Need Help!- haas sl-20 screeching problem when stopping

[katsbobo]

I have a haas sl-20 big bore lathe. With the chuck on the machine would screech when it would start spinning. ( It doesn't do it with the 5c collet system presumably because it is not as heavy). It sounds like a loose belt some where. But now when the spindle tries to orientate and or lock, before the live tooling engages it gives a double screech. When observing it trying to lock it would rotated past its point screech really load and then rotate back the other way to hit the orientation point and screech as well.(Not even a half of a rotation) Question is: does this sound like a belt issue or a brake pad issue. Does anyone have any information on how to tighten the belts or change brake pads, or even what is the proper code for orientating the spindle. It does look like the bake is worn a little more on the middle part of the disc as opposed to the outer portion. Any information would be great. Thx - Mike

[MikeOD]

You're not using your c-axis if you're using spindle orientation to degree the spindle. M154 will engage the C axis, and M155 will disengage it, this is a much stronger more rigid method of using your live tools. Just call out a C-axis position. If you just want to lock the spindle (not really necessary when the C axis is engaged) use M14 to lock it and M15 to unlock it. This is only possible on a c-axis machine, but it will actually engage the brake. M19 will not, M19 is only using the servo to hold the spindle.

As far as the screeching noise...I don't have an answer for you. Sorry.

[stucaruk]

Look inside and see if the spindle encoder on your lathe is driven by the belt. When the bearings on the encoder go bad, the timing belt pulls the timing gear into the spindle drive pulley. Your about to spindle have encoder faults as well if this is the issue...

[whiteboy]

Mike,
You (or your Haas Service person) need to replace one or all of your main drive belts. Our SL20 was also doing the screech (with CHUCK installed) upon starting up at @ 2500 rpm. Screeching is from belt(s) slipping. Easy way to check this is:
1) Make sure machine is OFF !!!
2) Open access door below Tailstock and Chuck Pressure gauges so you can get to drive belts
3) Make a chalk mark evenly as possible across the three main drive belts
4) Close access door
5) Fire up machine and in MDI give it a spindle command of @ 2500 RPM, this should cause loose belt(s) to screech if your chuck is installed.

If you hear a screech, shut off machine, open access door and look at chalk marks on belts. If you can't see marks, rotate spindle by hand until you see one or all chalk marks. One or two will probably be way off from others. This indicates that one or more of the belts are slipping.

I helped our service man change ours, and it is doable by yourself, but it IS NOT going to be any fun at all....especially if you have a C-Axis machine like we do.

Hope this helps,
Steve

[Geof]

Originally Posted by whiteboy ......rotate spindle by hand until you see one or all chalk marks. One or two will probably be way off from others. This indicates that one or more of the belts are slipping....

I don't follow your logic here; how can only one belt slip?

[whiteboy]

To be honest, I'm not real sure how only one belt could slip. I do know that before our service man came in, he had me do the "chalk test" and it verified that only one belt was (way) out of line with the other two. Thinking about now however, I seem to recall his telling me that some oils (like those in coolants, way oils, hydraulic oils, etc.) that are always present in the "guts" of a machine can break down a belts composition. Perhaps our loose belt (and maybe yours?) had suffered this problem.

Steve

[Geof]

I think it is one belt slips on one pulley and the other two slip on the other pulley. I was certainly puzzled when I once saw that the belts had slipped 'differently'.

[HAASboi]

we use Pyroil Belt Dressing in our sl20 when it screeching

http://www.valvoline.com/pages/produ...asp?product=32