Z lock

This topic contains 31 replies, has 8 voices, and was last updated by  Ryan 1 year, 10 months ago.

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  • #4111

    Simon
    Participant

    How do you assemble the z lock nut. Mine keeps slipping. I have the spring and the longer nut and the regular 5/16th in nut. What am I doing wrong, this is driving me crazy. I keep ruining wood stock.

    #4112

    SteveC
    Participant

    Make sure the Z lock is not upside down. The hex opening for the nuts is at the bottom, the round hole and clamp screw are on the top. The longer nut goes on the top against the upper surface/round hole of the Z lock and is clamped by that screw. The entire Z assembly is held up by the clamping friction against the longer nut. The spring and lower nut are free within the Z lock. https://www.vicious1.com/z-nut-lock/.
    Steve C

    #4114

    Jason
    Participant

    I have run into the same problem where the lower nut pops out of the bottom. Should I just try and crank down the z lock to make sure the nut doesn’t spin free inside the Z lock?

    #4115

    Simon
    Participant

    I will re assemble it. Also is there any reason I should be getting uneven resistance when manually turning the threaded rod. At some points I can’t manually turn it and at others it is extremely smooth. I lubricated everything so I am thinking about picking up a new threaded rod. Any suggestions?

    #4117

    3dTI
    Participant

    Did you check that your threaded rod was perfectly straight? Any bend (even very slight) will cause issues with your z axis.

    #4121

    SteveC
    Participant

    @jason,
    If either of the nuts spins freely inside of the Z lock then you have a really big problem with the printed part or a nonstandard nut dimension. The long top nut should just barely and tightly fit inside the hex hole when inserted all the way to the top of the Z lock. Then the clamp screw should prevent it from sliding down. After the spring, the lower regular sized nut should fit snugly but not tightly in the lower hex area of the Z lock. Nothing is clamping the lower nut in place. It can slide up and down inside the hex channel but it cannot spin. The threaded rod keeps both nuts the same distance from each other with the spring providing tension between them. Any looseness (backlash) in the nut/rod threads is reduced by the spring tension.

    To put the assembly together start with the long nut clamped tight within the Z lock. Make sure it is inserted all to way to the stop at the top. Then screw in the threaded rod 1/2″ or so starting from the top of the Z lock. Next insert the spring and the regular nut. Push that nut with your finger to compress the spring as tightly as you can. Keep it compressed while you screw the threaded rod in further until it engages with the regular nut.

    It’s kind of funny when I accidentally raise the Z axis too much and the smaller nut and spring are shot out of the bottom :).
    Steve C

    #4124

    Ryan
    Keymaster

    Just to make sure there are no other issues, try just using the coupling nut. No spring, no second nut. See if that keep everything smooth. It can be easy to overtighten the anti backlash. I might just sell the kits with a longer coupler nut and skip the whole anti backlash. I’m not sure its is needed or is even strong enough. Kind of hard to test really.

    Clean the coupler nut before you clamp it in for a solid clamp.

    Just to cover all the bases. The most recent one I put together was having z issues, turns out it was kind of lopsided. The threaded rod was visibly crooked. So i loosened the whole middle assembly gave it a wiggle to seat everything and tightened it back up. Works perfect now. So check to see if the rod is equal distance from the bolt heads.

    Maybe its time to design a new 2 piece middle.

    #4167

    Simon
    Participant

    Solved it. I reprinted the z lock and scaled it down a hair and now it really holds the nut tightly. Everything is printing consistently now.

    #4305

    Joshua Stump
    Participant

    AllTed,

    I you didn’t use the anti-backlash feature with the spring, how long would the coupler nut be? 1″, 1.5″?

    I would like to experiment with both.

    Thanks,

    Josh

    #4306

    Ryan
    Keymaster

    A bend shouldn’t have very big of an effect. It is pinned at the top with the “z motor mount bearing and in the middle with the whole middle assembly. Different from a 3D printer.

    #4307

    Ryan
    Keymaster

    The longer the better. The goal of the spring is take out any slop in the coupling nut. The longer the nut the less slop they typically have. I have been messing with it I haven’t found any real need for this all the forces tend to be in one direction consistently. When I designed this I thought using it as a mill would push back on the whole thing turns out it pulls on it in the same direction as gravity, meaning slop isn’t really an issue.

