What to expect Tramming Cutting

[RJSakowski]

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]

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]

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]

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

 

[M.T. Pockets]

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]

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]

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]

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.

 

[srfallsallot]

Oh my this is getting complicated. Thanks.

 

[Cadillac]

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.