Interesting Feeds and Speeds Info

Guys and Gals, I recently cut a 3d model of the Tree of Life. Even though the carve failed due to a computer crash (Windows 10, not UGS or Grbl) I experimented with some fast feeds and speeds. The material I was using was poplar which is a softwood like pine. I ran the roughing pass using a 1/4" down cut end mill. I set the speed at 120"/minute for X, Y and Z. Stepover was 40%. Each pass was taking about 3/16" of materiel both in depth and width. I bumped the router rpm’s up to about 19000. I must say it was smooth as glass while cutting. Then to top it off I went even faster with the finishing pass. I used a 1mm tapered ball nose (3.82 degree, stepover 8%). I set the speed at 150"/minute for X, Y and Z also (even though Z max speed is about 120"/minute). This path was just as smooth as the roughing pass. It cut 4 hours off of the finishing pass time. The carve was very smooth with no bit track lines. Again I was using a soft material. I recut my plaque with red oak which is a hardwood. I was afraid to try these speeds on this material so I cut the speeds back to 100"/min X and Y and 50"/min for Z for the roughing pass. I set the finishing speed at 100"/min X, Y and Z. Then while cutting the finishing pass I decided it was running too slow so I bumped the speed up to 150"/min for X, Y and Z. The LM handled it just fine. Oh, and I switched from the tapered ball nose to a 1/8" ball nose on the finishing pass. Do not use my experiments as a set in concrete set of feeds and speeds. Use your own judgement. It’s just to me that to help speed up finishing the Z speed is the controlling factor in how fast the cut is made. Also finishing passes usually cut very little material as long as you run a roughing pass or your model is very shallow.

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I would have been apprehensive to use such fast feed rates. Thanks for sharing. Like yourself, cutting down on time in complex projects is of significance to me. While I recognize that you are not necessarily endorsing these settings it is none the less very helpful to hear of their use and results. I will soon be bumping up my speeds to see if I get similar results. Although I don’t usually cut that deep. Generally .0625 or .125 in and effort to not stress the tool and machine. That may all change too.
Thanks.

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@Heyward43 Excellent info, H. Tks much. I’ve read on a few sites that, when we are doing intricate 3D or 2.5D pieces like these, the machine never really gets up to the speed we set. The ramp up time gets in the way. In pieces like yours, where there are a lot of small moves in all axes, I’m betting that this is the case.
I tend to be very conservative in plunges in particular, but I do end up using the feed speed bump up feature in UGS quite a bit.
Thanks again.

Another tidbit of info on the poplar material. Being soft like pine it cuts very easy. One advantage I’ve noticed is it doesn’t leave “feathers” or “fuzz” all over the place like pine. It cuts very cleanly and makes sanding or hand finishing much easier. And Grant I used CNCjs for this one. You can bump up or down by either 1% or 10% at a time. I bumped mine up from 100% (100"/min) to 150% (150"+/min) a little bit at a time listening to how the bit sounded. Wasn’t much difference in the sound each time so I let it fly. I think 150"/min is about the maximum you can run the longmill. It was actually a noticeable difference in movement.

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@Heyward43 H: I make picture frames for 2 local artists and I use a lot of poplar. Here in the Great White North, I’ve learned that is a different species than in the southern US. I understand that, up here, it is a bit harder. I love working with it. It mills very well, takes stain very well and as you have said, it routes well, too. On top of that, it’s not too pricey.
Thanks much for the feeds and speeds info. I’m still playing with that, and any experience that I can grab onto is very welcome.

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Heyward, good info on the poplar speeds & feeds. It’s a wood I haven’t tried, but I’ll certainly add it to my next order list.

Another positive for cncjs. I’ve been using it almost exclusively. If they ever get the autoleveling working I’ll be locked in.

@BillKorn Thanks Bill. I really like the poplar. The grain is so much finer and it really carves well. Plus you can find pieces with some color such as browns, purples, blonds and greens running with the grain. CNCjs has really been doing the work for me. I will probably stick with it for a while at least. Is the autoleveling something you use on your CNC mill or is it for 3d printing? I haven’t come across that before in cnc work.

Autoleveling was originally developed to help circuit board makers. Since they cut traces that are very shallow anything that makes an area of the board higher or lower, like boards that are not flat, causes incomplete traces or traces that are so wide they run into the adjacent trace. I thought it would be an easy way to use boards with cups without surfacing them, or large intentionally non-flat stock like previously milled topos. I tried bcnc, but it is really flakey, and has about the most cluttered and confusing UI I’ve seen. Another sender, OpenCNCPilot, has a decent autoleveler, but the manual controls are hard to get to, and I broke a couple bits and pegged the X axis when I thought I had zero set correctly but didn’t.

I’ve been impressed with your long jobs. The longest I’ve been able to sit and watch the action has been about two hours, even if I’m doing something else at the same time. Are you keeping an eye on things directly, or are you using a camera? Or have you done enough of them that you’re comfortable leaving them unattended? BTW, there’s a phone app called DroidCam that uses your phone as a web cam. I loaded it and it works, but I’m still antsy about walking away.

Two last question about poplar. How does it finish - Is it stainable, paintable, etc.? If it machines as well as it looks in your pics I’m thinking it’s going to replace pine and plywood. And, is it available in 8 or 10" wide boards?

Thanks.

Bill

@BillKorn. Glad you like the jobs, Bill. I haven’t tried to stain any of the poplar yet. I may give that a try today on the Tree of Life that crashed. I have several different stains and finishes I can try. Dark mahogany, Danish oil, light walnut shellac, clear shellac and clear acrylic. I’ll cut the crashed piece up into smaller pieces and try them all. I’m fairly sure it will paint ok.

