horrible accuracy issues + bit question

[Kenm810]

AskBud,

Sorry still out of Focus,

[jerryherb]

Follow-up:

I took the machine's cover off and cleaned the crap out of it. i found no play in the bearings that move the head in y and z direction. I noticed a very slight play in the gear boxes when reversing direction, slightly more in y-axis, and dont know if this is normal or whether there should be not play all. Again they are very slight and i switched the big wheel plastic cogs that run the belts (between y and z) to see if it would make any difference. After reassembly i ran a simple 4 square cut path job in pine on a 2 foot board (stayed under rollers, snap to grid, mirrored across y axis, pressure at about 83lbs, masking tape applied, optimal setting, .125 per pass with 1/8 bit). The job came out the same as the original problem. i closely watched the job this time, as well as recorded the best i could and posted on youtube (links below).

Observations:
the head slows down prior to every turn and speeds up after at about 3/8 inch each (this is exactly when the snipes are formed, at slow down and speed up in y direction). prior to changing direction from x to y, it jerks (speeds up for a split second, and goes back to slower speed); after changing the direction at the point of speeding up again (in y direction) i can see a jerk of the belts and the snipe is created. as it reaches the other corner and changes the head speed again the belts jerk in the other direction and another snipe is created (see the original pictures). it only does it as it cuts in y-direction; x-driection cuts are smooth. also the upper left corner of the square (panel being the bottom) is way wider than the others, and the lower right is much tighter than the others. Also the head does not slow down at all when reaching lower right direction change from y to x.

Has anyone experienced anything like this? Is this the x-drive, how do i get at it and what do i need to fix it? please see the videos for both the head movement and belt jerking. thanks!

http://www.youtube.com/watch?v=6A-lGFVQMME
http://www.youtube.com/watch?v=ZUgivRglcK8

[Digitalwoodshop]

Well the videos help..... What you are seeing is the 1st gear and 2nd gear Feed Rate for a Cut Path..... This is on LHR's "Yes they want something else..." List... During a Cut Path like that "I" would like to be able to select in the depth of cut menu to stay in 1st gear the whole time.... Like you pointed out... The 2nd gear feed rate leaves a less desirable cut.... Not to mention how many $40.00 bits snapped when the cutting feed rate sped up in hardwood. This is the same result I was seeing cutting my plastic tags on the carrier board using a 1/16 end mill and depth of cut without tabs using double sided tape.

The FIX came form LYNN here on the forum... In MY case I design the rectangles using the 1/16 end mill bit and NO Tabs and NOT using cut path but use DEPTH OF CUT.... The tabs could fracture off my plastic making for bad edges. The double stick tape holds the piece in place.

SO back to the plan.... Design it in 1/16 inch for depth of cut.... When done select all the cut paths and change the bit to the 1/4 ball nose bit. In your case you will still cut with the 1/8 inch bit but ASSIGN the 1/4 inch ball noes. This locks the feed rate into 1st gear for the whole cut. The depth of cut will change when you select the new bit, so remember to change it....

You will need to leave a skin at the bottom of your blocks to hold it in place... Fail to do that and the wood will move and pinch the bit and snap it.... So leave a skin at the bottom or use double stick tape.

Good Luck,

AL

[jerryherb]

Well, i tore off the bottom and side panels as per instructions on the carvewright website. it appears that there is a lot of play between primary and secondary gear, and by messing with mechanics i have proven that it is enough to cause the belts to be able to jerk during speed/direction change. I also notice that the primary gear has a crack in it (between the screw hole and the brass embedded gear. since my somewhat retrofitted type A needs a new x-drive gear box, i hope the new replacement C-type design will fit and fix this problem (old system = two parts MWM A2036 and MWM A2049, new = one part MWM A2129). I hope its available for purchase as i can replace it myself and do not want to have to send it in. I am also confused as to the shifting gears phenomenon. there is not any kind of transmission system in the x-drive gearbox and the only speed adjustment is the code on the controller telling the motor to speed up or slow down as far as i can tell by looking at it. any staff members care to chime in? thanks!

[Digitalwoodshop]

In your video you can clearly see the turns are at a slow feed rate.... then the feed rate speeds up..... then slows down at the next corner.....

I call it 1st Gear and 2nd Gear for Simplicity.... The Feed Rate is actually controlled by the SOFTWARE and no shifting gear boxes... SERVO SPEED... Slow or FAST.....

