Can we cut steel on a desktop gantry router? 

I think this is one of the more useful suggestions. Too many people come into cnc and are trying to use toolpaths that extremely expensive and rigid machines would use when there are completely differant ways to go about cutting on less rigid machines, not just continually adapting the same toolpaths down to lower performance specs.

The end mill is pushed AWAY from the work on a climb cut. It is pulled INTO the work on a conventional cut. The toolpaths he programed are the only way to use this light duty machine. The only problem with climb milling is backlash.

Matthew Rossilini's concern below is true. Conventional cutting may simply pull the cutter into the work on a less-stiff router table (given the high efficiency milling he is trying to achieve). Also, re-welding of chips onto the workpiece is another very real concern with conventional milling, and this just doesn't happen as much with climb milling. Yes, I know that conventional milling is usually the better choice with a loosey goosey table. You may very well be correct.

Not true at all!!! With climb cutting the cutter wants to PULL itself into the workpiece. (like climbing up a hill) Conventional pushes it away. Google a picture of climb milling and you will see the difference. The problem with climb milling is that it will intermittently pull any backlash out of the system. That's where the chatter comes from. Conventional milling forces continuously push the the nut firmly against the lead screw. @@matthewrossilini5808

Thanks for the help! Really appreciate it! I admit, despite knowing that HSMAdvisor was giving skewed suggestions... I still used it as a guide while tweaking. I'm definitely interested in trying more tests, especially as I get a better feel for how the machine performs. That's interesting re: larger end mills. It's one of the issues I was battling, my spindle max is 24k RPM... but feeds faster than >150-200 IPM start to visibly shake the machine. So I found myself running up against the 150'ish IPM limit, which was driving bigger chipload instead of faster feeds. I didn't think about stepping up to larger end mills though. I guess I was mentally assuming the machine couldn't handle larger than 1/4" end mills, but that's probably silly in retrospect. I think I'm going to try and address the feed rate issues first before trying another test; I want to significantly increase the mass of the machine (both so that I can deck off a known flat surface, and to increase the mass) and improve how it's mounted to the table. After that I think it'll be a lot happier moving 200-300 IPM But ++ to retesting with appropriate HSM methodology, rather than increasing chipload like I was doing. Definitely makes sense having been through it once and seeing how the machine reacts. Out of curiousity, what's the best way to measure wall taper? Would be interesting to measure how much the tool is deflecting, since that's probably directly related to the gantry being torqued rather than tool deflecting (just a guess). Micrometers and gage blocks seem subjective to get good wall taper readings, and I don't think I can quite afford a CMM yet :) Are micrometers my best bet?

@@BreakingTaps Use a dial test indicator clamped to a dowel and held in your spindle, then just move your Z-axis. One important point about HEM machining. Always repeat your last finish pass convention milling to remove that last 0.001 (or whatever) taper. You aren't stepping over, mind-you, your just recutting. If you conventional mill to remove taper, your end result won't be as good because your tool will deflect trying to "climb" the material. Some will argue you need a more rigid machine to do that. Concentional does require more rigidity, but were only talking about a very slight amount of material here do you'll have no problems.

Doh, yeah a dial indicator makes sense to measure that. Thanks! Noted on the spring pass, will make sure I add those in the future.

Would you be willing to point a learning machinist in the direction of some documentation on HEM?

I am looking for a CNC that is capable of cutting small parts (watch hands) out of .3 to .5mm steel. Do you know of anything suitable?

Mist is OK on uncoated, but you're right. Most coatings are made to handle heat and can't withstand the thermal shock of hot cut and then coolant. AlTiN coating especially

That's interesting because I run flood coolant on all my carbide end mills...no worry about thermo shock...now an insert cutter I run dry as thermo shock then becomes an issue

it lubricates the cutting edge. I've always flooded it with coolant using full carbide tool, with inserts the COE of the two different materials will crack the insert so I run most of them dry depending on the stock material.

Glad it was helpful! There's another video on cutting steel if you're interested, has some more refined recipes once I figured out what I was doing (as well as experimenting with conventional vs climb, high-feed tools, etc).

That's hilarious honestly. Gotta learn somehow though. I've seen some pretty bad stuff in the shop from people who should know what they're doing so don't feel too bad.

I was going to return my first set of collets until one of the collets snapped into the nut. Then it all became clear.

Bruh

Thanks for stopping by! I would guess the 2z2 will do even better, I suspect it will be slightly more rigid due to being a bit more compact. Good luck, lemme know how it goes!

