Need Help!- Simple Problem -

[bzepeda]

Set up and goal:
Drafting with alibre. Using sprutcam 2007. Wanting to remove simple cylinder worth of material. Using pocketing to machine it. I have machined a few drafts with acrylic to confirm the code outputs the desired diameter.

Problem:
Diameter of my test acrylic run is never the diamter I intended it to be. I figure its just me experiencing a learning curve. I need help figuring out what my diameter of the final piece will be based on the g-code. I hate wating a hrs for a test piece to finish.

Im falling behind real quick on my project. Im a total newb.

Attached is one of my several failures. I thought I almost had it on this one when I saw the stock paramater setting.

[levon18lopez]

hello" i will download your file

[bzepeda]

Originally Posted by levon18lopez hello" i will download your file

thank you!

[pit202]

what is your desired diameter ? what are your desired tolerances ? are you using same tool in SC and on the mill ? why have you used
"pocketing" instead of "rough waterline" if you are importing IGS file , similar effect you can achieve in "Hole operation" and choice "Hole pocketing" strategy.

feel free to ask , I can make you a video if you like , just tell me what is your goal.

Peter

[bzepeda]

My final goal is to make threads on a block of aluminum. I need to make both internal and external threads on this part. However before I can even embark on learning to thread I need to make the major and minor diameters on the stock. Correct?

Desired diameter is 2.0475'' with tolerance of 0.0001''. 1/2" end mill on both SC and mill. Using PCNC1100 machine. I have not used waterline because:
1. I am not familiar how to create that type of of tool path.
2. I am not sure what are the advantages and disadvantages of them.

Therefore if you can point me in the right direction on how to learn how to create these diameters cuts it would be a life saver.

[wvines]

The top of the hole is larger than the bottom. This is caused by the "Relief angle" setting on the Parameter dialog being nonzero. The default value is 3 degrees so change it to zero and it should work.

Here are a few more suggestions:
- Check your feeds and speeds. A Tormach can do that cut in MUCH less than an hour.
- I never do a straight plunge if I can avoid it. Try using a spiral or zigzag plunge.
- It's very unlikely that you will need 0.0001" tolerance anywhere, especially on a threaded hole. Even if you need it, it's unlikely you can achieve it.

[bzepeda]

Thank you for the advice on the relief angle! Will try.

What feeds and speeds do you recommend for cutting aluminum 6061 with carbide end mill?

What is a reasonable tolerance?

[wvines]

Get a free (for now) copy of G-Wizard. It has a feed and speed calculator that works well. The feed rate given by G-Wizard works well for straight-line cuts. But since you're cutting an inside arc the feed rate will need to be reduced to keep the same chipload. Take a look at this book for a formula.

G-Wizard also has thread data in a handy format that shows the tolerance range for many thread dimensions. Otherwise, check out the tables in Machinery's Handbook.