What to expect Tramming Cutting

srfallsallot

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Hi all. Just learning. I do not know what to expect nor what I am looking at. I trammed my PM932 with the device I made attachment 1. As you can see it seems to be very square. Y axis is the same. I trammed my vice it also is the same. My rpm was 1970 feed rate 2.75 in/min. Cutter 2.5' face mill with 4 carbide inserts. The brick is Al from scrap yard one end was badly damaged. I cleaned it up some on the ends . Attachments 2 and 3 show the dimensions as best I can measure. I do not necessarily believe the 4 digit. So what do you think. Is this ok.

The zoomed in attachment 4 shows a pattern of arcs across the whole part. If i take a 123 block and lay that on it with a strong back light a very small gap barely visible shows up in the middle of the arc. Why?

The zoomed in attachment 6 shows a pattern of arcs across the whole part. This is the opposite side of attachment 4. This was done with multiple passes. If i take a 123 block and lay that on it with a strong back light a very small gap barely visible shows up in some of the passes but not all of the arcs. Why?

Thanks for your patience and insight.
 

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benmychree

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If the tool pattern is hollow in the center and the pattern is not cross hatched, it shows that the tram is not set properly, or that there is flexibility in the machine itself, with the force of the cut pushing the spindle out of alignment with the table. Taking light cuts for finish would not, I think, cause that.
What would happen if you just read one indicator and swung it 180 degrees, is the reading the same?
 

srfallsallot

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.005" cut depth. That is what I thought maybe the tram is not good but it reads .001 or less over 11 inches. Could the head really be that flexible?
 

francist

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My first thought was whether the material might be springing after the cut was taken, maybe from the clamping method or as a result of taking the cut off of one side. I know this is more typical in cold rolled stock, but it still crossed my mind.

-frank
 

srfallsallot

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The Al brick is~ 10" long ~2" thick and ~2.7" wide held in a 5 inch vice with the overhang equal on both ends.
 

projectnut

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Are you absolutely sure your trimming tool is parallel to the table and the indicator and mounting holes are absolutely square to the bar? An easy way to tell is to rotate it 180* and see if the readings are identical. Another way is to set up a test indicator on the table and run it across the bottom of the trimming bar.
 

srfallsallot

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As you can see in attachment 1 the tramming indicators read zero. Yes the device was zeroed by tuning it 180. It reads the same in the y axis. Many hours learning to tram the mill.
 

AGCB97

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Were both indicators zeroed at the exact same spot on the table? In other words zero one indicator and mark the spot on table then rotate tool so other indicator is on same spot and zero it.
 

Cadillac

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My guess would be spindle deflection. Either within the spindle bearings maybe the preload or in the tooling. Your holding a 10" piece in a 5" vise so theirs 2.5" of material unsupported and your measuring .002 diff. That's not to bad. Gibs tight table could be lifting with movement of table. What type of inserts are you using molded or ground. I'd be looking for something sharp.
 

RJSakowski

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A face mill in a properly trammed machine will make contact at both the leading edge and the trailing edge of the pass. However, it is common to see an arc with a depression in the center and/or the absence of cross hatching on smaller machines. There will always be a small amount of deflection due to the cutting force. Due to the relatively large diameter of the face mill, a small angular change will cause a noticeable vertical shift.

To see if it is a tramming issue or deflection, run the face mill in the opposite direction. If the pattern is still in the same direction, it is a tramming issue. If the pattern reverses, it is a deflection problem.
 

srfallsallot

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A face mill in a properly trammed machine will make contact at both the leading edge and the trailing edge of the pass. However, it is common to see an arc with a depression in the center and/or the absence of cross hatching on smaller machines. There will always be a small amount of deflection due to the cutting force. Due to the relatively large diameter of the face mill, a small angular change will cause a noticeable vertical shift.

To see if it is a tramming issue or deflection, run the face mill in the opposite direction. If the pattern is still in the same direction, it is a tramming issue. If the pattern reverses, it is a deflection problem.
A face mill in a properly trammed machine will make contact at both the leading edge and the trailing edge of the pass. However, it is common to see an arc with a depression in the center and/or the absence of cross hatching on smaller machines. There will always be a small amount of deflection due to the cutting force. Due to the relatively large diameter of the face mill, a small angular change will cause a noticeable vertical shift.

To see if it is a tramming issue or deflection, run the face mill in the opposite direction. If the pattern is still in the same direction, it is a tramming issue. If the pattern reverses, it is a deflection problem.
WOW that makes sense. The attachment 2 is exactly that experiment and the pattern reverses. So it is a deflection issue.
 

srfallsallot

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My guess would be spindle deflection. Either within the spindle bearings maybe the preload or in the tooling. Your holding a 10" piece in a 5" vise so theirs 2.5" of material unsupported and your measuring .002 diff. That's not to bad. Gibs tight table could be lifting with movement of table. What type of inserts are you using molded or ground. I'd be looking for something sharp.
My ignorance is showing. I have no idea what kind of insert. Whatever came with the face mill. The gibs seem to be adjusted well. There seems to be no slack in the adjustment. Just snug. .001" is not bad in 10?
 

srfallsallot

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I have laid a 123 block across the largest arc. A 0.005 shim will not go under it.
 
