Climbing vs. Conventional Milling [Advantages and Disadvantages] (2023)

Here's a nice video overview of Climb vs. Down vs. Up Milling:

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Read on for more detailed information on conventional drilling and uphole drilling.

What is down milling versus conventional milling (down milling versus up milling)?

As a general rule, CNC users always climb milling machines and hand machinists always conventional milling machines. It is probably true that manual machinists should stick with conventional milling as a milling style, as the kickback of their machines makes climbing milling dangerous.

But CNC users should know that there are times when the mill needs to be sized and there are times when conventional milling works better. Before we get into when to use each, let's briefly define the differences.

The first thing to consider is the terminology. Some will say "Up Milling vs. Conventional Milling", while others will say "Down Milling vs. Up Milling". They are one and the same:

• Down milling = down milling
• Conventional milling = conventional milling

Up milling is when the direction of cut and the rotation of the cutting tool combine to try to "suck" the cutter up (hence called "up milling") or away from the workpiece. Produces the best surface finish. Here is a graph showing milling versus conventional milling for various orientations:

Arrows show workpiece movement, not spindle movement!

Note that in this figure the workpiece is moving, not the spindle. On some machines, such as B. a portal mill, the spindle moves, so the labels would be reversed. I'll keep things clear by thinking of the spindle as a pinch roller that can help move the workpiece in the direction it was already going (up milling) or fight it off (standard or conventional milling).

Do the experiment on your dual milling machine and you will find that milling is much smoother and produces a better surface finish (there are often times when traditional milling produces a better surface finish, see below) than traditional sanding. Keep in mind that depending on which direction you are milling in, you need to make sure your workpiece is well supported in that direction.

Pros and cons of down milling and down milling (conventional vs up milling)

Advantages of the conventional milling process (Up Milling):

• Chip width starts at zero and increases as the cutting tool stops cutting.
• The cutting edge meets the workpiece at the bottom of the cut in conventional milling.
• Upward forces tend to lift the workpiece during conventional milling.
• Conventional milling requires more power than conventional milling.
• The surface finish is worse because the chips are carried by the teeth and fall in front of the cutting tool. Many chips are cut. Flood cooling can help!
• Conventional milling is preferred for rough surfaces.

• Tool deflection in conventional milling tends to run parallel to the cut (cf.tool deflection sectionfor more).

Advantages of up-milling (down-milling):

• The span width starts at the maximum and decreases.
• The cutting edge meets the workpiece at the top of the cut.
• The chips stay behind the cutting edge without cutting.
• Less wear with up to 50% longer service life.
• Improved surface finish with less chips.
• Less electricity is needed.
• Upmilling applies a downward force when facing, making it easier to clamp and clamp parts.Downward force can also helpReduce vibrations during machiningon thin floors because it helps hold them against the underlying surface.
• Reduced up millinghardening.
• However, due to the hardened layer on the surface, chipping may occur when milling hot rolled materials.
• Tool deflection during down milling is normally perpendicular to the cut, which can increase or decrease the width of the cut and affect accuracy.

So what is the preferred method? The fact that it improves tool life so much is reason enough to stick with conventional milling. However, look at the other pros and cons, as there are cases where conventional milling wins a lot.

Upward milling kickback

There is a problem with up milling, which is that you can have problems with backlash if the cutter forces are high enough. The problem is that the table tends to pull towards the cutter when the grinder is lifted. If there is indentation, this allows some leeway to pull at the indentation level. If there is enough kickback and the cutting tool is operating at its maximum capacity, breakage and possible injury from flying debris can occur. For this reason, many shops simply prohibit upmilling on any manual machine that has clearance. They always use conventional cutting as the required milling style. Some machines even featured a "backlash eliminator" whose main purpose was to enable up-milling and the benefits that came with it.

One way to think about this is to look at the chip shop concept. This is a measure of how much material each cutter tooth is trying to cut. Typical values ​​for finishing would be 0.001 to 0.002″ per tooth. For roughing jobs, this can increase to 0.005″. Now, in the worst case scenario, the cutter can grab the table and slam the workpiece against the cutter at full recoil while a single tooth is cutting. So you can add the chipload response to see what your new worst case effective chipload might be. Let's say you grind 0.005″ per tooth and have 0.003″ clearance. In the worst case, your chip load will explode to 0.008″. It's probably not the end of the world, but it's a burden. Now let's say you have an older machine with a 0.020" gap and a 0.005" chip load. Worst case your chip load will explode to 0.025″ which will likely blow the mill and is very dangerous.

