r/CNC • u/Demon_scared • 3d ago
HARDWARE SUPPORT Help with HAAS z-axis falling
My Z-axis keeps gouging my parts everytime there is a power fault/ blackout. Even when owing emergency it drops a little. Recently my second haas been reported to start moving on other axes as well while it drops, the x and y axis is also moving and gougingthe parts along the length while it drops. It ruins the parts and tools every single time.
11
u/BMEdesign 3d ago
Why are there so many power outages that this is a problem?
6
3
u/Demon_scared 2d ago
There is line work going on around the area so there are a lot of outages going around.
3
3
u/eskregg 2d ago
I hate to be a defeatist...but I think someone else mentioned that Haas mills from that era are notorious for this. I ran similar Haas mills from like 2012-2017. These may even have been a bit newer than yours. We didn't deal with power outages a lot, but when they did happen the Z always dropped. And at that point those machines were relatively new compared to what you're dealing with.
Someone else said it too. Regular power outages and CNC machining just aren't compatible. The Z doesn't even have to drop to wreck a part. Tap cycle, deep drill, ream, corner engagement with an end mill etc.
It's going to cost a lot, but if you're dealing with regular outages, you really should consider a shop wide power backup system. That at least gives you enough time to cycle stop and shut all the machines down properly.
3
u/Demon_scared 1d ago
Yeah I understand that. But I have the machines now and have to do something. I will exhaust every single option before giving up.
5
u/hestoelena 3d ago
This is normal and there isn't a way to fix it. Gravity is pulling the Z axis down. The motor is using it's torque to hold it up. When the power is off there is a brake that holds the Z from falling. However when the power is turned off to the motor (e-stop or power outage) there is a slight delay before the brake engages and the z axis falls slightly before the brake catches it.
3
u/Demon_scared 3d ago
Isn't that counterintuitive, if I have to press E-stop or there is a power outage the machine will just pull down 0.2mm (0.008"). It digs into the part and gouges pretty bad. A lot kf my critical parts have been scrapped because of this
6
u/TriXandApple 2d ago
This isn't a haas thing, it's 100% normal. You can't expect the brake to engage instantly, that head weights like 900kg. In fact, this is the whole reason machine too builders recomend you hit the e stop before turning the control off. when you hit the e stop, theres a minute delay, to allow it to turn the brake on before depowering the servos. I also dont think youre being very fair, CNC machines arn't buit or designed around the idea that the power can go out. it's like moaning your lathe isnt cutting parallel, when you've put it down on a sand pit
1
u/Demon_scared 2d ago
Yes sure, I understand that. But none of my other machines do this. Today it ruined a part by dropping half an inch and cutting the work holding as well
4
u/TriXandApple 2d ago
Replace the brake then. I don't know what to say to be honest, "my power will probably go out at an unknown time" is not compatable with CNC machining. Also, I edited my comment.
2
u/Demon_scared 2d ago
Yes you are right. They are not designed around that premise. But I have to find a solution nonetheless
2
8
4
u/hestoelena 3d ago
No, it's not counterintuitive. It's physics. Gravity exists and affects everything. Your Z is literally hanging off of the motor and screw. If the brake was not holding the screw from turning, the head would just smash into the table when the power went out or during an e-stop event.
You shouldn't be using your E-Stop while you are machining, unless there is truly an emergency. If there's truly an emergency, your part is already ruined. Use the cycle stop button and this won't happen.
If power outages are common enough in your area to cause you to scrap parts regularly then you should be thinking about an industrial UPS big enough to give you time to safely stop the machine.
4
u/Demon_scared 3d ago
I meant in the sense that none of my other machines have been reported of doing this. This only happening on my haas machines. They don't drop near as much as these two machines are dropping. If there is a situation like this z- axis shouldn't drop this far.
My machines also dont seem to be equipped with the power fault detection module. Will that help me if I install it in my machines?
3
u/ShadyMeatVendor 2d ago
They're old machines, brakes wear out over time taking longer and longer to immobilize the axis. There is nothing unusual going on here. It may be time to replace/rebuild your z-axis motors or replace the brakes if they are a seperate item in the assembly.
I don't have a solution for your power issues short putting monster UPS's in but as others have mentioned stop using e-stops for anything other emergencies.
3
u/Demon_scared 2d ago
Is there a way I can check if the brake needs replacement or how to replace the brake?
3
u/ShadyMeatVendor 2d ago
If your axis is dropping more than a mm, ideally less, the brake is no longer doing it job.