Lets hope the cracked gear fixes the problem.....

Good Luck...

AL

[jerryherb]

Further attempts to repair still futile!
Just to reiterate the original problem: the belts jerk and cause an uneven cut when engaging/disengaging the "2nd gear" or high speed head movement, but only in y-direction.

I replaced the x-drive gear set and the problem persists.

the next thing in line is the motor itself; swapped the x-motor with y-motor, problem still persists.

Does anyone know what x-termination board does and if that would have an effect on the x-motor jerking while the y-motor engages/disengages high speed movement?

x-termination board is part number MWM A2074 which can be found on page 7 of the parts manual: http://www.carvewright.com/2010CWweb...ist_manual.pdf

any advice greatly appreciated! thanks!

[Digitalwoodshop]

The X Termination Board does 2 things... It Passes through the X Servo Signals and has the Q1 Transistor that turns on and off the Cut Motor.....

This jerking could be your head pressure it TOOOOOOO High...... I believe there is a PDF that has the instructions for using a bathroom scale.... A simple thing to do is crank off 1/16 of a turn to reduce the pressure.....

Another thing I just remembered... The Brass Roller between the belts needs to be moved away from the rubber belt by drilling or filing the holes oblong... IF this is NOT DONE.... Then the belts bulge when you crank the head down and the rubber belt touching the Brass Roller could be your problem... IT CAUSES JERKING......

The guy doing the Referb might have just BENT the Roller Bracket or not thought it was needed..... That topic has been posted here before... Me... I like the Sand Paper Belts.... Gives me things to work on.....

So I think the problem is the Brass Roller needs to be moved more..... This could come down to a case of the "Botched Rubber Belt Change Out"... "

Look at the pictures... Check your board for Burning.... The Broken C1 just effects the starting of the Cut Motor... I have 3 out of 4 broken C1's.... Before the ROCK.... Whole Lot of Shaking going on.... QC.

AL

[jerryherb]

i checked the pressure and its continuously recording between 78 and 80 lbs. I also checked the rubber belts install manual and all the washers/spacers appear to have been installed. I did the "paper pinch" test (step 30 of the rubber belt upgrade manual) and it successfully passed. tomorrow i will try some kind of clear media to see if there is any interference between the belts and roller, however the belts appear to be installed correctly. the x-termination board also looks fine. Could it be firmware issue with A machine and the controller losing it? does anyone have the first release of project designer i can try? im at loss here, i guess the only thing i can try is to fool the machine with the 3/16 bit trick, however that is a BS work around, and im disappointed in the carvewright's software limitations. there needs to be a way in software to slow the machine down/keep it running at low head speed for EVERY bit without exceptions, as well as vertex attachment for resizing the route designs. not to mention the ability of what order the user would prefer things to be cut. Manual control of the head in x-y-z would be nice as well, and im sure it can be done via the "serial" port on the back of the system. I think that is what im going to work on next, or maybe i just need to get me a real CNC with mach3 ....

[liquidguitars]

Could it be firmware issue with A machine and the controller losing it?

no

the belts jerk and cause an uneven cut when engaging/disengaging the "2nd gear"
or high speed head movement, but only in y-direction.

Sounds like a few things like a worn y pack, dirty bearings 8 ea, uneven sled, loose chuck parts dull bit, y belt tension. Plastic gear chips in the x drive. I assume all the bearings are tight, the truck should not wiggle at all.

[jerryherb]

Sounds like a few things like a worn y pack, dirty bearings 8 ea, uneven sled, loose chuck parts dull bit, y belt tension. Plastic gear chips in the x drive. I assume all the bearings are tight, the truck should not wiggle at all.

All these things have been checked; the head is tight, the bearings appear clean and tight, y-belt is tensioned, bit is brand new, x-drive has just been replaced, the x and y motors have been swapped with no change in behavior. Sled is taken out of equation as it performs these "cut errors" on any size and thickness board without the use of the sled just the same. the problem is caused by belts jerking, yet there is almost no play in the x-drive gear set. it seems the controller is sending deliberate instructions to the x-motor causing a quirk in x-direction (belt jerk) when the y-direction head movement changes speed, hence the firmware question. I have a few more variables to check and will post a response when complete. in the meantime please throw ideas at me as i am desperate to try anything to get this fixed. thanks!