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M.T. Pockets

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I think this is most likely a deflection issue. Are all your gibs properly adjusted? Are you locking the z and y when doing these cuts? A simple brute force way to find deflection is to put a TDI in the spindle measuring off the table and then push on different parts of the machine as hard as you can and watch the TDI move.
 

srfallsallot

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I think this is most likely a deflection issue. Are all your gibs properly adjusted? Are you locking the z and y when doing these cuts? A simple brute force way to find deflection is to put a TDI in the spindle measuring off the table and then push on different parts of the machine as hard as you can and watch the TDI move.
I will try that. Thanks.
 

srfallsallot

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I will try that. Thanks.
I just did what you suggested. No mater how hard I pulled pushed on any and all parts of the machine I could get no measurable movement. I am now totally confused. i will start from scratch.
1 Tram the table.
2 Tram the vice.
3 Take very light cut in both directions to observe the pattern change or not.

If this is not the way to do this please chime in. Be patient please.
 

RJSakowski

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An important note is that when we tram the spindle to the table, we are assuming that the table is parallel to the ways. I know from experience that this is not always the case. The problem is compounded when we tram a vise. A properly trammed head is perpendicular to the ways, The x axis and the y axis define a plane or series of planes so that the x and y axes are parallel to the plane. It is one of these planes that is cut when we move the table by x and y. The table surface is a proxy for one of those parallel planes

Think of it this way. If you mounted a bar in the vise so it was inclined at a 10º angle and you trammed to that bar, you will have a head that is tilted by 10º.

As I said, my table is not parallel to the ways, as indicated by sweeping the table with a dial indicator. This is mostly due to the fact that the table lifts on the ways as it is dirven away from center due to clearance in the gibs. Since it is a CNC mill, it isn't possible to eliminate the clearance but it will definitely affect any tramming. To get aound that, I have an alumium plate that I mount to the table and mill a circular path the diameter of my tramming tool sweep, using a 1/4" end mill. This provides a fresh surface that by definition is parallel to the ways. I then tram in x and y on that path.
 

Cadillac

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One thing to remember is when most tram the head they are doing so in the middle of the travel of the table. The head will be trimmed at that spot of the table. Once you start traversing the table the head can come out of tram with the table from variances in table. Also when the table moves from side to side the weight of the table can be twisting the saddle causing out of tram conditions. Mount a gauge in/on the spindle and zero it out. Then traverse the table and see what you get.
Keep in mind that milling under .001 capacity is gonna be a challenge and the machine needs to be rigid and dialed in, tooling needs to be on point also.
 

srfallsallot

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Having spent 2 more days trying to tram and better understand the geometry of the machine I think I have an acceptable result. I measured the table in both x and y in relation the the spindle on the full travel of both axis and measured no deviation. That was a big surprise for me. I tried to tram this thing for many hours and could just not get it done. Finally got it less than .001" in both x over 11" and y over 9". I gave up at that point. I re-machined my Al brick again and as you can see it has cut pattern in both directions. You can see the cross pattern is not consistent but it is there. I cannot slip a .0015 feeler gauge between a 123 block and the surface and I can see no light between them. The thickness as best I can measure varies ~.0005". I do not know what to expect so this will have to do for now. My patience for this task is gone.

Thank all of you so much for your input and patience. I learn so much from you all.
 

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srfallsallot

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I just did what you suggested. No mater how hard I pulled pushed on any and all parts of the machine I could get no measurable movement. I am now totally confused. i will start from scratch.
1 Tram the table.
2 Tram the vice.
3 Take very light cut in both directions to observe the pattern change or not.

If this is not the way to do this please chime in. Be patient please.
I did not do this right the first time. I only set up to actually measure vertical motion. The second time I measured horizontal motion and got about ,011" in all directions.
 

M.T. Pockets

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I think the numbers you posted are more than adequate and about the best you could hope for given this class of machine. I doubt you will be making parts for the next Mars mission and for hobby use I'd say thats more than good enough.

Congrats, you've reached the final step of learning to tram a mill, where you just don't give a @#$% anymore! :cheer:
 

srfallsallot

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I think the numbers you posted are more than adequate and about the best you could hope for given this class of machine. I doubt you will be making parts for the next Mars mission and for hobby use I'd say thats more than good enough.

Congrats, you've reached the final step of learning to tram a mill, where you just don't give a @#$% anymore! :cheer:
Thank goodness I am not making parts for any one. I am just killing time learning how to do things.
 
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