Preset location changes every time I restart the bot.

[Mark Owen]

PRS9648
I am trying to build the Russell Crawford stools he has listed on the Vectric site. These stools require two sided machining and holddowns inserted into either the spoilboard or another board on top.

My issue is that my machine changes where it thinks it is when I switch off the machine and turn it back on again. I C3 every time the machine starts to get to base co-coordinates then press my preset location #2 on the keypad. This should take me consistently to the same place, it does not. It vacillates back and forth between the points .177” apart.

So far in an attempt to resolve this I have reverted back to the default settings, upgraded to the latest software and firmware, trued the gantry via the stop blocks but I still get the same result.

Now the fact that it is exactly two different spots along the X axis, leads me to believe it has to do with the two motors being out of sync and one takes priority one time and then another time the other one wins the battle.

I am working with Support but thought I would post here also.

Any assistance greatly appreciated.

[Brady Watson]

It is critical that the machine runs true without any motors engaged & that the table is level.

You can get better repeatability from the proxies by setting the gap between the sensors and bolts. Grinding the heads of the bolts down perfectly flat (in metal lathe best) will make it even better. However, you should be able to achieve +/-0.03" or less when they are properly setup right out of the box. Be sure to power up & shake the machine down on all axes. If you perceive any slop, adjust it out. Pay close attention to the pinion to rack mesh.

Are your parts coming out square? Have you done a 3-4-5 to check? Lightly scribe your table or scrap cutting a 30 x 40" rectangle. Measure the diagonals. They should be exactly 50". If they are light/heavy one way or the other, this will point to the gantry being out of square.

In the meantime...if you have a living to make...Pick a spot on your table after you set your 0,0 point either manually or via C3. Run your bit into the table at a round number location (say 12,12 etc). Write the coordinates (in this case 12,12) in pencil on the table next to the point you just made. The next day if you run C3 and then command the tool to 12,12 and it is off, open up keypad. Goto Fixed mode via the D key. Change the distance to move in the textbox to .01 or .005 and move the tool until the smae size bit will fit down into the little hole you made. Then close out keypad. Type in VA and enter 12 into the X and 12 into the Y. You have now assigned this location to those coordinates.

I have proxies on my Desktop, but not my big tool. So I do the aforementioned technique all the time. It works for me when precision is imperative.

-B

[Mark Owen]

Thanks Brady. I will try this tomorrow morning.

[Brady Watson]

I forgot to add that you want a gap of .02-.04 between the highest part of the bolt (don't forget there are raised forgings on them). You want to make sure that the prox tip doesn't rub against the bolt.

-B

[Mark Owen]

Brady,
I snugged up the motors, double checked the pinions are tight too. I will also check 3,4,5 tomorrow.
However, I feel the most accurate and best method is doing what you recommended. So, I drilled an .125" hole at my intended 0,0 for these files and will confirm every time I cut them and adjust as necessary. It would be nice to trust the proxies but if they're off even .01" the flip op will fail and I would have wasted time and material.
Thank you kind sir. Beers on me next time we meet.

[scottp55]

Mark,
Make sure and post pics of stool when finished.
LOVE how tight Russell's circular Maloof's are cut on the CNC:)
scott