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Author Topic: Can't raise feedrate past 50 in./min. without messing up... suggestions?  (Read 9191 times)

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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
« Last Edit: March 13, 2012, 09:19:26 PM by Overloaded »
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
« Last Edit: March 13, 2012, 04:25:45 PM by mp2008 »

Offline 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
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
Thanks for resizing my images Overloaded. I'll remember to resize any future images I post.

Offline RICH

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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


  
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
« Last Edit: March 14, 2012, 11:18:12 PM by mp2008 »

Offline RICH

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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
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