TM1-P, limit switch

[jheyliger]

I'm using a Haas tm1-p and keep losing the Y-zero. A guy from Haas came out last week to look at the problem and said it was chips on the limit switch. Its happend 2 more times since then. I have a call in to Haas now, but wondered if anyone had an easy fix for this situation.

thanks Jon

[serviceman]

if it is a limit switch then it is not a chip it is probably a proximity sensor it is pretty easy to access and keep clean it is on the left side of the table .

[pmanning@energy]

I've encountered a similar problem when starting up the machine and have found clearing chips and restarting usually works. Would be interested to hear what Haas tells you.

Phil

[gar]

070629-0839 EST USA

Do you have a mechanical limit switch or a prox switch? Ours are mechanical limit switches and in 14 years have never had a problem.

From what I read on the Internet persons with prox switches have chip problems.

Put an air jet near the prox to blow chips off before use.

.

[HAILINHAAS]

Are you able to post a picture ... operating condition .. no clean up .. to see how chips are getting into the housing

[pmanning@energy]

Ours is not a problem with chips getting into the housing, but seems to merely be an accumulation of chips near the proximity switch.

[HAILINHAAS]

The Y-axis prox sensor is on the leftside of the base .. visible from inside of the machine ... there is a sheetmetal housing for the sensor. You should be able to see it .. below the table/saddle assembly.

[Geof]

Originally Posted by gar 070629-0839 EST USA Do you have a mechanical limit switch or a prox switch? Ours are mechanical limit switches and in 14 years have never had a problem. From what I read on the Internet persons with prox switches have chip problems. Put an air jet near the prox to blow chips off before use. .

The proximity switches are prone to problems with chips. And I find the advice to blow them of a bit ironic we have signs on our machines saying do not use air gun below table level because we find chips get blown through gaps in the way covers and get on the sensors.

[gar]

070629-1511 EST USA

Geof:

Good point. How are these prox switches mounted and why so much trouble? Are these out in the open and not inside under the covers like the mechanical switches? If these are in the open it would appear to be bad design.

With the mechanical switches and associated motors the only problem we have had is coolant getting into the motor and of course on the PVC cables. The PVC cables on the X-axis fail because the coolant leaches the plasticizer from the PVC causing hardness and cracking. To solve the problem of coolant dripping into the motor we created an aluminum shield over the motor.

No solution for the cable. If it were Teflon there would be no problem except stiffness. Tape wound Teflon should solve this problem.

.

[Geof]

On the MiniMills at least they are buried under covers but the covers are not good enough; there are large gaps facing down. They work fine if gravity is the only thing pushing the chips and coolant around but as soon as you use and air gun or poor in a bucket of coolant chips can get knocked upwards through the gaps.

Several times we have had chips blown through the gaps and interfere with tsensor; never once have we been able to stick an airgun in the hole and just blow them off. It is always take out numerous little screws, flick the chip off and replace numerous screws.

On the bigger machines the covers are pretty well continuous all the way around so it does not happen.

[gar]

070629-1939 EST USa

Geof:

When I was referring to a blow off of the chips my thought was a permanent jet inside near the prox switch.

From this discussion and others it appears that HAAS has a design problem relating to the decision to use prox switches, or at least how they are applied.

Thus, the question is how can the problem be solved. Is the prox switch an inductive type sensor, or a DC magnetic field detector? My guess is inductive and thus no bias magnet.

Do chips around the outside of the prox, but not on the face, have an effect on the threshold point?

Is the prox actuated by a change from a large air gap to a small gap from a piece of metal passing by the face of the prox?

If no chips what is the distance from the prox face to just make the prox when the test plate is parallel to the prox face and much larger and encompasses the whole face of the prox?

Same question but a square bar with one face parallel to the prox face and the adjacent face coincident with an axil line thru the prox? This will be closer than the solid plate value.

If a rectangular plate has its face coincident with the plane of the face of the prox, then as this plate is slid in said plane how close to the prox, or how far over the prox does the plate have to move to trigger the threshold?

What lead screw pitch is on these machines?

How can we make an inductive sensor be less sensitive to chips? If chips around the outside the sensor modify its trigger point, then make that diameter larger. A Nylon ring for example. If chips on the prox face are a problem, then maybe a brush type wiper could precede the actuator edge to wipe the prox face clean.

Does the chip accumulation get so great as to indicate actuation when the actuator is not even close?

.