high feed milling and keeping things flat | Manufacturing Forums

We have a couple plates coming in. Roughly 34" x 80" x 2.25" stock thickness. They need to go down to 1.9" thk. But also kept pretty flat. Not grinding flat, just good machined flat. I also don't want to flip this part more than once.

I'm thinking of using a 4" high feed facemill using SDMT inserts to take about .150" off the top (in several passes) and then two finish passes taking .010-.015 off with a 6" APKT facemill with finish inserts. Thinking the sharp APKT inserts will remove any surface stresses that I put in using the SDMT's. Flip and repeat.

Am I overthinking the need to deal with surface stress and keep it flat? Note, I have never used the SDMT tools so IDK what I am in for with high feed cutting. '
Thanks I run a fair amount of feed mills. While I can't comment on stresses as I've never noticed a difference, I do have a few suggestions on the tool.

First off I would be looking at something that takes a specific high feed insert that is better optimized for high feed cutting. Kyocera LOGU inserts have a very high positive for a feedmill, though I'm not sure how big of a tool they make for these inserts.

Tungaloy SQMU inserts take a beating but Kenna XDLT seem to cut quieter and I suspect with less force.

Unless you are talking about a 4" tool with a dozen or more inserts I would be looking at a 2"-2.5" tool with 5-6 inserts. Provided you have the HP and speed to take advantage of the higher rpm on a smaller tool.

Walter P-1.0 and -2.0 are also inserts I have had good success with. I realize this doesn&#;t really answer your question, but I wonder if you have considered getting this material Blanchard ground and just skipping this step yourself? (Is there much additional work in the part, or is this the bulk of the job?).

I haven&#;t had to deal with plates this large myself, but have a couple of material vendors local to us that will supply material already ground (double disk for smaller stuff, and Blanchard for larger stuff), and it ends up working well for us. One of the vendors will also take care of annealing/stress relieving too....ends up being slightly cheaper for us to buy it this way when I capture the costs to do it ourselves. After some research and dropping the SDMT... Have you used any SECO ONMUANTN inserts? I was thinking with a SECO Double Octomill R220.48-05.00-09-15M holder.
It looks like this could be a good combination for low rpm high removal rates?
I can get the same body in 8 flutes, as opposed to this one with 15. If chip evac was an issue, why would they make that many anyway?

As for blanchard grinding, it was suggested to me before, I just don't have a local resource for plates this big and shipping cost would cost us more than just machining in-house. There are tons of holes and counterbores so as long as the results are good, makes sense to do it here.
But I should get quotes on grinding for information purposes. It would influence how we quote these if they come back around.

SD&M, based on your experience with blanchard grinding, what do you think ballpark would be to remove 1/4" from a 34x80 steel plate?
When you stated &#;A-36 CS&#; are you referring to a cold rolled A-36? Morally it&#;s hot rolled and holds flatness really well.

I&#;ve had my fare share of 36x240 ripping from 1.25 to 1.000 +-.010 with 2 flips using an 18&#; S-Max but that&#;s on hot rolled. I would suspect CR would flop all over the place even with several flips.

As far as the grinder goes, my Blanchard 120&#; rate was $170 an hour. That much material removal would eat up well over half the segment length of the rocks. Not sure how much time you have on a Blanchard but changing segments doesn&#;t make the operator happy.

Blanchards need a lot of down force to keep from glazing the stones otherwise you&#;re constantly reaching up and running the dresser. For a part that size I would set the feed between .016-.025 downfeed per minute to keep from glazing. You can figure a feed that hard will take about half of the downfeed in metal removal and the other half in rock loss.

So, pulling .35 of material off would take a tad over half hour plus the flip. Then probably get a charge to change segments. That may take a little longer in some places. I figure they gave me 200 horsepower I&#;m gonna push it till I see the part slipping on the magnet&#;.

I run a fair amount of feed mills. While I can't comment on stresses as I've never noticed a difference, I do have a few suggestions on the tool.

First off I would be looking at something that takes a specific high feed insert that is better optimized for high feed cutting. Kyocera LOGU inserts have a very high positive for a feedmill, though I'm not sure how big of a tool they make for these inserts.

Tungaloy SQMU inserts take a beating but Kenna XDLT seem to cut quieter and I suspect with less force.

