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    Default Re: Counter balancing Z axis..

    Quote Originally Posted by louieatienza View Post
    I suspect now that's a 2-start ACME, which should be exactly 10000 steps/inch, and you've compensated because there's some compliance somewhere, which made you come up with 10166? Or a 5-start which should give you exactly 4000 steps/in (as in your original build thread? Changed screw?
    For a 5mm pitch ballscrew, (200 step * 10 microstep * 25.4/5 =10160 steps/in)

    10166 steps/in is almost exactly what a 5mm pitch ballscrew needs and he alluded to having a ball screw in post #16 when he said .

    louieatienza, isn't the microstep tied to the ball screw pitch?




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    Default Re: Counter balancing Z axis..

    Quote Originally Posted by 109jb View Post
    For a 5mm pitch ballscrew, (200 step * 10 microstep * 25.4/5 =10160 steps/in)

    10166 steps/in is almost exactly what a 5mm pitch ballscrew needs and he alluded to having a ball screw in post #16 when he said .
    The picture is clearly an ACME screw... hence the confusion. Maybe a picture of the current setup would shed some light. The original build shows a steps/in on the Z of 4000, which was a 1/2"-8, 4 start or 1/2"-10, 5-start.



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    Default Re: Counter balancing Z axis..

    Quote Originally Posted by NIC 77 View Post
    That is exactly what I have been thinking of over the past several hours. Thanks to 109jb's comments.

    P1V1 = P2V2. Thanks for the reminder on the equations 109jb!

    It appears to me that a 5 gallon tank is not required to use a gas cylinder! The higher the pressure you use, the less volume is required.
    What you point out is correct. That is how gas struts have a somewhat constant rate, they are rather high pressure.

    That's something we need to pin down. How much leakage? For a gas strut, zero leakage. For an air cylinder, how much? Could I run a machine for a week on a closed system without topping it up from a compressor?
    Good question, and the answer is: I don't know. I just have mine connected to shop air which is pretty much always on when I'm in the shop.

    Why did you choose the value of 30 to 40 PSI? Very important to know.
    I chose that value so I could turn it up if needed and it seemed like a reasonable value. There was not a lot of engineering involved. I have found in some heavy cutting conditions with large endmills that to overcome the down force of the cut I have had to go up to about 60-70 PSI. There is about 0.015 backlash in the system without the counterbalance. Also I am using a Harbor Freight portable air tank, no point in pushing my luck


    Of course, a gas spring without dampening could do this too, but not be adjustable. The less expense gas struts don't even mention dampening, but I assume that they are all dampened to a large degree.

    So feel free to point out errors in my reasoning, I won't be offended.
    All of the gas struts that I have had experience with seem to be pretty heavily damped. I think it is possible to get them without, or at least minimal damping on special order.

    http://www.cnczone.com/forums/knee-v...-software.html

    Nice work Sir! I've read that build thread but didn't equate your name to it. I was considering a mill conversion, but it just didn't have the amount of movement I need. So I ended up on another CNC build.
    Thank you for the kind words.



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    Default Re: Counter balancing Z axis..

    Wow! thanks for all the posts... so to clear up some of the confusion on the Z axis, it originally started off with a 5start acme screw and plastic nut but there was some binding in that setup so I rebuilt it, you can see all that on my Wordpress page if interested (https://qnap.hostingky.com/WordPress/?p=919). The Z axis is now using a Ballscrew - 1605-L500mm, 16mm/5mm pitch.

    Maybe the calculations are wrong??? I just went out and grabbed the Stepper Calculator worksheet and got a different number than what I currently have in Mach, ugh!

    The axis weighs in at about 25 lbs and moves quite smoothly on the linear slides. I'm also am using a 48v power supply, but with the G540 the only adjustment is on the pot trimmers on each axis and there is no specific information on voltage output that can be adjusted.

    Lost steps on this axis has been an issue since inception, originally when it was using the 5 start acme but I attributed that to binding. After replacing the the lead screw and properly redesigning the Z axis and adding a ballscrew the lost steps have disappeared, well almost.

