Wiggly cuts

[BensPlasmaAu]

I am still having grief with the cuts on my machine. All axis and drives are solid. My CAD files are straight and curves have low node counts. It just loke the thing decides to wiggle and adjust the motors constantly. Its driving me nuts.

I have tried with the torch height control off, no change. I cannot think of anything else. Again, machines drives are solid so there us no movement, slack or backlash.

I sorter out the bevelling issue by adjusting the torch volts down by 3 volts.

Photos of crap cuts

[Gamelord]

I have seen the Powermax 45 cut. If is has clean and proper air supply then it is not the plasma. If your files are straight and sharp then the only thing left is your table. The wave has to be coming from either a loose belt, loose bearing, bad gear, loose gear, loose shaft or just poor design on your gantry/table runners. The only other possible thing that it could be is slat wave, if your slats are waving back and forth from the movement of the table it will cause this. I still say it is something in your table that is not tight or not rolling smoothly or slipping etc...

Have you put a pen in place of the plasma to see if it draws straight? One other thing you may be able to check.

[acourtjester]

You need to divide the problem in 2 parts, plasma or mechanical. If you do the pen test as Gamelord says this will show if it mechanical. watch the video I made some time back (I know its slow) Make sure your pen has a solid mount. The pen tip is very narrow less then a torch kerf and will show any movement problems. If you see things there you found what you need to correct. If it is smooth with no wiggles then it's plasma.
https://www.youtube.com/watch?v=z56Hjot7dSQ

[BensPlasmaAu]

Thanks guys. I will investigate further. I have done the pen test etc, but will run it again. Got to be something ive overlooked on the thing.

[beefy]

Don't know if this is worthwhile but what about a pen test WHILE cutting. If a dry run pen test comes up good but the same run while cutting comes up bad, then is the problem noise related and causing the PC to go a bit wonky.

Just a thought.

Keith.

[BensPlasmaAu]

Still no luck. Total crap even with a pen. My drives are solid. All of them. The steps per are correct i am smack on 1000mm when i go through the step calibration. Yet circles are out of round. Nothing is working right. Also i have been using bobcad successfully for everything in the past, and it seems to work great to design and send dxfs to sheetcam. All of a sudden the node count goes through the roof, things are terrible. I am at a complete loss now. I have nowhere to go...........

[BensPlasmaAu]

Videos i have taken of the table doing its stuff.

https://youtu.be/3OzoGs5lemY

https://youtu.be/UvqsOOkXGU4

https://youtu.be/UvqsOOkXGU4

[beefy]

Ben, does it make any difference if you try the pen test at a much lower feedrate.

Just trying to figure out if this is hardware or software related.

With a Google (Mach3 circles out of round) another suggestion was "Disable backlash comp, restart Mach and see how things are".

And another Google result:
"Do your circles look like circles in the Mach3 preview window?
If yes, you can eliminate the CAD software and the CAM software.
The problem will be either your CV settings or mechanical problems."

I take it your chains/sprockets are not worn, etc and are meshing perfectly.

Keith.

[exapprentice]

Hi Ben

What happens to the problem areas as you show in your first video if you make the circles a lot bigger?
if you run the same circle file over and over again from the same datum do the faults come in the same place every time on the circles??
If you rotate the circle 90 degrees do the faults move with the rotation or stay in the same place???
when you increase the size of the circle do the faults size change with it or stay the same as when you try a small circle????

if they move with the rotation then it must be the file
If they stay in the same place after rotating the file then it must be the table

only trying to help hopefully it will get sorted

[BensPlasmaAu]

Ben, does it make any difference if you try the pen test at a much lower feedrate.

Just trying to figure out if this is hardware or software related.

With a Google (Mach3 circles out of round) another suggestion was "Disable backlash comp, restart Mach and see how things are".

And another Google result:
"Do your circles look like circles in the Mach3 preview window?
If yes, you can eliminate the CAD software and the CAM software.
The problem will be either your CV settings or mechanical problems."

I take it your chains/sprockets are not worn, etc and are meshing perfectly.

Keith.

Hi Keith,

the chains and sprockets are brand new. I went through everything again to make sure there was no slack in anything. Removed the grub screws, refit them with loctite etc etc. Totally rigid. No flex in the gantry.

Where is this "disable backlash comp" i have not seen it before. I am leaning towards a CV setting problem. It seems like there is no constant motion happening and it pulses randomly. Where does one go to have a go at changing CV settings? I was going to attach the .tap file for the parts above, but it won't let me.

[BensPlasmaAu]

Hi Ben

What happens to the problem areas as you show in your first video if you make the circles a lot bigger?
if you run the same circle file over and over again from the same datum do the faults come in the same place every time on the circles??
If you rotate the circle 90 degrees do the faults move with the rotation or stay in the same place???
when you increase the size of the circle do the faults size change with it or stay the same as when you try a small circle????

if they move with the rotation then it must be the file
If they stay in the same place after rotating the file then it must be the table

only trying to help hopefully it will get sorted

Hi Peter,

I am not sure, i will give it all a go tomorrow after work. I'll take any suggestion at the moment.

[tnbndr]

I was going to attach the .tap file for the parts above, but it won't let me.

You can attach if you put it in a .zip file.

[acourtjester]

Ok it seems the problem is in the movement of the table as seen in your tests. So far the mechanical section been checked and seems to be ok, there may be a electronics problem. In the videos you show a notch or bump in the circle edge, this could be caused by a broken wire, a signal drop on the DIR signal, or some outside noise influencing the motor drive. Try doing the pen test with a circle and overwrite the same circle a few time to see if the notch occurs at the same spot each time. It may be easier to see if you use a ball point pen in place of the sharpie you re using, it will appear clearer and not as wide.
AS you can see many here are watching and will have good ideas to try, we are with you. The videos were a great help too.

