Nice! - can I add it to mine too?
IMO you really need to know K factors to calculate all the appropriate milling parameters - chipload doesn’t do that. I’ve tried to make that easy on the workbook’s “Working Spreadsheet” by entering measured HF Spindle currents or Router powers during operations.
Yes of course! …
Hmm, I’m sure you’re right… but IMHO this is for noobs like me and your suggestion may be too much for Julien’s simple spreadsheet aimed at basic Shapeoko users? Speaking for myself, I think all I need right now is a much better way of setting F&S that is superior to the default and often misleading ones set in Carbide Create. This will also lead me to better understanding before I get in too deep.
Your excellent advanced spreadsheet is the place to go for advanced users with exotic requirements and so on?
That’s what I’m after: a beginner version that grants a workable (albeit not technically ideal, or you could even call it “wrong”) feedrate , based on very few parameters. Then it’s easier from there to learn a smarter way, involving unit power, deflection, etc…
just a matter of not drowning in too many things to learn at once
That’s not my intention. I was hoping that it would help people (including me) better understand what I consider to be the basics. Maybe this will help with that.
Since you’re a retired woodworker, I imagine that you have experience using routers. With router bits less than 1” diameter, you probably use the maximum speed supported by your router (22,000 – 30,000 RPM) because you can advance (“feed”) the router or workpiece faster without pushing harder (increasing the “feed” force). My default router table “feed rate” seems to be around 100 inches per minute (IPM) and my router’s maximum speed is 25,000 revolutions per minute (RPM). So, the workpiece advances 100/25,000 = 0.004 inches per revolution. So, with a two-flute router bit (or endmill), the workpiece advances 0.002 inches per flute/tooth (IPT) - that’s the “chipload”. If the workpiece shows signs of burning, I decrease the depth and/or width of cut to safely enable a feed rate increase. A typical 10-inch combination blade for a table or miter saw has 40 teeth and spins at 3450 RPM. A 100 IPM feed rate produces a 100/3450/40 = 0.0007 IPT chipload. Recent experience suggests that chiploads of about 0.001 IPT are acceptable for almost everything that folks use Shapeokos (and Nomads?) for (so enter 0.001 in cell D10 of the workbook’s “Working Spreadsheet”).
Properly operated power tools do all the cutting work, the operator (or CNC machine) just positions them. Positioning them properly requires that the operator or CNC machine counteract the cutting/milling forces generated by the tool. (Most of the force produced by routers is perpendicular to the feed direction - i.e. toward the fence on a router table.) The amount of force produced by the tool can be calculated from the magnitude of power it uses when cutting/milling. The magnitude of that power can be calculated from the material removal rate (MMR) if the material’s K-factor (cubic inches per minute of material removal per horsepower (HP)) is known (and entered in cell J15). It can also be approximated from the measurement/entry of the tool’s input power when not cutting/milling (cell D32 of the workbook’s “Working Spreadsheet”) and when cutting/milling (cell H32). Note that other sheets in the workbook show known(?) K-factors and your Janka hardness values – thank you for that!
The maximum amount of allowable machine force used for the calculation of the cutting/milling parameters can be entered into cell J13 of the “Working Spreadsheet”. The default value of 18 lbf is reportedly what the standard X-axis stepper motor can provide. The usable value will be far less than that due to the lack of machine rigidity. That lack of rigidity causes the cutter to be deflected from the intended position due to force exerted by the cutter. Deflection vs force is easy to quantify with a luggage weight scale and a ruler or calipers when the machine is on with a stationary unpowered router. I’d be reluctant to enter more than 3 lbf for starters in cell J13.
The cutting force on the endmill will also cause deflection/bending. The amount of allowable deflection (at the end of the endmill) is entered into cell D13. Too much deflection will break the endmill, but 0.003 inches is likely plenty safe, at least for 1/8” endmills and larger. (That’s probably more that an order of magnitude less than machine flexure induced deflection.) Other required information about the endmill is entered into cells D4 – D9.
Entries in rows 1 - 3 of the “Working Spreadsheet” aren’t necessary but may prove useful for documentation and sharing purposes. (I hope you do both.)
