Was going well...

Darren Wright

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I decided I'd try to replicate our mission statement from the institute's lobby on a plaque.
MissionStatement.jpg 2015-11-03.jpg

I received the paint mask that I ordered earlier this week and decided to give it a go on a plaque that had some corner damage as a test.

All was going well, however I lost steps on my Y axis after about an hour. I'm thinking the motor over heated as I could hear some chirping, and it's possible the threaded nut was sticking. I think I may have lost some steps on the Z as well as the lower text and some of the tree lost definition as it worked from the center area out.
2015-11-04 23.16.58.jpg

Other than that, the detail was looking pretty good. I went ahead and painted it to test out the paint mask, we'll see if I need to do anything different there.

I do plan to build a new enclosure for the controller and add another axis to it, so will be checking all my voltages at that point, the current enclosure is entirely too hard to get into for doing maintenance and and too small for any updates.
 
All was going well, however I lost steps on my Y axis after about an hour. I'm thinking the motor over heated as I could hear some chirping, and it's possible the threaded nut was sticking. I think I may have lost some steps on the Z as well as the lower text and some of the tree lost definition as it worked from the center area out.

Probably a dumb question, but if you're loosing steps over a long period of time would it make sense to periodically re-zero? I mean not loosing steps is obviously the goal, but it seems like a lot of these systems that ends up being somewhat of a long-path-to-get-there so in the interim..
 
Probably a dumb question, but if you're loosing steps over a long period of time would it make sense to periodically re-zero? I mean not loosing steps is obviously the goal, but it seems like a lot of these systems that ends up being somewhat of a long-path-to-get-there so in the interim..

Not a dumb question or suggestion. I plan to do that on the next attempt, but this was such light work for the cnc and all with the same bit that I didn't think I would need to. For most of my other files I've ran, most operations are about 20 minutes long, this was over an hour and 20 minutes, so heat hasn't been much of an issue. Will be doing some voltage measurements/adjustments this weekend to verify that isn't an issue.
 
Still, once you lose steps, unless you catch it, it's game over.

Would have to have limit switches installed though so you could go back to an accurate machine zero, then go to the workpiece zero and start over.

Seems like it'd be a lot less hassle just to get to the reason why the steps are getting lost and fix that. There's usually a reason, unless I miss my guess.
 
Looking at your third photo, are you sure the board is flat? It appears everything in the middle of the board is carved pretty well, but the farther from the center, the lighter the carve got. As to the circle being so far off, that has to be a bad case of losing steps on the Y axis.

I've had issues with a board being flat but not perfectly level on my base board. I have now started flattening my waste board using a 1.25" bowl bit; makes a ton of difference.
 
Looking at your third photo, are you sure the board is flat? It appears everything in the middle of the board is carved pretty well, but the farther from the center, the lighter the carve got. As to the circle being so far off, that has to be a bad case of losing steps on the Y axis.

I've had issues with a board being flat but not perfectly level on my base board. I have now started flattening my waste board using a 1.25" bowl bit; makes a ton of difference.
Yeah, the carving started in the middle and worked its way outward. I think it lost steps on the plunge.

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Still, once you lose steps, unless you catch it, it's game over.

Would have to have limit switches installed though so you could go back to an accurate machine zero, then go to the workpiece zero and start over.

Seems like it'd be a lot less hassle just to get to the reason why the steps are getting lost and fix that. There's usually a reason, unless I miss my guess.

Yeah I wasn't thinking it would be a long term solution so much as an interim work around.. since it ?appears? that sometimes tracking down lost steps can be a bit challenging. It seems that for most things if you loose ~1+- step~ you can probably fudge it on a lot of projects (like this one) with a little hand work. If its a lot more then its probably hosed so this might save you in that case.

You might also be able to get it to report when zero wasn't zero and then see how far off you were from zero with a wee bit of clever programming... basically step into the limit switch (machine) zero and then record the delta of how far off you were from where you thought zero was.
 
Still, once you lose steps, unless you catch it, it's game over.

Would have to have limit switches installed though so you could go back to an accurate machine zero, then go to the workpiece zero and start over.

Seems like it'd be a lot less hassle just to get to the reason why the steps are getting lost and fix that. There's usually a reason, unless I miss my guess.

Well...maybe. I know I'm a bit of a renegade at times and this is one of them. I don't use a machine zero. Early on in my CNC adventure, I decided I like using the center of a project as my 0,0,0 point. Having that point marked in some way means I can always get back there. To start a project, I move the spindle XY manually to the center of the project, then adjust Z down to the surface. I use UGS for everything; it sets machine and work to 0,0,0 when you open the connection.

As to fixing the problem with why steps get lost, I finally whipped that by measuring the stepper voltages on the drivers and adjusting to the recommended level based on the stepper spec sheet. To keep the driver chips from overheating, I added a small fan about 2" from them.
 
Well...maybe. I know I'm a bit of a renegade at times and this is one of them. I don't use a machine zero. Early on in my CNC adventure, I decided I like using the center of a project as my 0,0,0 point. Having that point marked in some way means I can always get back there. To start a project, I move the spindle XY manually to the center of the project, then adjust Z down to the surface. I use UGS for everything; it sets machine and work to 0,0,0 when you open the connection.

As to fixing the problem with why steps get lost, I finally whipped that by measuring the stepper voltages on the drivers and adjusting to the recommended level based on the stepper spec sheet. To keep the driver chips from overheating, I added a small fan about 2" from them.

