• This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn more.
  • PLEASE: Read the FORUM RULES BEFORE registering!

Taking the CNC Plunge

jbolt

Active User
H-M Supporter-Premium
Can you post a better picture of the cut finish?

Have you tried a 2 flute end mill? With a 2f carbide end mill I would run that at 6000 rpm (my max) 22 ipm with a 40% step over for the roughing and a finishing pass at 10 ipm and .015 cut, both run as a climb cut.

The only 4 flute end mills I use on aluminum are the corn cob roughers. I prefer single flute chamfer end mills for chamfering.
 

Davd Flowers

Active Member
Active Member
No. I roughed out a 1.240" through pocket in a piece of 1/2" thick aluminum. The gcode I sent you is the pocket finishing pass.
Ok so the second pass

Finishing pass with a spring pass?? Ok going to back up a bit. have you checked the backlash of your X Y ball screws and what are your drivers set too? Micro stepping? What file format is the cad model in?
 

TomS

Active User
H-M Supporter-Premium
Can you post a better picture of the cut finish?

Have you tried a 2 flute end mill? With a 2f carbide end mill I would run that at 6000 rpm (my max) 22 ipm with a 40% step over for the roughing and a finishing pass at 10 ipm and .015 cut, both run as a climb cut.

The only 4 flute end mills I use on aluminum are the corn cob roughers. I prefer single flute chamfer end mills for chamfering.
I'll try to get a better picture. Haven't tried a 2 flute because the finish is so bad with the 4 flute.

I normally would run this job at 8000 rpm and 60 IPM with .1 stepdown and stepover for roughing. Finishing is done at full depth (.5) and stepover at .01 and 30 IPM. I've played with speeds and feeds to see if the surface finish get better but no change. I ran some mild steel parts before I changed out my electronics and the surface finish was superb. I'll try and get a picture of that part as well.
 

TomS

Active User
H-M Supporter-Premium
Ok so the second pass

Finishing pass with a spring pass?? Ok going to back up a bit. have you checked the backlash of your X Y ball screws and what are your drivers set too? Micro stepping? What file format is the cad model in?
Yes, finishing pass with a spring pass. My drivers are set for microstepping. I'll have to look at the specific setting. Can't remember because it's been so long since I set them up.

I have some backlash. About .002" in X and Y but as I said in my previous post the mild steel parts I made before the electronics upgrade had a very good surface finish.

The CAD model is Fusion 360 format. I've attached it below. Change the file type from .txt to .f3d and it should open.
 

Attachments

Davd Flowers

Active Member
Active Member
Dont know if you feel safe about running some one else's g code but if you do... Stock is 3"x 3"x .5" and X Y zero is center of stock and z zero is top of stock. I used a .250" engraver for the chamfer, but any size would work as long as it comes to a point.
 

Attachments

jbolt

Active User
H-M Supporter-Premium
Are you running the ESS on a dedicated 5v power supply?

For your finishes to degrade after changing the electronics suggests a problem with the settings or possibly electrical interference. I will see if I can get screen captures of my ESS configuration for comparison.
 

TomS

Active User
H-M Supporter-Premium
Are you running the ESS on a dedicated 5v power supply?

For your finishes to degrade after changing the electronics suggests a problem with the settings or possibly electrical interference. I will see if I can get screen captures of my ESS configuration for comparison.
Yes, I have a dedicated 5vdc power supply to the ESS.

Here's a picture of a steel part I made before the electronics changeout. Notice the very smooth machined edge.
20170720_083723_resized - Copy.jpg

A picture of the pocket in my test piece. Notice the faceted finish.
20170720_084639_resized.jpg

This is the part I made last week that prompted this thread. The exterior profile surface finish is "ugly".
20170720_084350_resized.jpg
 

TomS

Active User
H-M Supporter-Premium
Dont know if you feel safe about running some one else's g code but if you do... Stock is 3"x 3"x .5" and X Y zero is center of stock and z zero is top of stock. I used a .250" engraver for the chamfer, but any size would work as long as it comes to a point.
I'll see if I can find some time today to run the code. If not then it will be a week or so. Heading out of town in the morning.

Thanks for your input. I really appreciate it.
 

TomS

Active User
H-M Supporter-Premium
Yes, finishing pass with a spring pass. My drivers are set for microstepping. I'll have to look at the specific setting. Can't remember because it's been so long since I set them up.

I have some backlash. About .002" in X and Y but as I said in my previous post the mild steel parts I made before the electronics upgrade had a very good surface finish.

The CAD model is Fusion 360 format. I've attached it below. Change the file type from .txt to .f3d and it should open.
For reference my X and Y axis drivers are set for 1000 microsteps.
 

Davd Flowers

Active Member
Active Member
The finish on the first steel part is pretty amazing, no faciting at all.
On the aluminum one, i see some chatter marks as it comes past the ear. (Much better pics btw) Ive had similar when my headstock gibs were loose. It was more apparent on the backside of the part then the side facing you. Maybe try milling a square noting the axis on it and compair finishes on each side??
Not saying that its the problem your having, but making note of the axis on the part may help point in some direction.
 

