Messages

2411

General Mach Discussion / Re: Odd glitch in movement?

« on: April 28, 2014, 05:02:38 PM »

I could run the same speed and part with THC off to prove the point, but I'm fairly certain it's belt flex. I have the THC rate very low, 8 or 10% i think! I don't think it would react fast enough to oscillate that rapidly. Plus the sheet is pretty flat so I doubt THC is doing much at all in this instance.

Will try tomorrow though just for confirmation.

It's more likely because I have under specified my belts, they are only 10mm wide, Y has two and Z has one. To make matters worse, they are full loops too so are about 2m long each. I could have halved that by mounting the motor on the gantry and using the belt as a rack but that would make the gantry far heavier which I thought would be a worse situation.

Live and learn, it's almost pretty damn good and that will be good enough for my uses I think, little bit more fiddling and learning should have it nailed.



Just thinking on, my settings for vel and acc are higher than yours, would I not get exactly the same results as you by setting them the same?
Just wondering.

2412

General Mach Discussion / Re: Odd glitch in movement?

« on: April 28, 2014, 01:15:12 PM »

Well at least I'm getting somewhere now thanks to all the help

I might try and se what happens if I knock it back another 50 maybe, just for reference purposes but as it is, I think it's a 100% better.

Question - as it is I now know it will work at 3300mm.min on 1mm sheet very nicely. If I then go for thicker metal, say cutting at 700mm.min, will the acceleration have less 'bite' than it does at this higher speed.?

My guess is it will be gentler as there is less speed to reach but I'm still a bit foggy on how it affects the process.

2413

General Mach Discussion / Re: Odd glitch in movement?

« on: April 28, 2014, 10:33:39 AM »

OK, educational half hour for me...

Speed was set at 3300mm/min in the file, THC codes removed, all CV config boxes cleared, THC turned on and ignored by me

In the first picture we have, from the back, acceleration values of 2000, 1500, 1000 & 900mm/s/s

As you can see, the higher the acceleration, the worse is the ripple effect caused by my belt drive system or machine design being taxed too hard.

Once I hit 1000mm/s/s I dropped to the smaller increment to see what happens and the 900 seems to be pretty acceptable i think?

The second picture shows the 900mm/s/s cut face-on and the nasty exit slope seems to be all but gone now which is good.


A question..

Is it worth going any lower on acceleration as the quality likely will not improve much as it seems pretty good bearing in mind this is the thinnest/fastest material I have (1mm)?

2414

General Mach Discussion / Re: Odd glitch in movement?

« on: April 28, 2014, 06:46:18 AM »

Just out of curiosity, and I know it's machine specific, but what sort of figure do you have for relative G force on your setup??

2415

General Mach Discussion / Re: Controlling THC?

« on: April 27, 2014, 04:48:20 PM »

Fantastic, now that really made sense.

Many thanks

2416

General Mach Discussion / Re: Odd glitch in movement?

« on: April 27, 2014, 04:07:14 PM »

Brilliant, thanks

Looks like I'm shooting too high on the speed and too low in acceleration.

Does my tuning strategy seem correct?

2417

General Mach Discussion / Re: Controlling THC?

« on: April 27, 2014, 12:39:20 PM »

Thanks again, I will tune for as much acceleration as possible without losing steps or shaking the table to bits

2418

General Mach Discussion / Re: Controlling THC?

« on: April 27, 2014, 11:49:21 AM »

Of course, yes, got it now.

Lol! Yes I do tend to think a lot, it's just the way I am, when faced with a new task-plasma CNC for instance, I like to try and gain answers before getting into a situation where that answer is needed.  At least you too can see how a dumbbell shape or similar could be an issue

Hopefully I can significantly improve things by tuning

2419

General Mach Discussion / Re: Odd glitch in movement?

« on: April 27, 2014, 10:39:21 AM »

Brilliant, thanks Stirling.

As I said, I will be clearing that cv angles box this week and then retuning.

From what I've read, it seems I need to set my max speed (pretty much where it is) and then push acceleration until it fails through lost steps or gets too violent and then back it off maybe to 70% of that value?

Does that seem correct?


What are your views on speed? I have currently set my max at 9000mm.min as I could not see any point in setting it higher, but is that still too high for such a small table?? The reason I ask is that speed and acceleration seem interdependent so I don't want to waste time on one if the other is wrong, I think that's logical

2420

General Mach Discussion / Re: Controlling THC?

« on: April 27, 2014, 10:31:24 AM »

Yes, I can fully understand that, but what if you have a job with small holes plus large cut areas too?

My guess is that I would separate the holes into another layer in sheetcam, do the THC off and speed reduction business and then do the other features as a standard cut at normal speed with THC.

That I think is correct, but falls apart when you get a job like the dumbbell shape I was messing with, a long straight where I guess you want THC that then blends directly into small near-circles - you can't turn the THC off for the circles without a macro glitch but as it needs to be slowed down to cut, the anti-dive will not function?

These are the questions that cause me to pose questions because I can't answer it