[Hack]

I am currently using allthread with a delrin nut for the lead screw of my cnc router (1/2-13) and 276 oz steppers, xylotex board and 24 v power supply and Turbocnc.

In order to get some more speed for my rapids, what would make more impact:

Upgrading to a more efficienct lead screw (probably acme due to budget)
Increasing stepper size (can't go much bigger with the xylotex board)
Upgrading to a bigger power supply (can run up to 35 volt max with xylotex)
Changing computers and software to drive everything (perhaps to Mach 2)

Thanks

Hack

[CJL5585]

This is an educated guess but believe it is a toss up between the leadscrew and the power supply voltage.

A different leadscrew will definately help. However, replacing a leadscrew is a lot of re-engineering and work with the bearings, motor couplings, etc.

The 24 VDC supply is probably the least expensive route to take as it will also give you additional speed in rapids. Also, it is probably the least amount of work to change out.

Steppers with higher inch/oz rating should not make any difference in speed. Just in torque. However, higher voltage should also increase the torque rating at the present speeds.

Hope this helps,
Jerry

[ger21]

I'd try 1/2-8 2 start acme. 6 ft is only ~$25 at http://www.mscdirect.com
You can also get premade anti-backlash nuts from here. http://gonebowlin.com/dumpsterCNC/


Like you said, you can't reall use bigger steppers. And anything over 30V can easily damage a Xylotex. I've heard people say Mach2 runs smoother, but I doubt it will go much faster. Maybe a little.

If changing to the acme doesn't help, you probably need to go with Gecko's and at least 48V. You could build drives from http://www.embeddedtronics that will run @ 48V. Not sure what they would cost, though.

[jgro]

Another option is to change the microstepping of your Xylotex. I ran my machine with 1/2-10 ACME with a 24 volt power supply and 116 oz steppers and was getting around 60 ipm. That was with it set at 1/8 microstepping. I've since changed it to 1/4 stepping and am getting around 115 ipm. If you figure it out:
200 steps per revolution X 10 threads per inch X 4= 8000 steps per inch.
1 inch divided by 8000 = .000125 inches per step.
I can live with that kind of resolution.

jgro

[Hack]

I have thought about changing the microstepping as well. I read an article on the net saying that microstepping is bad for torque in one way or another. http://www.machinedesign.com/ASP/vie...strSite=MDSite (Thanks GER21)

Also think that I can turn the VREF setting of the xylotex board up a bit as well. Currently set a 3.4 and I beleive the max is 3.62. I'm sure that would help some as well.

I was under the impression that with a power supply, if you double the voltage, you will double the performance. (with in reason). So I am thinking that going from 24 v to 30v power supply, I would gain another 25% performance. Is this correct? Any recommendations for a good 30V power supply?

Thanks all?

[anoel]

I'd try 1/2-8 2 start acme. 6 ft is only ~$25 at http://www.mscdirect.com
You can also get premade anti-backlash nuts from here. http://gonebowlin.com/dumpsterCNC/

I'll second DumpsterCNC...

I just had him make up 3 1/2-10 2 start nuts for me. He was very quick and the nuts are very cleanly made. The quality is seriously as nice as the simliar ones from Nook and other places.

[DieGuy]

Don't turn up the Xylotex Vref. It only limts the amps and a .2 increase to 3.6 volts is on the ragged edge. A 30 volt supply is a better option, you will need to find a 20-22 volt transformer. I run mine at 28.5vdc. It depends on the back emf your setup produces as the total you can drive it to is 35 vdc. Make sure you have adequate active cooling for the heatsinks, I run 2 12 vdc fans in series to blow diredctly on the heatsinks. When my vref was set to 3.6 vdc I lost steps left and right and the machine would not accelerate without dropping steps, Mine is now set to 3.4 vdc and it works the charm.

[Hack]

I emailed Jeff at Xylotex and asked if he could supply jumpers for me to switch to 1/4 microstep instead of 1/8 (he said I could find them at a local computer or electronics store - Man is his support fast - Excellent job Jeff), and he wrote this:

"The only reason you should want to go to 1/4 step is your pulse
generator can not make a fast enough pulse train. You will loose
some of the microstepping smooithness by doing so, and it is not
particularly recommend to run at lower than 1/8th step."

Ok can someone translate this to English for me. What is the pulse train? I was thinking this had more to do with the computer processing speed than anything and not necessarily of importance here. Shows how little I know. I also can't see loosing much smoothness by switching to 1/4 microstep.

[strat]

Another option is to change the microstepping of your Xylotex. I ran my machine with 1/2-10 ACME with a 24 volt power supply and 116 oz steppers and was getting around 60 ipm. That was with it set at 1/8 microstepping. I've since changed it to 1/4 stepping and am getting around 115 ipm. If you figure it out:
200 steps per revolution X 10 threads per inch X 4= 8000 steps per inch.
1 inch divided by 8000 = .000125 inches per step.
I can live with that kind of resolution.

jgro

am i glad to see this i just changed to 1/4 instead of 1/8 also and i also nearly doubled my speed ..... glad to see the same effect from someone else

[ger21]

I emailed Jeff at Xylotex and asked if he could supply jumpers for me to switch to 1/4 microstep instead of 1/8 (he said I could find them at a local computer or electronics store - Man is his support fast - Excellent job Jeff), and he wrote this:

"The only reason you should want to go to 1/4 step is your pulse
generator can not make a fast enough pulse train. You will loose
some of the microstepping smooithness by doing so, and it is not
particularly recommend to run at lower than 1/8th step."