TomS

Active User
H-M Supporter-Premium
I'll see if I can find some time today to run the code. If not then it will be a week or so. Heading out of town in the morning.

Thanks for your input. I really appreciate it.
I ran your code. Results were the same as the parts I posted above. What CAM program do you use?
 

TomS

Active User
H-M Supporter-Premium
The finish on the first steel part is pretty amazing, no faciting at all.
On the aluminum one, i see some chatter marks as it comes past the ear. (Much better pics btw) Ive had similar when my headstock gibs were loose. It was more apparent on the backside of the part then the side facing you. Maybe try milling a square noting the axis on it and compair finishes on each side??
Not saying that its the problem your having, but making note of the axis on the part may help point in some direction.
The faceting is the same all the way around the pocket/hole. Looks to me it's not axis related.

My headstock gibs, if anything, are a bit on the tight side. I haven't checked the X and Y gibs yet but it's on my to do list.
 

Davd Flowers

Active Member
Active Member
I ran your code. Results were the same as the parts I posted above. What CAM program do you use?
I'm using sprut cam all though I have been tempted to switch to fusion 360, but I would have to learn thier cad as well. I use alibre for cad and like it better than fusions.
 
Last edited:

Davd Flowers

Active Member
Active Member
The faceting is the same all the way around the pocket/hole. Looks to me it's not axis related.

My headstock gibs, if anything, are a bit on the tight side. I haven't checked the X and Y gibs yet but it's on my to do list.
Im at a loss....I do get some faceting but its pretty minimal. Ill have to see if I can get a pic uploaded for you to see.
 

TomS

Active User
H-M Supporter-Premium
Im at a loss....I do get some faceting but its pretty minimal. Ill have to see if I can get a pic uploaded for you to see.
A comparison pic would be great.

I've just about exhausted the possibility of a mechanical problem, except for checking the X and Y gib adjustment. I have to believe it's an electronics issue because I was able to get good surface finishes before I installed the new stuff. I'm hoping it's a simple fix.
 

TomS

Active User
H-M Supporter-Premium
Are you running the ESS on a dedicated 5v power supply?

For your finishes to degrade after changing the electronics suggests a problem with the settings or possibly electrical interference. I will see if I can get screen captures of my ESS configuration for comparison.
Jay - I agree with you that it's a configuration issue or electrical interference. That's the only thing that's changed since I ran parts with good surface finish. Screen shots of your configuration would be great.

Thanks
 

jbolt

Active User
H-M Supporter-Premium
Jay - I agree with you that it's a configuration issue or electrical interference. That's the only thing that's changed since I ran parts with good surface finish. Screen shots of your configuration would be great.

Thanks
Will do. I should have some time tonight to do that. Between work and remodeling a bathroom there has been no time to play!
 

jbolt

Active User
H-M Supporter-Premium
Tom PM me your email. I thought I had it but I'm not finding it. I had to take photos of the screen since my machine pc does not have a way to properly save screen captures. The files will reduce too much if I post them here to be useful.
 

jbolt

Active User
H-M Supporter-Premium
Another thought. I can get poor finishes if the coolant isn't filtered or the coolant spray isn't flushing the chips away quickly enough.
 

TomS

Active User
H-M Supporter-Premium
Another thought. I can get poor finishes if the coolant isn't filtered or the coolant spray isn't flushing the chips away quickly enough.
Don't think it's coolant because straight cuts in X or Y leave a very smooth finish. The rough surface finish appears on radius', angle cuts, and circular pockets.

I've read quiet a bit about improving surface finish and found a few tweaks for my CAM software and Mach3. Tried them out today and no change. Next I tightened the X and Y gibs until the motors stalled then backed off the gib adjuster until the motors would move the table and saddle to there extremes without missing steps. Still no improvement in surface finish.

I've got a Gates drive belt on order to replace the eBay import belt I'm running now. You never know.

I've heard that some people have had surface finish problems with angular contact bearings. I don't understand that comment mainly because high end precision spindles almost universally use AC bearings. On the other hand I could have a bad bearing. If the new belt doesn't help the situation I'll start looking for a new lower bearing.
 

jbolt

Active User
H-M Supporter-Premium
Don't think it's coolant because straight cuts in X or Y leave a very smooth finish. The rough surface finish appears on radius', angle cuts, and circular pockets.

I've read quiet a bit about improving surface finish and found a few tweaks for my CAM software and Mach3. Tried them out today and no change. Next I tightened the X and Y gibs until the motors stalled then backed off the gib adjuster until the motors would move the table and saddle to there extremes without missing steps. Still no improvement in surface finish.

I've got a Gates drive belt on order to replace the eBay import belt I'm running now. You never know.

I've heard that some people have had surface finish problems with angular contact bearings. I don't understand that comment mainly because high end precision spindles almost universally use AC bearings. On the other hand I could have a bad bearing. If the new belt doesn't help the situation I'll start looking for a new lower bearing.
If the straight cuts are smooth I would not suspect the bearings.

I'm not sure this is related to your problem but have you tinkered with the CV setting in Mach3?

http://www.machsupport.com/wp-content/uploads/2013/02/Mach3_CVSettings_v2.pdf