blind dado/double machining not lining up

[Alex Bowler]

Hi,

I am having trouble with the tongs of the blind dado not being exact. For example I
recently cut a unit with blind dado fixed shelf, on one side the blind dado was cut into
to shelf and on the other side there was excess material on the tong resulting in a gap
on one side.

I have tried a few things to resolve this but it is not completely fixed:

-Setting the trimming feature to ensure the board is square after the drilling and rebates are done when double machining
-ensuring that all tooling has the correct Dia
-checking the operator has the board hard up against the stops

It is a new machine (MTR 21 metric version) I think that it maybe that the fixture offset
is not correct, maybe change in the conversion from imperial to metric?

Our stops are at the opposite end to 0,0 so I think it uses a fixture offset then references
this to bed size to set start point over to the other end of the bed. But I am not sure on this
and I am not sure on how to check that it is correct, so any advice would be great.

[Scott G Vaal]

Alex,

I find the best way to check this is to put a precision pin into one of your tool holders (I use a 3/8" diameter pin and measure it with a caliper). Next, raise the pins and place a sheet of your typical material into them (ensure you are flush against each pin), then turn on vacuum to hold the sheet in place. Now, lower the pins and move out with this pin and touch each side of the sheet on the side that the pins are on and in the area that the sheet touches the pins. Raise the tool up at each spot and then move back the radius of the pin so it is center over the edge of the sheet. Write each of these values down (for X & Y). Now, if you are using a fixture offset, go to the fixture table for the offset number being used and compare and or change if needed.

[Alex Bowler]

Thanks Scott when i check the fixture offset that is referenced in the G code it is the opposite side to our stops. Our bed is 2700mm by 3600mm
and we mostly cut 1220mm by 2440mm sheets on it, so i think that e cabinets calls up a sub program to flip the fixture offset
reference point to the other side so the sheet is against the stops. But i am not sure of this process and with the fixture off set point being at the corner with out the stops
i have nothing to position the board against to check it.

At a guess i would say i would have to put a sheet against the stops check the corners then reverse the sub program to see if the router goes back to the fixture point?
Or maybe i could check it buy adding the table size to the fixture offset and seeing it it goes to the corner of the sheet when against the stops?
Is the table size enter in the nesting settings the same one that is referenced in the program?

[Scott G Vaal]

Thanks Scott when i check the fixture offset that is referenced in the G code it is the opposite side to our stops. Our bed is 2700mm by 3600mm
and we mostly cut 1220mm by 2440mm sheets on it, so i think that e cabinets calls up a sub program to flip the fixture offset
reference point to the other side so the sheet is against the stops. But i am not sure of this process and with the fixture off set point being at the corner with out the stops
i have nothing to position the board against to check it.

At a guess i would say i would have to put a sheet against the stops check the corners then reverse the sub program to see if the router goes back to the fixture point?
Or maybe i could check it buy adding the table size to the fixture offset and seeing it it goes to the corner of the sheet when against the stops?
Is the table size enter in the nesting settings the same one that is referenced in the program?

Alex,

You do not need to worry about material sheet sizes, Control Nesting takes care of shifting it for the sheet size. All you need to do is get the values as I mentioned and then make sure that this is what they are set to for the Fixture Offset or Fence Macro that is being used. This is usually the G52L1 if set to use fixture offsets or the G901 if not checked to use fixture offsets (Fixture offsets are the recommended method). In {Control Nesting} -> {Settings} -> {Fence/Fixture & Park Locations}, you will see what fixture offset or fence macro is being used. Also, if the pins are located in the corner opposite of HOME for both axes, then the X Adjust and Y Adjust settings will/should be checked. This is what lets CN know if it should adjust the origin back for the sheet size or not. Fixture offset values are changed in the {Fixture Offset Table} and fence macro values are changed in the {Machine Variables} area.

[Alex Bowler]

Hi is was not using a fixture offset so i changed it to use one, changed the G901 codes to G52L1 and the set that fixture offset as you describe and it
is dialed in perfectly. Thanks for your help.

[Scott G Vaal]

Alex,

No problem. Great to hear it is dialed in for you now.