A2Z Monster Mill: Circular Pocketing

20/10/2012

I've to blame Terence again (seemed like he is so nice to pin all the blames on...). He mentioned that his mill couldn't cut a true circular pocket while he was working on the turner's cube on his mill. His remark reminds me of the video posted by Hossmachine. He was testing the backlash compensation settings on Mach3 by milling circular pockets. This stirred me to do the same test as the backlash comp in my Mach3 setting was just done a couple of weeks back.

The test was done on the same piece of aluminium stock used in the afternoon to test DOC. The Circular Pocketing Wizard in Mach3 was used to generate the GCode for a 20mm diameter circular pocket. As the test was to see how round will be the circle, I set the DOC each pass conservatively at 0.25mm.

Mid way through pocketing. The feedrate I set is painfully slow at 150mm/min.

Done finally...

4 measures were made. The closest to the diameter I set: 20.24mm. Why the 0.24mm from my 20mm diameter?!

My circle is not very round too - I'm out by 0.03mm.

2 things I've to get settled before I start on any projects using this mill:
1) Motor Tuning - to make sure that when I say move 10mm, the table indeed move 10mm (or within a certain range which I'll try to figure out what's good enough).
2) To measure backlash again - Maybe 0.03mm is good enough but let's see how much more I can bring this down. Again, no target set yet.

I've a video taken when the mill was making the 2nd last pass. I am wonder, if any kind soul out there can help answer, if the sound created by the endmill plunging into the workpiece is a sign of things not done right.

Do drop me a comment please.

Ok, I'm supposed to get ready the Sherline Lathe so that Terence can pick it up tomorrow night. I want him to try playing on a lathe before deciding which one to buy. Problem is, I'm feeling really tired. I'll try setting it up tomorrow morning if time permits. Got to reach Alicia's church by 9.30am.

I am tempted to go for the Wabeco D4000 when Terence asked me if I am thinking of letting go of the Proxxon PD400. This presented an opportunity to go for the lathe I always wanted but settled for my 2nd choice due to budget. I'll have to give this some thought given the uncertainty in the market. Also, I've not explored the full potential of the Proxxon. It will be a waste to swap it out at the moment. I'm rather divided...

12 Comments

Gene King

20/10/2012 10:29:52 pm

Wong, on the plunge, that is just what mine sounded like. I started using the circular ramp in BobCad and got rid of the shuddering plunge. Your .25 mm depth of cut is about the high end of what I use on my mill.

GeneK

Wong link

21/10/2012 12:58:13 am

Hello Genek,

You mean 0.25mm for the monster mill set up is already about the higher end? I was hoping for a deeper depth per pass. Otherwise, I'll have to take like 2 hours to even longer to finish each job... sigh...

Looks like I've to figure out how to CNC my Wabeco Mill...

Wong

Gene King

21/10/2012 06:04:05 am

Wong, I tend to cut shallow and run at higher feed rates on pocketing so that the chips are like dust and don't pile up and break the bit. On profiling I run deeper since the chips fall away.

GeneK

Gene King

21/10/2012 06:04:29 am

Wong, I tend to cut shallow and run at higher feed rates on pocketing so that the chips are like dust and don't pile up and break the bit. On profiling I run deeper since the chips fall away.

GeneK

Gene King

21/10/2012 06:04:44 am

Wong, I tend to cut shallow and run at higher feed rates on pocketing so that the chips are like dust and don't pile up and break the bit. On profiling I run deeper since the chips fall away.

GeneK

Gene King

21/10/2012 06:05:10 am

Wong, I tend to cut shallow and run at higher feed rates on pocketing so that the chips are like dust and don't pile up and break the bit. On profiling I run deeper since the chips fall away.

GeneK

Loke-Yeow Wong

21/10/2012 06:28:23 am

GeneK,
I see... What feed rate do you normally use for pocketing?

When profiling, how deep do you normally go? How fast?

Regards,
Wong

Gene King

22/10/2012 05:10:48 am

Wong, I haven't run for quite a while so I looked back at some older projects. On pocketing I ran about .006" deep and 8 to 12 inch per min. Profiling was 0.125" @ 20 Ipm. Remember I am still running sherline steppers on their controller. I haven't gotten the money together to upgrade to a Gecko controller and larger steppers.

GeneK

Loke-Yeow Wong

22/10/2012 01:59:18 pm

GeneK,
Thanks for your input.

Converting the numbers:
0.15mm at about 200mm/min for pocketing & 3.175mm at 300mm/mm

Seemed like I'm still too conservative. Like what Bob Warfield said, I'm babying the cut. Just don't have the guts to try. Maybe I should. Break a couple of endmills and learn from there.

Terence Ang

22/10/2012 04:40:23 pm

3.175mm @ 300mm/min? Seriously that scares the shit out of me. I really got to tweak my mill, tighten the gib on the X axis and Z axis, Y seem to be perfectly fine. Also took Wong's advise to mount the Mill on something, got some MDF and now looking for some nice rubber feet. My plunge cut sounded worst than yours on the video, somehow ramping the plunge don't work for Sheetcam, I simply cannot figure it out. In the end my workaround is to do .1mm spiral plunge cut in the middle at F200, then another pass to cut the circles at around .3mm at F180 to 200.

Loke-Yeow Wong

22/10/2012 05:13:43 pm

Terence,

I'm still too chicken to go beyond 1mm. F300 sounds scary to me too. But if GeneK can do it, we should be able to do the same.

As for the rubber feet, simple ones will do. I bought mine from Homefix.

Wong

23/10/2012 02:51:14 am

Wong, I'll ad that in pocketing I usually run a 3/32 inch end mill and profiling usually 1/4 inch. Other than breaking end mills when they are small my main problem is losing steps.

GeneK

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A2Z Monster Mill: Circular Pocketing

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