Awesome, congrats! Have to let me know how it goes once you get it up and running. Feel free to ping me if you have questions :)

@@BreakingTaps Thank you! I have to say, I actually spent an awful lot of money a few years ago on a grantry style router which while perfect for my needs at the time (accuracy on it is fantastic!), wouldn't touch steel - nothing like this anyway! I'll keep you posted! If you're interested, this is my Instagram: instagram.com/outpostworkshopuk/

Glad it was helpful! Thanks for watching

Will keep that in mind! I guess pushing it a little harder gets it out of the current resonance that it's in, so helps settle down the chatter.

This variety: www.ebay.com/itm/Tool-Holder-Clamping-Locking-Tightening-Fixture-50mm-ISO30-SK30-HSK50-C5-Capto/352472546124 Looking forward to seeing how your FM30 performs! The slower speed is very compelling for steel, I bet you'll have a lot less trouble than I did finding a good recipe.

That's great to hear! Happy that my feeds/speeds help get you up and running :)

Yes sir. Keep that chip load down! I agree. Keep that spindle speed up there.

That's an interesting idea. Conventional cuts take more force and should be worse on a light machine in general, but if there's any significant play in the axes then conventional would be a lot more stable in the cut.

@@captainmcderpyderp I have a small milling machine and fight rigidity issues with it. It looks to me like you have the same thing going on. What works best for me is to do most of my material removal with conventional milling and then take the last few thousandths with climb milling. The climb milling leaves a beautiful surface finish, but I have to keep the cuts light to avoid the chatter and vibration.

I wasn't planning on doing more tests in steel (honestly only intended to use the machine for aluminum), but so many suggestions have come in I now want to see if I can tweak it some more. :) Will try out conventional and see how it fares, thanks! I wish I had a better way to measure deflection and rigidity during the cut itself :( Trying to understand what's going on from the cut sound and surface finish feels like a proxy at best... I wonder if a high-speed camera could capture the dynamics during a cut to analyze objectively. Hmm...

@@BreakingTaps There are systems that do that very thing, but pricey. Some high dollar cnc machines have it built in, but on my modest budget I find listening closely watching the finished surface will usually tell me what I need to know. I will often put my hand on the machine to feel for vibration. Never forget, everything is a spring.

Brian has a great idea. If there's any play at all in the travels, climb cutting is disastrous. But this thing seemed to be doing okay, seemed more like rigidity issues to me.

Oh awesome, thanks for stopping by @HSMAdavisor! Really enjoy your software, as a newbie it has helped me find good starting points even if it needs tweaking afterwards. Appreciate the confirmation that my understanding of how it works wasn't way off base. I wonder if there is a good way to "de-rate" the estimations that HSMAdvisor gives to compensate for smaller machines? Set the spindle HP lower so it doesn't give as aggressive of cuts? I find with the 3HP spindle that even with the finishing slider maxed out it can still be too aggressive. Perhaps some kind of "low-rigidity" mode could be toggled that has different set of assumptions? Dunno, might not be possible at all since the variables in a "low rigidity" machine are so much different and probably not consistent. Anyhow, thanks again for the software!

@@BreakingTaps I made an analysis of your video on my blog: zero-divide.net/?&article_id=5258 Basically the solution to prevent the power of the spindle exceeding the rigidity is to Dr-rate the spindle using "Warning At" field in the Machine Profile dialog.

Very cool, thanks for the writeup/analysis and the tip! Will try that on future cuts.

@@HSMAdvisor Isn't it more about cutting force (which is inversely proportional to spindle speed and endmill diameter) than spindle power for these types of machines? Maybe a "Warning At" or "Maximum/Target" cutting force = *** for these types?

@@gmack4097 I agree. There probably should be a "Max cutting force" value in the machine profile. I will add in the future updates.

Ah that's a good idea, will give that a shot next time.

I as well and I learned the best way. I ordered a set of er32 collets off of evil Bay and was not familiar with them cuz I was used to using r8 or 5C so I brought it over to my local machine shop and ask the guy he could turn it down on his lathe I didn't have my lathe at the time and because it wasn't seating properly. And his response was a very good laugh at my stupidity 🤣 but by asking he did then showed me how they properly seat. Live and learn 🤟🤣

Yeah, I get the impression they aren't used to these machines being used for metal. I asked some questions and they were helpful to a degree but didn't have specifics regarding metal, tolerances, etc. They have been great in answering other questions regarding pinouts, etc. Although I've also been talking to internal support engineers and not sales reps, so that probably helps too

Hehe, definitely lifted the idea from ToT. I love trying to find the hidden "Subscribe" in each of his videos, like a machinist-youtube-where's-waldo :)

Thanks Will definitely post a wiring video at some point. Few odds and ends to finish up before then: need to finish enclosure (~80% done), wire in the low pressure fault sensor and wire in that drawbar interlock. Think those are the last things that need doing, then I'll put together some diagrams of the wiring and pneumatics (and extra parts that are needed).

