Dear all of the Deckel-party hi,
I would like to share my latest adventures today, trying to perform a highly advanced machining operation, and ask for your thoughts on, at least one, of the problems I...faced! The advanced machining operation was to ... face the top of a 400 x 250 mm cast iron plate flat...
My machine is of the early, 500 mm X variety, so the 400 mm of the plate should pose no issues. Regarding the 250 mm dimension, I did not feel like moving the piece or the long-reach head, so I just opted for a largish (100 mm) indexable face mill. Sure, it is not ideal not to exit the piece at both sides for each pass, but nevermind, the requirements for accuracy and finish are not tremendous.
So, I mounted the part on an old mag chuck and started experimenting with speeds/feeds. (the latter did not end up well at all, see end note for this...). Took the first pass along the X, then moved the Y (in the direction away from the machine) and took another pass along X. To my surprise, there was a considerable step between the first and the second pass!!! Did not measure it, but it seemed and felt like 0.1 mm at least, which is huge! And the funny thing, the second pass, the one further from the machine, was HIGHER!
Unable to explain it at the moment I reversed my way of working, switching to facing along Y, stepping over at X and taking the next pass along Y. (of course, since I was not able to exit the part after each pass, the finish was 'compromized', as if it was any good at all to begin with...). Now there was no step between one pass and the next one, so I went on like this till the end. (my old mill has a bit of knee rock, but not so much that it would end up showing as step between each pass after stepping over at X).
Trying to explain my initial issue, I tried to analyze the (crappy) finish, have a look:
(you can all see the excellent quality of the casting, I think I would have done it better if I tried myself...)
Ignoring the awfull rubbing during stepping over, one can see that my face mill is not cutting all the way round. It seems to be cutting only with the part furthest from the machine as would be the case if the head was not perfectly trammed in the nod direction and, of course, if it was a Bridgeport and could nod! (ok, there are Deckel heads that can nod also, but not mine). If the head is set this way, that is the axis of the spindle not parallel to the Z ways, but at an angle towards the Z screw (you know, nod), then I would both see the head cutting only at the front when working along Y and see a step when working along X and stepping over along Y, which exactly what I have. Nod it is then...
Unless I am completely stupid, these stand:
- the setting of the tilting table, or the condition of the mag chuck, don't play any role at all. Whatever you place under the spindle and hold it firmly enough, should end up flat.
- since Y on our machines is not on the table, there are no weight transfers and table droops for the different Y settings. (flexing could be increased milling further from the table base, but would not end up in such huge problems)
- since my mill is far from new, there could be wear in the Y ways that would end up in ram droop as it exits the machine. However, this droop would be gradual and would not end up in steps or uneven facing, it would just mean that my machine's Y axis is not any more square to Z. I would have trouble in squaring items but they should still be flat!
Based on the above, I can only imagine that there is some kind of nod in the long-reach head. I can't imagine why the round front surface that allows for tilting would have worn unevenly but I have to check.
At this point I have to admit that I have mistreated my long-reach head since I got the machine, one year ago. I mean that should have repaired the rear clamp (manual's "clamping strap") which is worn to the point that the slot has closed (I think this is a regular failure) and, well, replace the front missing clamping strap, which was absent when I got the machine....I know, many points removed from me for that....A good friend suggested I should ask Singer for the part, I said I'll make it a project, and this is what it still is, one year later...
In any case, since I am not at the workshop and I am not sure about the geometry, could the missing clamp, if installed, help raise the front part of the head? I recall that the head has an angled surface there and the clamps press against it, it could be that, if the clamp was there, it would push the head upwards and restore the nod?
If I have got it all wrong here, can anyone think of a, realistic, explanation of the nod, or my problem with the steps altogether?
Looking forward to the forum's input!
Many thanks in advance!
BR,
Thanos
ps. So, my speeds/feeds (1250 rpm, around 100 mm/min) were not good. Or, at least, not for the depth of cut (very shallow, 0.2 mm tops) I needed. So, I think I ended up rubbing instead of cutting, piece got hot, facemill got hot, spindle got hot, quill got hot, and, exactly at the last mm of machining, something seized! Spindle stopped, quill did not move, IR thermometer measured 100 deg C at the face mill and around 80 at the spindle and the head casting....I did not do anything stupid with water or spray cans, just dunked the face mill in motoroil and dripped motor oil onto the casting as well. After a while it cooled down, and it seems to be working ok now. Still, I think I should take it apart and replace the grease on the spindle bearings, since it took some heating and that can't be very good...
Not only do I lack the experience to properly set my machine/cutting tools, I also lack the common sense to probe for temperature increase. Just put your damn hand on the head stupid, it would suffice....
I should probably have gone to the beach instead of the workshop today...