As for the long jobs. I usually sit and watch the carve from start to finish. Yep, it’s boring but it has been so cool (40, 50, 60 degrees) I don’t think it’s warm enough to try finishing in my shop/garage while it’s carving. I may run into the house to get a drink, food or potty break but it’s usually for only a few minutes. Like you I don’t want to leave it unattended for long. I’ll check out DroidCam. Sounds interesting. I’m not comfortable enough to be 30-40 feet away if something goes wrong.

I buy my poplar at Lowe’s. They have a section of precut pieces of pine, red oak, poplar, plywood and MDF. From 1x2, 1x3, 1x4 up to 1x12 and up to 48" long. I need to check out Home Depot to see what they have too. It can be a little expensive but the pieces are usually cut and finished very well. The 12"x24" piece of poplar I used was just under $12. I bought a 12"x24" piece of red oak and it was right at $16 but it was as close to perfect as one could expect. Of course you need to check measurements to be exact when using.

Thanks for the explanation on autoleveling. At this point I don’t really see a need for me.

I’ll post some pictures of my finishing experiment on the poplar soon if the weather will cooperate. Right now it’s about 55 degrees with the wind blowing 20-40 mph. Not good for finishing in the shop and my wife won’t let me stink up the house.

Poplar is great for painting. Staining, however…

It can be pretty blotchy if you use a penetrating stain (or any dye). If you want to go the stain route, your best bet would be a wiping stain or a gel.

@Iguana, @BillKorn, Thanks for the tip Mark. I sure you have the experience but I still want to try penetrating stain just to see what happens. I think I have seen some videos showing what you are talking about. I’ll have to pick up some wiping or gel stain.

@Heyward43 @BillKorn @Iguana I use a lot of poplar for picture frames. I think maybe the base of the penetrating stain may make a difference. I use both a wipe on and a spray on lacquer based stain, and I get no blotches at all. One key for flat work is to sand to 120, no finer. The fumes are likely taking years off my life, but other than that, it’s a great product. I get it from a local supplier, so I can’t point to it at any box box store.

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You can also use a stain conditioner to reduce blotching with a penetrating stain. The drawback is that conditioners reduce the ability of the wood to absorb stain, and therefore you don’t get as dark or saturated color as you might want.

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Hey guys, thanks for the info. It’s apparent I’m way behind in my wood finishing skills. Maybe we should have a section for what you do with your prize milling job after it comes of the table.

I’m with you Bill. I’m not very experienced with the finishing skills. Just what I see on youtube. I’m sure there are a lot of people on the forum with lots more experience. Mark, Grant - hint hint. Sounds like we need another category for the forum.

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@Heyward43 @BillKorn @Iguana Guys: I’m happy to help any way I can. I’m far from expert, though. I have an excellent local source of lacquer based stains and use them almost exclusively. The only other stain that I use is a gel that is also very good. Wipe on, wipe off. For clear coat, I spray pre-cat lacquer mostly.
I laughed when Bill mentioned another section for our prize milling jobs. In my case, almost all of them go into the recycle bin. The exception being the few inlays that I’ve done.
I’d really enjoy seeing what the others here are doing, though.

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@andy @chrismakesstuff @gwilki @BillKorn @Iguana - Chris or Andy what think you about a Finishing Techniques category? Might help us less experienced finishers. There are so many different kinds of wood, shellac, paint, lacquer, dyes, etc. out there it’s hard to figure out which to use. It’s too expensive in some cases to experiment even with scrap pieces.

I’ll open one up because you asked Heyward :wink:

I don’t mind opening up a new category if it seems that it will help to better organize and share information :+1:

EDIT: here it is: https://forum.sienci.com/c/finishing let’s give it a try

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Thanks Chris. Hope it starts to fill up soon.

There’s a whole science about feeds and speeds to maximize the life of the bits and produce the best cuts. A couple of years ago I purchased a license to a feeds and speeds calculator called GWizard. It does an incredible job of giving the correct feeds and speeds for just about any size bit, including the 1/8" shank bits with small cutting tips. With my previous CNC machine, it gave me very close to ideal results and I had to hand-tune only slightly on occasion, due to the fact the spindle I was using was a fairly low-power spindle (< 100 Watts, if I recall).

The relationship among the size and composition of the bit, the depth of cut, the power available from the spindle/router, the speed of the spindle/router, the feed speed, and the type of bit can get very complex; the program allows you to input all those variables and produces the resulting unknowns, including a warning about exceeding the amount of deflection that increases the possibility fo broken bits. Believe me, from experience, you don’t want a bit spinning at 20,000RPM breaking and flying off into a random direction. Fortunately, the one time it did that for me, it went in the opposite direction, but took a chunk out of the enclosure in the back. The only other times I’ve had a broken bit was when I had my zero point in the wrong place and the bit ended up digging far too deep into the material I was cutting. In those cases, the broken end was buried in the material.

For anyone who is interested (no, I don’t get any kickback), it is based on what I call a pseudo-subscription. For each year you pay, you get an additional 1HP rating on the spindle/router you use. During the time you pay, there is no HP limit, only if you stop paying. So, for example, if you pay two years and then stop, you get 2HP of power for the calculations. I don’t get any kickback from this, so, if you’re interested, just look for Gwizard using a Google search to find it - there’s a free trial period.

Michael