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Thread: one wavy line of text on 3 line carve

  1. #31
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    Quote Originally Posted by Wood Art 1 View Post
    I've only had the 3/4" UHMW bottom rails on the carrier since Sat nite. One layer of masking tape. The carves that I did over the weekend reflected almost the same tendencies as the previous plywood rails.
    Ok, nothing to do with the UHMW bottom rails. It must be x drive problems. Maybe, as MT says, because of cold.

  2. #32
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    Thanks guys. I've got lots of stuff to check and watch. No evidence of deformed rubber rollers. Temp at machine is now 70.
    I'm not going to say it can't be temperature, BUT why do I have about a dozen examples where the last line on a two-sided carve is the ONLY line to ever screw up? Right now I am not carving any text with a .5 attachment. We'll see if it screws up again. 2 done OK.
    Just a thought...I will try a plaque in the modified UCB with a filler block at the top and instead of going to the center, start at the corner - the block will prevent the rollers from coming off the plaque onto the fixture.
    Back to the shop, got plaques to do.

  3. #33

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    I was going to suggest trying a jig such as Al suggested, but that is really changing the nature of the problem. But if it works reliably then at least you have a means to complete your projects.

  4. #34
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    Thanks Dick. Used a flat fixture like Al suggested. 3 plaques OK. None of those were .5 attached.
    I'm now thinking it may have something to do with the roller coming off the plaque onto the fixture. Will add 3 1/2" extension to the top of the plaque in the modified UCB to eliminate the .5 attachment issue. Back to the shop, got work to do.

  5. #35
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    Quote Originally Posted by Wood Art 1 View Post
    ...I'm now thinking it may have something to do with the roller coming off the plaque onto the fixture...
    Yes, that could certainly be it alright. Both rollers should remain in firm contact with the material (or jig) during the full run - - never coming out from the captivity of either roller, and the continuous contact should be without any "speed bumps" (no matter how tiny) due to an uneven surface. Not following those "rules" always invites tracking issues. Only "luck" prevents tracking problems if a project is run without constant captivity of both rollers at all times.
    Michael T
    Happy Carving!


    ═══ Links to Patterns & Resources for CompuCarve™ & CarveWright™ ═══

  6. #36
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    I think it is clear that this is a tracking issue. From my understanding, the cause of such issues, for whatever reason, is a disagreement between the tracking roller and the x motor encoder. The controller goes into a brass roller fail state and abandons the correction routine it uses the brass roller for. (The brass roller data is also ignored when a roller drops and switches.)

    Rolling off of the board onto the rails of the carrier does not rock the carrier off of the brass roller or switch the roller switch. The only way I can see that this could be connected to a tracking issue is if the tracking is affected by the switching of a little head pressure from both belts to the front belt. If this is the case, it means that the x belt system has a problem. Too much drag or backlash.

  7. #37
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    Yes, we have identified the symptoms, now to deal with the disease. I'll bet giving the pressure rollers a continuous, smooth ride whilst both remain in constant contact with a flat surface might be the cure. I sure hope it's that simple, anyway.
    Michael T
    Happy Carving!


    ═══ Links to Patterns & Resources for CompuCarve™ & CarveWright™ ═══

  8. #38
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    Michael, you are implying that the fault is in the design of the UCB. I do not believe this is the case. The main point of the carrier is to stay under the rollers and solve the tracking problem. A great many of these have been made and used and this is the first I have heard of any tracking problems. I recall you saying that you have never had tracking problems. Well, many of us have had tracking problems. I was plagued by them until I started using the carrier bases.

    Having the rollers roll up and down an eighth inch bump is nothing compared to rolling on and off the end of a board down on the belts. If the CW was as sensitive to bumps as you say, the CW would not even be able to measure a board.

    I am worried the carrier base may have damaged the underside of the rubber belt. Jerry has been using the thing for years and it seems possible that the narrow rail pressure on the edge of the belt may have taken a toll. Maybe the underside of the belt is worn ragged and is causing extra friction.

  9. #39
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    Mike and Dan. Okay, I carved 8 plaques today. All of them the same size 8"x5.5". A variety of graphics and text. All of them in font Arial Rounded MT Bold. Carving on both sides, approximately 30-40 minutes of carving time on the front. 3 lines of text - 1) at top .6 or .7 attach below the top. 2) bottom line .5 attach above the bottom. 3) a line just above the bottom line no attach. All of them in my modified UCB. Plaque is approx. 1/8" proud of top of fixture. No additional spacers or fillers. Machine Z temp this morning when I opened shop was 55 deg. When I closed tonite the thermometer beside the CW was at 75 deg. All plaques turned out fine, no wavy text.
    I did not try to replicate the problem today nor did I change any processes (other than the .5 to .6 or .7 attach).

  10. #40

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    Quote Originally Posted by bergerud View Post
    Having the rollers roll up and down an eighth inch bump is nothing compared to rolling on and off the end of a board down on the belts. If the CW was as sensitive to bumps as you say, the CW would not even be able to measure a board.
    This is one of the cases where I do at times see tracking errors. If I am using a long board or a long sled and the outfeed rollers are not adjusted just so, I will get a tracking error when the one roller drops while measuring the board. I'm not saying this is the same thing going on here, just observing that when a roller drops the dynamics change and it can lead to tracking issues.

    The type of sled that I use is not as flexible as the UCB but it does have some of good characteristics. Once the project is measured the rollers never drop even a small amount so consistent pressure is maintained during machining. The base of the sled is full width so full contact is maintained on the belts with no narrower pressure points. The spindle is kept away from the roller while machining and I believe the mass of the sled also reduces vibration to avoid vibration-induced tracking errors. I too have suffered from tracking issues, even fairly recently when I was cutting out a sign without a carrier (due to the width of the board) http://forum.carvewright.com/showthr...n-using-a-sled. I eliminated the problem when I used a sled.

    Wood Art 1 stated that in his latest run his board was 1/8" proud of the fixture. Hard to tell but in the photo posted earlier on it looked like it was more than that.

    No criticism of the UCB intended. It's a clever design and I agree many people are using it with success. We seem to agree that this is some kind of tracking issue, but the exact root cause appears yet to be in question.

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