Got the same setup, s30c spindle and avid cnc. I'm on my 3rd vfd and the delta vfd from cnc depot is the best one so far to work with the avid electronics package. Awesome setup, would highly recommend

100%! I don't think I'll be doing steel very often, but it's nice to know I could knock out a part without having to fall back to like 10ipm to do it :)

Yeah, it's a fair question... not sure! I guess we'll see in like a year :D Most of the machine components (on my benchtop version) are pretty robust. E.g. the ballscrew bearing supports, the gantry beam, the linear slide attachments, etc. I am keeping an eye out for bolts slowly loosening over time due to vibrations though. No indication this is an issue yet, but I could see it causing problems in the future and might need some threadlocker to remedy.

Ah that's a good idea, will try closer to the edges of the machine... and definitely thinking about getting an adapter so I can use a torque wrench on those tool holders :)

Oh that's very interesting re: Sandvik... I definitely trust them to know what they're talking about! And I have for sure noticed chips sticking to walls due to the mist of coolant. Seems like it provides just enough stickiness that the airblast can't always dislodge it. Funny you should mention high feed mills, I picked up a few the other day. Just small, solid carbide ones to start. But if those look interesting/promising, I wanted to investigate the insert variety (Kyocera Raptor, etc) because they seem easier to get in a variety of sizes, and should help my wallet a bit. Will post a video eventually when I get around to testing them! Really interested as well to see how they perform on the router. Since they put most of the force up the spindle, it seems like a perfect match for less-rigid machines.

@@BreakingTaps interesting...did this video get made?

@@philipsommerton4280 yep! I tested a high feed mill in ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-fEJ0z1uuni0.html

Happy to help! I'll see what I can do for some more tests, I was wanting to try out a few different end mills anyhow (and all the suggestions in this video). Unsure when I'll be able to get to it though, just a nights/weekend hobby for me right now :) 1. I briefly looked at the Stepcraft lineup (since they have ATC), but wasn't impressed with the v-wheel style motion system, and read some poor reviews on them in general. Also considered the wide variety of 60xx chinese routers (the larger 6090s, etc) but they are tailored for wood and also hard to know what you're getting, dodgy QA/support/etc. Tormach didn't have their router at the time, but I think I would have passed since it looks geared more for wood too (and expensive) The other machines I was seriously considering were "mini VMCs", like the Tormach 1100mx, Syil X7, SkyFire SVM2, etc lines. And maybe a Haas MiniMill on the upper end. 2. Very possible :) It's also better than Avid specs the machine, so it could be luck (or conservative specs on their part). I didn't do rigorous testing mainly because I hadn't done any tuning yet. Just tuned the steps this weekend, need to re-tram, fiddle with CV mode, etc. I'd also like to do some repeatability tests with indicators, etc 3. Hopefully soon, once I work up the motivation. Been putting it off because I need to unwire some stuff to put in a proper enclosure 4/5. Unsure, I haven't run it slower than ~8000rpm so far. Max torque for my spindle is ~18k based on the spec sheet, so I suspect low-end torque to be quite low. There is a torque boost setting on my VFD but I haven't played with it yet. I was planning to threadmill rather than trying to get a tapping head to work (also because they eat a lot of Z and there's only ~9" to work with)

@@BreakingTapsI'll stay tuned, thanks and good luck!

@@BreakingTaps Stepcraft does not use a V-wheel in our systems. If you would like to ever discuss I would be happy to talk info@stepcraft.us

@@StepcraftInc Sorry, should have been more precise in my wording. By "v-wheel style motion system", I was referring to your steel rollers on round rails (i.e. www.stepcraft.us/web/image/74255/allsteelmotion.jpg). I wanted something with linear rails so this ruled them out.

Thanks! I also have the NEMA 23's fwiw... the Avid folks mentioned the larger NEMA 34's wouldn't be useful to me because their higher torque would mainly be useful at higher feeds, but higher feeds would also start to induce whip in the ball screws. Might be less of a problem on the 2x2 though, since they have a smaller y-axis I'm picking up some singlue flute "O" end mills to play around in aluminum, but I don't think they will be helpful in steel. Having such a large gullet is helpful in removing chips (which helps prevent welding in aluminum), and also logically helps keep the feed rate down. But it also weakens the end mill due to so much material being removed, which can be a liability in steel. The extra deflection caused by a less-stiff end mill can start to chatter/resonate when hitting the harder steel and leads to failure. That's why most end mills for harder materials are 4+ flutes. Recutting chips is still and issue, but since you don't have to worry about welding it's less of a driving concern and more of something you keep in mind.

