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Brother TC-S2Dn Y ball screw replace - Encoder Reset?

Pete Deal

Stainless
Joined
Apr 10, 2007
Location
Morgantown, WV
I bought this machine last year and the Y axis had about .0015" of backlash. I did lots of testing to get to the bottom of it- checked the thrust bearing, looked for something loose, etc but it was in the screw. To check I wrote a program - move to a Y position A, move .005" from there to position B, move another .005" to position C, then back to position A in an endless loop and a 4 sec delay at each position.

Anyway, got the new ball screw, nice thing is it came complete with the thrust bearing and housing all mounted. Funny thing about this was that after ordering the new ball screw I made a spanner to get the nuts off the end of the ball screw to remove the thrust bearing. This took the most time and I didn't need it since the new screw came with the bearing assy. The replacement process is about a half day. Pretty easy.

I suggest for anyone that owns a Brother vertical that you do a yearly PM to slide the Y axis way cover back and make sure you're not letting chips build up under there. This now my second used Brother, both well used, that I had to replace parts in the Y axis because the previous owners neglected this area.

Now for my question- I pretty much followed the maintenance manual on replacing the screw. The thing I didn't do was to put a test indicator on the table to check position prior to disassembling. I think the purpose of this step is so that when things are all put back together any fixture work offsets can be used without resetting. Not super clear. To reset the counter I lined up the front of the saddle with the little 5mm hole in the sheet metal then I went through the I/O menu, -9999, F7 process to reset the encoder. After doing this and tramming the table in Y it would hit the bumper in the back and I could see it would still not go quite all the way forward in Y. I tried it a few times with the table just in front and just behind the little hole in the sheet metal but it still did the same.

I think I have it now. I wound up hitting the release button and moving the table a little more toward the front then reset the encoder to 0. To do this I put 0 in the "adjusted MC coord" field and then a 1 in the "oper" field for Y. It did change the machine zero so it now trams without hitting the end.

Anyone understand this encoder reset procedure well? I did work with the local tech svc on the diagnosing the screw but not this yet.
 
Hi Pete. the factory sets the X and Y axis off the center key groove for X and the Center t-slot for Y. This position is not super critical on a non-twin arm tool changer style machine. For example on a Speedio S500, the center of the center T-slot is -200.000 mm machine postion for Y, and the center key way is -250.000 mm in X. What I usually do is if I know where a work offset is on a fixture, I will just set that. Using the slots, you can indicate the slot or just eyeball a tool there. When setting encoder for Y for example, you set the position after set to -200.000 then perform a '2' operation to adjust the position. If you know a work offset was -8.000 inches in X and -3.000 in Y, indicate that position, then set the X position after set to -203.200 mm and perform a '2' operation to adjust, set Y pos after set to -76.200 and adjust. Do not change these #s after setting on the absolute encoder reset page. Test that the machine does not hit hard stops slowly with handwheel and run it.
 
I see what I was doing wrong. I missed the important detail that I need to enter a "2" into the "Oper" field instead of a "1". I poked a spot drill down to approximately the middle of the center T slot, entered -200 (center of y travel in mm) into the "Adjusted MC Coord" field, entered a 2 into the Oper field and it did as you say. Thanks!

The tip of using the T slot for center is a good one- thanks for that! The maintenance manual says to use a little hole in the sheet metal below not quite so easy.

Thanks!
 
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