Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: mp2008 on March 06, 2012, 02:51:50 PM
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I recently bought a new desktop to replace the old one that ran Mach 3 for my CNC machine. Because the new one doesn't have parallel ports I also bought a SmoothStepper to convert to USB and to also take some load of the computer. When I was using the older computer without the SS, I couldn't go above about 50 in/min without having it dive to deep or mess the carving up(this is the reason I decided to replace the computer and get a SS). So I got a new desktop and hooked up the SS and everything is running great, just the way it was before if not more smoothly, Except when I tried to cut a drawing out at more that 50 in/min(bumped it up to 70), it still messed up and ruined the carving partway through. I just don't know why I can't go higher than 50 in/min. I know its not in the process of generating the code with Meshcam(which I do on a separate $2000 desktop) cause it works with the same carving at lower feed rates. To me it seems like something can't keep up? I don't know, any suggestions or advice?
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Sounds like you may have underpowered equipment, hard to tell without details of your system. Post them and maybe something will standout enough to get you suggestions.
I just also upgraded one of my routers - larger power supply - SmoothStepper - C25 CNC4PC BOB - Gecko drives. The improvement over my old setup was amazing. If I change lead screws and nuts, I'll get even more improvement, but likely not worth it at this time.
Regards,
John Champlain
www.picengrave.com
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Sounds like you may have underpowered equipment, hard to tell without details of your system. Post them and maybe something will standout enough to get you suggestions.
I just also upgraded one of my routers - larger power supply - SmoothStepper - C25 CNC4PC BOB - Gecko drives. The improvement over my old setup was amazing. If I change lead screws and nuts, I'll get even more improvement, but likely not worth it at this time.
Regards,
John Champlain
www.picengrave.com
What do you mean exactly when you say "underpowered equipment" ? Would you elaborate a little? I don't see how upgrading my "router" would have anything to do with my problems. The router has nothing to do with the movements of the machine. I'm guessing you were using it as a more broad term for the whole machine but what exactly would I be upgrading? I didn't set this machine up so I'm not familiar with exactly how it works, I'm learning as I go so bare with me. All I know right now is that I have a DynaCNC RTR-1000 Controller and Machine with 4 Gecko Drives and its hooked up to a SmoothStepper. I can give Specs. on anything but that would have to wait till tomorrow. Thanks for any help!
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Could be that you just don't have the torque available from your steppers to do the short fast moves that are being demanded by the code.
RICH
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Could be that you just don't have the torque available from your steppers to do the short fast moves that are being demanded by the code.
RICH
This sounds promising. How would I go about getting the torque needed from my steppers. Would I have to just upgrade my steppers?
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Can you increase the amp's and voltage with in the range of the stepper and driver?
If below allowable then you are not taking full advantage of your motors capability.
You can get bigger steppers that for the same given voltage and amp settings you will get more torque / acceleration / and also more usable velocity.
RICH
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Can you increase the amp's and voltage with in the range of the stepper and driver?
If below allowable then you are not taking full advantage of your motors capability.
You can get bigger steppers that for the same given voltage and amp settings you will get more torque / acceleration / and also more usable velocity.
RICH
That makes sense. It makes me understand picengravers post better too. I'll have to check it out tomorrow. Thanks for the advice.
Mike
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Can you increase the amp's and voltage with in the range of the stepper and driver?
If below allowable then you are not taking full advantage of your motors capability.
You can get bigger steppers that for the same given voltage and amp settings you will get more torque / acceleration / and also more usable velocity.
RICH
Well, I don't really know how and where I need to check the amps and volts. I found out I have 4 G201 10 Ustep Gecko drives. How would I know whether I'm using them to their full capabilities and if not, how would I increase the power supplied to them? I'll post a pic of my drives, stepper, etc. if needed.
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The G201's are capable of 7A and 80 volts max. If you don't use a resistor to set / liimit the amps then the drive can output the max current.
The amps and volts available to the drives are determined by the power supply. You need to look at the motor rating since they may limit current and
volt use.
RICH
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The G201's are capable of 7A and 80 volts max. If you don't use a resistor to set / liimit the amps then the drive can output the max current.
The amps and volts available to the drives are determined by the power supply. You need to look at the motor rating since they may limit current and
volt use.
RICH
Exactly what I needed to know. Thanks a lot!