    I have learned a lot since I started this. I was pretty sure wood would be out of the question, turns out even aluminum works well.

    #4317

    TheWiz
    Participant

    I bought a coupler nut at the local hardware store out of the drawers. It’s 5/16×18 thread, but it measures 11mm (7/16″) across the flats instead of 1/2″ (13mm) like every other 5/16×18 nut in the joint. It’s obviously unusable with the standard printed Z-Nut lock.. Watch out for this..

    #4318

    Ryan
    Keymaster

    I made a znut lock for both sizes.

    #4329

    ualdayan
    Participant

    Ahh, now this is a problem I had many many times. I kept thinking ‘Now it’s fixed’, only to find it dropped out and it’d drop down cutting through an inch of MDF and into the table it’s sitting on (that DW660 just keeps on cutting through whatever it seems). I even tried scaling it down – which worked at first, but then it seemed to eventually work it’s way out still. The other day I finally scaled it down even more, printed in ABS this time, then used super glue (which is why I used ABS). I initially had the same problem of it feeling uneven in torque required to move it too – but after using some white lithium grease it became smooth enough for the motor to handle that it doesn’t seem to matter.

    Personally I also found things went better for me when I changed the speed and acceleration settings, it seems you can go faster than the default speeds, you just need it to accelerate into it slower, here’s what I’ve been using:
    “M203 X75 Y75 Z15 E45”
    “M201 X30 Y30 Z4”

    The X/Y could probably go faster, but the Z is the biggest difference for me because I seem to gravitate to 3D designs, and the slow Z limit of 5 on the stock firmware was really slowing things down for me. Note: You’ll need to change the microstepping before changing Z to above 10mm/s, the Arduino CPU can’t do more than about 40,000 steps per second, and at 1/32 microstepping that means you’re maxxing out the CPU at only 10mm/s.

    Also, I just learned about this, and haven’t had time to try it, but for bit changes you can do M84 S0 to keep the motors on. If you’ve ever had it turn the motors off in the middle of you changing a bit you know what that’s like.

    #4336

    Ryan
    Keymaster

    Glad you got the z nut lock worked out.

    I’ll look into the z accelerations and make a firmware update. I never even considered maxing out the arduino, that is some good information. What happens when it gets maxed out, missed steps or will it just not go faster?

    #4340

    ualdayan
    Participant

    It missed steps for me if I tried going faster than 10mm/s on the Z. After I changed the stepping from 1/32 to 1/8 I was able to do 15mm/s, but there were points where like the OP it seemed to have more trouble turning the allthread and at those points it would start going slower. I then adjusted the acceleration, and by easing into and out of the 15mm/s it seems to have a balance between being faster (accelerating at 5mm/s which was the previous max feedrate) and still being accurate.

    In Marlin you’ll see something like this:
    #define MAX_STEP_FREQUENCY 40000

    So at 1/32 microstepping and over 4000 steps per mm on the Z, trying to go over 10mm/s starts dropping steps (I believe it’s just suppose to slow things down, but Marlin seems to drop steps completely instead – although a dev posted here that it was fixed in the dev branch). By changing to 1/8 that dropped it down to 1133.86 steps per mm bypassing that 40,000 limitation.

    I’ve seen that you are against limit switches elsewhere, but never why. Are you afraid of false triggering? I was planning on adding some purely for homing. I figure if I get a new wasteboard, add limit switches right at my maximums, then drill into the wasteboard every 100mm, I could line my pieces up right along the drilled holes, use threaded inserts to clamp the piece down, then at the start of my postprocessor have it do a G0 X100 Y100, G92 X0 Y0 and have a setup that after changing end mill bits would go back to the same exact spot every time. Would that work or is there something I missed there with that idea?

    #4343

    Ryan
    Keymaster

    Learn something new everyday!

    I need to clean up the shop a bit but then I would like to mess around with the speeds and accelerations. I know if you slow down the X and Y accel you will get funky corners on 3D prints, right now I believe the X and Y are as low as they should go but I might try turning them down a bit in order to gain some better rapids. The Z definitely needs tuning seems like some people are having plunge rate issues, and I would love faster 3D milling!

