cnc programs cutting wrong sizes (new bantam tools cnc )

[rajsumanth9]

Hi  ,

this is Rajsumanth , we recently bought bantam tools desktop mill .

we observed that we don't get  the results correctly to the required dimensions. I have attached the file we used for test , we are using 1.5mm flat endmill 6mm shank , in the design there is 1.9 mm hole and 30.10 mm profile to be done

after machining we get results of 2.5 mm center hole and 30 or 32 sometimes , we are in a situation that is this the problem in the machine or my programming mistake.

we are  also ready for remote guidance through teamviewer or any

thank you
Rajsumanth Banepalli

[HughesTooling]

You have your 2 OPs set to in computer compensation so Fusion is creating the toolpaths offset by the radius of the cutter.

Checking the posted code in NC Corrector shows the code is correct, 0.4 diameter for the inner hole and 31.6 for the outer. The small hole could be a problem at the feedrate you have selected, the machine in going to struggle doing a 0.4mm circle at that feed. Don't think I'd want more than 200 mm/m, even that might be too high,

You might want to download NC Corrector here.

Mark

[rajsumanth9]

 sir , how can i get accurate sizes and what should i set the compensation type to

[HughesTooling]

There's nothing wrong with the code, it's your machine. For the small hole I'd guess the feedrate is too high and the machine is losing accuracy might also be the same problem with the outside diameter as well. You'll need to experiment with slower feed rates to see what is best.

[rajsumanth9]

sir , generally I use default feeds while programming but i run the machine on 10% feedrate even the i get above 31mm for outer profile instead of 30.10 mm and 2.5 mm for center holes 1.9 mm

the machine is new , I'm in a bit dilemma is this the fault of machine or my programs

[HughesTooling]

Have you checked the machine to make sure it's setup correctly. 

[rajsumanth9]

sir , I'm using automatic probing for stock location and Z-depth  , I also tried manual xyz locating also

[HughesTooling]

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@rajsumanth9 wrote:

the machine is new , I'm in a bit dilemma is this the fault of machine or my programs

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The program is correct. Download NC Corrector so you can check the code yourself.

Mark

[rajsumanth9]

yes sir , thank you for your help , now I can confidently talk to the machine supplier

[HughesTooling]

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@rajsumanth9 wrote:

sir , I'm using automatic probing for stock location and Z-depth  , I also tried manual xyz locating also

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Have you tried to check the size of a known length to make sure the machine. Measure something like a 100mm slip gauge.

[rajsumanth9]

sir , I didn't understand known length , can you please let me know how to check the machine

[HughesTooling]

Use something of a known size like a slip gauge.

[rajsumanth9]

now i understand its used for measuring the accuracy

[rajsumanth9]

hi ,

we started milling on bantam desktop milling machine and we get 0.3 variation , even with the drilling operation with 1/4 inch bit we get 6.7 mm dia hole , couldn't figure  out where we are getting wrong.

used low feeds high rpms , low feeds moderate rpms but get 0.3 0.2 variation always

could anyone please help us

[HughesTooling]

OK, this sounds like the tool is running out, not concentric with the spindle. Do you have a dial test indicator? Test if the tool runs out if you turn the tool by hand.

Similar to this but against a part of the tool above the flutes.

[rajsumanth9]

okay sir ,

i trust your suggestion and I will follow that .

i have recently met the support  and explained him the problem , he suggested me that there is no problem with the machine but there is problem in your calculation ,

I used the same tool which I programmed with , but get these variation in all the programs.

I feel there is nothing wrong in my programs and what can go wrong in a simple drill program

[seth.madore]

If you're drilling with an endmill, these results are not surprising. What material are you working with? Is your tool "center-cutting"? Endmills are not the typical "tool of choice" for axial drilling into solid material, as they are not designed for that task. What ends up happening is your tool starts "walking" around as there is unequal pressure on the flutes, unlike what happens with an actual drill, where the grind of the tool equalizes the cutting forces (assuming a properly ground tool point)

[rajsumanth9]

sir ,

i'm using aluminium 6061 , general 1/4 inch flat endmill four flute

[rajsumanth9]

okay sir , I will use for drill for making holes , but i'm getting 0.2-0.3 mm variation in the final result struggling to verify if its my fault or machine fault

[b.page12]

Just FYI, through excessive testing at our shop, the Bantam CNC Desktop Mill does not have enough torque to do drilling operations.  This is very frustrating, as all of our designs require mounting holes.

I have tried drilling using speeds of 28,000 rpm with a peck depth of .001", and it still locks up the drill.  This machine is just not robust enough to do it.

Just as you cannot mill more than .001" of material at a time.  if the motor beefier, it would be a much better machine.