New project - Mini VMC

[moto52000]

Hi, I used a old LM guide and bearing block with a large weight attached to it for my counter weight. Fortunately for me I have ~14 7ft long guides with bearings sitting around. (removed from robot assemblies) How long of a guide would you need? I hope to someday use them to make a mill similar to yours.

[Hack]

I ended up going with the cylinders for the counterweights. Used 2 equally sized ones - 1 on each side of the 2. The best I could find was one that will give me about 12" of z when done. Not to bad. I've got them mostly installed but have to finish them up. I had them on, but took them back off to paint the munting brackets.

Now my next road block. I am getting quite close to finishing this mill, just working on some bellows for the ways, but now i need a motor for the spindle.

I have purchased an R8 minimill spindle to use and wanted to use one of the motors from Keling, but I have read several bad things about the lack of torque here on the forum http://www.cnczone.com/forums/produc...ldc_motor.html.

I had even gone as far as machining a mount for the 1100W one. Now, they appear to be "out of stock" at keling, they are refunding some peoples money due to poor quality (not the fault of Keling, they are just providing excellent service in a bad situation). So now what.

Anyone got any suggestions for a motor around 1 1/2 HP with a frame size similar to a nema 34 notor? Will a servo motor work?

I want variable speed, controlled by mach 3, ability to tap, and decent rpms (say up to 5-6k). I'd like to keep the price including everything to 5 or 6 hundred if possible. Suggestions?

[CPK_Jim]

Did you ever find a motor for you spindle?

Jim

[Hack]

I ended up going with a marathon 1.5 hp 3 phase motor controlled with a vfd. I get reliable rpms up to 3500 controlled via mach 3. Works pretty well in forward, still need to figure out how to wire the vfd and controller for reverse, but it isn't something I have worked much toward as I am busy making parts and enjoying the mill.

I also need to get the reversing and braking working if I ever want to do any tapping. However, I ran across a tapping head that does not need spindle reverse to operate, so I may try that.

Machine works good, just learning my speads and feeds to quit wrecking tools so soon. I just bought g-wizard a while back and that has helped. I had no idea that this mill could cut so agressively until I tried some of the recommendations from it.

Dan

[asuratman]

Hi Hack,
How much total weight of spindle R8 plus motor 1.5 hp including box (I mean total weight milling head). I just built cnc mill, total weight spindle BT 30 is 18 kgs, motor is 15 kgs, box is 9 kgs. This is heavy, I think. I will use 1125 oz in servo DC from kelling (on order). Thanks.

[Hack]

You are about right. The total weight was about 90 lbs. I ended up adding a couple of cylinders (50 lbs each) to counterbalance the entire head assembly weight.

I use 1200 oz/in steppers with no trouble thus far.

Dan

[CPK_Jim]

What is the RPM of the motor?

Jim

[Hack]

It is 3600 rpm running one to one pulleys to the r8 spindle

[The Aspirator]

GREAT thread Hack! Just found it cause I'm planning my own build. I currently have an X2 mini-mill converted and it works "okay", but I want more rigidity, faster rapids, way more table size, and more power. Finding your thread was perfect for inspiration.

For aluminum is your 3600rpm enough? I keep mine at 4500 for pretty much everything, and could easily make use of 6000 or more for aluminum. Good choice with Gwizard, I love mine too!

What rapid speeds are you getting? I'd LOVE to see some more pictures and videos of this beast. Did you ever get flood cooling set up? You'll love it when you do.

John

[Hack]

Thanks for the complements. I originally started this thread with the intentions of documenting the entire build, but not many people appeared to be interested so I quit maintaining it.

The 3600 rpms seems to be ok. Most of my milling is with 1/2" end mills (2 flute) and the sweet spot seems to be about 3000 rpm for most of the aluminum work I do. I do run an occasional 1/4" end mill and on those occasions, it can be a limiting factor. I am pretty happy overall. I wouldn't want to go any less though.

I can get about 200 ipm rapids, but choose to limit it to about 120. I keep the accel rates pretty high so it gets to the 120 pretty quick. If I go to high though, it will stall. I attribute this to lack of precision surfaces where I mounted the rails. It binds just a bit. Nothing major, but it does limit performance. This thing is easily outperforms my old mill / drill in every way I have tried so far.

I did not set up the flood yet. I have had good luck machining dry and only using a squirt bottle with some liquid (dish soap and water) as needed.

An early "http://www.youtube.com/watch?v=6sc_qXkQE_A&context=C307fa2dADOEgsToPDskJHgEMDI5-yxpNlSzgztGve"]video before really tuning it.

And "http://http://www.youtube.com/watch?v=zTURgQz35hI&feature=mfu_in_order&list=UL"]reaming some holes

Dan

[jsheerin]

Dan, what I've found while doing my own build log is there are typically a lot of people who are interested and read your posts but don't post anything in response. Consider that there are 45 posts in this thread and almost 12000 views. That's way better than my ratio of 240 posts and ~30000 views. That's probably because you've built something while I'm still planning.

In any case, nice job - reaming the holes on your table looks like fun. Just sit back and watch it create tons of precisely placed holes...

[Hack]

You are probable right, about the people watching but not posting.

I have a full rightup of the mill fixture table on my website with more pictures if your interested in them.

Router Bitz - Home

Look under the "Current Projects" header.

Dan