    NIC 77

    Oh hey adam_m,

    You fly RC? me too.
    Yes, I used to but ran out of time... I love the building process and will get back into it as time permits... I flew an super Sportster .60 and it flew like a dream!

    Adam,

    Attached Thumbnails Attached Thumbnails Counter balancing Z axis..-snag-0084-jpg  
    G540, Rack and Pinion Drives-X/Y axis, 1/2-Ball Screw-Z Axis w/THK HSR 25 Linear Slides, Steppers KL23H2100-35-4B, Power Supply-KL-600-48


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    Quote Originally Posted by adam_m View Post
    Wow! thanks for all the posts... so to clear up some of the confusion on the Z axis, it originally started off with a 5start acme screw and plastic nut but there was some binding in that setup so I rebuilt it, you can see all that on my Wordpress page if interested (https://qnap.hostingky.com/WordPress/?p=919). The Z axis is now using a Ballscrew - 1605-L500mm, 16mm/5mm pitch.

    Maybe the calculations are wrong??? I just went out and grabbed the Stepper Calculator worksheet and got a different number than what I currently have in Mach, ugh!

    The axis weighs in at about 25 lbs and moves quite smoothly on the linear slides. I'm also am using a 48v power supply, but with the G540 the only adjustment is on the pot trimmers on each axis and there is no specific information on voltage output that can be adjusted.

    Lost steps on this axis has been an issue since inception, originally when it was using the 5 start acme but I attributed that to binding. After replacing the the lead screw and properly redesigning the Z axis and adding a ballscrew the lost steps have disappeared, well almost.



    Yes, I used to but ran out of time... I love the building process and will get back into it as time permits... I flew an super Sportster .60 and it flew like a dream!

    Adam,
    There's always binding with an AB nut, as the surfaces rub against each other. Shouldn't affect the function of the axis however.

    Your calculation for the ballscrew was fine, though I'd put the actual count first 10160. You cannot set voltage on G540 only current via resistor on pins 1-5 of the DB9 connector. You can run it without one and it will run at 3.5A but you won't have idle current reduction.



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    Default Re: Counter balancing Z axis..

    I'd check the ballscrew for binding. If you remove the motor, you should be able to easily turn the screw, and the axis should probably fall under it's own weight.

    Gerry

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    Default Re: Counter balancing Z axis..

    What current limit resistor is installed in the G540? Also, have you tried running the Z-axis from either the X or Y driver?

    BTW, since you confirmed that you have linear rails, and a ballscrew, I really don't think a counterbalance is your problem .



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    Default Re: Counter balancing Z axis..

    Yes, Gerry removal of the stepper leads to the axis falling... well almost, it's very close to it, spins freely.

    The cables I used are from CNC Router Parts - I'm thinking they already have the resistor molded into the plug, is there a way to test to be certain?

    109jb, I can swap the motors on the XY and Z axis as they are all the same. This missed step issue seems to happen after about a 30-40 minute run. I had a spare motor that I just swapped in but haven't tested it yet.. I'll try to re-run the VCarve job again this weekend and see what results I get.

    My G540 has a heat sink on the back of it and a fan drawing air across it so I don't think it's over heating.. but possibly the Z motor, what temp should these things run at?

    Adam,

    G540, Rack and Pinion Drives-X/Y axis, 1/2-Ball Screw-Z Axis w/THK HSR 25 Linear Slides, Steppers KL23H2100-35-4B, Power Supply-KL-600-48


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    Default Re: Counter balancing Z axis..

    This missed step issue seems to happen after about a 30-40 minute run.
    Have you touched the G540 to see how hot it is? The fact that it happens after 30-40 minutes imo would point to the drive overheating.

    Have you touched the Z motor? If it doesn't burn you, it's probably not too hot.

    Gerry

    UCCNC 2017 Screenset
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    Mach3 2010 Screenset
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    JointCAM - CNC Dovetails & Box Joints
    [URL]http://www.g-forcecnc.com/jointcam.html[/URL]

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)


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    Default Re: Counter balancing Z axis..

