Machine is Air Carving

[SharonB]

My "A" machine has started air carving for the first five or 6 passes then it finally hits the board and completes the pattern. I know I could compensate for the difference in the depth of the pattern and carve regions but the centerline function just verily cuts into the board (using 60* bit). The bit hits the swing plate as it should...you can see the swing plate dip a little as it touches. I just did maintenance on the machine and all bearings seem to be in good working order. No sawdust in any of the motors. The machine might have made one or two passes above the board before maintenance but it is really off now.

I know I've read of things to check when machine air carvings but for the life of me can't seem to find them today. Hope there is an easy solution as the machine has been down a month waiting for brushes and I just got it going again. Sharon

[dehrlich]

My A machine does that too, only the first 3 or 4 passes before you notice a mark on the board. It's always done it, never knew it was an issue.

[chief2007]

Not sure if it might be a problem with the MPC file or the machine.

Have you reformatted the card and reloaded the project to see if that cleared it up? Conforming vectors checked correct?

I have had that happen with the 1/16th bit at optimal setting when using feathering on a carved region, but not with the 60 degree bit.

[SharonB]

Chief... no, I didn't reformat the card. When the machine checked both the 60* bit and the carving bit all things seemed normal. But when it started carving the pattern it did not tough the board for at least six passes. Since depth, at this stage, didn't matter all that much I just let it go ahead and carve. But when using the 60* bit you could see that the bit just verily went into the board.
The shallow parts of the fonts hardly cut at all.

[Digitalwoodshop]

I am thinking that your bit plate is BENT DOWN and if you bent it up so it is level when out that the first few air strokes will go away....

This gives the machine a false sense of where the tip of the bit is.... It is the only thing I can think of and especially since it is happing to 2 separate machines... that takes out the Encoder, FSC Cable and such...

Just a WAG.... Wild AL Guess.....

Taking advantage of the Warm day and have been cutting sheet stock into tags all day with the machine... :)

AL

[aokweld101]

I have gotten my new machine back in sept. last year, I didn't think it would be an issue either mine does that and I thought it was normal....

[henry1]

I didn't think you could ben that plate it is pretty rigid

[SharonB]

I remember something about bending the swing plate but couldn't remember if it was up or down. If you couldn't bend it up could you put a thin piece of material on the plate.

[bergerud]

On the three machines I have looked closely at, the bit plates were all a little different. They are not that hard to bend. I suppose the correct height is to be perfectly horizontal. But I do not think the problem could be the bit plate height. The touch on the board is where the machine gets the zero height reference. One could certainly bend the bit plate up but I think if the bits are actually touching the plate and the board, it must be something else. Maybe the z belt system. Could the belt be slipping in the clamp? Is the white pulley rotating freely, cracked.? Seems like a strange one. I will be interested to find out what it is.

[SharonB]

Checked the pulley when doing maintenance. But I could re-set the screw and see if that makes any difference.

[badbert]

Mine does this on Optimal. Always has. I use jog to touch. Does it mostly if the first edge is long and feathered. Like a picture frame. But I have always had a problem with small letters too! Hmm.... We need to all try the same MPC and gather data. I unfortunately have no cut motor. But I guess I could let it run until it stalls!

[bergerud]

Maybe this is a backlash thing. The brass gear on the z motor may not be meshing properly with the big white gear and/or the bearings may be loose. As the bit touches the wood, some slack in the gears or bearings is taken up as the bit is pushed. The encoder then reports the board is lower than it is. Later when the carve starts, the "slack" does not get taken up again until the bit bites in. The carving bit would get pulled down to take up the slack but other bits would not.

Just a wild guess.

[henry1]

that makes sence bergerud the backlash would do what you just said I never thought of that one and so true

[SharonB]

Not quite understanding about there being slack ... if there was slack wouldn't it let the bit dig deeper into the wood than carving above it or in the case of the 60* bit ... carving shallow?

Do you think a check on the z-motor bearings would be in order then?

[bergerud]

I think you are right, the bit would dig deeper but only after it got a bite into the wood. It would hover like described until the wood pulled it in. You might not notice that. The V bit would get pushed up and that fits. This is just a guess but I would take a close look at the z bearings and gear clearance.

[SharonB]

Thanks... I don't have time to check it out today but will try and get to it by the weekend.

[Digitalwoodshop]

Rather than trying to bend the Bit Plate up level, try taping a quarter on it and see if the project carves different.... I am still on the Bit Plate Thing... Backlash on the Gearbox is adjusted with the Oval Holes meshing the big gear to the servo motor splines. Too tight and it binds and too loose it has slop or backlash....

We are talking bending the bit plate up the thickness of a quarter.

The Z Truck backside belt is held by some screws and I had them loose once on a refurbished truck.

You can see how the mesh is adjusted by the oval holes in the pictures.

I once had problems with fine text disappearing on one side of the board toward the bit plate and found the head was not level.

Look at all the options.... We all have great ideas.

