Tricks for properly referencing back side carvings

[deemon328]

I'd appreciate any help I could get on this subject. I have a board that's 1" thick, and I have a model that I want to carve on both sides. The machine loses its reference point when I flip the board and the back side carving doesn't line up. I have the pattern centered on both sides, but I'm still getting the problem.

http://photos.yoderwoodworks.com/images/A_2/4/0/5/15042/DSC04597_d37a3.Large.jpg

http://photos.yoderwoodworks.com/images/A_2/4/0/5/15042/DSC04595_59189.Large.jpg

My workpiece is 4" x 4" x 1" if I use a custom sled. I still have to remove the board to flip the piece over inside the sled, so that's not really helping except for making less waste stock.

The offset seems to be about 1/32" and it's parallel across the piece, so my board is moving straight. I checked the outside of my board for square. One end is perfect, and the other end is a degree off or so. Could this really be the culprit?

Anyone have any tips to gain accuracy?

[Paul Brown]

If you just flip the board end over end, it should give you same reading. Unless you might not have a true 90 degree cut on one of your cross-cuts on one of the ends. (maybe?) Anyway, hope ya figure it out and let us know the results. You know this is one the best ways I've learned, reading other peoples problems. Paul Brown , good luck

[Jeff_Birt]

Run a piece of painters tape along the edge of the board that will contact the board tracking sensor (the little brass wheel). This gives the sensor something to bite into and greatly improves the accuracy along the X-axis.

[deemon328]

I figured that if the board was being measured at the center, that it would reach the same measurement even if you had the board a little out of square. I can see it mattering more if it were measuring along one of the edges.

Thanks very much for the replies! I'll give the tape a try on the next carve. I was putting tape on the top of the board where the board sensor traveled during measurement. I guess that was the wrong spot.

[Dyna Rider]

Hi Dustin

I have already been wrong once so I won’t offer a solution. But a 1 degree angle over a distance of 1 inch will give you an offset of .0175 inches. So when you cut the board you have two settings that could introduce error the cross cut and the bevel setting. I believe the sensor that finds the board end is looking for reflected light. So if the board edge is not razor sharp there may be variations in the board edge from side to side that may also introduce differences in measurement.

Bill

[deemon328]

Ok, here's a dumb question regarding sleds...

When you flip the piece over, do you keep the sled the same and flip just the piece in the sled, or do you leave the piece alone and flip it and the whole sled at the same time?

I just got done with a carving where I flipped the piece over and left the sled the same. My results were way way off on the Y axis. Ironically, my X-axis was pretty good this time.

Thanks Dyna for that info. I'm not sure how much closer to square I'm going to get. I'm 1/32" off over 5.3", however that works out. I resquared the jig just now and got it as reasonably close as I could without completely working over my table saw. The other problem is that I don't trust my estate auction engineering squares.

[HighTechOkie]

I'm with Jeff on this one. I'd bet the board just slipped once while moving to carve region. Lay that board on something flat and see if it twisted after carving.

Since those are 1", why not do a cut path? That would avoid the need to flip, but slippage would still be an issue.

Rob

[HighTechOkie]

... I'm not sure how much closer to square I'm going to get. I'm 1/32" off over 5.3", however that works out. I resquared the jig just now and got it as reasonably close as I could without completely working over my table saw. The other problem is that I don't trust my estate auction engineering squares.


You do know the CW/CC has a squaring function right from the keypad. :) 4 joint

Rob

[deemon328]

I did get marginally more consistent results on the last test by using tape on the edge, but it's not quite as good as I would like. At least it's sandable now. So there's a partial success. This last test was done using the sled as well. I think I'll explore that squaring function tomorrow. Thanks for reminding me about it :D

I didn't use cut path because I wanted draft on the figures and I wanted the real products to be 1 1/8" thick, but I think it's becoming more pain than it's worth. My plan is to square the sled with the CC, apply tape and try one more test. After that, it's on to cut path and 1" stock even though I really wanted 1 1/8".

Thanks very very much guys for helping sort this all out! I really appreciate all of the advice!

[Jeff_Birt]

You might also try to calibrate your machine. You need a 3/8" straight bit to do so. The procedure is in the back of the users guide.

[Dyna Rider]

If you just flip the board end over end, it should give you same reading.
I belive both the top and bottom surfaces can be of equal length and their centers still offset from each other, if certain conditions exist. Click on the first figure below(Off Set), I have exaggerated the condition for clarity.


You might also try to calibrate your machine. You need a 3/8" straight bit to do so.
I don’t believe calibration will help, but it won’t hurt. I don’t believe the problem is one of absolute measurement. A short tape will measure long and a long tape will measure short. If your only concern is to fit a piece between two point, you’ll only run into problems, if you use one tape to measure the distance between the points and the other tape to measure the piece that is to be cut. The second figure (Tape) below might help explain this somewhat confusing statement, then again maybe not.The machine is using the same device when measuring both sides to find the center.

