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View Full Version : 2 start vs. 5 start



bradtal
04-20-2009, 11:17 AM
Hello All-

I've built a Joes2006 machine and have had pretty good luck with it so far. However, I tend to run into some issues after awhile. For example, I've been making some cool pencil holders and have a large order for them. I'll make like 15-20 with no problems, and then suddenly, my x-axis (long axis) will skip steps and it ruins the board I'm cutting from.

I'm currently using standard 1/2 inch threaded rod. I've always wanted to "upgrade" to the 5-start 1/2 rod from McMaster-Carr. After doing some research, I see that people are 50/50 on whether to use 5 start or 2 start.

I'm using the HobbyCNC board with 305 oz steppers with a 24V transformer.

I've read that steppers have more torque as slower speeds, so the 5-start makes sense to me. But then I also read that your motors have to be "strong enough" to be able to turn the rod at that slow speed.

I guess after all this typing, my question is... What makes more sense? 2-start or 5-start? I don't want to invest a bunch of money and regret it afterwords.

Thanks for your help.

Brad

BobF
04-20-2009, 12:56 PM
Brad,
I built joes2006 as well. I used 1/2-8 2 start. This gives 4 tpi. Lots of the builders of Joes 4x4 have used the 1/2-10 5 start, which gives 2 tpi. I think that will work on the 06 and am looking into getting some, but don't have any yet.

I can tell you that the 1/2-8 2 start works well.

calgrdnr
04-20-2009, 03:19 PM
Howdy Brad ,

I switched out my 10tpi 1 starts to 5starts . I can now routinely cut mdf at 150 ipm I have rapids of 320ipm. I went with the 4 Axis HCNCPROPKG Package w/ 200oz-in Stepper Motors. I used to have problems with Zaxis losing steps, since the change I have had no problems. I am sure it is because the torque is greater at lower speeds ( only use 30ipm for Zaxis)

you should also check to make sure acceleration not set to high this can cause you problem I believe.

good luck Kent

bradtal
04-20-2009, 03:37 PM
Howdy Brad ,

I switched out my 10tpi 1 starts to 5starts . I can now routinely cut mdf at 150 ipm I have rapids of 320ipm. I went with the 4 Axis HCNCPROPKG Package w/ 200oz-in Stepper Motors. I used to have problems with Zaxis losing steps, since the change I have had no problems. I am sure it is because the torque is greater at lower speeds ( only use 30ipm for Zaxis)

you should also check to make sure acceleration not set to high this can cause you problem I believe.

good luck Kent


Kent-

Thanks! This is exactly what I was hoping to hear! Thanks also for listing your specs. Made it easy to compare your setup with mine.

Brad

calgrdnr
04-21-2009, 01:28 AM
Brad,

Glad to be some help, that is what is so great about this site . Ask and you get answers. might not always be real quick or what you want to hear.
but you will get responses.. Please make sure to share some of your results of your creativity and your CNC .
let us know how it work Kent

AJ Negvesky
04-21-2009, 12:34 PM
I have finally finished cutting out and asseblinng all the pieces for Joe's 2006 R2 and went with the Probotix

3x SideStep Bi-Polar Stepper Motor Driver
2x HT23-400-4 400ozin Stepper Motor (X- & Y-Axis)
1x HT23-260-4 260ozin Stepper Motor (Z-Axis)
PBX-2 Parallel Port Breakout Board
24Volt 4.3Amp Switching Power Supply

Mach3 and Vcarve pro V5 software


I now need to select the lead screws. I understand 5 start would give you higher speed, but do you loose accuracy? Any help on which way to go and what the settings would be best in Mach 3 would be greatly appreciated..:drowning:

TchTchr
04-21-2009, 02:17 PM
Are three anti-back lash nut and flanges needed from dumpstercnc when going with the 5-start?

thanks,
Brad

Realmseeker
04-21-2009, 02:35 PM
Does McMaster carry the 1/2-10 5 starts? i am having problems finding it on their site. Can someone link it please?

Seems about 40$ for 1/2-8 1 or 2 starts vs 60$~ for the 5 starts on 6' lengths,
Basically adding about 40$ to a build,
Even on a budget,
thats not to bad

AJ Negvesky
04-21-2009, 02:39 PM
http://www.mcmaster.com/#=1jlp9n

AJ Negvesky
04-21-2009, 02:41 PM
search for number
steel
99030A704 $60.74

Black-Oxide
98940A020 $82.26

Realmseeker
04-21-2009, 03:56 PM
much thanks AJ :)

TchTchr
04-21-2009, 07:40 PM
I found the answer to my question below in the parts spreadsheet.

3 backlash nuts and flanges

sorry for unneeded post

BobF
04-21-2009, 10:58 PM
I have finally finished cutting out and asseblinng all the pieces for Joe's 2006 R2 and went with the Probotix

3x SideStep Bi-Polar Stepper Motor Driver
2x HT23-400-4 400ozin Stepper Motor (X- & Y-Axis)
1x HT23-260-4 260ozin Stepper Motor (Z-Axis)
PBX-2 Parallel Port Breakout Board
24Volt 4.3Amp Switching Power Supply

Mach3 and Vcarve pro V5 software


I now need to select the lead screws. I understand 5 start would give you higher speed, but do you loose accuracy? Any help on which way to go and what the settings would be best in Mach 3 would be greatly appreciated..:drowning:

Most steppers are 200 steps per inch these days look in your specs and see what yours are. It may say 1.8 degrees.
Steps per inch = screw pitch * 200 full steps per rev * microsteps so
1/2-10 5 start gives 2 tpi effective pitch.
2*200=400 full steps per inch.
If your drives do 4 microsteps you now have 1600 steps per inch. This would give a little better than .001 which is probably as good as you can hope for with a homebuilt.
With your 1 start screw you would have had 10*200*4 = 8000 steps per inch.
yes in theory you traded speed for accuracy, but could the machine really resolve 1/8000 inch?
Microstepping seems to be fairly common in drives and I have seen 2,4,8,16,5, and 10 listed in various drive specs. There are probably other numbers that some do.
So you could choose 800, 1600, 3200, 6400, 2000, 4000 steps per inch depending on the microstep settings available.

AJ Negvesky
04-22-2009, 06:11 AM
Most steppers are 200 steps per inch these days look in your specs and see what yours are. It may say 1.8 degrees.
Steps per inch = screw pitch * 200 full steps per rev * microsteps so
1/2-10 5 start gives 2 tpi effective pitch.
2*200=400 full steps per inch.
If your drives do 4 microsteps you now have 1600 steps per inch. This would give a little better than .001 which is probably as good as you can hope for with a homebuilt.
With your 1 start screw you would have had 10*200*4 = 8000 steps per inch.
yes in theory you traded speed for accuracy, but could the machine really resolve 1/8000 inch?
Microstepping seems to be fairly common in drives and I have seen 2,4,8,16,5, and 10 listed in various drive specs. There are probably other numbers that some do.
So you could choose 800, 1600, 3200, 6400, 2000, 4000 steps per inch depending on the microstep settings available.



Thanks didn't look at it that way the stepper drivers have full half 1/4 and 1/8 step and the steppers themselves are the 200/1.8 degree. By looking at the specs I would really want to keep the steppers under 700 rmm for the higest torque, so with your formula at full step and 5:1 at 500 rpm 250 inches per min would the effective travel rate. Sounds like alot of people like the 5:1 and for like 5 dollars over the 2:1 not much of a diff on the lead screws. I was also worried about the angle being too steep for the steppers to move it but from what I am reading I don't see that as the case.

BobF
04-22-2009, 06:22 PM
multi start screws are usually more efficient as well.
Look up Nook industries. They have lots of good screw info on their site.

bradtal
04-28-2009, 01:11 PM
Hello All-

Well, thanks to all the help from everyone on the board, I bit the bullet and ordered the 5-start rod from McMaster-Carr and the DumpsterCNC parts.

I installed them last night and all I can say is "Wow! Wow! Wow!" What a huge difference. Not only is it faster, but it is much smoother. The stepper doesn't have to spin as fast, so the rod doesn't whip. This minimizes the "jerkyness" I was getting with the old 1/2-13 threaded rod.

I definitely recommend the 5-start rod if you are thinking of upgrading.

Brad

AJ Negvesky
04-28-2009, 01:19 PM
Well I did the same mine all came in over the weekend went with the dumpstercnc clamping collars too. I hope mine is as nice as yours sounds.

calgrdnr
04-28-2009, 01:39 PM
"Wow! Wow! Wow!" What a huge difference

:banana::wee: Just wait till you start cutting , and save all kinds of time with the quick/fast rapids .

You mentioned jerkyness are you still getting it? Is it just from inertia?
Are you using Mach? If so, try tuning your motors. I really have no jerkyness in my system is why I am asking.
It moves real smooth on all axis’s.

After my upgrade I was amazed on how much more professional/efficient the
machine sounded and ran also. It was worth every penny and as far as I am concern
and should be done at the beginning ,if just starting a build . Skimp on clamps / t rails,
what ever else you may need to skimp on .
but not starting with these screws is pretty much a waste of monies. Not to mention time ( cutting slower )

enjoy your “NEW” machine :cheers:

multiplex
04-28-2009, 01:53 PM
i'll jump in on the 5 start bandwagon :rainfro:

i recently upgraded from 2 to 5 start 1/2-10 using McMaster screws and Dumpster components. What an amazing difference.

My max rapid before was 120 IPM (sometimes 150). Now i have my rapids set to 400 with no problems. I'm also 1/16 stepping my motors I believe.

bradtal
04-28-2009, 04:01 PM
:banana::wee: Just wait till you start cutting , and save all kinds of time with the quick/fast rapids .

You mentioned jerkyness are you still getting it? Is it just from inertia?
Are you using Mach? If so, try tuning your motors. I really have no jerkyness in my system is why I am asking.
It moves real smooth on all axis’s.

After my upgrade I was amazed on how much more professional/efficient the
machine sounded and ran also. It was worth every penny and as far as I am concern
and should be done at the beginning ,if just starting a build . Skimp on clamps / t rails,
what ever else you may need to skimp on .
but not starting with these screws is pretty much a waste of monies. Not to mention time ( cutting slower )

enjoy your “NEW” machine :cheers:

Calgrdnr-

Thanks for the comments. I mentioned "jerkiness" when using the old 1/2"x13 1 start threaded rod. It was spinning so fast, it would whip ever so slightly. However, that "whipping" seemed to make my rapids "jerky". Like every time the rod would rotate once, I'd experience a little "jerk" of the gantry. Multiply that by how many revolutions it took to move the gantry, it seemed to "stutter" slightly as it moved. Hard to explain...

With the new 5-start rod, the stepper doesn't have to spin as fast, so no whip and no jerkiness. Way cool.:banana:

spjuenger
08-29-2009, 09:44 AM
Hello All-

Well, thanks to all the help from everyone on the board, I bit the bullet and ordered the 5-start rod from McMaster-Carr and the DumpsterCNC parts.

I installed them last night and all I can say is "Wow! Wow! Wow!" What a huge difference. Not only is it faster, but it is much smoother. The stepper doesn't have to spin as fast, so the rod doesn't whip. This minimizes the "jerkyness" I was getting with the old 1/2-13 threaded rod.

I definitely recommend the 5-start rod if you are thinking of upgrading.

Brad

So what dumpster parts did you get? I'm trying to put together a parts list for a new build. The plans call for 20 amce nuts, but the 3 dumpster antibacklash nuts replace 6 of those twenty. Did you use any of there clamps?

joecnc2006
08-31-2009, 05:17 PM
The original design uses a double acme nut locking system against the bearings for the leadscrews, these are eliminated when using different leadscrews and or the dumpster clamps.

AJ Negvesky
09-06-2009, 08:14 PM
I got 6 of their smooth clamps 1 for each end of the lead screw i got 3 of their couplers and 3 of their backlash nuts. I also got thrust bearings from McMaster carr and put that between the clamp and the bearing allowed me to preload the bearing a little more with virtually no drag.

Serb
09-24-2009, 02:08 PM
I had my machine for almost 2 years now and the first upgrade I did was on the Z-axis holder/slider. I got rid of all the original parts and made a solid aluminum holder with linear bearings. It brought the cutting head much closer to the Y gantry and it eliminated some of the vibration. But I'm still not happy with the precision so I have decided to completely redo the Y gantry and make the whole thing out of metal and use linear bearings all around. I guess the only thing that would be left from old Joe's would be the table, it's solid enough and it's bolted to the steel structure below it.

My question would be concerning the lead screws. I really do not care about the speed as much as I care about the precision of the cut. I'm looking for something that will give me a smooth, lets say circular cut, without having any of the cutter bumps on it. What would be a decent configuration without spending too much?

multiplex
09-24-2009, 02:18 PM
during my last rebuild, i 'upgraded' to 5 start from 2 for speed. but the downside to that is you do loose resolution. I found this out quickly on a patter that repeats a 8 x 8 grid. By the time i got to the 64th location in the grid it was drastically off from where it started.

To counteract this, i needed to make sure my microstepping was set pretty high. In some cases this might be limited by your computer speed, etc. I can't recall off the top of my head what it is currently set at but I was able to get my location back in line

Granted i did gain some speed, and my rapids are increased. However i still found myself limiting my rapid speed to make sure I didn't loose any position.

Long story short, I'm not 100% sold on the improvement I made.

If you are looking for accuracy, i'd stick with 2 start

calgrdnr
09-24-2009, 06:07 PM
Hello Multiplex,

I cut most of my Lithophanes with a Vbit, I tell software is a .03 Ballnose with a 10% stepover ie cut a line every .003 of an inch.
I have cut at least a hundred lithophanes and never had a problem short of lost steps due to binding or motors not tuned correctly in Mach 3. I started with the 1 step screws max speed 85ipm I routinly cut at 120-150 with rapids of 340 with the 5 start . I have never experinced and problems with resolutions .... There is now way I would ever change it out ....There is alot of people using this set up with no problem ... I think you might want to check your settings and make sure you have no binding ... good luck Kent


http://www.cnczone.com/forums/showpost.php?p=602644&postcount=13 shows settings and resolution should get with 5 start

ger21
09-24-2009, 06:43 PM
during my last rebuild, i 'upgraded' to 5 start from 2 for speed. but the downside to that is you do loose resolution. I found this out quickly on a patter that repeats a 8 x 8 grid. By the time i got to the 64th location in the grid it was drastically off from where it started.


What you are describing is not a problem of resolution. Lack of resolution does not cause cumulative errors. With lower resolution, your pattern would still be in the right location, but the size of the pattern might vary by a few thousands. Say you cut 20 2x2 squares, with a 1" space between them. The second would be at 3", the third at 6"....... one square every 3", ± roughly your resolution. It will NOT cause a gradual shift of the squares location.

What you were seeing was a loss of steps, or an improperly set steps/unit setting.