[gamble]

I'd had this problem a few times. Is the torch wobbling ? Make sure it's tight
Just checked your video. I have the same z axis plate and torch holder. Make sure that bolt that holds the torch on is tight!

[Nacs Fab]

I have had the same problem before where a circle cuts out like that and every time it ended up being my x axis pinion setscrew was loose enough that it would create this exact movement. It is funny, the circle actually cuts circular, then about half way through it - the torch offsets just slightly, then goes right back and creates the circle even back to the appropriate lead in. I know you say your chains are tight and so forth, but I just bet you have a pinion slipping on the shaft and that is nearly unnoticeable when trying to "rock" the machine with the motors powered up.

[beefy]

Hi Ben,

this YT video shows where you'll find backlash settings and enabling/disabling. Searching Mach3 backlash on YT comes up with a few more.

https://www.youtube.com/watch?v=u0uzS_S4VL4

For another straw to clutch at, circular motion is supposed to be one of the most computationally intensive operations for a cnc controller and the smaller the circle the worse it gets. That was the basis of my suggestion to try a lower speed and see if the results are the same. Kind of thinking this isn't the problem because of the problem on the bigger circles but it's a simple test.

Likewise you could even try a 2nd PC and see if you get identical results. You haven't got any other stuff running on your PC have you ? Windows is a mulitasking system and the less it has to do the more Mach3 can focus on what it's doing.

Would drawing the same circle at different positions on the table give exactly the same bad circle. Zero your co-ordinates at different positions and "draw" the circle again. Any differences point to mechanical problems.

Also using absolute co-ordinates and MDI, and tracing paper (a bit see through), you could come back to the same positions, re-zero your work co-ordinates and draw the circles again at exactly the same place. You'll see through the tracing paper if the circle underneath is identical. Just looking to see if the problem / differences in the problem is repeatable with differing locations on the table.

Keith.

[blackandtan]

I have had the same issue as Nacs Fab a set screw that feels tight because it has slipped enough that it was wedged on the round part of the shaft instead of the flat but I could not make it slip by hand. Dont just make sure they are tight make sure they are tight on the flat of the shaft. Maybe that makes sense. That's the only suggestion I have.

Rodney

[Nacs Fab]

Rodney made me remember something to post about the slipping pinion. My motors did not have flats when I built my machine. I actually used a air cutter with cut-off wheel and lightly ground a flat in the place where my pinion set screw would bottom out, this along with loctite cured my issues.

[acourtjester]

Not sure if this will help but this image may help to see where any slipping will occur. The time slippage would occur would be after any change on direction by either the X or Y direction, and most likely would occur in two places around the circle 180 degrees for each time. Where it occurs will also tell which axis is slipping. I also thing the slippage would cause a bump to the outside of the circle IMHO

[BensPlasmaAu]

You are all a bunch of legends!!! Couldnt ask for any better help (apart from buying a plane ticket to Australia).

Next step of the saga. I decided today to completely remove the drives off the machine and triple check all the grub screws etc. So i removed them and discovered that they were basically bound tight in 85% of their travel. See video below........

https://youtu.be/pdXJbkBFO0E

I thought the problem was mainly that the chain was not aligned to both the sprockets. I had to set up the oxy gear and break the locktite on the grub screws. Out they came after some coaxing and swearing and a bent allen key. I aligned the sprockets and even after this they were still binding. The tension in the chain was backed off and everything started to run smooth. Now theres slack and backlash in the chain which is shit. So i decided to use my finger as a chain tensioner and see how that went. Backlash removed, but on doing this the next problem surfaces. It seems that the guy i got to bore the holes in the sprockets has stuffed the job. Not by much, but enough to have a noticeable run out in the large 30 tooth sprocket. This causes the chain to tighten and slacken off as it rotates.

AWWW MAAANNNNN!!!!!!!!

So, does anyone want to help me out and be my US address to get the Precision Plasma belt reduction assemblies?? Or can anyone suggest where i can get a set of 3 belt reduction assemblies from. I unfortunately just dont have the time at the moment to redesign and make them.

Or i need a spring loaded chain tensioner to help take the slack up when it runs forward and reverse.

The only other thing i can think of is going out and getting a business loan and buying a proper machine with technical and parts support.

[exapprentice]

Hi Ben

It would be far cheaper to have the gears re-bored and sleeved and then come up with a sprung belt tensioner
or change to belts
unless you really want to borrow a shed load of dosh

I know what direction I would go, but then thats me and where I started from going the DIY route

[tnbndr]

So, does anyone want to help me out and be my US address to get the Precision Plasma belt reduction assemblies??

So you want to purchase them and have them shipped to a US address? Then I ship to you? Or what is the plan, I'd be more than happy to help you out.
You can email me direct at xxxtnbndr@att.netxxx, remove the x's.

[SeanP]

I would be swapping the chain for belt drive Ben, mine were not bored very well but it's forgiving enough with the belts even with a good tension.
I would have thought you could use the same assembly just swap out the cogs.
Is your pinion gear spring tensioned?

[blackandtan]

Maybe these guys can help if nothing else. I don't know if Ron will just sell the belt reduction.

http://www.cncrouterparts.com/standard- ... 46_39.html

[Nacs Fab]

I sent a PM about a possible reduction solution, but here is a link to some machine bored sprockets. Select the finished bore sprocket and then it will let you define chain size, bore size and teeth count. Should get you close - then if needed you could buy oversize and buy a sleeve that fits your drive pin. If you go this route, I would then drill and tap that hub another spot or two and install more set screws to make sure it holds real well.

http://www.mcmaster.com/#roller-chain-s ... s/=146zasr