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Well I need some help. Right now all four of my geckos have 68k ohms resistors which puts the current above 4 amps. The motors on my CNC machine(http://www.kelinginc.net/KL23H51-24-8B.pdf (http://www.kelinginc.net/KL23H51-24-8B.pdf) have a max amps rating of 3.4A in bipolar parallel(which I don't know if mine are hooked up this way?). So should if I were to replace the resistors on the Geckos with 45k ohms resistors(which would put the current just under 3.4 amps), would I be able to go with higher feed rates? Or should I invest in bigger motors that can take the 7 amps possible with no resistors?
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Bump... sorry, would like to get this figured out quick, losing money.
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What is the power supply VOLTAGE to the drives That more than anything will set the max speed of the motor. What are your motors rated for?
(;-) TP
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What is the power supply VOLTAGE to the drives That more than anything will set the max speed of the motor. What are your motors rated for?
(;-) TP
I didn't set it up so I'd have to test it to know the Voltage. My motors specs are in the link in my post at the top of this page.
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I would check your voltage then contact the motor manf and find out what the maxium voltage the motors can safely run . The Geckos can handle up to 80 volts but i would give it a small safety and just use up to 70-75 volts.
AMPS in general give you torque and VOLTs give you speed.
(;-) TP
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Can you give some info on your machine?
For a CNC router your usualy interested in fast feedrates so you won't burn the wood with the router bit. Stepper motors are somewhat limited in how fast they can rotate.
At higher motor rpm's you have less torque so even if the torque requirements for moving the axis are low you still need enough to take care of the machining and reserve just for the sake of reliability. The higher feedrates are achieved by using multi start screws or gearing. So have a look at comparable machines and make note of components used along with feedrates achieved. You need to look at the whole system and what you want to do with it. There are plenty of post's about routers and certainly worth some searching.
RICH
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Can you give some info on your machine?
For a CNC router your usualy interested in fast feedrates so you won't burn the wood with the router bit. Stepper motors are somewhat limited in how fast they can rotate.
At higher motor rpm's you have less torque so even if the torque requirements for moving the axis are low you still need enough to take care of the machining and reserve just for the sake of reliability. The higher feedrates are achieved by using multi start screws or gearing. So have a look at comparable machines and make note of components used along with feedrates achieved. You need to look at the whole system and what you want to do with it. There are plenty of post's about routers and certainly worth some searching.
RICH
Machine:
Travel: X-24",Y-36",Z-5"
X & Y Axis uses precision ground cnc linear rails.
Z Axis uses 2 linear bearings on .75 DIA 440 hardened Stainless Steel Round Bars.
X, Y, & Z Axis Stainless Steel Acme Lead Screws
Anti-backlash Acetal Nut on X, Y, & Z.
Uses 2 paired motors(Y & A axis-one on each side of table) to run the Y axis.
Right now my Geckos have 55 Volts running to them and Idk what my motors max Voltage spec is or how to find it.
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I just think you need different motors since the ones you have are 160 in oz motors. Have a look at the motors on Kelings site
and you will find some 360 to 500 in oz that can be run at 3 amps and should be able to almost triple your speed.
Review the motor curves to compare if they list a curve for the motor.
RICH
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I just think you need different motors since the ones you have are 160 in oz motors. Have a look at the motors on Kelings site
and you will find some 360 to 500 in oz that can be run at 3 amps and should be able to almost triple your speed.
Review the motor curves to compare if they list a curve for the motor.
RICH
I had a feeling all along these motors were my problem. I've been to their website and found the biggest 8-wire NEMA 23 stepper motor:
2: NEMA 23 BIPOLAR STEPPER MOTOR 425 oz-in
KL23H286-20-8B (1/4” shaft with a flat) Specification or Specification Price: $49
425 oz In. Hybrid Motor
1.8° /200 Steps Per Rev.
2.8 Amps Current Per Phase ( Bipolar Parallel)
8-wire Bi-polar or unipolar, NEMA 23 Frame
Compared to the ones I have now:
5: NEMA 23 BIPOLAR STEPPER MOTOR 156 oz-in KL23H251-24-8B ( ¼” dual shaft with a flat) $26.95
Specification , Torque-Speed-Curve
156 oz In. Hybrid Motor
1.8° /200 Steps Per Rev.
3.4 Amps Current Per Phase ( Bipolar Parallel)
8-wire Bi-polar or unipolar, NEMA 23 Frame
Do you think the bigger motor listed above would be enough to make the machine as fast as I need it(150-200 in/min)?