Unless you are talking about a 4" tool with a dozen or more inserts I would be looking at a 2"-2.5" tool with 5-6 inserts. Provided you have the HP and speed to take advantage of the higher rpm on a smaller tool.

Walter P-1.0 and -2.0 are also inserts I have had good success with.

If you use Tungaloy you should check out their DoFeed (LNMU) instead. I have been using them almost exclusively in the 20mm-100mm range for the last five years or so, phasing out Sandvik R210 for our larger high feed tools.

I have one of the SQMU cutters (an 80mm 5fl) that the rep gave me as a freebie, and honestly it's not great. The inserts can't handle the same chipload as the LNMU, at least in materials with high specific cutting force.

I also have not noticed any difference in warpage between slabbing down with high feed vs plain face milling. The A36 is hot rolled, my CS was just an abbreviation for Carbon steel. I usually use CR for cold rolled.

I have zero experience with Blanchard grinding but I&#;m amazed that much material is a 30 min job! With the flips and stone change, if I read between the lines it&#;s maybe a 500$ job? That&#;s much faster than I was expecting. I&#;ll have to get some quotes and find a relatively close vendor next time.

Good to hear that no one has seen much difference in warpage from the higher compressive stresses that high fees cutters put into the surface skin. Or do much to mitigate it with good results.

After some research and dropping the SDMT... Have you used any SECO ONMUANTN inserts? I was thinking with a SECO Double Octomill R220.48-05.00-09-15M holder.
It looks like this could be a good combination for low rpm high removal rates?
I can get the same body in 8 flutes, as opposed to this one with 15. If chip evac was an issue, why would they make that many anyway?

As for blanchard grinding, it was suggested to me before, I just don't have a local resource for plates this big and shipping cost would cost us more than just machining in-house. There are tons of holes and counterbores so as long as the results are good, makes sense to do it here.
But I should get quotes on grinding for information purposes. It would influence how we quote these if they come back around.

SD&M, based on your experience with blanchard grinding, what do you think ballpark would be to remove 1/4" from a 34x80 steel plate?

I only have one Seco feed mill and I have yet to buy inserts for it. If you have the HP, speed and rigidity to run a fine pitch body then that is what I would go with. If it's an even number of flutes you can always leave every other insert out.

The A36 is hot rolled, my CS was just an abbreviation for Carbon steel. I usually use CR for cold rolled.

I have zero experience with Blanchard grinding but I&#;m amazed that much material is a 30 min job! With the flips and stone change, if I read between the lines it&#;s maybe a 500$ job? That&#;s much faster than I was expecting. I&#;ll have to get some quotes and find a relatively close vendor next time.

Good to hear that no one has seen much difference in warpage from the higher compressive stresses that high fees cutters put into the surface skin. Or do much to mitigate it with good results.

In 08 I&#;d say $500 for that would have been inline I haven&#;t bought segments in many years so I don&#;t have a clue what they add in for that now. Tue problem you may run into is a lot of shop have just fine to a medium fine grit because they&#;re trying to hold tolerance or just get that rotary finish.

Blanchards can really rip material off with the right grit, heck, the downfeed goes all the way up to .100 per minute. Wow! I&#;m glad g-coder05 weighed in on this one! I kinda recall he had lots of experience with big parts & machines. (It must have been that story about getting a broken leg running some big VTL!).

I&#;ve never dealt with stuff that big (a big part here is ~20&#; x 40&#; or so-LOL), but for the occasional plate job I&#;ve learned to just buy the plate &#;ready-to-go&#; if possible. We have a really good local vendor (TCI Aluminum/ North) that does this (for AL, anyway), and have also used a shop that just does Blanchard grinding for the rare steel plate. It always seems reasonable when I compare it with dealing with it in-house by other (inferior) means.

Getting parts out the door efficiently and affordably is a productivity requirement that has remained constant for mold and die producers. In order to remove a significant amount of metal during roughing operations, conventional wisdom of the past has guided shops to choose tools based upon their metal removal rate capacity. This would result in using the biggest tool possible to start the roughing operation and then working down in size until reaching the required shape and finish. Typically, ballnose endmills or button cutters would be employed. However, this methodology can produce a lot of stress that requires a strong robust machining center, hearty workholding and tough tooling.