Most motor brakes are integrated into the z axis so replacing the brake entails the motor. They are electrically released when the drives are given a drive enable. I've seen a number of brands of cnc's have a physical pneumatic brake that resembles a miniature car brake, in which case you could have a sticky valve, caliper, or degraded brake shoes.
Im not a haas guy, not sure what style they use, that needs to be established though I'd wager it's an integrated motor brake.
1
u/hestoelena 3d ago
HAAS has a reputation for making cheap disposable machines for a reason unfortunately.
Its possible that a power fault detection module will help. You'll have to talk to your HAAS rep about it.
3
u/Demon_scared 3d ago
Is it possible to retrofit a counter balance in these machines?
3
u/hestoelena 3d ago
Potentially, though it will affect the tuning of the servo motor and possibly the accuracy. You'd need someone to retune the servo and check the accuracy.
The reason I'm saying it may affect the accuracy it is depending upon the wear on the ball screw. Right now with gravity pulling the head down all the force on the ball screw is on one side of threads. By adding a counterbalance, you will reduce the amount of force on that side of the threads which may allow the head to shift or bounce on the threads. This is an unknown factor and depends completely upon the amount of wear on the ball screw.
2
u/Demon_scared 2d ago
That sounds like a bit of a hassle, but I guess I'll have to get it installed if it’s necessary—any tips on how to go about it?
2
u/hestoelena 2d ago edited 2d ago
My only tip is don't bother. It's going to be way more of a hassle than It's worth. This is an engineering problem that you're going to have to take the machine apart and figure out how to add. Then you're going to have to design it, build it, install it and hope that it works right. But the hardest part of all is you have to know exactly how much the head weighs because a counterbalance is an opposite force to the mass of the head.
If somebody asked me to do this for them, I would no quote the job. I would have to tear the entire z-axis apart and take the head off to weigh it. Then I would have to figure out where I can put either a physical counterweight or a counterbalance air cylinder. Neither of which the machine is designed to incorporate so who knows if I could even get them to fit. I may get the machine apart and realize there's no way to do it. Which inevitably would make the customer very unhappy because they would still have to pay me for the work I did to get to that point.
1
u/Demon_scared 1d ago
I can see how easily this could turn into a massive project that still ends up failing if the measurements or spaces don't line up perfectly. No sense in tearing the whole machine apart for something that might not even fit. Thanks for the advice.
1
u/Siguard_ Repair 3d ago
Sure.
For the amount of money you'd spend you would out the cost of a better machine altogether.1
u/doctorcapslock 2d ago
you can't just fit a counter weight to a machine, it increases the inertia of the system which means the motor needs to be tuned again
1
u/Demon_scared 2d ago
Yes that would be the case. How do I do it ?
2
u/hestoelena 2d ago
You hire HAAS or an Independent service technician to come in and retune the motors which they may or may not be willing to do.
1
u/Bitter-Payment8933 3d ago
Its the nature of the beast... youre basically like a lathe guy asking how to not kill threads in a power outage...
Your machine drops a lot, but I've seen worse.
0
u/Demon_scared 3d ago
Yes, I do expect some drop as the brake engages and mechanical backlash. But this is way too much compared to my other machines. Is there a way to fix it?
2
u/rickwurm 3d ago
.008” is barely anything. I’ve seen some older CNCs drop their Zs almost an inch before the brake grabbed.
1
u/Demon_scared 2d ago
That's pretty bad. In my case I have some thin parts being made which ruin altogether with even this much
1
u/shoegazingpineapple 2d ago
That aint backlash, most motors have the brake on the shaft with zero play, thats just the axis drive cutting off before the machine cuts power to the brake, timing problem
1
u/Demon_scared 2d ago
Can you please tell me what parameters do I have to look up to fix this issue?
1
u/shoegazingpineapple 2d ago
I dont think you can fix this without rewiring the machine to cut the brake as soon as the power is lost even then it might take a while to demagnetize, you might be implement that with a power loss-phase loss relay hooked in series to the brake coil but that might make the brake engage before the axis loses power and thats no good either, you might also need to hook the relay to the feed hold too
.2mm sounds very normal for a non counterweight machine, power loss is a nono for running big machines unfortunately, ups will probably cost as much as an old haas if not more
1
u/Demon_scared 2d ago
Well the problem is that it's not staying there. It increasing and damaging parts quite often.
