How can I increase the feed rate of my machine?

I have a diy (mdf with steel reinforcement) router machine for wood routing. The cutting area is 20" x 40". I'm running Mach 3, with 425 oz/in nema 23 steppers, C-10 bob, 1/2-10 Acme lead screws, and a 24v power supply. My machine runs smoothly at 35 ipm. When I try to increase this in motor tuning the motors "whine" and the gantry stops moving or "slips". There is not a lot of friction in the machine as it moves quite freely when I hook up my 14v cordless drill to the leadscrews. Does anybody have any ideas as to some good starting settings for velocity and accel? I would like to get this to 80-100 ipm. I was told that a Smoothstepper might accomplish this by changing the connection from parallel port to usb. Is this correct? Any other ideas? How do some of these machines with smaller steppers possibly run at 200-300 ipm and more?

Thanks, Jeff

Jeff,

What stepper driver are you using?

Need more info.

Jeff...

This might help.

http://www.cnczone.com/forums/showth...639#post256639

Hi Jeff,

You didn't mention what stepper driver you're using. If the driver can handle more voltage, go for it. More voltage = more power to the stepper.

You can also replace the 1/2-10 acme rod with a 1/2-10 2 start acme rod. This will give you twice the linear speed at the same rpm.

My drivers are Keling 4030's. How do the 2 start acme screws change the speed at the same rpm? Will they also increase the load on the motors? I've seen them but don't understand them.
Thanks, Jeff

Dampers will help a lot if this is what you are experiencing.

[ame="http://www.youtube.com/watch?v=8Am69_F93yA&feature=channel_page"]YouTube - 65 ipm[/ame]


After adding dampers you might consider raising the power supply voltage to 36-40 volts, that will increase rpm about 30 percent.

Changing the screws to 2 start would double your feed rates.

Jeff...

Screw Start Diagram:

The number of starts on most threads is one (single start). However, a number of thread series including Roton's Hi - lead(r), Torqspline(r) Lead Screw, and Ball Screw series screw threads may have from 2 to 20 starts or more. Multiple starts are used to increase the lead (linear advancement per revolution). In most cases, increasing the number of starts is preferable to increasing the pitch because larger pitches reduce the minor diameter. A small minor diameter decreases the screw stiffness and makes it more difficult to tap nuts because of the likelihood of the tap breaking during tapping. Also, for the same lead, increasing the number of starts actually increases the thread contact area when compared to a thread with the same lead but using fewer starts and a coarser pitch. Close examination of the thread will reveal the number of starts (Figure 49). Simply place a pencil or marker pen in the thread groove and rotate the thread one revolution. If the end of the pencil mark is in the adjacent thread groove, the screw has a single start. If there is one thread between the beginning and the end of the mark, it is a two start thread, two grooves, a three start thread and so on. Another way to discover the thread starts is to examine a transverse section of the screw. As illustrated in Figure 49, if the end view is an offset circle, the screw is single start. A two start thread will have roughly a football shape, a three start thread will have a tri-oval shape and a four start thread will be noticeably four cornered. Usually, five starts and up can simply be counted in the transverse section.

Thanks Jalesi,

That is an excellent description of the screws. So with 2 starts, will the same nuts work? They will just move across twice the distance per revolution, correct?

Thanks, Jeff


About the dampener, That video could be from my machine, That's exactly what it does. What can I use as a dampener and how do I determine the weight? The one in the vid looks a bit dangerous to me. I think I prefer the disk type.

Thanks again, Jeff

Woa, I've seen the word Dampers thrown around before but it is the first time I've seen one in action. It looks like something I would be interested in putting on my machine once it is done.

Is the point of them to help the steppers to not loose steps by giving it a little torque support? If you have any additional infor and their prs and cons I'd really like to read about them.

Quote:

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Originally Posted by jalessi

Dampers will help a lot if this is what you are experiencing.

YouTube - 65 ipm


After adding dampers you might consider raising the power supply voltage to 36-40 volts, that will increase rpm about 30 percent.

Changing the screws to 2 start would double your feed rates.

Jeff...

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FandZ,

The damper helps to suppress resonance, see the attached documents for more info.

http://www.ferrotec.com/products/fer...nertiaDampers/

Jeff...

Quote:

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Originally Posted by jalessi

FandZ,

The damper helps to suppress resonance, see the attached documents for more info.

http://www.ferrotec.com/products/fer...nertiaDampers/

Jeff...

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Thanks for the link. I guess I'll see how my machine does once it is up and running. I'm just glad I'll be ready for the problem if it pops up.

Unfortunately, you need a multi-start nut (with the same number of starts and pitch as your screw) if you switch to a multi-start screw -- you cannot use the original nut. It will not physically fit.

That being said, I highly recommend multi-start screws. My machine went from ~110 IPM to 300 when I went from single start ACME to 5 start ACME. There are two big advantage of multi-start screws for stepper applications. 1 is the increased linear speed at the same RPM, as stepper motors produce more torque at lower RPMS. 2 is the increased efficiency of higher lead screws. This is just an inherent reduction in frictional losses due to the higher contact angle of the threads.

Hope that helps,

Ahren
www.cncrouterparts.com

Thanks, Ill check into the multi starts.
Jeff