Bill

[Jeff_Birt]

I don’t believe calibration will help, but it won’t hurt.

Oh, yea of little faith ;)....check out this post by one of CW's engineers...

http://www.carvewright.com/forum/showthread.php?t=5302 Post #9

I have copied the salient point below...



One final note, we apply offsets to the board edge calculations to account for vertical inaccuracies (both yaw and pitch). So when you remove your board sensor, it is best to run the "user calibration" under the options menu. This will recalculate these offsets. Now, it is not always necessary to run the "user calibration", just suggested.

[deemon328]

How often should one perform calibration? I calibrated a week or so ago when I brought my new machine home.

Are there specific things that can cause the machine to get out of alignment that I may be doing without realizing? The CC is sitting there bolted to my table, but I can imagine that there's something I'd consider routine like moving the Y and Z around by hand to clean that could be causing a need to calibrate.



Also, I just wanted to clarify that I'm really happy with this new machine, and I'm in no way complaining about it's overall quality. I'm just trying to get it as close to perfect performance as possible. Just thought I'd mention that after all the headaches with the first one and my lack of positive mental attitude.

[Jeff_Birt]

I think CW aid about every 10 hours or so would be good or after taking your board sensor out for cleaning. The good thing is that it only takes a few minutes to do.

[deemon328]

Oh, 10 hours? I'm ready for my next calibration then. Thanks!

[Dyna Rider]

Hey Jeff
Thanks for the heads up and a link to the post. After reading what you have selected as the prominent point, I was a little confused as to the use of yaw and pitch. Although after reading your post that the procedure is required every 10 hours I now can see I bought a helicopter. So, out of the complete post, why do you feel that the last two sentences in that post, is the major point?

Bill

[Jeff_Birt]

Calibrating the board sensor compensates for any tilt in the sensor itself. If this were not compensated for then if your boards end was slightly beveled top to bottom and your board sensor was not calibrated for tilt in the X-axis it would tend to increase the error of reading the boards end depending on if the tilt of the sensor was in the same direction as the bevel of the boards end or not.

[deemon328]

Thanks for clarifying that. I was confused by the whole pitch and yaw thing.

It's pretty interesting to note how critical the calibration is. With this knowledge, it's suprising to me that we have to buy the 3/8" bit seperately to keep the CW calibrated. I wonder why it was determined that we couldn't use the 1/8" bit that came with the machine.

[swhitney]

Thanks for clarifying that. I was confused by the whole pitch and yaw thing.

it's that NASA terminology carrying over I guess


It's pretty interesting to note how critical the calibration is. With this knowledge, it's suprising to me that we have to buy the 3/8" bit seperately to keep the CW calibrated. I wonder why it was determined that we couldn't use the 1/8" bit that came with the machine.

I agree. Either redo the calibration program to use the included bit, or include the 3/8" bit with the initial purchase. I think there are better ways to entice us into additional purchases!!

I still am amazed at what this machine can do....

[Jeff_Birt]

The 1/8" bit would tend to flex a bit (potentially) and would not leave as nice a surface as the 3/8". I think the 3/8" bit is nice to have regardless of its use in calibration. As for it's use in calibration, I kind of see it like having the proper tool for the job. (Just like any other tool.)

[Dyna Rider]

Calibrating the board sensor compensates for any tilt in the sensor itself. If this were not compensated for then if your boards end was slightly beveled top to bottom and your board sensor was not calibrated for tilt in the X-axis it would tend to increase the error of reading the boards end depending on if the tilt of the sensor was in the same direction as the bevel of the boards end or not.

Hey Jeff

I don’t see it, sorry, it just doesn’t make sense to me. Now unless I have missed something the sensor has two emitters and one detector. And the light from emitters converge on detectors Z-axis at a fixed distance form the detector. If this distance varies ether in the plus or minus the energy the detector receives will be less then optimal. Depending on the type of detector it will either change its output voltage or its resistance.

So in your explanation what are the variables that are adjusted and how does this adjustment compensate for the tilt in the sensor. Secondly how does a bevel on the end of the board introduce an error into an uncalibrated sensor?

Bill

[dandrea]

Not sure if I'm missing something, but if I want to do two sided I just cut that part in half and then cnc them side by side. When its all done I just glue the two pieces together.

Would this work for you?

Dan

[deemon328]

Thank you for the suggestion. Yes, I could do that, but it's a function of the machine to do 2-sided carving, it shows a glue line, and it's an extra step that takes more time. If I can perfectly center a project in the front and back in Designer, then that accuracy should reasonably translate into the finished product. It's not so bad to do this on one piece, but on 500 pieces, I just added a week of work and downtime waiting for glue to dry.

I want these discussions to help LHR in their next iteration of the CW. Accepting a work around that doesn't forward the machine doesn't help them make a better machine. I hope that they fix the machine's weaknesses in a way that eliminates the these issues that we're currently putting up with.