If you use a HF Spindle, leave/make cell J4 blank and enter the spindle’s info into cells G5 – G8. If you use a router, leave/make cell G5 blank and enter its voltage and current ratings into cells J4 and J5 respectively. They’re more indicative of actual router output power than the advertised router power. Leave J7 at 50% unless you know otherwise. Enter your router’s maximum speed into J10.
Some manufacturers specify endmill maximum operating speeds as the tangential speed of the cutting edge expressed in Surface Feet per Minute (SFM) rather than RPM. If SFM is entered into cell E17 when cell C17 is empty/blank, the resultant spindle/router speed will appear in cell J17. Recent experience suggests that maximized cutter or spindle/router speeds are best for virtually everything that folks use Shapeokos (and Nomads?) for. I usually don’t use endmills from manufacturers that don’t provide speeds and feeds information, they may not be safe.
The desired depth and width of cut (DOC and WOC) are entered into cells J21 and J22 respectively. IMO, a good/safe starting value for DOC when cutting slots (i.e. DOC = WOC) is the endmill diameter for all but the hardest of woods. Since MRR (and force) decreases proportionately with width of cut, DOC can be increased accordingly as the WOC decreases. I.E. a DOC of twice the endmill diameter with a 50% endmill diameter WOC seems appropriate.
The entered WOC, endmill diameter, and required chipload are used determine an IPT (cell D11) for the feed rate calculation that compensates for the “chip thinning” when the WOC is less than 1/2 the endmill diameter. That feed rate, shown in cell C24, can be over-ridden by an entry in cell E24.
I hope this helps. Try it, you might like it! Help me improve and/or explain it? Feedback from anyone of any type is welcome and encouraged.
2019-08-04 Speeds and Feeds Workbook.zip (168.3 KB)
thanks a lot for the explanation- that helps a lot! I will work through this over the next few days.
I think there is more than enough justification for both yours and Julien’s spreadsheets. They both move us all into deeper understanding and better cutting results.
I have to say though, that the folks at Carbide3D (@robgrz) should incorporate the basic learnings here to improve the F&S defaults in Carbide Create as they are improving it. All it would take is to have a drop down parameter in the job set up to specify whether you have a DeWalt, Makita or Carbide3D router and then deal with the rpm and feed speeds accordingly. The pain, uncertainty, confusion resulting in prematurely ruined cutters and spoiled jobs for new and inexperienced users could be substantially mitigated!
The highest speed of the Makita and Carbide3D is 30,000 RPM and the DeWalt’s is 27,000 RPM. From a purely technical point of view there’s never a reason to use anything other than those speeds if the endmills allow it.
Yes - so I now understand - but Carbide Create recommends speeds at the low end of the router’s capabilities and in many cases far lower than the DeWalt can possibly go. That is my concern with the defaults that CC gives - they are just non-helpful in those cases.
For instance for Hard Wood using the #201 .25" cutter for an outside profile CC gives a rpm of 8333 - which is quite impossible for a DeWalt which can only go as slow as about 16,500 rpm. I bet most new users just shrug their shoulders and go with it (as I did) and then saw their cutters overheat and the wood burn (especially MDF at those speeds and feeds even though they put the rpm up at a still impossible 12.5k). It would be a brave person to then set the router at max 27,000rpm and the feedrate at some unknown higher number without any guidance. So as a new user I gradually increased both and it is still clear that I was nowhere near optimum.
These excellent recent discussions and spreadsheets have been invaluable and timely to get my understanding and results far better and to treat the CC defaults with a lot of suspicion when the suggested rpm is less than 16k
IMO, you would do well to disregard what GWizard advises too. But you can use it to vet my analyses by forcing it to use locked speeds and feeds. Beware that the K-factors used therein are generally quite inaccurate though. Thanks for the feedback!
I’ve seen many posts where Dewalt users always operating at max speed were complaining of burning through their brushes very quickly.
Regarding the feed and speed of Carbide Create, I understand that they were developed for the Nomad and they are carrying on and CC does not make a distinction for the machine you use. The Nomad spindle speed is from 2000 to 10000 RPM so if CC recommended 25000, the Nomad users would have to correct the F&S instead of the Shapeoko users.
This is definitely something else that should be fixed in a future version of CC.
