double sided machining problems

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double sided machining problems

Postby gadgetman48 » Thu Jan 31, 2019 5:37 pm

I am trying to do my first double sided job, some simple hold downs. I have it indexed with dowels but the bottom side job doesn't work right. It seems to jam the z axis carriage and then loses zero.
setup shot


at the end of the milling the recess on the bottom it did this. ![20190131_083348|281x500](upload://g25RQY9hBnwljECtKNfr7T1FS7L.jpeg) went all the way through the side of the board and raked across the spoilboard. Yikes.

this is the toolpath settings
I am trying to do my first double sided job, some simple hold downs. I have it indexed with dowels but the bottom side job doesn't work right. It seems to jam the z axis carriage and then loses zero.
setup shot
![Screenshot%20-%201_31_2019%20%2C%209_01_35%20AM|150x500](upload://1ZC3JUhVJEvATajg8uDJVygEsNR.png)

at the end of the milling the recess on the bottom it did this. went all the way through the side of the board and raked across the spoilboard. Yikes.

tool setting and material setup below.

Must admit I am confused by 2 sided machining and don't want to destroy my machine.
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Re: double sided machining problems

Postby adze_cnc » Thu Jan 31, 2019 6:11 pm

I suspect that the "Zero off same side" needs to be unchecked. But am not too sure.
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Re: double sided machining problems

Postby garylmast » Thu Jan 31, 2019 6:58 pm

I was running into trouble on double-side jobs because after glue-up, I would trim the sides, making the material slightly smaller than then what I had in the job setup, and too lazy to correct the job setup. Because of that, I started Centering the datum instead of using the corner. Also, after several times of setting the dowel in a different holes in the spoil board (after a lot use, there's a lot holes), I was getting misaligning cuts on the backside. AND BECAUSE I LIKE TO DO SIMPLE THINGS SO MY BRAIN DON'T HURT, instead of dowels, I started using a very simple Jig, shot in the spoilboard with brads, then either screw the material to the spoilboard, or on thicker material, screw from the jig into the material. THIS SETUP TAKES SECONDS. Also, I UNCHECK the Zero off same side, if for nothing else, most of my jobs are set at material surface and I don't want to make a mistake by zeroing out the Z datum wrong. Another quirk I do, is because wood has different thicknesses (i.e. 3/4" may measure 0.73"), when referencing Home, When I set the Z height, I bottom it to the spoilboard, but mark the Zero Z position as a -0.75.

I now have done several dozen double-sided projects and so far have not had a problem. I know others do it the way the tutorial suggests, but my way, is simple, it takes seconds to do, and so far, no errors.

Gary
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