    Quote Originally Posted by adam_m View Post
    109jb, I can swap the motors on the XY and Z axis as they are all the same. This missed step issue seems to happen after about a 30-40 minute run. I had a spare motor that I just swapped in but haven't tested it yet.. I'll try to re-run the VCarve job again this weekend and see what results I get.
    My point is have you done this to see if the missed steps follow the drive. If you switch X and Z and then lose steps on the X axis then you likely have a driver problem.



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    Default Re: Counter balancing Z axis..

    Have you touched the Z motor? If it doesn't burn you, it's probably not too hot.
    Even if it does it may not be too hot. Most steppers have case temperature ratings of 100 C. (212 F), which will burn you in seconds.



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    Default Re: Counter balancing Z axis..

    Quote Originally Posted by adam_m View Post
    Yes, Gerry removal of the stepper leads to the axis falling... well almost, it's very close to it, spins freely.

    The cables I used are from CNC Router Parts - I'm thinking they already have the resistor molded into the plug, is there a way to test to be certain?

    109jb, I can swap the motors on the XY and Z axis as they are all the same. This missed step issue seems to happen after about a 30-40 minute run. I had a spare motor that I just swapped in but haven't tested it yet.. I'll try to re-run the VCarve job again this weekend and see what results I get.

    My G540 has a heat sink on the back of it and a fan drawing air across it so I don't think it's over heating.. but possibly the Z motor, what temp should these things run at?

    Adam,
    Even though the screw spins freely now, after a 30-40 minute run, it is possible that the lubrication inside flows more from getting warmer, causing contamination inside to "jam up" the BBs. Especially if it's happening at the same part of a job where the Z is traveling farther than in any other point before. Although, the fact that this has also happened with your ACME screw setup leads me to believe it may be an electrical issue.

    Yes, the CNCRP cable has them. You can take a multimeter, set it to Ohms, and check between 1 and 5, it should read around 3.5kO+/-5%

    The G540 shouldn't overheat to the point of failure; I've run one with ambient temperature and one with a fan just blowing on the back with no issues... on a 4.5 hour run... cutting G10/FR4, which is pretty brutal on the machine. As to the steppers, you'd think 70degC is hot - usually the wire insulation inside is rated to about 170degC or more. If it's as hot as black coffee in a paper cup without a sleeve, it's probably fine. Next time you do a long run, feel the cables, especially at the connectors. If they're hot, they may be arcing and need to be replaced.

    BTW that stepper calculator is a bit complicated. It's very simple. 1" = 25.4mm. 25.4 / 5 = 5.08. 5.08 * 2000 = 10160.



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    Default Re: Counter balancing Z axis..

    Thanks guys for the input.

    So, my take away from the thread is to try the following:

    - set stepper to 10160
    - change out stepper motor (run job)
    - verify cable has correct resistance 3.5K +/-
    - check heat on G540 and motors (I have a temperature gun)

    Just to clarify, you guy's do think the image I posted of the item being milled (flourish) is a missed step on the Z axis, correct?

    Adam,

    G540, Rack and Pinion Drives-X/Y axis, 1/2-Ball Screw-Z Axis w/THK HSR 25 Linear Slides, Steppers KL23H2100-35-4B, Power Supply-KL-600-48


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    Default Re: Counter balancing Z axis..

    Something else I've noticed from my previous research:

    https://www.linengineering.com/resou...-vs-amps-peak/

    So your G540 may not be supplying all the amps needed to get the maximum out of that motor. So when we look at the Torque vs. Speed graph, you could be down a bit, and that isn't the most powerful stepper to start with.

    So I have delved into the world of trying to accurately predict ballscrew performance using inertia. I have already delved into this for rack and pinion.

    I put your numbers into my new spreadsheet, and even with inertia included and 50% efficiency I couldn't get you below 100 lbs available cutting force at 100 IPM with a 50lb z axis at 0.2 G. That's 150lbs total available with 50lbs used to offset the Z and an additional 0.2G acceleration.

    So no point in posting a graph.

    But then again, I could have made a mistake in my spreadsheet.

