Trouble with my new plasma table...

[Red Earth]

Hello folks,

The ideas and help here have been outstanding! Now it's my turn to throw a wrench in the gears.

I have a few issues with my new table and can't seem to get them right.

I can't get the table to cut a decent circle. We use Corel X3, BCC , SheetCam and Mach 3. By using several different programs and many different codes we have deduced that its not on the "smart" end.

Every circle, no matter the size, has two points where the timing should start changing in motors. Approx. 1 and 7 O'clock. If it were a keyway issue wouldn't it occur on exact opposite sides as well?

Phil

[Torchhead]

If you are using X3 with the native DXF exports your circles are coming out in straight line segments. It may get fixed in BobCAD on it's DXF export.

You don't give enough information for me to give any advice. What in the world does "timing should start changing" mean? A circle should cut in one smooth motion with no bumps, hitches, or anything along the path. What the artwork looks like (number of nodes in the circle path in SheetCAM will determine some of the settings in the CV mode in MACH3.

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Red Earth'
I have had problems making round holes with my table.
I found part of my problem was the gantry not being square. Also you could have backlash in your drive system. I am assuming "timing should start changing in motors"
Means when 1 of the motors reverses direction?
Cutmore

[Zumba]

Is this a rack and pinion system? A ballscrew assembly could have either backlash problems or axial play. Ruled out if it's R&P though of course.

[Red Earth]

The table was built by Dyna CNC. It has been plagued with problems from the start.

We have checked the backlash settings in Mach 3...to no avail.

I drew the exact size circle in BCC and Corel and get the same results using it in Sheet Cam.

The gantry moves freely on the tracks with and without power.

I assume the areas where I am getting the notches are when the motors reverse directions.

I was told it could be a keyway issue. But I would expect it to be identical on the opposing 2 areas if so.

This is my first table and new to the operation.

Phil

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Red Earth,
You said you checked the backlash setting in mach3, did you change them & nothing changed or just checked them vs. a measured amount of backlash?
I would set the X and Y axis backlash to zero then try again to see if the circles change.
Earlier I mentioned my gantry not being square, Did you check this?

With the power on, push & pull on the gantry, & the z carriage with light force.
Look to see if any thing is moving, if so investigate further.
Could you post some pictures? That may help diagnose the problem.
Cutmore

[Red Earth]

We did check the backlash, disabled it and ran the programs again with no change in the circles.

We did check the gantry again today..... There is a slight "catch", for lack of a better word, in several areas.....When I looked into it further.... The drive belt jumps a bit when its moving at faster speeds....not always in the same exact spot or same timing...but quite often. I can also feel a slight drag when pushing it by hand as well.

I also went back and re leveled the table in a slightly different spot...but that wasn't off that much.

I noticed there wasn't a key in the keyway on the Drive Wheel, not sure if there needs to be one there as it seems to have a set screw.

Phil

[Apples]

Yeah.....Make SURE that you have a set screw, keyway etc in there.

The motor shaft WILL slip. I know as I have had loose screws on my spur gear on my motor shaft.

Peter
Australia

[bogger44]

I also have a Dyna table. Is the belt tight for the x axis or the y for that matter? There are two guides tighteners that run on either side of the belt. These guides are two allen head bolts with brass cylinders on them. You should have extra of these cylinders with the table by varying the thickness of the cylinders you will create more or less tention on the belt wich will give you more or no backlash. I had the same prob. and made a thicker brass cylinder to go on the bolt to tighten the belt and changed the setting in mach to no backlash and it was good. If it's not clear post back and I will take a pic.
Also you could try while it's moving (just turn plasma cutter off and thc off in mach) if you do that the machine will think it's cutting a part but all it's doing is doing is moving the torch around and put your hand on it with a little pressure against it then you will see if it's spinning on the shaft.
All the shafts will have keyways on them.

[Red Earth]

Thanks guys......

I am missing the key on the driveshaft gear... Chalk up another fine detail missing from Dyna! Any idea where I can find one?

I do have one extra brass cylinder that came with the machine. I will look into that tomorrow. Like I mentioned the drive belt does jump when the gantry is moving at 50%.

Thanks for the help,

Phil

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Red Earth,
Why not contact Dyna CNC for the missing Key? If that doesn't work try mcmaster carr.
Cutmore

[Weldtutor]

Originally Posted by Red Earth Thanks guys...... I am missing the key on the driveshaft gear... ! Any idea where I can find one?

Most industrial suppliers sell square keystock that you can cut to the required length. Hardware stores often have the same material.

You will need to know the size to purchase, which is the same as the keyway width.
Ex. 1/8" or 3/16" etc.