Second, you must consider whether the shear forces are strong enough to pull the table through the gap. A lot depends on the exact cutting scenario along with your machine. If you have a sophisticated low-friction linear guide machine, you can easily pick it up. If you have a lot of irons on the table and maybe run with a bit of a narrow form, it gets harder. There are ways to calculate cutting force, but in general, smaller endmills, shallower depths of cut, lower feeds, and slower spindle speeds reduce cutting force and make it less likely that the cutter will pull the tool gap. table. and create a problem.

In general, CNC machines should not have any noticeable backlash, so they are more problematic with manual machines.

Up milling creates negative cutting edge geometry under certain conditions

By now you've probably gotten the idea that you must always size the mill in CNC milling operations. Ultimately, it leaves a better surface finish, requires less force, and is less likely to deflect the cutter. On the other hand, manual machinists are often taught never to drive in the factory because it is dangerous to do so on a stowed machine. The truth is somewhere in between. ABTools, makers of the popular AlumaHog and ShearHog clippers, suggest some helpful rules of thumb:

– If you are cutting half the cutter diameter or less, you should definitely use milling (assuming your machine has little or no clearance and it is safe to do so).

– Up to 3/4 of the cutter diameter, regardless of the cutting direction.

– Conventional reaming should be preferred when cutting 3/4 to 1x reamer diameter.

This is because the geometry of the cutter forces the equivalent of a negative rake angle for these heavy 3/4 to 1x diameter cuts. This is definitely not the best thing for tool life!

It appears that the Dapra Corporation first discussed this phenomenon in 1971.g-magoNow he reminds you with a little tip which one you should prefer:

G-Wizard tips tell you what to do: "Use conventional milling"...

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Tool concentricity and cutting accuracy with conventional milling compared to conventional milling

How does up-milling affect tool concentricity and accuracy compared to conventional milling? The following image contains small arrows (often referred to as vectors) that show the direction of the tool's deflection as it moves along the path:

The arrows show where the cutting force is trying to deflect the cutting edge. Conventional cut on top, rise cut on bottom.

Note that with conventional milling, the deflection force vector is more parallel to the cut (although the arrows are longer and indicate higher cutting forces). In conventional milling, the arrow is almost perpendicular to the cut. If your cutter is off 0.001″, don't you want it to go almost in the direction of travel? Alternatively, the cutter can penetrate deeper into the wall or move away from the wall. In either case, more errors are introduced into the part being machined.The counterpoint is that vector lengths are longer with conventional milling. This indicates that the cutting forces are greater and the tool is more likely to deviate in conventional milling.

Try to go roughing as you can rough rough faster and the effect of tool compensation on accuracy doesn't matter - the finish pass provides accuracy. You can rough faster because cutting forces are lower and the thick to thin chip profile transports heat into the chip. This very thin thickness + heat dissipation is especially important for hard, work-hardened materials such as stainless steel. It also leads to a better surface finish if you can step up to the final pass.

Consider conventional milling for finishing passes

It is counterintuitive to many mechanics, having been trained for most of their careers, that scraping produces a better finish than traditional scraping. All other things are equal, it is true, but all other things are rarely equal!

The problem is that deflection also affects the surface finish. If the vector is nearly parallel to the path, you may consider the part of the vector that pushes it "out of parallel" to be very small. Therefore, the tool has little tendency to drift and ripple the wall you are finishing. Note that this can be especially important for thin-walled jobs with weak walls!

Therefore, if you have deflection problems, you should switch to conventional milling for the finish pass (useg-magoto see if the diameter and roughness of the tool results in a small enough deflection for your finishing pass).At a minimum, too large a depth of cut should be avoided when counter-milling to produce less tool deflection. The same article suggests that when runout needs to be minimized, no more than 30% of the cutter diameter should be used for conventional milling and 5% for conventional milling.Again, of course, if you have the G-Wizard you'll know what kind of drift to expect and if that's a problem.

The upcut to finish coarsely and conventionally is consistent withthe consensus on the practical machinistin addition to that, moreover.

Proper deflection management can help avoid the need for additional spring trimming, saving time and money.

I would keep going up to Millbevel cutteror Roundover Mill because they can vibrate a little and reducing the cutting force helps to minimize this.

For micromachining, consider conventional milling

For the same reasons, but taking into account the deviation, it is much worsemicro milling, you should prefer larger scale conventional milling to micro milling. The biggest tool life issues with micromilling are runout and concentricity. If the reduced cutting forces (and therefore reduced deflection) of conventional milling benefits tool life more than the deflection direction of conventional milling, it is a small compromise, but conventional milling wins. check out ourmicromachining pagefor more information.

Conclusion

Deciding between up-milling versus conventional milling is more complex than most operators realize, but now you are in a position to decide which style of milling is best.

Frequently asked questions about up milling vs conventional milling