G0704 RAPID SPEEDS

My last post I questioned feeds, speeds, etc in an effort to reduce machine times. Since then I have been using Inventor HSM (HSMWorks) and HSMAdvisor to set my cutting parameters and it has helped alot. Now I'm looking to bump up my rapids. If I remember correctly My X and Y axes will do over 300IPM but I could only get up to 145IPM on the Z axis before stalling on the way up. Going off the 'find max speed before stalling and then half that for a reliable speed' I set the z axis just under at 65IPM max.

I am pretty sure I have seen references to z axis speeds of 150IPM for rapids during operations. I wouldn't mind getting up to just 100IPM. Maybe there is something easy I could do such as scrape the ways, or bearing upgrade. I had a couple of other Ideas also.

Replace the 570oz Nema 23 with a 907 or 1200 nema 34.
Belt drive the Z axis with some reduction keep the nema 23.

So I guess Im wondering if that 150IPM is something I am imagining, and whats the best way to get there?
Is that halving of the Max speed before stall the best method?
What are your rapids, and what did you do to get that high?

Looking over your build thread I noticed you did not attempt to counterweight the head at all. I would think to find some way to start their either with air springs or physical weight. A belt drive would reduce the speed your head can move at, although the increase in torque might be helpful.
The Z I think should always have a much more stout motor compared to the X/Y.

It isnt a stepper issue. Those steppers are capable.

There are many factors that come into play to obtain fast rapids. Proper gib adjustment, lubrication, motor tuning will all have an effect. Though many of us have seen speeds in the 300ipm range inevitably steps are lost and detuning is necessary.

In fact you might have seen my test on a G0704.
331IPM
G0704 @ 331ipm in Y - YouTube

I agree, the motor isn't the problem, 300ipm on the Z is possible with the proper driver and power.
The pc is a likely place for improvement, older ones like I have in the video still have good parallel ports that put out good pulses, otherwise look into getting an ethernet smoothstepper.
A bigger motor isn't a guarantee for improved speed, they have more mass to move.
A gas spring isn't needed with the stock head and keep in mind they will only extract at a certain speed so the stepper could be fighting it beyond a point, I never put any on mine.
Hoss

https://www.youtube.com/watch?v=WFMY_FqbBKs

Thanks for the replies. I think the electronics are setup well, I have ess, and voltage and current are set for the steppers. It will do 300 on the x and y no problem. I have seen that video, which is why I wonder if there was something else I would have to do in order to get those speeds. I tried loosening up the gib on the z but no help on the way up. Everything is lubed and clean also.

Maybe I will try swapping motors with the X axis and see if it is the stepper.

I only got that speed on the Y. I was around 140-150 on Z and X IIRC.

Oh yeah, do you still have that Z axis setup retaining the crank handle and gears?
That's a lot of friction most of us don't have with our conversions.
Hoss

I did end up taking it off. The gears ended up not meshing quite right after adding a thrust bearing. I remember when I wanted to keep the hand wheels.. I still have them x and y, but I'm planning to remove or replace them soon.

I still need to try swapping motors, or maybe just motor leads in case its the driver. If those don't make a difference what should I look at next?

Just an update from over the weekend. I tried swapping steppers, no change, tried to loosen the gib, no change. I went to take out the ball screw and noticed that the four bolts that hold the bearing plate were slightly loose. Took the ball screw out and noticed its a bit bent. There are a few bends in it, but more than anything that the machined end isn't essentric with the screw. I bent it a bit straighter, set the preload on the bearings better and reinstalled it. I got the rapid up to 160IPM but after that it would stall pretty consistently in certain parts of the travel. At least I knocked the backlash down from 4.5 thou to 3 thou.

I think I'm going to replace the ball screw, and the stepper with a new 1605 and a 907 or 1200 oz nema 34.

On a side note I hit 420IPM on the X and Y axes. Though the X stalls out if starting from the outside 2 inches of travel. It was pretty cool to see it moving that fast. I think I ended up setting X and Y to 120IPM, 40 Accel, and Z to 85IPM 40 Accel. It will be cool to get them all to 120 Rapid speeds, I guess we will see after a new ball screw and stepper.

Isn't the Z axis a 2005 ballscrew?

Mine is a 1605 ball screw. I was thinking of sticking with this size since I have the ball nut adapter, and an extra ball nut already, it would make it easy to double nut it. If it wasn't for that I would switch to 2005 instead. I thought I read somewhere that the 1605 was more than enough. I'm not opposed to the 2005 if there are some benefits.

More closely matches what the original screw was. I just got mine in.. and it's double nutted. I can't say much as to why bigger would be better for the Z except maybe less chance it'll be bent.

That's a good point. I think from load rating the 1605 is more than enough, but I would think the 2005 would be more rigid and possibly less friction assuming it has more ball bearings.

You just got yours in? What and where did you order from? I wouldn't mind buying a double nut vs making two single nuts work.

Got it from Chai, (I.E. Linear Motion Bearings 2008) Sent him a email and got all my screws.. all of them are double nuts. I've not installed them yet.. so.. Not sure what my Z rapids would be. I would be happy with anything over 100IPM though.

The 1605 is most likely adequate as is the stepper. Z doesnt need to be a fast unless your doing 3D work.

Yeah.. Maybe I have just caught the bug after seeing some demonstrations of high speed machining. I know I cant cut at those rates, but something about maxing out a machine is becoming appealing to me. Just moving to HSMWorks and using HSMAdviser for toolpaths has made things a lot quicker and impressive to watch. 50 IPM cutting is pretty cool.

I have to do something with my Z axis ball screw either way, which I think will require a new bearing block and stepper mounts. It appears most kits come with a 2005 screw and a lot of electronics packages I've seen are coming with the nema 34.

What are your guys ideas behind setting up rapids? Is there a number you shoot for? What are you currently running?

I thought I would update this thread with what I did. I replaced the Stepper, bearings, and ballscrew. The main thing is probably the stepper. I have a 604 ozin nema 34 installed. I didnt check the current setting on my driver, but it should be running at 48V 6A. I am up to 240ipm from 145ipm and 0.001 in backlash from 0.003 in backlash.

I get a nice consistent 180ipm from my Z, but I'm not even close to pushing out 6 amps, so I'm certain I will gain a good bit when I can turn that up. Smooth accelerations help my Z big time. I see consistent 200 on X and Y, again only pushing a about 70% of the available amperage that I could be.

its not amps that give you speed with steppers but voltage and inductance.

No stepper will be using full current at 150 IPM. Most will be drawing less then a third of there rated current.

For a given voltage system lets say 50V the only thing that will determine top speed is the inductance of the steppers.

For 300 IPM I think you need to spin a stepper at 1500 RPM with direct drive.

This is a chart of a 6.1A 640oz stepper.

http://www.automationtechnologiesinc...80-45-8ATC.pdf

As you can see it makes vary little power at 1500 RPM.

You could gear up you stepper or go to a faster screw but its hard to get steppers to work well at 1500 RPM.

The 570oz nema 23 stepper is really good in this way.