tolerance and roughness

[LeanitRoberto]

hi to everyone, I'm new to the forum, my name is roberto and I'm consulting for the streamlining of design and mechanical production.

I am making a project with a client who has a working department with nc machines, currently programmed by the keyboard of the machine, I found in the company a working mastercamx3 license, I believe purchased in 2008 and never used. as first step I want to use it to determine the processing times of new requests coming from the technical office, I have available the stp file of the finished and pdf design. Currently quotes are made in excel, I would like to make some experience and put in motion mastercam, then update the license and put it in production.

I have a couple of questions that are probably so basic topics that in the various tutorials I have seen on the internet are given perhaps for discount: I have to make trees with bearing mounting areas, pickers and sealing seals, they are usually more than 3 meters long details and therefore wrong the speed of advancement entails very wrong estimates of working times.

if I have to realize areas with roughness 1,6 or 3,2 how do I determine which progress to set? Is there any mastercam functionality that helps me (given the radius of the tool), or is it an information that I have to give to those who sell the tool plates?

regarding tolerances I have for example an area with +0.2/-0.2 and a zone 100h6 (which means 0/-0.02), there is a way to set on mastercam the nominal quota and make sure that the finishing process is automatically centered in the center of the tolerance zone (in the example would be 99.99)?

I expect that if I have to make a diameter with +0.2/-0.2 and roughness 3.2 the finish is much faster than the same processing (same diameter and same length) but with h6 tolerance and roughness 1.6

hello to all and thanks for the collaboration
good day and good work
roberto

 

[NL2500SY]

I don't know if there's a mastercam way to handle various advances along the profile, I usually attribute a speed at the time of choosing the tool to use and then I differ the various speeds in the list that comes out from the postprocessor, relying on the experience gained in the years.

 

[NL2500SY]

the formula I have here is rmax= (f[SUP]2[/SUP]/(8*r))*1000 [µm]where rmax is the final roughness you find on the design
where f is the advancement to the round
where r is the radius of the plaque

from this equation you should be able to get the data you need using the known data.
I hope I've helped you.

 

[ninfh]

The only real answer... It's just needing experience

the tool supplier can also give you some data, but the parameters you find in the tool catalog will never be the ones you really use in the machine (even if it is a pass to grow)

depends on the material, the machine, the geometry of the piece, how long you want the tools to last etc etc.

 

[LeanitRoberto]

thanks for the info, in fact I am a little rusty on the topic, I removed the dust to the book of mechanical technology of itis and I recovered some info, adding the experience of the lathers that I have in offina and the information of the catalog sandvik I found that:
- larger radius = greater robustness but greater power and greater vibration
- generally advancing must be less than half point radius


therefore for example ra 6,3 with radius plaque 2,4 involves advancing max 0.53, while ra 1,6 with radius plate 0,4 involves advancing max 0.11mm/turn (using the formula nl2500sy turn out advancements about half, the experience will tell me if I have to stay more conservative and use the formula or can go faster as the catalog of plaques says).

If the cutting speed "normal" (duration 15 min.) is 250m/min, the cut at 0.75 for a 45-minute duration and the cutback of 0.778 due to the hardness of the material to be turned, it turns out that for a diameter 200 each meter of turning it involves 9 minutes to high roughness and 41 minutes to lower roughness.

I found a guide where I found a whole set of basic info here:http://www.vfioraso.it/4anno/aula_digitale/pagine_htm/data/2/guida_tornitura.pdf

ciao