RoxanaPS wrote: ↑Mon May 01, 2023 8:26 am
Before making all these changes I ran it at 3000ipm fast travel ............
That's not quite accurate, 3000 IPM is about 4 feet a second. Isn't your machine frame roughly 4x4? The manufacturer states 500 IPM max speed with their stepper direct driven on the rack and pinion. I know you changed motors but with that gearbox you just added you are now going 10 times slower. You now have gobs more torque (yes "gobs" is a unit of measure ) but you killed the one thing you love, speed.
this reminds me of a retrofit job i did in Alabama about 20 years ago. The machine was a 4x8 router that was controlled by a stepper based CNC controller. I upgraded it to a centroid over a 2-day period working right beside three other identical machines in the same room that were in production right beside me the entire time I was doing the retrofit upgrade, noisy and hot. The customer was cautious and just wanted to upgrade one machine at first to see how it would go before upgrading the other three to the new centroid system. When I did the final configuration and tuning and got it running well, the shop floor manager and the operator of the other machines beside me came over for a demo. I gave them a quick tour showed the machine cutting some wood with a program that they were using on one of the other production machines. I gave them a demo of the centroid software from an operator standpoint and showed them the differences from the old system they were using and some new features that they now have with centroid such as stopping and starting easily in the middle of a job. Everything seemed to be going really well and then the operator asked me one question and then to my surprise and shock announced that the whole retrofit project is a failure and he doesn't want it in his shop!
The question he asked me was "What is the maximum cutting speed?"
I told him 420 ipm.
He then announced that the old machines are currently cutting at 600 inches a minute therefore the Centroid has to go, 420 is unacceptable.
After being stunned with the operator and shop floor manager getting ready to kick me and my equipment out of their shop, I regained my wits and decided to take a closer look at those old machines. The operator proudly walked me and the shop floor manager over to a antiquated dos-based monochromatic CNC control screen while the machine was running a job and pointed emphatically at a number on the screen that sure enough said 600 inches a minute! Who could deny that?
Well even at that stage in my career having been around enough machines to be able to look at it and least have a rough idea how fast it's going and that machine was not moving 600 inches a minute. However, the operator and the shop floor manager believed it, it said so right on the screen!
So, to save the whole situation I proposed a simple test to measure the average cutting speed of both machines (not taking into account the small acell decell slowdowns in the corners.) Running the same program on both machines at maximum cutting speed. A 4 ft x 4 ft rectangular frame mill was cut and timed on each machine. With a known distance traveled with an accurate as possible time measurement I calculated pretty closely to the cutting feedrate. The old DOS machine was actually moving 260 inches a minute. The new centroid was running double that. Now I can forgive the shop floor manager from not knowing what he's looking at but, I was surprised that the operator was being so emphatic that his machine was doing 600 inches a minute just because it said so on the screen. He even thought I was pulling a fast one on them with the test and math calculation for a little while and then conceded that I was correct. So, for all these years that they had those machines running their g-code programs that had 600 inches a minute in the part program for the feedrate (F600) and the CNC software was displaying 600 inches a minute because that's what the g code program said to do but, the machine was actually moving at 260 ipm. The old software was setup to display programmed feedrate not actual feedrate (it maxed out at 260). After the next day they put in the order for the other three machines to be upgraded.
I agree with the questioned speeds. I don't know much, but I have a hard time believing that a machine running steppers if going to be going 3000ipm/76,200mm/min, legit impossible if you ask me. A Brother Speedio tops out at 50,000mm/min.
Let's go back to basics to see what can be done at this point to increase axis speed.
If the axis stalls at 200 inch per second with 3,200 steps per revolution, what happens if you set 1,600 steps per revolution? How about 800 steps per revolution? How about 400 steps per revolution? See what happens when you trade resolution with speed. At what point do you see chatter when cutting circles? I'm thinking that on a router you would get acceptable circles at 800 or 1,600 steps per revolution. It depends on what you're cutting. MDF doesn't show cut marks as vividly as aluminum or plastic.
You can increase the size of your pinion gear. Bigger pinion = faster speed.
Try a few things. See what gets you as close to where you want to be. Find out what trade-offs you have to make.
Richards wrote: ↑Wed May 03, 2023 6:37 pm
Let's go back to basics to see what can be done at this point to increase axis speed.
If the axis stalls at 200 inch per second with 3,200 steps per revolution, what happens if you set 1,600 steps per revolution? How about 800 steps per revolution? How about 400 steps per revolution? See what happens when you trade resolution with speed. At what point do you see chatter when cutting circles? I'm thinking that on a router you would get acceptable circles at 800 or 1,600 steps per revolution. It depends on what you're cutting. MDF doesn't show cut marks as vividly as aluminum or plastic.
You can increase the size of your pinion gear. Bigger pinion = faster speed.
Try a few things. See what gets you as close to where you want to be. Find out what trade-offs you have to make.
Thanks. I will try those settings. I have also ordered a larger motor double the size for the X axis.
Of course it depends on the motor, brand, etc., but as a general rule, in the same brand when you increase the motors torque (add more windings) you decrease the RPM range in which it operates well.
Most decent motors will have a spec sheet that along with the specs will show a torque/speed chart. In order to build a properly operating system you must balance the motor's rpm and torque range to the mechanical reduction, (if needed) and the drive mechanics (rack & pinion or ballscrew) turns per inch. Compare the one you are considering against the one that you have. And remember that many components (like ballscrews) have a maximum RPM.
Gary Campbell wrote: ↑Fri May 05, 2023 9:06 am
Of course it depends on the motor, brand, etc., but as a general rule, in the same brand when you increase the motors torque (add more windings) you decrease the RPM range in which it operates well.
Most decent motors will have a spec sheet that along with the specs will show a torque/speed chart. In order to build a properly operating system you must balance the motor's rpm and torque range to the mechanical reduction, (if needed) and the drive mechanics (rack & pinion or ballscrew) turns per inch. Compare the one you are considering against the one that you have. And remember that many components (like ballscrews) have a maximum RPM.
) but you killed the one thing you love, speed.