Thanks for the help,
Mike
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Mike,
What is the max Kernel Speed you can use?
What are your steps per unit?
Post a pic of your machine.
RICH
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Mike,
What is the max Kernel Speed you can use?
What are your steps per unit?
Post a pic of your machine.
RICH
My Kernel Speed set in mach 3 is 35k, I wouldn't know how to determine my max?
My steps per in mach 3 are around 32000 for y-axis and roughly 25000 for the x-axis.
My machine pics are below(having a bit of trouble so may take a bit).
Thanks again,
Mike
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I do have more pics including some of my geckos, power supply, etc. if needed. Sorry about the big sizes, that was probably why I was having problems, I'll have to remember to resize them.
Mike
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Just making a pit stop on the forum so maybe get back tonight ( boys monthly night out takes precedence). ;)
RICH
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Just making a pit stop on the forum so maybe get back tonight ( boys monthly night out takes precedence). ;)
RICH
Haha, alright Rich, I'm in no rush now, as you can see I've been carving away just at low feedrates.
Mike
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Thanks for resizing my images Overloaded. I'll remember to resize any future images I post.
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Mike,
Didn't see a motor curve for the 425's but did find one for the 156's you currently have. Without a motor curve at the supplied voltage, amps, and pulse rate one would use we would be only guessing the preformance to be had by a motor unless you had a very similar system to compare to. So i am going to ramble some in general.
Using a G201, micro stepping at 10, 2:1 ratio, 8 tpi screw gives you the 32000 steps per inch. At 50 ipm your current motor
rpm would be 800. At that rpm you are on the bottom of the motor curve in terms of torque. At 50 IPM you have about 55 in oz
available and at 70 ipm you skip because the torque drops to maybe 40 - 45 in oz. That suggests that you need 50 in oz to move
the axis and it leaves no power for acceleration and machining. Make note that the motor curve is for 30V & half step, But irrelevent your motors are just turning fast with no torque. 40 oz in can be achieved with two fingers and light pressure to turn something.
Should you change out the screws to multi start you can reduce the rpm and move the motors operating rpm into a higer torque region. 2 start screws would almost / maybe double the torque available. The calculated resolution is still good but you'll never achieve it with the screws you currently have. Would guess that you could live with .001" resolution with wood working and probably even less.
If you look at the 382 in oz you'll find a curve but that curve is for a differnet motor 500 in oz and Keling can't confirm what it's for. You can still look at the curve to see it's affect on incresaing the torque and feedrate. Never found anything which provides power required to do wood working.
There are router users in here and probably someone will be additive to this post.
RICH
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Thanks for taking the time to explain all of that Rich because I was definitely confused with what I've been reading for the past couple days :D .
So from what I understand the screws I have now are more for precision rather than speed and because mythe motors have to spin at such a high rpm to go fast feedrates, they do not do not have enough torque?
So you suggest that a option is to replace the screws I have now with multi-start screws, which would allow me to lower the rpm of the motors to achieve the same distance or feedrate as with the original screws? This would also give the motors more torque and make the machine more reliable?
I've been researching Acme Multi-start screws and notice they have some as high as 8 start that move 1" per turn. What would be the difference between a 2 start and a 8 start? I understand one moves farther in one turn but I'm not sure what are advantages and drawbacks of each and which would be best for my machine and motors?
Mike
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Mike,
Here is a link to a stepper calculator:
http://www.machsupport.com/forum/index.php/topic,16315.msg110286.html#msg110286
You can vary the axis inputs and see the affect of the changes as it relates to steps per , IPM and motor rpm, resolution, etc.
Than you can use the info to see where you are on the motor curve. Multi start screws give you increased axis speed
and lower motor rpm which allows for increased torque. Actualy you are interested in power. All of this is a comprimise since each change affects another.Be carefulll on the motor curves as to what they are based on. I didn't even mention servos since you have G201's. What modifications you want to do to achieve something is up to you. Each part of the SYSTEM must be comlpiment the rest of the system.
RICH
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That's a pretty handy tool there Rich. I think you've definitely helped me out more than I expected on here so I greatly appreciate it! I'm going to have to commit a day or so to some research to better understand everything because like you said, each part of the system must compliment each other. I don't want to replace one thing and then find out another major part of the system has to be changed to compliment the first change and so on. I'm sure you'll be hearing from me soon :D
Mike