    At around 200 IPM however, you would loose steps at any efficiency.



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    Quote Originally Posted by NIC 77 View Post
    Something else I've noticed from my previous research:

    https://www.linengineering.com/resou...-vs-amps-peak/

    So your G540 may not be supplying all the amps needed to get the maximum out of that motor. So when we look at the Torque vs. Speed graph, you could be down a bit, and that isn't the most powerful stepper to start with.

    So I have delved into the world of trying to accurately predict ballscrew performance using inertia. I have already delved into this for rack and pinion.

    I put your numbers into my new spreadsheet, and even with inertia included and 50% efficiency I couldn't get you below 100 lbs available cutting force at 100 IPM with a 50lb z axis at 0.2 G. That's 150lbs total available with 50lbs used to offset the Z and an additional 0.2G acceleration.

    So no point in posting a graph.

    But then again, I could have made a mistake in my spreadsheet.

    At around 200 IPM however, you would loose steps at any efficiency.
    Just from experience, I know that the OP should have enough to move that Z. Especiallywith a ballscrew thay has 85-95% efficiency.

    I have a similar setup on my mini mill; even with cast iron head, 3HP spindle, and medium preload LM bearings I could still get 180ipm rapids. I also built a couple mini routers using 166oz-in steppers and 1/8"-8, 2 start screws and rapid the Z over 400ipm. My own router table had an 8 start screw and a 400oz-in motor, still had no issues. In fact, you should be able to raise the axis by spinning the motor coupling with your fingers. The axis also drops freely when powered off, so binding may not be the issue.

    Adam, I know you swapped drives on the Z but ha e uou tried motors? I'd swap both motor and cable. I don't think it'd hurt if you did get a stepper with more torque provided it ran at 3.5A. But what does hamper high speed torque is voltage. The down side is that the drives are more expensive.



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    Default Re: Counter balancing Z axis..

    Are you using the parallel port with Mach3?
    I'm wondering if this is an issue with your PC?

    Gerry

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    Default Re: Counter balancing Z axis..

    Yes, Gerry I'm using my parallel port with Mach3.

    I ran a test this weekend of the same part after changing out the motor with a spare, its still a keeling (KL23H2100-35-4B). The part ran for approximately 45 minutes before it totally had a meltdown (see attached).

    There was one thing that may have impacted this and it was me surfing the internet on the same PC that was running the job...?

    I also took some temperature tests on the G540 and if the numbers are correct they were about 85F-95F, the motors were 115-125. I failed to test the resistance on the cables... I'll do that next.

    Adam,

    Attached Thumbnails Attached Thumbnails Counter balancing Z axis..-img_1220-medium-jpg   Counter balancing Z axis..-img_1221-medium-jpg  
    G540, Rack and Pinion Drives-X/Y axis, 1/2-Ball Screw-Z Axis w/THK HSR 25 Linear Slides, Steppers KL23H2100-35-4B, Power Supply-KL-600-48


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    Default Re: Counter balancing Z axis..

    There was one thing that may have impacted this and it was me surfing the internet on the same PC that was running the job...?
    If you're using the parallel port, you shouldn't touch anything on the PC while the machine is running. Just clicking in the Mach3 toolpath window while it's running can cause lost steps.

    Gerry

    UCCNC 2017 Screenset
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  19. #59
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    Quote Originally Posted by ger21 View Post
    If you're using the parallel port, you shouldn't touch anything on the PC while the machine is running. Just clicking in the Mach3 toolpath window while it's running can cause lost steps.
    For sure... in fact should be ran maximized...



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    Default Re: Counter balancing Z axis..

    OK, now we're getting somewhere...

    So, is this a Mach issue or a PC issue?

    Is this a PC problem or G540 problem?

    I'm guessing a PC issue - a communication problem... assuming this is the case are there ways to improve the performance and harden the communication between the PC and the G540?

    Adam,

    G540, Rack and Pinion Drives-X/Y axis, 1/2-Ball Screw-Z Axis w/THK HSR 25 Linear Slides, Steppers KL23H2100-35-4B, Power Supply-KL-600-48


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