Hehe, it has definitely crossed my mind :) The upright L-shaped gantry supports would be an easy candidate for conversion. Simple part, doesn't need careful alignment, and could replace without disassembling the entire machine. Deflection of the z-axis forward/back when the spindle is extended, and torsion of the x-axis (caused by pushing the z-axis forward/back) are probably the main modes of deflection on the router, so replacing parts on the gantry assembly would be the next best thing to do. Would require more work since you'd be re-aligning the ballscrews and linear rails. A steel table (or even a big chunk of aluminum) would be a nice upgrade too. That's probably going to land on my todo list at some point. Would be nice to replace the t-slot extrusions with something solid and flat.

Stiffness isn't the primary parameter for stability in cutting machine tools, damping is, and steel is not much different to aluminium in that respect. That's why cast iron (or sometimes epoxy granite) is used. Stiffness can be achieved by geometry rather than materials selection to the extent that it is required.

Hm fair. I might break out some indicators and try to measure deflection at rest (e.g. push on various parts of the machine while the motors are engaged to see how much different components move). Would give a better idea where stiffness is needed, and where it's just poor vibration control.

I have the (much) smaller benchtop version, only 2x3. The Avid support folks said the benchtop version would handle metal better, since it's a lot more rigid due to small size. So the fullsize version might be able to handle steel but it'd probably have very different cutting parameters, and is probably less rigid overall due to all the extra travel. That said, plenty of folks have cut aluminum on their full size machines (Robert Cowan comes to mind: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-ii7HRgV-wbY.html)

Generally, that's correct! Feed rate is mostly tied to number of flutes and the chipload (which is a combo of width/depth of cut and material). But you wouldn't want to run a single flute in steel for example, because the tool wouldn't be rigid enough... that's why 4+ flutes is generally recommended in steel.

Hmm. I got bit by step calibration because I only did it in one location... so if you calibrate make sure you repeat in several locations, and try to calibrate across large distances if possible. Otherwise, a sturdy table is really needed. Once you get the machine moving fast, it has a bunch of inertia and can throw the table around if it isn't stout (which then causes issues in the cut because things are waving about). Otherwise I've been pretty happy with it. Goodluck!

Breaking Taps I’m using my own electronics so I’ll have to calibrate on my one but I appreciate the heads up. I doubt I’ll be cutting any steel.....other than clamps!

I would say otherwise. You can see in the finish of the bottom of the last completed cut that the corners of the mill were already damaged. They just did break away on the last one. My attempts to cut 3 mm (0.112 in) steel plate with a 3 mm mill failed similar, after one or two feet of machining the edges crumbled, started to glow and then the whole mill broke off. So your results were far better than mine. There aren't that many possibilities for the damage to the edges: overheating or thermal shock. To high cutting forces would break off the whole mill. Because the coolant only partially and intermittently reaches the lower edges, I'd think of thermal shock because some of these mills can even used dry or with air. Because I feared overheating, I tried to keep my cutting speed much lower, you are using about 750 ft/min (250 m/min) which is way above the mills I could get here in Germany. Most are rated with 100 m/min in mild steel which means only around 5000 rpm for a 6 mm (1/4 in) mill, and all the spindles I know lack torque and/or a torque steady for a full rotation for these low speeds. You would need something geared which simply doesn't exist.

Thanks! My taig actually has the old custom collet system before they switched to ER, so it just "sits" inside the closer without any snap fit. So, theoretically, those were loaded correctly :) And yeah, it really was a real bear haha. I felt pretty foolish after discovering I had been using them incorrectly... in retrospect it definitely messed up some of the tests I ran on the first aluminum video without me knowing about it. Serious facepalm moment for me :)

Breaking Taps I commend you for sharing the collet experience - most learn more from a mistake, I know I do anyhow. Let me know if you want to upgrade that Taig to an ER spindle! I’m working on some Taig CNC mill tutorial vids now. Keep up the great content!

@@BreakingTaps Is the original collet chuck on a Taig similar to the original E16 collet chuck, or completely different? Pictures I've seen show weird collets similar to but not the same as ES16 (an early, compatible, derivative of E16). I have an original E16 collet chuck for my Unimat but only a few collets. ER16 collets have the same taper angles as E16 but are slightly longer, so they fit, but the nut doesn't screw on far enough for safety. But... On my E16 chuck, the nose thread is 20mm dia x 1.5mm pitch. A standard ER16 nut is 22mm x 1.5mm. It turns out 20mm helicoil is a perfect fit in an ER16 nut and it made a very effective conversion. A friend of mine adapted a collet block to fit the spindle nose on a Taig.