1
u/shoegazingpineapple 2d ago
Well, i guess you can play around with the relay idea but i dont have an idea about how much of the machine you understand and i also have no idea about haas, also even if it had a counterweight it would still be biased to run down for preload
The iffy thing is the z brake usually is part of the e stop circuit so if you intentionally want to release the brake early you will need to delay the axis drive stop signal by some ms which sounds like tampering with safety systems which might not fly in your shop
You need enough power to hold the axis until the z brake clamps which might be impossible with the existing electronics too
1
u/zoraccer 2d ago
Don't know about Haas machines, but modern Fanuc cnc has a "z-hop" seting : when e-stop is engaged or power monitor on driver module says input power is faulty, CNC uses energy stored in DC-link capacitors to quickly hop Z axis up by a set ammount of distance and then engages brake. Saved me a ton of jobs, tools and nerves.. maybe Haas has something similar?
1
u/Demon_scared 1d ago
What if you are using an under cutting tool tho?
Can I set something like this up for my haas machines as well?
2
u/PrototypENote 3d ago
A slight Z-axis drop when servo power is lost can happen, but I wouldn't assume 0.2mm is normal without checking the brake. I'd have Haas service inspect the Z-axis brake and its engagement timing. The reported X/Y movement is also worth investigating separately. Definitely a safety concern if it's happening consistently.
1
u/Demon_scared 3d ago
It keeps happening regularly, it's there a way to mitigate this issue? Can I equip my machine with a power fault detection module and an external UPS of some sort?
2
u/Siguard_ Repair 3d ago
Industrial ups start in the tens of thousands of dollars
1
u/Glockamoli 3d ago
Any way to keep power to the axis servos and controller without having to back up the spindle as well?
1
u/Siguard_ Repair 3d ago
If you were speaking Fanuc. Usually they are connected in series. So all axis and spindles depending on draw are one.
You'd be spending a ton money to reengineer the panel inserting the ups and add a possible second psu.One of my clients spent bought 7 and the total was over 1.2 mill usd.
2
u/shoegazingpineapple 2d ago
Parallel, all fanuc drives are connected to the dc bus in parallel usually, big fat copper bars at the top of the drives, dont drop your wrench in there
Some machines have a normal vfd that does have their own dc bus inside and takes normal 3ph but still hard to implement any backup, maybe a phase loss relay wired directly to the z brake with the estop coming in after a couple ms after the brake actuates if there is enough capacitance on the dc bus, most vmc brakes are configured to clamp when no power is applied
Haas guys are on crack man, what is wrong with some chains and a hefty counterweight
Milltronics guys are on super crack tho, belt drive z axis with brake on the motor, lose the belt and the z comes down lol
1
u/Demon_scared 2d ago
Both of my haas have no counter balance at all. The axis on the belt is borderline dangerous.
1
2
u/Demon_scared 2d ago
Well, my fanuc machines have counter weights on the z-axis. They dont drop this much. But for some reason my haas vf4-bhe doesnt have any counter balance with the servo on 40-50% company load. Pressing e-stop drops the axis a little while cutting of power drops it quite a bit. While working on a program it drops the axis even more on a power outage. Can I implement some sort of backup power that engages the brake at the right time?
1
u/PrototypENote 1d ago
Since you're seeing a bigger drop during a full power outage than an E-stop, I'd be curious whether the brake engagement timing has been checked. A UPS might help with controlled shutdown, but I'd want to rule out a brake or control timing issue first. Has Haas service looked into that yet?
1
u/Demon_scared 1d ago
No, haas service hasn't looked into it yet. Is there a way to check the brake timing, because i think I have had seen the parameter once and it had its delay set to 0. But ill recheck if I find it. Is there something else I need to check for thr brake timing ?
1
u/PrototypENote 1d ago
A delay setting of 0 doesn't necessarily mean the brake engages instantly. I'd also check the brake's holding ability and whether it engages before servo torque is lost. Given the Z-axis drop, I'd have Haas service verify both before changing any parameters. What year is your VF-4?
-2
u/lusciousdurian 3d ago
Yes. Get rid of the haas and get something real. Or don't buy haas without counterbalances.
1
1
u/Thanatomania 2d ago
Power Fault Detect Module (PFDM) may be your friend here. I do not have access to more information right now so I can not verify if this is a go on classic controls or not. Your HFO can find out pretty quickly for you however.
2
u/Demon_scared 2d ago
I am considering to buy a module and check if it works. One of my machines even has it lresent in the electrical schematic on the electrical cabinet door. But the machines dont have it. I dont know for sure if it will work or not and need help for that. I don't know how can I implement it....yet.
