Z axis doesn't hold when power is off

Questions/answers/discussion about initial setup of your CNC Shark

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Z axis doesn't hold when power is off

Postby pungent333 » Thu Jul 11, 2019 12:43 pm

Hi all,

New to CNC here. Purchased the Shark HD4 unit with the water-cooled spindle. I have discovered that when the power is cut to the machine, the z-axis drops.

I contacted Nextwave support back when I first set up the machine and noticed this and they said that was because with the loss of power, the braking of the z-axis motor is also lost. According to them, it is normal. I mentioned that the exact same setup at my local Woodcraft doesn't do it and they didn't really have an answer for that beyond what felt like a shrug.

This is bad enough when one is done with the cut and shutting down for the day or when one needs to change a bit (have to have power to the system to hold the spindle high enough to do the bit change), but it's even worse when the spindle is running and one hits the emergency stop because something is wrong with the cut. While my X/Y moment stopped, the spindle was still running and the motor drilled right into my spoil board. Thankfully, I was able to grab it and keep it from going down into the aluminum bed.

I wanted to ask others if they also have this issue and, if so, how do they deal with it. If it is rare, does anyone have any suggestions about how to fix it? I may try contacting Nextwave again, but since they seemed to imply it was not a malfunction to begin with, I am guessing they won't be much support on the issue.
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Re: Z axis doesn't hold when power is off

Postby MCanfield » Fri Jul 12, 2019 4:46 am

I have noticed the same thing. I've hade mine for 6 months and do not recall that happening when I first got the machine but I may be wrong. I have just learned to live with it.
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Re: Z axis doesn't hold when power is off

Postby Jim N » Fri Jul 12, 2019 9:57 am

I have the same issue. With the extra weight, try rigging rubber bands or weak springs to counter the weight. The stepper motor may thank you also when it is pulling up. Go easy though, you want to fight gravity but not work against the stepper motor pulling down. If anyone thinks this is a bad idea, please chime in.
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Re: Z axis doesn't hold when power is off

Postby OCEdesigns » Sat Jul 13, 2019 1:58 pm

Mine does NOT move at all. I can leave it for days and no movement.
Shark HD4 Extended Bed, Water Cooled Spindle. VCarve Pro 9.5
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Re: Z axis doesn't hold when power is off

Postby pungent333 » Tue Jul 16, 2019 10:11 pm

I sure wish mine held. I just got the laser module and it's quite a bit wider than a bit. It was bad enough trying to change sharp bits with a 2x4 holding the system up but it's a lot worse with the laser module. There's not much space. While it's not as safe to have the system on when inserting the collet, I may have to.

I wonder if it has something to do with the motor. Perhaps some are better quality than others.
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Re: Z axis doesn't hold when power is off

Postby MCanfield » Wed Jul 17, 2019 5:04 am

Yesterday I moved mine all the way up to remove my work and it did not drop when I turned off the power
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Re: Z axis doesn't hold when power is off

Postby TAW » Fri Jul 19, 2019 10:14 am

I have 4 yr old extended bed shark and mine stays where ever it is at- when powered down.
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Re: Z axis doesn't hold when power is off

Postby BladesNBarrels » Tue Aug 06, 2019 2:17 pm

My Shark HD4 does the same thing. The Spindle drops down when the power is off.
I have a 2x4 piece I slip under when the power is off.
I had not considered the Emergency Power Off does not shut the Spindle off.
I will have to really watch that.
Sorry, I do not have a solution to the problem.
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Re: Z axis doesn't hold when power is off

Postby sharkcutup » Tue Aug 06, 2019 5:28 pm

When I had first got my Shark CNC the Z-axis at first used to drop down after all power was cut off from the unit. But as I after using the machine several times it tended to stay up on its own. I am not sure if this has something to do with the stepper motors or not it just started staying where it was when the power was cut off.

As for the Emergency Power to the spindle I realized the same thing that the Controller does not cut it off when you hit its big red button. So I installed a second Emergency stop that cuts off all (EVERYTHING) from the power source as in the photo below. Something all Spindle owners should consider installing!
20190806_171104[1].jpg


I also shot a photo of my Z-axis showing it in the upright position where last left at power cutoff.
20190806_171140[1].jpg


Photos show correctly when clicked on. Not sure why they are skewed here.

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Re: Z axis doesn't hold when power is off

Postby WNC_Ed » Tue Aug 06, 2019 5:54 pm

Mine sinks on power off but I have a 4" vacuum line and a 4" vacuum hose holder that adds weight.
Before all of that it would stay up on it's own.
I have a small piece of scrap wood that I use for the "kickstand" to hold it up.
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