@pnt103 The original Taig collets appear to be their own creation, probably wouldn't fit E/ES16. The ones I have look like this: www.soigeneris.com/taig-lathe-collet-set-1040 Notably, the collet closer/nut pulls down tight against the flat on the collets, which makes me think they wouldn't be compatible with the top taper on an E/ES16. I can grab some dimensions later today if that'd help. At some point Taig switched over to standard ER collets if I'm remembering correctly, so it probably depends what year/make you find.

@@BreakingTaps Yeah, that's the sort I've seen in other pictures. So unless the Taig back taper matches the ER16 back taper, and the nose thread is compatible, allowing you to use a new nut, my trick isn't helpful.

If it is blowing air out of the bottom it is probably similar to mine: that air pressurizes the spindle case and keeps debris/liquid out of the labrynth seal around the spindle nose. I wouldn't submerge it or anything, but it should keep chips, dust, mist, etc from getting inside the spindle. I have mine pressurized to around 30psi...not sure the optimum pressure but since I won't be working with dust (wood) it seemed a reasonable value.

@@BreakingTaps thanks its very solid little 6040 cnc, been cutting slate stone plaques with good results. But may upgrade to cheep 1500 watt aircooled spindle to try steel.

Already picked two of those up! I grabbed the 0.240 and 0.120 high feed mills a few weeks ago, but haven't had a chance to test them yet. Was thinking the same as you: the high axial load should be better for relatively non-rigid machines like routers. The high feed rate are what have given me pause so far, mainly because really high rates tend to throw the machine around. But I've been dialing in the acceleration so it doesn't jerk the machine quite as much... feeling more comfortable with higher feed rates now. I'll try to get them tested sooner than later!

Noted, thanks! Might dial up the fogbuster next time so it's more spray and less mist.

This is not correct. Tool life is maximised in steel when cutting dry, so long as chips are evacuated effectively (which air blast should accomplish). Steel does not exhibit the chip welding or adhesion issues that aluminium does.

And for titanium you should always use coolant just for safety reasons.

Huh, interesting. I guess I'll have to try it both dry and with heavy coolant now too, just to see for myself. Conceptually I can see the argument: since steel doesnt have welding/adhesion issues, the main thing coolant is battling is heat build up. So as long as you are transferring enough heat into the chip and not the workpiece or tool, you're ok to run dry (and as long as you don't recut chips as you mentioned).

@@captainmcderpyderp I work in the Aerospace industry with all types of tool steals and nickle allows. When we are using tools we go for the maximum allowable use of whatever tool it is that always far exceeds the manufacture tool life specifications. It is important to remember that when using a tool at the wrong speed or feed and not using coolant when you should or shouldn't will result in a damaged tool after only one revolution of the tool. Once the tool is damaged it becomes more damaged a lot quicker to the point of tool failure or the tool to worn to create acceptable finish or cut.

420 oz-in NEMA 23 steppers, although I do wish I had splashed out for the larger Nema 34s instead. Or just gotten servos. Oh well :)

@@BreakingTaps that's exactly what I wanted to hear. Thanks. I just ordered some nema 23 motors and that looks powerful enough for my needs, gotta redesign the whole machine to make them fit but it looks like they'll be worth it. My Nema17's lose steps when they need a little lubrication, even while not cutting anything. Squeaking is one thing but losing steps is another

:) There's a full shot in one of the earlier videos: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-qiM20-woEOk.html

Width of cut should stay constant, as that's a function of the axis motors positioning the endmill relative to the work. Rotation rate should, in theory, remain constant as well. In practice it'll slow down to some degree depending on how heavy the cut is (the spindle controller has some rudimentary feedback control to sense RPM, but it's not super high resolution). Assuming those two variables stay constant, load-per-tooth will change as the IPM changes. E.g. you can see the IPT doubles between the first and second test because the IPM doubles, but all the other parameters were held constant. Usually you aim for a certain load-per-tooth range and then adjust the other parameters to suit (subject to limitations like spind speed or horsepower or machine feed rates)

@@BreakingTaps Ah, I see, thanks. I thought load per tooth was being kept constant because you didn't colour it haha

Pretty much the size of the table if you're creative with strap clamps and pre-drilling holes to fasten to the table. So a bit less than 24x36" sheets. Z height is limited to around 8" however, much less if you're using vises or it's off the table.