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Plunge milling became another highly favored way of hogging out metal quickly. Plunging transfers the forces axially up into the spindle rather than radially, which can create deflection, loss of accuracy and shorter tool life. An issue with plunging; however, is that the tool is constantly going in and out of the pocket as it indexes to each new position.

High-Feed Milling Basics

Today, as more shops are equipped with high-speed CNC machining capability and sophisticated CAM programs, high-feed milling (HFM) is becoming the methodology of choice to remove as much material as possible in the shortest time. Basically, HFM is a roughing method developed for high metal removal rates to increase productivity and save machining time. HFM uses a smaller depth-of-cut (usually no more than 2 mm), producing a thinner chip that carries the heat away from the cutting edge. It also runs a high feed per tooth: up to five times higher feed per tooth than conventional milling is common. This approach reduces heat generation to extend tool life and provides a higher metal removal rate than normal&#;over 1,000 cm per minute or up to 200 to 300 percent faster than traditional milling.

The reason for this is that the HFM method takes advantage of small setting angles (45º or less). This produces minimal radial- and maximum-axial cutting forces. Similar to plunging, the cutting forces are directed at the machine spindle in the axial direction, which reduces the risk for vibrations and stabilizes machining. This, in turn, allows for the higher cutting parameters even when machining with a large overhang. And, unlike plunge milling, in HFM the tool stays constantly engaged.

Another HFM time-saver is the number of operations. Since high-feed roughing with its small depths-of-cut generates a near-net shape close to the final requested form, semi-finishing operations can often be eliminated and NC programming is thus simplified. On top of this, the HFM process does not require increased rotational speed from the machine.

Getting Started

To accomplish a HFM strategy, users need to evaluate the overall machining system. Number one is the need for high-speed CNC machining control, high spindle accuracy and thermal stability against spindle growth. Secondly, is the requirement for a CAM software program that can handle toolpath smoothening strategies&#;such as corner rounding and helical cutting paths. Smooth toolpaths enable a gentle slicing of the workpiece through light engagement conditions while helical cutter movements reduce the cutting impact, energy consumption and cutting forces. 

Additionally, the inserts used in HFM are critical. They are thick and have a big radius and strong geometry at the cutting zone. This means you can work at high speed and still have reliable and safe machining. For most HFM operations, trigon-style inserts are preferred over round. The reason is that the main cutting forces are located at the bottom of the cutting edge. Of course, there are situations when you use square inserts, but with a small setting angle.

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Typically, this might be required in high-feed heavy roughing applications using powerful machines in stable conditions or in horizontal milling operations, making chip evacuation more effective. But in vertical operations or smaller machines with high rpm, trigon-style inserts are a safe choice, offering excellent chip evacuation.

Applications for HFM

Face milling, especially high volume, with the HFM method is perfect for creating a good platform for further machining operations or a final finishing. In most HFM applications, you&#;ll often get such close tolerances that only final finishing is needed. Since the work involves large blocks, tools with large diameters are most often used. This means using trigon-style inserts in cutters with cassette bodies. High-feed face milling is relevant for most soft materials.

The HFM method is highly effective in cavity milling, and especially suitable in mold and die. Recommendations for tool choices and other parameters all depend upon what is to be machined, the size of the component to be produced and the level of rigidity. Copy milling using the HFM method also is very practical for machining uneven surfaces.

In helical interpolation, the HFM method is a very suitable solution for making large-diameter holes&#;you can skip pre-machining or pre-drilling. The high-feed cutter has minimal contact with the component&#;s wall section. The advantage is more stable machining than with conventional milling cutters that have a 90-degree setting angle.

High-feed machining tools also can be applied to plunging operations. They&#;re especially appropriate for difficult materials like titanium and other light alloys. HFM is equally suitable for applications with long overhangs. The risk for vibrations drops, which extends the tool life. However, square inserts should be avoided for overhangs larger than 3 x D. Using HFM tools for plunging, however, relies upon normal feedrates used together with larger cutting depths.

Summary

Although HFM is not an end-all, be-all solution, it is a great method to achieve high metal removal, utilize the full capability of today&#;s machines and achieve long tool life.

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