    Ah…..End stops
    I absolutely love them, I feel that everyone should have max end stops on there machine for safety, and most should use minimums as well.
    I don’t recommend them or include them because it is the number one troubleshooting question I get. Everyine should run the machine without them first. That way you know everything works. So many people wire them wrong, or they want to use them like a 3D printer with a fixed minimum. I use my CNC for different things so there is no time difference in setting a home by hand or setting a minimum switch each time. That being said, for cnc work having a home is very convenient, for bit changes or if a bit breaks but you really need a touch off z home because the bits will always be a different height. Then that would confuse people that are dependent on them for 3D printing.

    Really its just a can of worms I don’t want to trouble shoot. I sell them because they are useful for people that have some machine experience and I’m sure most will end up adding switches. For beginners I feel its best to learn this one step at a time.

    #4350

    ualdayan
    Participant

    Ahh ok. I was thinking there was some horrible downside I didn’t know about. Yeah, I was thinking a touch off Z, and then changing origin to be at the bottom of stock instead of the top. I use calipers to measure everything so by inputting that in the software it should be able to reliable calculate how far to lift the bit with 0,0 being at the bottom. Right now I typically manually move it to a spot, then drill down, then raise it back up JUST until I can slide some paper under the bit. When changing the bit I try to not move it (keep the motors on), but if it does move I know I can line it back up with the hole (move it until it goes back down into the hole easy), then raise it back up to where a sheet of paper fits under it again.

    I was wanting to order the wiring kit from you anyway (wasn’t available when I bought my kit originally), so I think I’ll throw in some limit switches and wiring too. I soldered everything initially, but I need to desolder them to work on something. Figured as long as I was desoldering once might as well change over to your wiring for easy plug/unplug in the future.

    #4355

    Ryan
    Keymaster

    You really got me thinking about this. If you have some time tell me what you think.
    I really need a good way to test and quantify these settings. Other than just slamming the axis around. I figured do all the settings in the air, then use a cut pattern through some soft pine or something when it seems maxed out, and then back it down a bit for the masses/safety factor.

    To test I figure-
    Set a conservative accel, run iterations to find max speed for the axis for rapids. (Spec sheet says 200mm/s is half the torque of 20mm/s)
    Once the max speed is found, bump up accel until it starts to skip.
    Once that seems maxed out see if decreasing micro stepping really increases torque, Micromo says this 16ths is almost 2 times the torque of 32nds, pretty sure 8ths is a bit coarse for x and y but should be fine for Z double the torque again. There is a lot of controversy on this subject that is why I want to check it myself. I didn’t believe it when I built the machine but I trust micromo. Then this seems to make more sense because at 32nd steps we should have almost no torque according to micromo, and to me full steps and 32nd steps felt the same when I tested by hand that is why I went with 32nd.

    I did test the step size on the very first machine. I know we can’t do full steps. I did a circle as large as my build volume would allow and used the pen holder. At full steps it was visibly jagged, but now you have my thinking I should try 1/4th and 1/8th. But I really need to know if this increases torque because this would be hard to implement to all the current users an I only want to do it if it makes a measurable difference.

    Who doesn’t want free torque and speed!!!!!

    #4358

    ualdayan
    Participant

    From my understanding when it comes to torque and microstepping it’s torque AT that resolution. Meaning the motor will start to lose some of it’s microsteppings if too much force is required to move, but as long as you aren’t overcoming the motors actual torque ability it will ‘catch up’ at the next full step. I’m no expert on it, but here’s how I understand it. Picture the magnets pulling the shaft around inside the stepper, now imagine with microstepping that power is being changed so that the shaft is finding itself attracted between multiple magnets just enough to hold it in a specific area in between the two of them (there’s why you have less torque at that resolution – one magnetic field is ‘fighting’ another one and that’s what is holding the shaft where it’s at) The more you do that (1/8, 1/16, 1/32) the less the motor can hold in a specific position. Now, when it gets to the next full step though it’s going to deactivate those competing forces since it’s no longer trying to hold between two full steps, and the shaft will jump to the next step because it should be at full torque there. The shaft should ‘catch up’ in other words – it won’t always be where it should be if the forces are overpowering the microstepping, but you aren’t going to miss extra steps because of missing torque (when it gets to the next full step it’s going to jerk the shaft to the next full step where it should be).

