My Rapids are not very rapid

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danmst3k
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Joined: Tue Dec 23, 2008 8:31 am

My Rapids are not very rapid

Post by danmst3k »

I just got Cut3D (along with Cut2D) and I think they are just great. I did my first cut with Cut3D the other night (till 5:30 in the morning) and I noticed that when my mill does a rapid move to a new location it seems to go the same speed as when it's actually milling. I'm still new to the whole CNC thing so I was wondering if there's something I have to set somewhere (Mach3 perhaps? -Or-A preference in Cut3D?) to make the rapids go faster. Hopefully someone can help me figure this out. Thanks!

Dan D

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Thkoutsidthebox
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Re: My Rapids are not very rapid

Post by Thkoutsidthebox »

In Mach 3 select 'Config' > 'Motor Tuning' and you can set up your screws/motors, including the maximum velocity. Also, 'Config' > 'General Config' under 'Motion Mode' in the center, check that 'Constant Velocity' is selected. If you change to Constant Velocity, you may get rounded corners at high speed because the machine doesn't slow down on the corners, so again in 'Config' > 'General Config' under 'CV Control' in the bottom right, ensure that 'Stop CV on angles < ' is checked, and set the angle to something appropriate to your cutting speeds. I think mine was about 120 degrees before I took my machine apart.

danmst3k
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Re: My Rapids are not very rapid

Post by danmst3k »

Hey thanks V W for all the info! I will check all of these settings when I go home. I think I guessed on the velocity settings and they may be slower then they could be. This will hopefully save me a few hours of mill time. Every time there was a rapid I would manually crank up the inches per minute in Mach3 and then quickly crank it back down when it was about to start cutting again. Thanks again!

Dan

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Thkoutsidthebox
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Re: My Rapids are not very rapid

Post by Thkoutsidthebox »

When you start Mach3 press the 'Tab' key to see the interface pop-up. The velocity there should be set to 100%. You should keep increasing the velocity in the Motor Tuning for each axis individually until each Motor stalls or the cut quality is seriously degraded, then back it off about 15%-20% for each axis individually. While doing this do not change the velocity in the interface pop-up from 100%.

danmst3k
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Re: My Rapids are not very rapid

Post by danmst3k »

Thanks Thkoutsidthebox. I checked my settings last night and in the motor tuning section the velocity maxes out at around 25 inches per minute. I couldn't set anything higher than that. Could be because I'm running at 1/4 step? I actually ran my motors at around 15 inches per minute because I had a few glitches during my first cut attempt. I might have been trying to cut too much per pass on the roughcut because one of my steppers made a horrible noise then the cutter was in the wrong position on the piece. This happened twice so I kept turning down the inches per minute. I wound up recalculating the tool paths with less of a pass depth. This helped but takes a lot longer to mill. Last night I turned up the amps to the steppers from 1.5a to 2.5a, maybe this will keep them from stalling? I'm guessing when the make that noise that they're stalling? I'll look into the tab menu that you suggested. That's the jog menu I think, right? BTW what is MPG at the top of that menu? Sorry for all the questions. Anyway, thanks again for all the help and Happy Holidays!

Dan

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Thkoutsidthebox
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Re: My Rapids are not very rapid

Post by Thkoutsidthebox »

danmst3k wrote:.....in the motor tuning section the velocity maxes out at around 25 inches per minute. I couldn't set anything higher than that.
You couldn't set it higher in the motor tuning, or it wouldn't actually run higher? Can you jog faster than that using the arrow keys?
danmst3k wrote:Could be because I'm running at 1/4 step?
Not sure to be honest, I'm not an expert on Mach by any stretch of the imagination, but I don't think so. I'm not aware of a setting in mach that tells the software whether your at 1/2 1/4 or 1/8 step. Its a hardware setting on your driver board and a manual calculation.
danmst3k wrote:I might have been trying to cut too much per pass on the roughcut because one of my steppers made a horrible noise then the cutter was in the wrong position on the piece.
Generally its better to cut faster and shallower than slower and deeper, but 15ipm is very slow. Can you tell us more about your machine (Type, stepper type, driver type etc)?
danmst3k wrote:Last night I turned up the amps to the steppers from 1.5a to 2.5a, maybe this will keep them from stalling?
You should supply the max current to your steppers that they are capable of, and that your transformer will supply. 4 steppers at a max of 2.5Amps each (For example), your transformer should be capable of 10Amps +.
danmst3k wrote:I'm guessing when the make that noise that they're stalling?
Possibly, or maybe just not tuned well. How are your screws aligned...ok? Try 1/2 or 1/8 stepping.
danmst3k wrote:I'll look into the tab menu that you suggested. That's the jog menu I think, right? BTW what is MPG at the top of that menu?
Yes, and don't know what MPG stands for, I never paid too much attention to it!