I'm still trying to figure out how my work flow will go. So far, I've been doing similar, with the exception of centering. I'm using the lower left corner. In my work the origin is always the lower left with x going left and right and y going up and down, so I've adjusted my axis accordingly. Not sure my brain would like having something that fundamental changed on it. :D

Once I get the limit switches on it, I like the idea of zeroing out the machine, and being about to get back to the workpiece zero without having to do it manually. I can just have the workpiece zero (x, y, z) numbers recorded and go their without having to eyeball it.

My steppers can use more juice than the tinyg driver can provide, so was pretty simple just to twist the pots all the way to max. I did have some issues with missing steps when the pots were set to the midway point. Now the only time I've missed steps is when I've hit a clamp or something, but I haven't done a piece yet that requires a lengthy run time.
 
Well...maybe. I know I'm a bit of a renegade at times and this is one of them. I don't use a machine zero. Early on in my CNC adventure, I decided I like using the center of a project as my 0,0,0 point.

More questions illustrating my lack of knowledge :D How would that work if the center is part of what's being removed? Specifically thinking about the Z axis ...

Naively it seems like having the project center indexed off of the machine center would be more repeatable in the general case but I can see that being annoying in some cases.
 
More questions illustrating my lack of knowledge :D How would that work if the center is part of what's being removed? Specifically thinking about the Z axis ...

Naively it seems like having the project center indexed off of the machine center would be more repeatable in the general case but I can see that being annoying in some cases.

You aren't wrong. Though, it doesn't have to be machine center - it just has to be relative to a known machine coordinate of some kind - usually machine zero (or home). If you cut away your center and then hit a problem and have to restart, you will not likely get right back to where you left off to resume the operation.

Different strokes for different folks - i won't run a machine without limit switches and i home the machine every time because i can always go back to where i started that way. You can even set up specific fixture offsets that are saved - so you zero the machine and always jump to a specific fixture zero (like if you have a rotary axis over on one end) -- it's a real time saver and while you can get away with not doing so it's not optimal and very easy to put in place a better solution and workflow.

The location of part zero varies for me - it depends on the part, the starting workpiece, the operation, etc. For a V carving, i usually always start at part center and use a slightly oversized workpiece that i know will fit. On a flattening op, I usually start on one corner and traverse back and forth. For 3D ops, usually top center. Sometimes bottom center is great if i want to leave a thin onion skin of a known thickness (not super common, but sometimes handy).
 
More questions illustrating my lack of knowledge :D How would that work if the center is part of what's being removed? Specifically thinking about the Z axis ...

Naively it seems like having the project center indexed off of the machine center would be more repeatable in the general case but I can see that being annoying in some cases.

Actually, I ran into that situation - center being removed - on a piece I'm finishing. I didn't have a missed steps problem, but I wanted an engraved area to be a bit deeper. I used a straightedge across the piece and aligned the bottom of the bit to the bottom of the straightedge. The issue I would have with some of the items I've been carving is the number of bit changes and knowing where "0" really is. I know conventional wisdom is having the 0,0,0 point off the workpiece, but it became easier for me to use project center. Of course, I'm also not trying to do production work.
 
Cool idea. So this paint mask thing has me confused not that it takes much to do that.

So u cut out what you want and paint through it with I guess spray paint / rattle can and then have the image painted on the board? Or do I have the bull by the udders?

I have to say I really like the mission statement itself, gotta be cool working for a cause like that, sure beats pure commercial business.

Sent from my SGH-I337M using Tapatalk
 
Cool idea. So this paint mask thing has me confused not that it takes much to do that.

So u cut out what you want and paint through it with I guess spray paint / rattle can and then have the image painted on the board? Or do I have the bull by the udders?

I have to say I really like the mission statement itself, gotta be cool working for a cause like that, sure beats pure commercial business.

Sent from my SGH-I337M using Tapatalk

Yup, exactly, peel and stick on the work piece, carve out your design, spray paint, and remove the mask...at least that is the idea.

It does beat the old job, no shareholders to keep happy, and might help find a few cures.
 
Cool idea. So this paint mask thing has me confused not that it takes much to do that.

So u cut out what you want and paint through it with I guess spray paint / rattle can and then have the image painted on the board? Or do I have the bull by the udders?

I have to say I really like the mission statement itself, gotta be cool working for a cause like that, sure beats pure commercial business.

Sent from my SGH-I337M using Tapatalk


Not to piggyback on Darren's thread too much - but I took a bunch of pictures on one of my first signs that involved some complex masking. Keep in mind, a person with more patience with a brush than I have could have done this differently. I'm not that guy. I will go to great lengths to spray instead of brush. This was a unique sign in that it not only had painted grooves, but also different colors on the fields as well - this took a few maskings and a few carvings to get done, but ultimately the process is solid and doesn't really take much time once a rhythm is established.

Here are pics - i didn't do up a full on tutorial but I should one day - maybe a good subject for a video in the future...

http://gallery.beamerweb.com/index.php/Woodworking/Projects/Signs/Dean-s/

There's a "progress" folder in there showing basically the steps I took. The real key for all this for me was the first illustration showing how I wanted the machine to cut the mask so that it overlapped a little. Yeah, i need to do a video of this process - it's pretty interesting and i think it's the key to my having quality results in the end.
 
I can think of a couple of ways to recover from that.

1) flip it over and do the opposite side.
2) Face off the boo boo side and do it over (who said it needs to be 3/4 thick)

You could separate the engraving into 2 or 3 toolpaths. Just don't select everything all at the same time and create separate toolpaths. You can reset between cuts, or let the machine cool.

You can also look at the acceleration and slow that down.

On the paint mask - I seal with 2-3 coats of rattle can shellac - sand 220, clean, apply mask - carve - clean the grooves - spray shellac into the v-carving, paint.

There are a few more detail steps that I didn't list. You should seal after carving to prevent capillary bleeding at the top of the v-grooving.
 
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