Why doesn't 3/8" material work?

[heftyh]

I've had success cutting down to 1/2" thick material but when I try to run 3/8", the material just runs out the end of the machine.
I read the recent post on this and the answer from Digitalworkshop was that the board sensor can't distinguish between the end of the board and the sandpaper belt. However, on my machine, the board sensor does not pick up any signal from the sandpaper belt at all- sensor reading is 0. My 3/8" material is reading 140 which is well above the recommended minimum of 90 in the manual.
The compression rollers are clamping down on the material nicely, they register "closed" well before I run out of ratchet action.
The brass roller sensor is working also.
Obviously, I am trying to figure out what to get around to make it run the 3/8"; I can't see any reason why it shouldn't be able to handle it.
The reason I'm doing this is beacuse I have about 150 pieces of odd size polycarb that I want to run and it's not practical to make a carrier for each one. Also, I'm using the cut path and need the tabs to hold the pieces. When I use double stick tape, the tape gums up the bit and the polycarb doesn't channel up the bits flutes.
Thank's again!
John

[Jeff_Birt]

Quite simply the machine is not designed to handle pieces thinner than 1/2". The board edge sensor measures the difference between the top of the board and the 'background'. There may not be enough difference in these two readings for the machine to find the boards edge. I have also read that the down pressure may not be accurate for boards less than 1/2", but I have not tried to confirm this.

[heftyh]

Jeff,
That's what's confusing me. My background reads 0. It doesn't even see the sandpaper belts. I put masking tape on the polycarb and that reads 140.
It seems as though there is plenty of difference. Any other ideas?
Thanks,
John

[Digitalwoodshop]

There are rubber washers on each side or at least one side, the keypad side of the pressure rollers. I saw this today when blowing chips in my machine I blew one that got caught inside the sand paper belt big enough to jam and break the belt. So while I had it open I looked around and saw the rubber washer and saw it hit the bottom when I cranked the head all the way down doing lubrication with the cover off and no board. You could see the washer bend over. About 8 months ago I heard of someone cutting the washer back, that might help. But I am thinking it might me more the rubber roller washer.

AL

[heftyh]

AL,
I just checked the washers on the pressure rollers. I see what you mean when you crank all the way down they squash up on the bottom plate. With the 3/8" material in place, there is about 1/16" clearance between the washer and plate so while it's very close, it doesn't appear to be binding anything up.
Since the first post, I've gone back and forth about 10 times between the 1/2" and the 3/8". 1/2 inch works pefect, 3/8" won't register the end of the board. I even added more masking tape so the sensor now reads 151 on the tape and 0 with the board out of the machine.
This is driving me nuts!
I know the sensor is reading 0 on the sandpaper belt but I'm thinking of taking a Sharpee marker to the belt where the sensor measures as a last resort but this really should not help if it's already reading 0.
Keep throwing me ideas please- I'll try anything.
Thanks,
John

[heftyh]

Jeff,
I've very carelfully cranked down the pressure while watching the display/ listening for the click of the pressure sensors. They are engaging well before the clutch starts to slip. As in the previous post from AL, there is just enough clearance between the rubber washers on the pressure rollers and the plate to keep it from binding.
Thanks,
John

[rjustice]

John,
Does the machine measure the board, and error out when it does the bit touch off, or does it error during the board end measurements?

[heftyh]

Rjustice,
It actually doesn't error. In the first steps when it's measuring the 3/8" board (during the board end measurement), it just spits it out the end and will continue to run for about 4 minutes. Finally it stops and says "Check Board Sensor".
It acts like it doesn't see the end of the board, but the fact that the sensor value goes from 150 to 0 is what baffles me. When I run the 1/2" board, the sensor reading is 132 and drops to 0 when the board clears and it measures correctly. The 3/8" board has a higher difference between board and no board but still does not register the board leaving the sensor.
Thanks,
John

[Jeff_Birt]

Is the left side pressure roller switch releasing when the board comes out from underneath it? I'm wondering if there is not enough clearance for the roller to drop enough to release the switch.

When measuring the board length the machine feeds the board towards the left until the right pressure roller switch is released and then starts looking for the edge of the board with teh board sensor. If the switch never releases it will feed the board out of the machine.

Also, I got to thinking that you could use a single carrier board for your 3/8 stock. Just make a 1/4" thick carrier board long enough for your longest piece. Stick a piece of 3/8" stock to one end and stick a short piece behind it.

-----------------------------
stock to carve|short piece
-----------------------------

When you set up the project on the machine tell it to place the project on the corner and it wont measure to the end of the board (it stops measuring when it sees that it has enough board for the job). As long as the total thickness of your stock + carrier is <= 1" then you can still use the cut path tool as well.

[heftyh]

Jeff-
I think you may be right about the switch not releasing since there is only about a 1/16" between the rubber washer and the plate. Question- if this is the situation (I will verify tonight), can I cut down the washer a little without doing harm to any other function? Are there washers on the other end of the rollers as well? What is the purpose of these washers?
WRT to the carrier board, if I keep the total thickness <= 1", and I use the cut path, will it still keep tabs on the work piece or will it cut all the way through the work piece and tab the carrier? I'm trying not to use carpet tape on the work piece- it gums up the end of the bit and prohibits the polycarb shavings from evacuating.
Thanks,
John