Ok can someone translate this to English for me. What is the pulse train? I was thinking this had more to do with the computer processing speed than anything and not necessarily of importance here. Shows how little I know. I also can't see loosing much smoothness by switching to 1/4 microstep.

The pulse train is how fast the computer can send steps. I'm guessing you 2 were using TurboCNC, which can have a pretty wide range of step rates from PC to PC. Mach2, otoh, will always output 25,000 steps/second. With 1/2-13 and 1/8 microstepping, you need 20,800 steps per inch.

You didn't say what control software you're using, but go ahead and set it to 1/4 step, and see if it makes a difference. I'm a bit curious, actually. I'd be surprised if your speed doubled, though.

You didn't say how fast you're going, but to go 30ipm, you have to spin the motor at 390rpm. @ 24V, most steppers torque curves start dropping to about 1/2 or less by then. Consider that 1/2-13 is not very efficient, and you're wasting a lot of power there. 2 start acme screws are probably at least twice as efficient, and the motor will only need to spin about 1/3 as fast, where you'll have much more torque available.

I'd start with the cheap fixes first, and work you're way up until you get what you want.

[strat]

i'm using mach 2 but an old p300 and when testing for timing i had to go with the slow clock

[Hack]

I am using an old Pentium 200 MMX for my computer and TurboCNC V4 for controller. Is this computer to slow? How do I know or figure the pulse train?

I will try switching to 1/4 microstepping tomarrow and see if it works, if not, i will probably asdjust the vref a little higher then look for a different power supply. I think this is probably the route to go for the cheapest fixes.

Currently I am only getting about 22 IPM max and thats stretching it. I keep it set at 20. I was realy anticipating getting closer to 30 IPM with the 1/2-13

Thanks all

Hack

[strat]

thats about what i was doing in 1/8 i was getting about 28 i could bump to 30 but would start skipping steps with the 1/4 setting i can get 50 no prob and start dropping off about 55

[Hack]

Strat Wrote:

"thats about what i was doing in 1/8 i was getting about 28 i could bump to 30 but would start skipping steps with the 1/4 setting i can get 50 no prob and start dropping off about 55"

Could you please tell my what size motors that you are running and what type lead screw?

I changed the settings to 1/4 microstepping today and it did make a difference in speed. I also bumped the vref to 3.58. The added vref didn't make a noticable difference so I will probably lower this back to 3.40 or so. I am uder the impression this will keep the heat down a little?

I can max now out at about 38IPM but tend to loose steps. I set it at 30 IPM and it seems smooth. I am quite happy with this setting. My target was 30 IPM so I will probably be content for a few for days, but....

I would like to explore what improvement that I could get with a 30 volt power supply. What improvement should I expect from switching from a 24 volt?

I had to adjust my setting in TurboCNC quite a bit. Before I was running 8000 as max speed with 6500 fast jog and now I am running 6000 max speed, with 5000 fast jog. Why are these settings affected? Anything above this setting stall the steppers whether in 1/8 or 1/4 microstepping.

[H500]

Increasing your vref will usually give no improvement, since at the higher speeds, your current will never reach the set value. Using a higher power sup volt will help.

[DieGuy]

I suspect a 30 vdc supply will be about a 25% increase in top speed performance assuming all else is equal, like the ability to drive the pulse train, etc.

[strat]

i'm using the 276 oz-in motors my acme thread is 1/2 10 i'm using pacific bearing slides not roller bearings and 24 v for my power supply xylotec for controller when i first started into all this i was using 116oz in motors and changing to the 1/4 DID NOT have the same effect

[strat]

hack :
I would like to explore what improvement that I could get with a 30 volt power supply. What improvement should I expect from switching from a 24 volt?

i'm doing fine on 24v let me know how it goes if you change to 30

hack:
I had to adjust my setting in TurboCNC quite a bit. Before I was running 8000 as max speed with 6500 fast jog and now I am running 6000 max speed, with 5000 fast jog. Why are these settings affected? Anything above this setting stall the steppers whether in 1/8 or 1/4 microstepping.[/QUOTE]

i tried turbocnc when i first got into it but don't remember enough of it as far as the setting locking you the only thing i can think is a timing issue but i don't know enough about it anyo
ne care to give a good overview on the timing??????

[ger21]

The 8000 Hz setting for max speed is 8000 steps/sec. That means the most speed you could get with that setting would be 23ipm. 8000/200/8/13*60=~23
Using 1/4 stepping and 6000Hz, the max you'll get is 34ipm.

Are you setting it below the point where you lose steps? and did you adjust your start speed and accel as well, or just change the max speed? These settings can also have an effect on losing steps. I've read that by setting the start speed very low, you can set the acceleration much higher. If the accel was part of the problem, that may help

[Hack]

Well I got a chance to do some good cutting today. I had a file that took about 2 hours to cut and it got a few minutes into the file and started jerking and missing steps and cutting horrible on all 3 axis. Well I only applied the majority of the changes to my z axis except the VREF change, so I changed that back to 3.40 and cut the balance of the file without any problems other then a couple of broken bits (Cheapies from ebay - never again)

Runs pretty smooth. I will be changing the x and y Axis when I get a couple of days for the machine to be down. Got some other projects to cut right now.

Still looking for a 30v power supply. Any leads from anyone?

Thanks all