Good Luck,

AL

[bergerud]

Now that I think about it, part of my backlash story does not make sense. If the encoder measured the board was lower because of backlash, the machine would try to carve deeper to the lower board. (Maybe that was what you were saying Sharon? Al you are too kind - you should call me on stuff like this!) I still think it could be a backlash thing, but how exactly, I do not know. After testing the bit plate height theory, I would still look for something amiss in the z system.

[chief2007]

Sharon any chance of posting the mpc? I'm thinking it might be in there by chance.

[bergerud]

Did you ever find out why your machine was air carving?

[SharonB]

Over the weekend I took the machine apart. Went completely through the z-motor and didn't find a thing wrong with it... the bearings were tight, no broken teeth and even the encoder was clean. Relubed everything. Then taped a dime to the swing plate.

Today I ran a project with both a pattern and centerline text in a carve region. Both carved great. In fact the text was the best I've seen since the machine was new. It carved the letters nice and deep and the depth of the letters was the same through out the carving. Also, I was surprised to find the carvelines in the bottom of the carve region was less than they have been in a long, long time. Another observation...there was no air carving at all. In fact the bit went down into the wood a fraction more on the first bite than I've observed any time in the past.

My question is: By putting the dime on the swing plate how does this make the bit carve deeper? And if having less lines in the bottom of a carve region was the result of putting the dime on the swing plate what would be the reason behind this.

I'll be making more projects in the next few days and will be watching if there are any changes from what I saw today

[bergerud]

I wish you had tried the dime before you took it all apart. Maybe you "fixed" something by taking it apart. You will have to try it now without the dime. Good news that the problem is gone though.

[RMarkey]

By putting the dime on the swing plate how does this make the bit carve deeper?

It shouldn't. The position of the mechanical plate has nothing to do with the depth of the carve. Something else affected the depth... most likely the board surface test.

[eelamb]

It shouldn't. The position of the mechanical plate has nothing to do with the depth of the carve. Something else affected the depth... most likely the board surface test.

That is what I was thinking. The bit plate only measures the bit, to detect bit changes. the board is measured by touching the base by key pad, and the surface of the wood, difference being the thickness of the wood. And the surface tells it where the surface is to start carving.

[SharonB]

I will certainly play around with dime/no dime in the next few projects and see what happens. I couldn't see the correlation between the swing plate and the depth but something sure made a difference. Just removing the motor and re-installing it doesn't seem like it would make that much difference either....unless the pin holding the z-motor could have been slightly loose. The pin didn't seem loose when I removed it but I didn't try to tighten it first either. These machines are sure a learning experience in mechanics. I always feel grateful when I get it all back together and don't have any parts left over.

[Digitalwoodshop]

Wrong again... Bummer.... :)

So much for the 2 cents.... trick...

AL

[guido5286]

Hey I just saw this thread and I thought I could help. I'm a CNC Machinist and When you add the dime to the bit measuring plate you are basically lying to the machine about the length of the bit. This will make it go deeper because it thinks the bit is longer than it really is. That is what it is doing when it touches the plate is measuring the length of the bit. We do this all the time in the shop but we can manually enter the tool data so we just change the numbers. I hope this helped!

Now that I think about it if it thinks the bit is longer it won't go as deep hmm? Not sure about that one.

[chebytrk]

Wow..... I've read this complete thread because I too have this problem with my new "C" machine. It's about 3-4wks old and after the 2d week I started noticing this "air carve" as well. What I did (& do) is pause the machine and pull out the bit from the adapter (I eyeball it) just a "tad". I place it back in the CT and start carving. It does fine. I do recall seeing something right before it started doing that. I had just finished a project and when I pulled out the board I heard something fall on it as I slid it out. It was the top part (head) of a hex bolt. I noticed that it was actually broken off. Of course after a few nice words with my brand new machine I started to hunt it down. I couldn't find anything anywhere that was broken. I asked Chief2007 about it to see what he th oughtit might be. He suggested a few things and all was still there. I assumed that maybe this might have happened when it was being tested or checked out back at LHR so eventually I let it go cause everything was still running fine. It was after that (about 1wk) that I started noticing the initial "air carving" and started pulling down the bit by hand while eyeballing. It worked so I continued until I figured out what was causing that. Well.... it happened on a new carving one day. The Z truck went loose as it was measuring and it was the roller bearing (lower left side). It fell out and THAT's where the broken hex bolt came from cause the other piece was still in the roller. Lucky for me that I ordered a set of roller bearings when I purchased my CW cause I wasn't about to send it back under warranty and pay the shipping to replace 1 roller bearing. So I changed the roller bearing and all works fine except...... I still get the initial air carving so I still pull down the bit by hand. I know this isn't the right way to do it, but when I get a chance I'll start pulling all the tests that I can on it to see if they're all good. I had hoped that someone had figured out what it was so I could go straight to the culprit and fix it. When I get a chance, I'll do some testing and post my results.