    I just changed the Z axis on mine because it was hitting the Arduino Mega limit. I don’t think changing it on X/Y would make those axis go faster (at least not when milling since you aren’t going to be pushing those axis to 200mm/s when milling).

    In the micromo article they phrase it as: “The rotor will lag behind the rotating magnetic field until sufficient torque is generated to accommodate the load.” which I take to mean the example above – it’s going to lag behind where it should be if it can’t overcome the load for the microsteps, but then when it hits that next full step the magnetic field will have rotated to a point where it has normal torque and overcomes the load.

    In the end though if my Dewalt is being pushed towards something typically it gets deflected more than any .0001 inch difference that is ‘in theory’ the difference between 1/8 and 1/32 stepping (going from ~4000 steps per mm to ~1000 steps per mm) so changing to 1/8 won’t lose anybody any true accuracy either.

    #4361

    Ryan
    Keymaster

    That helped a lot. that explains the second article I linked. If he were to test torque of say 1/32nd step instead of at the full step mark it would be less. Awesome thank you.
    I will spend my efforts on testing the z axis and probably ship them at a different step rate now.
    I think the x and y could use a little accel tuning as well.
    Thank you for the lesson and motivation.

    #4369

    Ryan
    Keymaster

    You were very right I was hitting the marlin speed limit. I changed the z to 1/16th and not I can move it much faster. It would stutter or stop in 32nd and with to 16th, smooth as butter.

    These screen shots were z max on my better machine, I have another that is kinda tight so I want to try this on that one as well.

    #4381

    ualdayan
    Participant

    I’m finding for me a big limit on speed seems to be rigidity of the middle component. If I try going much faster through material the DW660 actually starts getting pushed from it’s intended path. It’s not the X/Y steppers though, it’s definitely twisting on the middle part. Sometimes I wonder – what if I took one of those $20 makerslide things and used it just for the middle? A mount that puts the X steppers slightly higher than where the Y steppers are now, then the belt goes across the middle pulling the middle mount along the makerslide.

    Although I’ll probably end up trying that wooden middle remix I’ve seen on Thingiverse (thanks to your work I have the machine to cut that wood now) before going the Makerslide route. I am however definitely going to try that $14 4 start leadscrew on Amazon. From my understanding at 2mm pitch, 4 starts, every 1 rotation of the motor SHOULD move it 8mm up or down. That’s a pretty huge difference from the 1.44mm per rotation of the all thread, and at 1/8 microstepping I still get a resolution of 0.000625mm per step which is accurate enough. If I wasn’t trying to keep the cost down to the cheapest stuff I’d just go ahead and get one of those stepping motors that has the lead screw built in for $36 from Robotdigg and get rid of the coupler. $14 vs $36 though – eh, I know I’m going to go the cheaper route. If I didn’t already have the stepper though it seems like it’d be a great deal to get stepper and lead screw all in one, and eliminate the need for the coupler at that price.

    The machine can already do some really amazing things – I just want it to go faster now.

    #4396

    Ryan
    Keymaster

    The biggest effect on the center rigidity is distance of the tool tip from the bottom of the gantry. Half the distance, twice the rigidity.
    When you say you are having a speed limitation how fast are you going now, through what material, how far from the gantry is your tool tip, and how fast would expect a machine under $10k to be able to go?

    I mill aluminum with the tool as high as possible, I actually have a new mount for the dw660 that should make things even more rigid but At the moment requires modifications to the z rails.

    No comment on the rail, at that point you are making a different machine.

    Why switch to a lead screw? Plunge rate through most materials is really slow, seems like a waste to change all that just to speed up your z rapids.

    #4400

    ualdayan
    Participant

    I like the 3D carving projects the best, but when doing a 3D Roughing if I set a pass depth of .06mm it will go along the contours of the 3D model in the wood, back and forth (I can select either X or Y axis) and where it needs to cut deeper it cuts up to .06mm there. The problem is with 3D the Z is constantly moving up and down, so the fastest you can go is the speed of your Z axis. For 3D to come out good I like to use thicker material that gives more depth. Imagine 3D printing something 13 inches by 9 inches by .75 to 1 inch thick and it is going at .06 layer height and limited to 5-10mm print speed. Most of the time it isn’t even cutting (just following the contours of the 3D model where it has already cut down enough). A 17 hour project would only take 8.5 hours if I could double the speed of the Z (and most of the time it is not plunging down into material). If I had a more rigid middle and was able to cut .1 inch per pass that might even come down to about 4 hours.

