Using a centricator

I've got a job that requires a lot of locating and reboring, so I have been using a centricator a lot lately. Which leads to some observations and a question or three. I'm using the FP2NC with D2, in modes 7,5&2, and with traversal speeds ranging from high to very low as it moves between holes or creeps up on zero. If it overshoots, i back it up and do it again so that the readings are consistent.

I get a lot of sticking unless lube pulses are frequent, especially in Y. Almost every rapid gets a lube pulse to counteract this. Maybe it's time to switch way oils.

Do FP dials wear out, or require contact cleaning after a lot of use?

The speed settings are not the same on X and Y. I.e. Y is slower than X for the same speed setting, by about one notch on the dial. Does this indicate a need for calibration? Tach contacts have been cleaned and no errors are seen. I see the speed difference by watching how fast the centricator moves to zero.

it's hard to see the way oil level, so I'm always afraid of running low. Is there a low oil level detector on an fp2nc?

Dave

Can't speak specifically to the D2 and FP2NC, but have some time on an FP4NC/D4.

1- Assuming you do not have a MPG (electronic handwheel)? If it can be fit to your D2 (usually just plugs into a multipin connector under the operator console), I would suggest getting one, it will pay for itself very quickly. You run it in Mode 4, can make large moves quickly and easily, also, small (.004") very small (.0004) and extra small (.0000,40 -there is kind of a "secret" mode) moves per click of the dial, depending on mode selected on the MPG.

2- Should be able to jog .0004" in Mode 4 using the big console Axis direction keys. Only one jog per press of the button (holding the button depressed does not provide continuous movement).

3-The machine should have a low oil reservoir alarm, (#2 from the left, red LED on the operator console, beneath the mode selector switch). The machine will throw a fault code when the oil gets low and/or the LED will flash, usually you can run the machine for a little after LED starts flashing, before it shuts down due to low oil.

4-On the FP4NC, the oil reservoir is on the side of the column opposite the operator's side, there is a large see thru window used to view the oil level. The FP2NC might not have that window, in which case the whole cover needs to be removed to view the oil reservoir.

5- Re the stiction problem--what lube are you using currently?
One thing that may help is run a warm up program before you start dialing in--have each axis move to each end of its limits and back, while the machine lubes it self (use the manual lube button on the console, or write a short program with M7)

If you need a lube pulse for every rapid move, something is very wrong. Is it possible the gibs are set too tight? Does the problem happen with all axes? I run my FP2NC with Vactra #4 way oil, and only have minor stiction issues on the Y axis, and only when the machine is very warm from hot weather and long high-speed running. The way I notice the stiction is a little "thump" when Y moves from sitting for a bit with the machine in this hot condition. I don't see how the axes feed rates can be different at the same settings without throwing an error, due to the scale feedback.

My lube reservoir is in the same place as Colt45's. You need a flashlight to really see the level well. I will be at Laguna Seca this coming weekend, staying in San Juan Bautista, so perhaps could drop in and see the problem for myself.


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Dave:
The above info is correct, some additional details:
There is as Steve states a low lube oil alarm.....One of the 4 LED's on the left side of the console just below the mode switch.
Lube alarm is a function of pressure.....When the tank runs low enough that the pump will no longer pick up the oil, it will fail to make a threshold pressure which will trigger an alarm....
If this happens while executing a program , believe the cycle will continue till a stopping point is reached.
Problem is that the pump does not just stop making pressure...it will suck air/oil when the level gets low and deliver some oil...and air bubbles will get into the lube feed lines....Those will
hinder the consistent delivery of lube....and take lots of lube cycled to finally get purged.
Point is that its best to be proactive and not let the tank to get low enough to trigger the alarm...

As to the suggestion to use an MPG...unfortunately the D2 does not support the MPG architecture....
Also be aware that if positioning via the control values there could be rounding errors....that will show control values that are not exact. Don't know about the D2, but this problem exists on the D4 control depending on the software level...
If positioning via values entered in the control run the machine in Metric....Machine will be more accurate.


Feed speed as rich points out should be the same...Control displays the selected feed rate.
If using rapid moves to position, then i believe there can be a difference in speed....there is a pot setting on the Bosch cards that set the rapid rate, and that might be set differently....Don't believe that affects the feed rate
but it might. Have you tuned the servos for drift and tacho ?
Could easily swap the servo cards between the X and Y and see if the change follows the card change...

As to stiction of the "Y"...take the side panels off to be sure that all the lube lines to the "Y" slide (top of the casting) are intact and full of lube....take each banjo off and cycle the lube pump to be sure oil is being delivered at each...You should be seeing a "burm" of oil forming along the intersection of the slide and column when you cycle the lube pump several times...
Generally the "Y" slides are pretty good, its the "Z" slides that are most likely to have problems.
Will second Rich's question..what oil are you using?

Cheers Ross

Thanks for the replies. Will attempt to answer your questions.

Way oil is probably Vactra 2. I finished the pail so I can't verify, but that is what the new unopened pail is.

i never see stiction in Z, seldom in X, mostly in Y. When I trigger a lube pulse I see the oil coming out along both sides of Y. The work I am doing gets oil well distributed on X and Z slides, but Y movement is much less, so I will try full range rapids on Y with a lube pulse every now and then and see if that helps.

Rich, I would love to have you stop by, but we are headed to Sonoma for the annual PAST tool show this weekend, returning home next Wed.

