Made a part today!

[mcphill]

A couple pix... Used this tool:



to create this surface finish:



VERY happy with it, I don't need a good finish at all and was "not even trying", but it turned out fantastic!

I then mounted my vise to finish the part, and did a better finish cut as well (last finish was done in three passes using 2 different clamp setups, in the vise I could do 2 passes in one setup and be done with it):



Put together a quick YouTube of the part I did today as well, will post in a reply when it is done uploading.

VERY successful day today, I am

[mcphill]

Here's the video:

http://www.youtube.com/watch?v=SSf8PRANhew]Mikini Machineing Ops - YouTube

[SWATH]

Nice job! Man that 6061 looks like it cuts like butter compared to what I'm trying to cut.

[mcphill]

Nice job! Man that 6061 looks like it cuts like butter compared to what I'm trying to cut.

In comparison you are absolutely right. HT Steel is tough stuff! Can you disclose the part you are making (what it is for)?

[SWATH]

In comparison you are absolutely right. HT Steel is tough stuff! Can you disclose the part you are making (what it is for)?

Rifle parts. I knew it was tough stuff to cut after I realized that I couldn't even bend one of the thin chips with my fingers. In my limited experience the issues with cutting this stuff is not so much dulling the carbide, it is chipping it. All my used carbide endmills are still very sharp (almost brand new like they had never been used) but the corners are chipped off. I suppose a radius endmill or ball mill may work out better in that regard but I've been slowing down the feed rate and avoiding any kind of plunging into the material and it had helped. I going to shift strategy and do like Brian suggested and aim to keep the recommended IPT, S, and F but limit the WOC first then the DOC next. As I understand High Speed machining strategy (which my CAM does not support yet), other than constant tool engagement, it tends to favor a heavier DOC and lighter WOC because you can use more of the flute length of the tool. I've also found roughers tend to offer significant resistance to chipping because they have radius corners and I supposed harmonic chatter is greatly reduced, I would also like to try variable flute endmills at some point and maybe even indexable endmills so chipping doesn't end up be so expensive.

[Brian L]

Chipping is almost always an indication of not enough feed, or chatter. The lack of feed results in too fine of a chip and you end up re-cutting them instead of having them evacuate the area.

It does help a lot of you have endmills without dead sharp corners too, either stone a small chamfer on the corners or buy endmills with specific radii ground on the corner.

[SWATH]

Chipping is almost always an indication of not enough feed, or chatter. The lack of feed results in too fine of a chip and you end up re-cutting them instead of having them evacuate the area.

It does help a lot of you have endmills without dead sharp corners too, either stone a small chamfer on the corners or buy endmills with specific radii ground on the corner.

Other than stalling that was the other reason I slowed down the feeds. I read that dulling tools is a symptom of going too slow and chipping them is a symptom of going to fast. I had done two identical cuts except the first time I did it I decreased the F with a 50% override and it cut fine. The the next time I did it I forgot to lower the feed so it was 100% and it chipped the corners of the endmill. I concluded that my DOC was too deep for such a fast F (both were full slots), and it put too much pressure on the flute tips. It also made more chatter noise that that was probably the immediate cause for the chipping.

Another instance was similar doing two identical cuts except one CAM path had the endmill slowly plunging in the the material for the Z step downs which chipped the edges of the endmill. So I tried it again but with a 2D side entry for every Z level instead, and this did not chip. I concluded that plunging puts too high of a load on the flute tips and have tried to do 2D side entrances from the side or first drilling out relief for the endmill to descend in to instead.

Another issue when I was trying to eliminate the chatter was adjusting the F during a cut. I would start out with a slow cut and it would chatter and squeal so I would gradually increase the F thinking that at some point it would go away, but instead it would just gets louder and louder and louder until either the spindle would halt, the axis motors would start stuttering, or the noise would just be out of hand and I knew that bad things were about to happen.

Conversely, I was MDI slotting to experiment with S and F and accidentally discovered something. At my "normal" S and F that is slow but doesn't squeal too loud was something like F5 or F10, in that range. I was adjusting upwards to find a happy place where it was relatively quiet as in no high pitched squealing or chirping. Again it kept getting louder and louder and I thought maybe I was going in the wrong direction. When resetting the location for another pass I commanded a G0 but forgot to go back and command a G1. So to my horror (at first) the endmill raced through the material at F75. The first thing I noticed was that it was far quieter than the slower feeds were. I also noticed the finish was not as good but who cares if your roughing right? I have been reluctant to try that again because that was awhile ago with a different spindle board and I'm afraid the current one would stall. In addition to being a pain in the ass to clear a spindle halt alarm, it almost always chips whatever tool I have in at the time because the axis is still trying to move with the cutter not spinning.