    #4403

    Ryan
    Keymaster

    Your middle should be rigid enough to cut much deeper than .1mm in wood per pass. My machine can’t handle a plunge rate of 14mm/s because of tool strength not just machine speed.

    How far is your material from the gantry?

    I cut that Brazilian walnut at 4mm (my full tool depth) in a single pass at 20mm/s, at 4″ from the gantry and easily had room to do much more much faster. That wood is super dense so if you are doing pine or something soft you should be able to go much more per pass. Try roughing using a waterline pass much faster with very few z moves and high step over and only use the contour cut for the final pass with a low step over.

    You haven’t given any information to determine if your gantry is loose or you are just trying to cut beyond the machines capabilities. Axis speed is not the only way to get a final product faster more efficient tool paths, larger roughing tools and smaller finishing tools help.
    The posts that just say it isn’t fast enough or it needs to be more rigid is bad press, so I do my best to help those people out. But not rigid enough for what material, what gantry distance, What spindle, what spindle speed, what cutting bit, what step over, what depth of cut? Your settings might just be off a bit and the problem would be solved or maybe you just expect too much.

    #4406

    ualdayan
    Participant

    Hmm, it is soft material, not hardwood. I know I can manually push on the Dewalt (with it off) and make it rotate a little around the middle. I calibrated for size, and all the bearings are making contact, but I kept having my PLA crack on me so I switched to polycarbonate. Is it possible polycarbonate is just too flexible? Dewalt DW660, spindle speed would be approximately 12-32k with a MCLS speed controller (setting of 3 to 10), Inventables sample end mill kit with 1/8 inch 2 flute straight, 1/8 inch ball nose, and 1/8 inch 1 flute upcut (also has some fishtail bits, but being 1/32 in size I really didn’t try to push depth per pass with those). 45% step over, 0.06 inch seems ok, but at .1 inch the Dewalt starts getting slightly pushed out of the way and no longer is cutting in a straight line. Sorry, just noticed I wrote 0.06mm earlier – I meant 0.06 inch.

    #4409

    Ryan
    Keymaster

    The 1/32 is probably moving more than the dewalt, that is a tiny bit, you should start with an 1/8″. Pushing on it by hand doesn’t mean much.
    How far is your work material from your gantry?
    How long are your axis?
    How fast are you moving when the bit strays off course?

    #4414

    ualdayan
    Participant

    From the wasteboard to the X axis it is 7 inches. The axis are 30 inches. 25-35mm/s feedrate.

    My all thread seems to have rougher spots where it doesn’t want to turn as well, if I make the gantry shorter it seems to run into one of those rough spots. That was another reason I was considering a lead screw – my first all thread came in the kit and I didn’t notice anything wrong with it when building everything, while the all threads at my local Home Depot visible aren’t perfectly straight across their length.

    #4415

    Ryan
    Keymaster

    7 inches is nuts, a lot of other small cnc’s only have a 3 inch Z. You should really bring that down to 3 or under. Your bit only has .5-1.5″ cutting ability anyway, you should always put your material to be cut as high as possible. If you are only cutting 4mm deep only leave 6-7mm room. Cleaner more precise cuts. Half the distance twice the speed. Think of it this way, most 3D printers only have a 8 inch z and you are slamming around a 4lb spindle+the drag from its cord.

    If your allthread has a rough spot take, it out and chuck it in a drill, lube up the rod and run it back and forth a few times until you feel the rough spot go away.

    I feel 25-35 is pretty fast, sure faster is possible, but I don’t think I have made any videos faster than 20mm/s, I go slow and just very the depth to keep cuts real nice with minimal finishing work.

    You machine sounds good your expectations just seem a little high. I can make the machine do more but, I am focused on making it easy to use for everyone, not just bleeding edge fast for perfectly adjusted machines.

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