Regarding feed speeds, I have the percentage dial set to 40, so each Bosch card is interpolating the set speed. Perhaps the pot that controls rapids comes into play when the percentage gets factored in? I typically will use a high speed to move until the centricator makes contact, then drop it to 80 while the centricator needle sweeps almost to zero, then drop to 25 to hit zero, all at 40%. I see the difference in X and Y speed at the 80 setting while sweeping the centricator. I'm using the long arm on the centricator.

Dave

Dave:
First off the manual for that machine calls for ISO 220 way oil....Some use Vactra #4...Me i go with the
Mobil "Vacuoline 1419" That product is blended to replicate the original Vactra, before Mobil changed it....
I believe the Vacuoline works better, but its just a gut feeling, no hard data to support ....
At any rate you need heavier oil in that machine above the ISO 68 of Vactra #2.

Second, if you are programming the moves to the next bore location (Mode7) and it involves moving two axis at the same time and you are using a G01 to make that move...

The slides are going to move at different rates as the machine is interpolating...making both axis moves arrive at the target at the same time...to do this the longer move must travel faster.
Of course if you are only positioning one axis at a time, then the above does not apply...

Cheers Ross

PS if you are coming up 101 on Friday, stop in...I should be here all day.

Cheers Ross

It makes sense that the lighter way oil is part of the problem. You should definitely get ISO 220 weight oil. I find that a tank fill lasts a long time even with reasonable lube pulsing and lube oozing out the slides and collecting in the bottom of the machine.

It sounds like you are using the feed rate override percentage to control motion. Is there a reason you do that, rather than change the actual feed rate itself? In your opening post, you mentioned using mode 2. Are you driving the machine in mode 2? On my D4 machine, mode 2 is for resetting the axes position values.

I think that if I had to zero a centricator on my machine without an MPG dial, I'd use only mode 5, and vary the feed rate as I approached zero. I'd keep pulsing the axes buttons on and off one at a time as I got close. On my machine, mode 7 is sort of a dumbed-down MDI, so I need to know the endpoint ahead of time, which I typically do not when centering things. (I don't have a centricator, so pick up holes with a normal DTI if I need high accuracy.)

I'm using heavier weight way lube on the FP2NC, I just don't have the original pail, it is in one gallon jugs and I've forgotten the details, except it is Vactra and I bought it before Mobil changed all the names of the oils. Thanks for reminding me not to use the Vactra 2 on the mill when the gallon jugs run out.

I like leaving the percentage dial set to 40 in modes 4&7, it gives me the option of increasing the feed during a cut. E.g. Usually the first pass of flycutting hits the high spots, so there is a fair amount of wasted motion. I'm facing and reboring 2bbl carburetors, so the high spots are always at the bolt holes.

Heres a more detailed description of the job. I don't see much opportunity for a D2 program, it is all manual. No coolant is used.

1. carb top is faced by hand, which provides a reference surface
2. Clamp carb to jig on mill, top down. The carbs are not perfect, so the jig centers the two bores within .006" from one carb to the next.
3. Install fly cutter in mill spindle
4. Set speed to zero, start and stop spindle
5. Move table in mode 4 to align cutter with low spot on carb, release quill lock and touch down, tighten quill lock. This establishes rough X 0, Y 0 and Z 0
6. Set Z zero and X 0.2 in mode 2, set percentage to 40, feed 100
7. Go to Z .005" in mode 7
8. Start spindle at 250 RPM, give lube pulse
9. Go to X -10.2, speed 100, mode 7. This faces the high spots on the carb bottom.
10. Go to Z -.002"
11. Go to X 0, speed 100. This finishes the carb bottom.
12. Go to Z 4", X 1", install centricator in spindle
13. Set speed 0, start and stop spindle
14. Rotate centricator so I can see it from console
15. Lower spindle in mode 4 into first bore
16. Move in +X to centricator 0
17. Set X 0 and Z -0.2 in mode 2
18. Move in -X to centricator 0 in mode 4
19. Go to X/2 in mode 7
20. Set X to 0 in mode 2
21. Move in -Y to centricator 0 in mode 4
22. Set Y to 0 in mode 2
23. Move in +Y to centricator 0 in mode 4
24. Go to Y/2 in mode 7
25. Set Y 0 in mode 2
26. Go to Z 0.1 in mode 7
27. Rapid to X -3, lube pulse
28 - 40. Repeat steps 15 - 26, except don't re-zero coordinates, record the four centricator 0 points, X1, X2, Y1, Y2. Center of second bore is (X1+X2)/2, (Y1+Y2)/2.
41. Rapid to Y 0 in mode 7
42. Rapid to Z 2
43. Insert 40.1 boring head, set speed to 250, lube pulse
44. Rapid to X 0
45. Rapid to Z 0
46. Set Z 0.1 in mode 2 (the boring head is slightly shorter than the centricator)
47. Start spindle
48. Go to Z -1.4
49. Rapid to Z 2, check and see if bore cleaned up. If not, repeat steps 42-47 with 40.2 boring head. If that still doesn't do it, repeat with 40.4 which always works.
50. Lube pulse, go to center of bore 2, repeat 42-47 with last used boring head

the place I see sticking is during the Y moves in mode 4 to centricator 0, so I almost always add additional lube pulses during the initial Y- move.

I usually skip the 40.1 boring head. These carbs were originally finished on a Solex production line where the butterflies were fitted by hand. The worker would inspect the fit by eye, then use a rotary grinder to get a better fit.... so the first rebore seldom removes the out of round grinds.

Dave