[Brian L]

Well, I agree with going to slow dulls them, I dunno about too fast chipping them..... I've never had that experience until you reach the point of feeding too fast and the endmill literally snaps off, I guess that qualifies as a big chip.... :-)

Plunging in with an endmill is never a great situation, either drill a hole first, start off the part and feed into the part, or ramp down into the part either with a straight move in one axis while feeding Z minus, or you can helical down into the part. I made some vise jaws for my Kurt vise the other day and made a video, it's pretty crappy at first, didn't realize the control cabinet was vibrating, but that only lasts about 30 seconds.... you can see where I feed across the part, that's 3000 rpm and 25 ipm, (I can't go a whole lot faster yet, still tuning my servo drives and above that amount I get a following error). Then on to the helical down into the counter bore, .76 diameter about .56 deep, think that was 10 ipm, and them thru the rest of the jaw at .520" diameter, that's with a .500 endmill, so only swinging a .010R circle, slowed that down to 3 ipm I think....

I wouldn't normally run like this as it's slow, but I didn't feel like changing tools...

<iframe width="420" height="315" src="http://www.youtube.com/embed/KsIdsVXYEZk" frameborder="0" allowfullscreen></iframe>

[BPR]

Aloha All,

I've been swamped lately and haven't had time to work with my mill until now. I am having problems with Mach3's latest version it seems. When the machine references home under Mach, the steppers seem to jump (the crunching sound) like when you try to use the Jog Pendant with X10 to fast. It jogs fine using the keyboard... smooth as silk, but when I try to run some code, NOT smooth. I have been waiting for Phil to call me back, but I won't hear from him until tomorrow I guess. BTW, I'm running the latest lockdown of Mach instead of the version that shipped with the mill. Don't know if that is part of the issue or not. What version are you guys running.

Anyway, if anyone knows what is going on, I'd appreciate the feedback, otherwise I'll post what Phil finds out tomorrow. Actually, he is supposed to come out in Jan for some R&R so I expect to spend some time with him on my mill.

I really liked what I saw with the UMC running Flash Cut! Wow! Man what a nice little machine. Wonder if you could get Dave to build one to sell? Damn, that was one of the nicest looking little mills I've ever seen. I love the detail and materials he used, like the bed not being cast. Sweet.

Anyway, MCPhil, how is your Mikini doing? Looks like SWATH has his under control. Ive had my share of little hiccups, but now I finally seem to have the bugs worked out, except for this latest crunching which I know is a software/Settings issue.

Anyway, just wanted jump in and see how everyone was doing. I'll try and be more active now that I am going to be using the mill. Later!

[mcphill]

My machine is going well right now. I have lost two limit switches, so I can't home anymore (I have one replacement that I have not gotten to yet). Not a big deal, though, as I am setting my 0,0,0 for each job anyway. The only PITA part is that I can hit the hard limits on the Mikini instead of soft limits in Mach, so I have to do an entire machine reset and re-0,0,0 when I run too far forward...

I finished the project that I started this thread for, will post more details in here later today - been WAY busy lately on the Mikini and other stuff!

On your homing issue, check the accelerations in your motor tuning section. Mine were X and Y at 35 (or 40?) and Z at 25 (or 20?). I was getting horrible stuttering on faster arc moves (anything over 40 ipm). I lowered the acceleration to 25/25/15 and the movement is now smooth as silk, and I don't "see" an change in speed. There is probably a measureable difference of a few seconds in a 15 minute job, but clearly it is better to have the accel lower rather than too high. I may even lower it more - I see no harm in it unless it gets so slow that the machine has to crawl to do speed changes and I am NO WHERE near that point right now.

The UMC 10 IS for sale. I e-mailed Dave. I got this reply from him yesterday:

I am putting together 12 machines which should be available in about two months. Price is $22,000.00 FOB

He had originally stated $18k, which I was considering, but now that the price has crept up and I have gotten more experience under my belt, I think I will stick with the 1610L. NO QUESTION that if I were to buy a machine today, though, it would be the UMC10. WOW! Feature PACKED and worth every penny, imo. The only downside I see is the table is a tad smaller than the Mikini (which at times already feels cramped for me)...

[mcphill]

Status Update.

Here is the first part coming out of the (first) aluminum mold I made:



Finished part top:



and bottom:



Learned a TON doing this, and pretty happy with the outcome. BUMMED because I am a dumbass and didn't design the part the right size, so the cover doesn't fit right!



Hopefully what they say is true: "It's the thought that counts"... A total of about 60 man-hours in to a 4 piece paperweight...

[Brian L]

Nice work! Pretty ambitious project, multiple piece injection mold. Size wise, too much shrinkage or an oops in calculations?