to machine parts today since it reduces the load from the cutting edge, leaves a better surface finish, and improves tool life. During Conventional Milling, the cutter tends to dig into the workpiece and may cause the part to be cut out of tolerance.

Have seen this article several times. One consideration is roughing, my observation is that the load against the cutter when cutting in the conventional direction is lower and reduces the risk of tool breakage. Another is where the tool-paths leave “posts” in corners and so-fourth when hogging out parts, conventional milling will not grab into a post and break the cutter. Another application is when making long thin flats in rod shaped parts either on a indexing head or on a swiss type automatic lathe through a guide bushing, the conventional path will produce less taper and more parallel surfaces. Just a few thoughts.

Conventionalmilling

This is great info. I have always conventional milled with face mill to remove the scale off of titanium. Tool life is increased and getting under that scale to machine it off instead of slamming the insert into the scale each time. Once scale has been removed, go back to climb cutting.

Added uses for conventional cutting: Never climb cut across the end of an upstanding thin rib in aluminum or plastic (You will rip it off). Use reduced feed and conventional cut it or use multiple small depth cuts. Commonly made cutting to length T or L extrusions. You’ll only make this mistake once. It helps to conventional cut torched or burnt out steel plate rough profiles first, then switch to climb cut after you mill through the slag. Same principal as case hardened material. Corn-Cob or serrated cutters work nice here too.

Aluminum is available in two basic forms: Cast and Wrought. Wrought Aluminum is typically stronger, more expensive, and contains a lower percentage of outside elements in its alloys. Wrought Aluminum is also more heat-resistant than Cast and has a higher level of machinability.

In addition, conventional milling should also be utilized on casting, forgings or when the part is case hardened. This is due to the cut beginning under the surface of the material, where it will gradually build a chip. Climb milling into these materials will see maximum chip thickness on engagement, which could lead to premature failure of the cutting edge due to the forces generated. print

I have a Warco 16B milling machine. This is a medium size manual hobby mill. I am confused as people recommend Conventional and Climb milling in about even numbers, this goes for YouTube too. What would you recommend on this type of machine? Your help would be appreciated as I last worked in industry in 1979 so I am extremely out of date. I generally mill Conventionally.

Is there an easy way to estimate the axial pull force created during HEM type roughing operations? I know this force can be quite high, often enough to merit the use of high grip tooling such as heat shrink or hydraulic holders. I’d be curious to hear some numbers, just to get a perspective on the forces involved and the necessary workholding requirements. For the sake of example, let’s say 6061 aluminum, 1/2″ 3 flute 45 deg. helix & 1500sfm.

Aluminum is a highly formable, workable, lightweight material. Parts made from this material can be found in nearly every industry. Additionally, Aluminum has become a popular choice for prototypes due to its low-cost and flexibility.

There can only be one way to interpret the cut because machines only turn in one direction. In the examples the view has to be from under the workpiece looking up at the tool

Great question Graham! There are many factors that go into choosing which method is best for you. Please send an email to [email protected] with all your information and they will be able to help you out as soon as possible.

Aluminum is a versatile material with a high level of machinability, but it should not be overlooked. Understanding the best ways to tackle it is important for achieving the desired results. Optimizing your tool crib, machine setups, and toolpaths for aluminum is essential to stay ahead of the competition and make your shop more efficient.

When machining aluminum, standard 2 or 3 flute tools will often get the job done. However, for certain applications and machine setups there are some more tooling options to consider for even better performance.

Up and down millingprocess

A helix angle of 35° or 40° is a good choice for traditional roughing and slotting applications. A 45° helix angle is the preferred choice for finishing, but also for High Efficiency Milling toolpaths as the high helix angle wraps around the tool faster and makes for a more aggressive cut.

As previously stated, traditionally conventional milling has been the common choice for most machinists. This is where the cutting edge of the tool is actually rotating away from the direction of the feed. An example of this is seen in Figure 2 below. Until recently, this has been the common choice due to backlash however, the rise of climb milling has caused machinists or machines to adapt and compensate for this issue.

Setting the right parameters for aluminum applications is vital to optimizing productivity and achieving better machining results. Since aluminum is an easier material to machine, pushing your machine to its limits and getting the most out of your tool is vital to stay ahead of the competition and keep winning business.

We thought you raised a great point about the high helix angle and how it wraps around the tool faster, making for an aggressive cut, and we agree that this could be misleading. We’ll rework this portion to provide more clarity. What we meant was that there are merits to using a high helix tool in an HEM fashion, since a higher helix causes more points of contact between the tool and the workpiece. This helps to provide stability to cut faster, and even provide more stability in thin wall applications. When we say “aggressive,” we’re referring more the nature of a high helix and less its use in HEM, specifically. A higher helix is more aggressive than a lower helix due to higher shear forces on the workpiece, and higher lifting forces, which can get too high in certain workholding situations.

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I think you left out force vectors during cutting. This can influence tool defection and taper on the side wall on the part. The force vectors are different magnitudes between climb and convectional cutting, so this impacts work holding and this parts or this walls.

Conventional Milling is the traditional approach when cutting because the backlash, or the play between the lead screw and the nut in the machine table, is eliminated as seen in Figure 1 below. Recently, however, Climb Milling has been recognized as the preferred way to approach a workpiece since most machines today compensate for backlash or have a backlash eliminator.

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That is not to say there aren’t benefits to climb milling. For example, this strategy offers a machinist more control and less vibration than its climb milling counterpart. Similarly, for materials that traditionally chatter or tear, conventional milling would be the proper strategy to choose. On the other hand, here are some reasons why it might be most beneficial to adopt a climb milling strategy: