to clear path or not to clear path that is the question?
hey guys I'm planning on building a 4896 and I'm researching the steppers and possibly the clearpaths and noticed most people are going for the nema 34s but wondering what the drawbacks are with the 23's, I keep hearing "inertia miss match" and "you need the 34's" is it simply a matter of cutting speed and rapids or is there accuracy and smoothness gained by the larger heavier stepper/servos?
also if anyone happens to know the inertia value for the gantry or if you've done the math for this specific machine id sure appreciate a simplified answer or example on that, thanks in advance.
Jonny.
Re: to clear path or not to clear path that is the question?
The simple answer is that every 48x96 I have seen has NEMA 34s or better in it. You need the torque to accelerate the mass of the gantry or table. The last upgrade I did on a 60x120 I used Clearpath SDHP NEMA 34s. Worked just fine and the customer was happy. Better might have been at least 750W servos on the gantry axis. I have NEMA 34 steppers on my 48x96, they work OK, but could use more power.
Re: to clear path or not to clear path that is the question?
Re: to clear path or not to clear path that is the question?
Quote:
Originally Posted by
Jim Dawson
The simple answer is that every 48x96 I have seen has NEMA 34s or better in it. You need the torque to accelerate the mass of the gantry or table. The last upgrade I did on a 60x120 I used Clearpath SDHP NEMA 34s. Worked just fine and the customer was happy. Better might have been at least 750W servos on the gantry axis. I have NEMA 34 steppers on my 48x96, they work OK, but could use more power.
That is a bummer, I have the NEMA 23 steppers on mine. It works as far as I can tell. But, I am not a production facility. I am a hobbyist and so far I have not run into issues. I could see being able to move much faster and the holding force being higher and allowing the gantry to stop more accurately. But I have not adjusted my setup to go faster than the default post allows for yet. I am learning still and I am not comfortable pushing it further than it is going now because I have messed up a few times and had to react to hit the stop and that was too fast for me to react to. I might have to end up upgrading in the future, but as of now I can do what I need at 100 ipm and below.
would upgrading reduce chatter? I do see some arcs produced by the fusion 360 post tend to make a weird chatter sound. It is not all of the time and I was thinking that it might be part of their way of evacuating chips well while still having a constant contact with the material. A jerky helical pattern or something. But maybe my motors are underpowered.
Now I am starting to have motor envy.
Re: to clear path or not to clear path that is the question?
What Nema 34's will do is allow you to increase acceleration, which can greatly decrease cut times, and potentially be more accurate.
Quote:
would upgrading reduce chatter?
No. Chatter is likely due to a rigidity or mechanical issue. I'd carefully inspect your rack and pinion setup and make sure everything is aligned and tight.
Re: to clear path or not to clear path that is the question?
A few years ago I built a MechMate router for a specific purpose. The machine has a cutting envelope of 72x144x8. This machine also has a very heavy gantry, well over 100lbs. I got tired of the poor performance of the crappy breakout board, the Geckos, the SmoothStepper, and the very noisy and hot steppers.
I replaced all that stuff with a Hicon Integra controller, four Teknic Clearpath NEMA 23 servos, and a single Teknic power supply. At first I was worried the little NEMA23's wouldn't be able to perform. But they have never failed once. They provide plenty of torque for the work I do, and they provide torque and performance to the machine limit.
Anyway, I'm very happy with these little 23's. I purchased the least expensive ones available, CPM-SDSK-2310S-RLN. They do not have the highest resolution controller, but in practice on my machine, I have found the lower resolution controller works just fine. I use the machine to cut aluminum, 2024-T3 and 6061-T6. I have used the machine to cut upgraded aviation instrument panels for Cessna Citation jets, Beechcraft King Air twin turbo props, and Mooney's. The instrument shop has been very happy with everything this machine has produced. I also use the machine to cut 1/2" aluminum motor plates and have cut aluminum thickness to one inch.
Sorry guys, I don't have theoretical answers for you. I can only report my experience with them. Are they the best NEMA 23 you can buy? Perhaps not! But they perform and do everything I ask of them.
Re: to clear path or not to clear path that is the question?
A couple of years ago when I changed to the servos, I decided to build a little test routine, a test routine to simulate peck drilling. So I fired up Mach and sent the machine out to simulate peck drilling, 45 drill sites. This would exercise all axis over the entire surface of the machine.
Shortly after I started Mach, watching the first hole being pecked or perhaps the second one, I realized something was wrong. I looked at the X-axis servo, and of course it was running with the green light indicator on. Then I looked at the A-axis, the slave axis, seeing the amber light on, indicating that it was off line and not working, not contributing to the drive effort.
At first I panicked, then realizing that I accidentally forgot to plug in the 'step/direction' drive cable, then I thought, 'just let the program run and let's see what happens'. So I did just that. I let the program run without the A-axis contributing. It was interesting to watch the one little NEMA 23 Clearpath servo drag that big MachMate gantry around at 400-IPM over the entire length of the table without the A-axis. Keep in mind here, that one servo was dragging the weight of the Y-Axis, the weight of the Z-axis, and the weight of the router. All the while, the servo never quit running and returned back to the exact position from where it began. The A-axis of course did not return to its beginning point, but for a 7+foot gantry without slave contribution, that's to be expected.
Having speed of 400-IPM is good for me, and these servos can easily do more. But I keep the IPM settings quite a bit lower, for one, due to the dynamics of the large machine. Consider the servos driving a mass exceeding 100 lbs at 400IPM. A lot of mass in motion. So my machine is dialed back to about 100 or so.
I'm running rack and pinion, with belt drive transmissions - 4.5:1. When I bought the transmission boxes I told the guy I wanted decent precision and that I was not so concerned with speed. Since he had the 4.5:1 boxes already made up, I bought them. You can run the NEMA23's easily 3:1 and receive good speed and nice precision.
I offer this. Know your feeds and speeds and make certain you understand your program routine. These little servos will instantly break a 3/8" endmill, or bog down a 3-1/4 hp Porter Cable router. I know, cause I've done that!!!
Re: to clear path or not to clear path that is the question?
34's vs 23's .....for a good comparison, what are the specs on the two motors that you are looking at?
Re: to clear path or not to clear path that is the question?
Sorry for the late reply to your question. I am running ClearPath SDSK 3421 motors on a FineLine Saturn machine. The gantry and Z axis combined weigh about 125 lbs on my machine. I have yet to see these motors work hard. When I tuned my motors, I placed about 65 lbs of weight on one of the motor carriages and went through the ClearPath tuning routines. During that process the motors went through some very quick accelerations on their way to 800 IPM oscillating about a foot back and forth. They never reached more than about 30% of max power. I typically run around 200 IPM cutting hardwood with 1/2" spiral uncut bits, taking as much as 1/4" in a pass. The motors barely get warm after an hour of cutting. I believe I could have used the 3411 size instead. In the ClearPaths, the NEMA 23 sizes don't really save much money (maybe $30-$40 each) until you drop way down in power, so why short-change the power. Driving the motor less hard will keep it happier in the long run.
If you do go with the ClearPaths, a reduction of around 3:1 or so on a rack and pinion (1" dia. pinion) makes alot of sense from a torque/speed perspective. To get better resolution, consider using the higher resolution versions of the motors. That will get you in the 0.001" resolution range. Depends on your needs, of course.
If you are really tech savvy, consider the SDSC motors. They are a little more expensive for the same ratings, but you can also run them as straight servos if you know how to program them for that.
-Robert
Re: to clear path or not to clear path that is the question?
im working on a build now for 60 x 60 inch machine
using https://www.teknic.com/products/clea...arpath-models/
yes, going for lower rpm higher torque ones.
just not sure which screw yet
2010 maybe 2005 but i want to keep inertia weight down but also dont want any whip not sure of 20 because of possible whip