I would like to share my latest adventures today, trying to perform a highly advanced machining operation, and ask for your thoughts on, at least one, of the problems I...faced! The advanced machining operation was to ... face the top of a 400 x 250 mm cast iron plate flat...
My machine is of the early, 500 mm X variety, so the 400 mm of the plate should pose no issues. Regarding the 250 mm dimension, I did not feel like moving the piece or the long-reach head, so I just opted for a largish (100 mm) indexable face mill. Sure, it is not ideal not to exit the piece at both sides for each pass, but nevermind, the requirements for accuracy and finish are not tremendous.
So, I mounted the part on an old mag chuck and started experimenting with speeds/feeds. (the latter did not end up well at all, see end note for this...). Took the first pass along the X, then moved the Y (in the direction away from the machine) and took another pass along X. To my surprise, there was a considerable step between the first and the second pass!!! Did not measure it, but it seemed and felt like 0.1 mm at least, which is huge! And the funny thing, the second pass, the one further from the machine, was HIGHER!
Unable to explain it at the moment I reversed my way of working, switching to facing along Y, stepping over at X and taking the next pass along Y. (of course, since I was not able to exit the part after each pass, the finish was 'compromized', as if it was any good at all to begin with...). Now there was no step between one pass and the next one, so I went on like this till the end. (my old mill has a bit of knee rock, but not so much that it would end up showing as step between each pass after stepping over at X).
Trying to explain my initial issue, I tried to analyze the (crappy) finish, have a look:
(you can all see the excellent quality of the casting, I think I would have done it better if I tried myself...)
Ignoring the awfull rubbing during stepping over, one can see that my face mill is not cutting all the way round. It seems to be cutting only with the part furthest from the machine as would be the case if the head was not perfectly trammed in the nod direction and, of course, if it was a Bridgeport and could nod! (ok, there are Deckel heads that can nod also, but not mine). If the head is set this way, that is the axis of the spindle not parallel to the Z ways, but at an angle towards the Z screw (you know, nod), then I would both see the head cutting only at the front when working along Y and see a step when working along X and stepping over along Y, which exactly what I have. Nod it is then...
Unless I am completely stupid, these stand:
- the setting of the tilting table, or the condition of the mag chuck, don't play any role at all. Whatever you place under the spindle and hold it firmly enough, should end up flat.
- since Y on our machines is not on the table, there are no weight transfers and table droops for the different Y settings. (flexing could be increased milling further from the table base, but would not end up in such huge problems)
- since my mill is far from new, there could be wear in the Y ways that would end up in ram droop as it exits the machine. However, this droop would be gradual and would not end up in steps or uneven facing, it would just mean that my machine's Y axis is not any more square to Z. I would have trouble in squaring items but they should still be flat!
Based on the above, I can only imagine that there is some kind of nod in the long-reach head. I can't imagine why the round front surface that allows for tilting would have worn unevenly but I have to check.
At this point I have to admit that I have mistreated my long-reach head since I got the machine, one year ago. I mean that should have repaired the rear clamp (manual's "clamping strap") which is worn to the point that the slot has closed (I think this is a regular failure) and, well, replace the front missing clamping strap, which was absent when I got the machine....I know, many points removed from me for that....A good friend suggested I should ask Singer for the part, I said I'll make it a project, and this is what it still is, one year later...
In any case, since I am not at the workshop and I am not sure about the geometry, could the missing clamp, if installed, help raise the front part of the head? I recall that the head has an angled surface there and the clamps press against it, it could be that, if the clamp was there, it would push the head upwards and restore the nod?
If I have got it all wrong here, can anyone think of a, realistic, explanation of the nod, or my problem with the steps altogether?
Looking forward to the forum's input!
Many thanks in advance!
BR,
Thanos
ps. So, my speeds/feeds (1250 rpm, around 100 mm/min) were not good. Or, at least, not for the depth of cut (very shallow, 0.2 mm tops) I needed. So, I think I ended up rubbing instead of cutting, piece got hot, facemill got hot, spindle got hot, quill got hot, and, exactly at the last mm of machining, something seized! Spindle stopped, quill did not move, IR thermometer measured 100 deg C at the face mill and around 80 at the spindle and the head casting....I did not do anything stupid with water or spray cans, just dunked the face mill in motoroil and dripped motor oil onto the casting as well. After a while it cooled down, and it seems to be working ok now. Still, I think I should take it apart and replace the grease on the spindle bearings, since it took some heating and that can't be very good...
Not only do I lack the experience to properly set my machine/cutting tools, I also lack the common sense to probe for temperature increase. Just put your damn hand on the head stupid, it would suffice....
I should probably have gone to the beach instead of the workshop today...