Dan[/quote]

danmst3k
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Re: My Rapids are not very rapid

Post by danmst3k »

Thanks Thkoutsidthebox for the info. I found out what MPG stands for, it's Manual Pulse Generator and I think it's a kind of Jog wheel that you actually hold in your hand (not simulated). Anyway, I played around with my machine a little. I turned up the amps for the steppers to 2.5a and it seems to have made a difference. I attached a couple of photos of my mill. I'm using the Probotix 280oz steppers with the Probotix drivers and breakout board. The steppers max out at 3.0a so I might go to that next. I'm using 5/16th inch threaded rod from lowes and they have 18 threads per inch. They seem to be working pretty good. I tried some carving tests and the machine overall seems to be pretty accurate. I've had some problems with the cutting head losing it's place but I've read some other posts on this forum and realised it might be a screensaver issue. My screensaver has popped on a couple of times and it seems the errors follow after that. Also some mentioned if your computer is on a network you could get problems from that. I guess I'll have to keep experimenting.

Dan
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Thkoutsidthebox
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Re: My Rapids are not very rapid

Post by Thkoutsidthebox »

Ahhh, now I recognise it! :D I just replied to you on the Gallery of Machines thread! :oops:

If your computer is a dedicated unit for your CNC you should clean EVERYTHING unnecessary off it, and turn off anti-virus, firewalls (Since its not hooked to the internet anyway), screensavers etc. It should only have the cnc program (Mach3?) on it, and NOTHING else to intefere. Is it on a network?...Does it really need to be?

If your steppers are rated at 3Amp's max, then you should let them have that much. Current does not work like voltage. With current they will only draw what they need. If you can set up your power supply to be capable of maybe 4A or 5A per stepper, then do, and they will only ever use the 3A that they max out at. Voltage on the other hand is a different beast, with voltage if you supply more than needed your components will fry. :shock: I don't know how your setting your current? I have always just bought a transformer capable of the max current for each stepper, multiplied by the number of steppers, plus a few extra amps. Ramp up the current supply and let them have what they need.

Scottee
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Re: My Rapids are not very rapid

Post by Scottee »

Hi Dan,

Don't know if you have solved this already, but I have thoughts on your limited speed.

It is possible you are limited by the "driver frequency" in Mach. Given you have such a huge steps per inch figure (15780) the freq at which you would need to drive the step pin on your controllers is quite high.

I would suggest either:
a) Don't 1/4 step. This should potentially increase you max speed by 4x. While as a bonus improving the torque from your steppers. It is also unlikely you need the extra precision gained from 1/4 stepping given you are using allthread, which has a high TPI anyway.
b) Increase the driver speed. I can't remember how to do it off the top of my head but if you have trouble let me know. When you do this, you also want to head over to the diagnostics tab in Mach3 and check that the freq there roughly matches the new driver frequency you configured. If it is too low or jumping around a lot, your PC is struggling to keep up.

Sweet guitar body by the way.

Hope that might be useful,
Scott

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Re: My Rapids are not very rapid

Post by Historiker »

I know I am necro'ing an old thread but I found Thkoutsidthebox's post extremely helpful and wanted to take the time to thank him.

So thanks! :)

I have been running my DIY CNC for a couple of years now and never realized that my rapids were affecting my corners so poorly nor that they were are the heart of the occasional mis-step.

I feel a bit silly now but at least I learn eventually.... :D

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