Problem after rubber belt upgrade

[jwshukis]

I just upgraded to the rubber belts. After the upgrade, I'm getting inconsistent length measurements and I'm seeing "stairstepping" across the X axis when carving a vector using multiple cuts. Ideas?

Problem 1: Measure a board and then measure it again a few times. The measurements vary and are often too short - never too long.

Problem 2: Draw a square on a board using Designer. Cut along the square path using the 3/8 jointing bit, four passes of .2" each for a total of .8" through a 1" board. The cuts that go across the X axis (from the front of the machine to the back) are offset by about .05" each pass.

Ideas?

Jeff

[Digitalwoodshop]

I have not done the Rubber Belts yet, but did you relocate the brass roller encoder? There are posts here that because the rubber belts are thicker the brass roller can rub on the rubber belt and the brass roller may be too low to make proper contact with the board and needs washers to raise it....

Search for the posts. There should have been instructions about that...

AL

[jwshukis]

Hi Al,

Yes, I inserted the shims per the instructions.

[Old Salt]

they talk about a new o ring on the brass roller needs to be put on

[Digitalwoodshop]

It's all about the brass roller.... It's not staying in contact with the bottom of the board.... TOO light of pressure holding it to the underside of the board....

Also saw posted that when the belts are compressed by the board the squished belt was bluging out in the center between the belts and touching the brass roller causing errors...

It's all about the brass roller......

With a Shop Bot the board is held solid and the motors move all 3 or 4 axis.... With the board moving on our machne, contact with the underside of the board is KEY to correct operation....

AL

[JLT]

Jeff,

I upgraded to the new belts and ran into an issue whereby due to the new rubber o-ring and the thicker belts, when the pressure from the board pushes down on the brass roller, the o-ring comes in contact with the rubber belts. This caused erratic board length measurements.

See post http://forum.carvewright.com/showthread.php?t=10599

Jon

[Digitalwoodshop]

There we go.... I knew I had seen it somewhere.... SO you need to over compensate the position of the brass roller.....

Someone who has done it and it worked needs to stick something like 2 Quarters Thickness between the belt and roller. This will give us a visualization of the distance. Like my idea of using white paper to give Board Detector readings as a standard.

AL

[jwshukis]

Following up, here is the solution that finally worked for my issue: I elongated the two mounting holes and two attachment holes that hold the board sensor, allowing me to slide the brass wheel assembly about 1.5mm to the 'left', away from the belt.

I suggest that CarveWright revise the plate in future manufacturing runs so that others who upgrade to the rubber belts don't have the same issue.

Jeff

[Digitalwoodshop]

GOOD JOB. Someone else posted about elongating the holes too about a month ago.

AL

[SteveEJ]

One of my belts just bit the bullet. If I upgrade to the rubber belts is masking tape still needed? Should I use the warranty belts or go straight to the rubber ones.. Rubber belt users out there.. What do you think?

[dbfletcher]

AFAIK.. the masking tape is solely for the brass tracking wheel. I have the rubber but havnt put them on yet.

Doug Fletcher

[SteveEJ]

Doug,
On hard and slick boards it was recommended that masking tape be put along the entire bottom to keep it from slipping on the sandpaper belts. I was not clear in my question.. I would continue to use it on the edge for the roller but could probably quit on the rest I assume..

Thanks,

[Steven Alford]

I never heard that one!!!
The only thing I have ever heard is that you only need to put the masking tape on the side that touches the brass roller. That is because if the wood used is to hard and smooth, it may not make good contact with the teeth in the roller. I would think that the sandpaper would not have a problem making good contact with whatever kind of wood you have, especially with 85 lbs. of pressure bearing down on it.

[AskBud]

I never heard that one!!!
The only thing I have ever heard is that you only need to put the masking tape on the side that touches the brass roller. That is because if the wood used is to hard and smooth, it may not make good contact with the teeth in the roller. I would think that the sandpaper would not have a problem making good contact with whatever kind of wood you have, especially with 85 lbs. of pressure bearing down on it.
Steven,
I have found that if the wood happens to be from a finished cabinet door (for example), it may be too slick for the sandpaper belts regardless of the pressure. I usually use a sled for that type of wood, if I do not plane some of the bottom surface away. Those doorfronts are very hard, in most cases, but finish nice if you are making Centerline signs.
AskBud

[Steven Alford]

Well that makes since. I have never done anything without a sled. So far it has been the only way I do my projects. Saves on a lot of wood.