1
u/zLanddy 2d ago
I had this issue when an error about the Z axis encoder popped up. We got a new cable for the encoder and it works agaib.
1
u/Demon_scared 2d ago
My machine has given an error on z-axis once or twice even without a power loss.
1
u/Seang2989 2d ago
On a new VF9 with a newer panel had this same error and it was the cable causing signal degradation resulting in this issue. It eventually failed all together and was unable to communicate withe Z-axis. We replace the cable and everything was normal.
As for your other issue the first thing I would do is check for a brake ether in the servo or that is a secondary brake outside. Eurotech and other machines specifically in your age range have brake pads that wear just like a car does.
On a separate note, the finish on the part is has me concerned that your spindle bearing are shot or you have severe backlash issues in your Z-axis that can be contributing to your issue. How does the spindle sound and how does it feel when you rotate it by hand. Have you measured to ensure you don't have backlash? Do you have any runout on the spindle at low or high speeds? All of these things are important to check when dealing with the with repeated problems with any Z-axis of a machine.
1
u/Demon_scared 1d ago
Could you please tell me how to check the condition of the brakes? I was kind of afraid someone will point that surface finsish out. The spindle doesnt feel raunchy when turned by hand nor does it start to whine before 5-6k rpm. I will check the backlash on the axis. I jave checked the run out and its below 10micron, the lowest normal shop dial measures.
1
u/Seang2989 1d ago
I'm rather confused at the fact you were afraid some would point the surface finish out. I don't understand what you are afraid of. When going over machine issues it helps to point out all of the information and the surface finish is a huge indication of other problems going on that can compound what you are looking at. If you have an issue where the spindle axis repeatedly dropping into material you could easily have damaged spindle bearings.
Before going any further with anything having to do with machine parts and retrofitting things on like you were speaking about before or even checking if you have an internal or external brake, you need a maintenance manual. Without a maintenance manual you're kind of shooting in the dark, because I vaguely know of the machine you have but it could have different options and things specific to just that machine. You should be able to get this documentation from HAAS by giving them the machine serial number, or by looking online for your specific mill. Given its age it should be available online but again you're going to have to look for the specific manual for your serial number or model number. I think once you find it it's going to make your life much easier and answer a lot of these questions.
1
u/Demon_scared 1d ago
I think I was just a bit self-conscious about showing a messy finish online, but you're totally right that it's a huge clue for what's going wrong. The part where the machine keeps dropping is my main worry, so you might be spot on about it causing deeper damage inside. I’m definitely going to take your advice. I have the manual for the machine and ill check that. Ill share it with you if you'd like.
1
u/Seang2989 18h ago
Yes, if you can send me a picture of the maintenance manual cover I can download one online and give you some more detailed information. I've done teardowns and spindle replacements and bearing changes on mills and lathes. Hopefully I can give you some guidance on what needs to be done.
1
u/doctorcapslock 2d ago
does the z axis brake have an override lever? my dad's machine had one and we didn't know that's what it was for and it also kept dropping until we figured that out
1
u/Demon_scared 2d ago
I have not checked that lever if I have it or not. I'll check and let you know
1
u/Swimming_dasa 2d ago
check whether the z axis brake is engaging properly and review the alarm history. the exact haas model and any servo errors would help narrow this down.
1
u/Demon_scared 1d ago
The axis does apply the brake and not falling entirely. Just enough to wreck the parts and tools. How can I diagnose the brake, is there a way to properly check it?
1
u/Kmd827 2d ago
Normal for those years of Haas. The ladder logic/wiring circuitry for the servo brakes on those models holds power somewhere and has a slight lag when activating the brake. I’ve seen anywhere from .001” to over 1/4” Z drop with larger machines like a VF9.
Main reason I swapped over towards Siemens controls
1
1
u/Deep_Ladder_4679 1d ago
Have you checked the counterbalance pressure and the brake after the outage, because ours only dropped like that once the nitrogen charge got low?
1
0
u/DesperateBox1276 3d ago
Have you inspected the code your cam software is out putting? Two machines doing the same thing makes me look at code not the machine. Just my two cents
1
u/Demon_scared 2d ago
I haven't yet taken a look at the code, the code works fine on multiple parts. Just when there is a power outage it gouges into the parts. I will take a look at the code nonetheless.
12
u/fortyonethirty2 3d ago
Is the counterweight cylinder pressure correct?