All the more reason to use a Makita, which runs faster and quieter anyway. Apparently @Vince.Fab has had good luck using one for years(?) milling aluminum at 30,000 RPM. Someone apparently posted speeds and feeds for Shapeokos here. It’s not clear where they came from though!.
I agree that the Makita is a better router but your advice for max speed all the time, I think is not good for all circumstances. Like running your car engine at full speed all the time will put more wear and tear on your engine and lead to premature failure but there are more reasons like noise that can be an issue to be mitigated.
Regarding the F&S chart, @WillAdams knows the source but what is not clear is how the different values were derived. Since they were derived over time, I also suspect that the Shapeoko was not quite as evolved as it is now when some of these were determined.
FYI the last time I checked, GWizard, despite BW’s claims, uses the same K-factor for all of the alloys in each material family. So forget about the “fine tuning”.
Nice job on the E-Book, it clearly took a lot of effort and required an really impressive understanding of the issues. Hats off to you sir!
And there is ample evidence here on the forum that this has confused many a new users. I cannot understand how this is not fixed yet, since indeed all it would take is linking the F&S formula to the EXISTING dropdown menu in CC where you select your Shapeoko model… Meanwhile, minor details in CC pro get fixed within 24 hours. Oh well, I guess at least it pushes frustrated users to look for understanding of how this F&S thing works…
A closer look at the additional information and links posted there (by @wmoy) suggests that the primary basis of that Shapeoko speeds and feeds guidance came from experiences shared by users of Shapeoko types of machines (i.e. what worked for them). In light of that, it does seem odd that CC doesn’t even use that guidance as @Julien pointed out.
IMO, experiences shared by users would be a lot more useful in developing speeds and feeds guidance if they provided additional details. Knowing exactly what the workpiece material was, how it was being milled, how much power was required, and how it turned out would be really useful in developing more accurate and useful speeds and feeds guidance.
It is interesting though that the calculated chiploads in the Shapeoko charts are on the order of 0.001 IPT for virtually all materials.
I suspect the mystery boils down to the SO3, having been designed as a sub $1000 entry level hobbyist CNC without a lot of history being melded into a young company, Carbide 3D, that produced a turnkey desktop CNC solution. The (SO3) focus was just not there .
It’s taken a while for the boys to realize which side of the toast the butter is on.
The very recent efforts re CC Pro and the hiring of Luke, MrBeaver lend some credence to my hypothesis. I think.
Floodgates open, let’s hear it!
I’m sure @WillAdams can give us a little lesson in Shapeoko history, and shed some light.
I suspect the Nomad was the crown jewel/core business, and they were surprised (maybe ?) by the rise of the demand for the Shapeoko, and have been playing catch up ever since ? It must be HARD to keep up with orders for HW alone, so I can imagine how software (=spending big bucks with no immediate returns) would not have been be a huge priority for a long time.
I’ve tried to record some facts/dates at: https://wiki.shapeoko.com/index.php/CNC_History#ShapeOko_3
I’m pretty sure that the Nomad was always seen as a tool with a specific/narrow market, and that the development of the Shapeoko 3 was the way to acquire a larger one.
The Materials page on the wiki has grown organically as folks have shared specific feed and speed values — I’ve never achieved a really solid grasp of the underlying math and concepts, so it’s been perforce limited in just recording information other folks have been willing to share. Lots of redundancy and conflicting information made worse by it covering 3 generations of machines.
Hopefully at some point Carbide Create will get a system for setting feeds and speeds suited for the Shapeoko w/ at least the Carbide Compact Router.
From the wiki we learn that the original Shapeoko was an open system build where 3 companies were supposed to build a $300 system as an entry level CNC for the hobbyists. Carbide 3D was one of the companies building the systems, I think that Inventables was another and the X Carve also evolved from the original Shapeoko design. The Shapeoko evolved over time and the SO3 is the 3rd generation. As Julien said, I think the Nomad was seen by Carbide as the machine for more serious people with a turnkey system while the Shapeoko was an assemble yourself system; learn about CNC with the Shapeoko and Carbide Create then come back to purchase a Nomad. So the Shapeoko played second fiddle. One could ask why is it that MeshCam is not at least a cheap option for people buying a Shapeoko while it is included with the Nomad?