[lapoltba]

Hello everyone. This is my first post, but I wanted to share my machine build with you all. I already have three videos I posted on youtube and the links are below.

I am starting with a stepper driven positioning stage from a decommissioned SEM (scanning electron microscope). I have all the stepper motors from it and it is driven by ball screws and has linear cross roller bearings. I chose to use the tbh6064 stepper drivers from massmind.org and I will be using Linuxcnc (emc2).

I am still waiting to order my spindle, but I plan to use a 0.8kw air cooled spindle from ugracnc.com.

I plan to document my build progress, although much of it has already been completed, here. If you have any questions please feel free to ask. I'll try to upload some static pictures tomorrow or this weekend.


First Run - CNC PCB router project - YouTube
CNC PCB router update 1/19/14 - Electrons - YouTube
CNC PCB router electrical panel finished. - YouTube

[lapoltba]

So I take it this part of the forum doesn't get much traffic.... I figured there would be at least a few questions about the positioning stage I'm using.

Anyway, just a little update. I got my spindle yesterday and the VFD last week as seen in the video. I decided to splurge and order from Ugracnc. I got the 0.8kw air cooled square spindle. First impressions yesterday was that it is a very solid spindle for the price. Fit and finish is excellent and it seems like some thought was put into the unit. I measured runout of the taper with a 0.00005" test indicator and it didn't even wiggle. I also put a brand new 1/4" collet and carbide end mill in and checked again with the same result. I'm guessing it's somewhere less than 25 millionths, simply amazing.

Tonight I soldered the connector and wired it to the VFD. Once I did a factory reset on the drive and set the critical parameters before doing an auto-tune, I had the motor running with no issues. I took another 30 minutes or so playing with the accel/decel times, braking, and current limits and I am very happy with the result. It spins up from 0-24000 RPM in ~5s and back to a stop in about 8s. I plan to get a braking resistor to help with the braking a bit, but it works fine as is.

Can't wait to get it mounted up and do some cutting.

[doorknob]

People (such as myself) are probably just envious of your ability to get your hands on a precision X-Y table like that.

Any more where that came from?

[Jay C]

That's a beast of a machine, what is your intended application?

[lapoltba]

I originally intended to use it for PCB routing and other routing type projects. It is a bit overkill for that, but I would like to be able to do micro-machining too. It has a very small z travel, but it should be sufficient, considering I won't be able to run large diameter tools anyway. I have a very nice grinding vice I plan to use and I would like to put some sort of walled table on it so I can use flood or mist coolant.

[lapoltba]

So I take it this part of the forum doesn't get much traffic.... I figured there would be at least a few questions about the positioning stage I'm using.

Anyway, just a little update. I got my spindle yesterday and the VFD last week as seen in the video. I decided to splurge and order from Ugracnc. I got the 0.8kw air cooled square spindle. First impressions yesterday was that it is a very solid spindle for the price. Fit and finish is excellent and it seems like some thought was put into the unit. I measured runout of the taper with a 0.00005" test indicator and it didn't even wiggle. I also put a brand new 1/4" collet and carbide end mill in and checked again with the same result. I'm guessing it's somewhere less than 25 millionths, simply amazing.

Tonight I soldered the connector and wired it to the VFD. Once I did a factory reset on the drive and set the critical parameters before doing an auto-tune, I had the motor running with no issues. I took another 30 minutes or so playing with the accel/decel times, braking, and current limits and I am very happy with the result. It spins up from 0-24000 RPM in ~5s and back to a stop in about 8s. I plan to get a braking resistor to help with the braking a bit, but it works fine as is.

Can't wait to get it mounted up and do some cutting.

The positioning stage, as I said came from a Scanning Electron Microscope (SEM). It was part of a semiconductor fab at my school. The Microelectronics Engineering dept. had a fairly good sized fab lab, but all the equipment was 20-30 years old. The machine this came from was being decommissioned and scrapped. I believe it was a photo-lithography/inspection machine of some kind, I never asked what it did exactly. The whole stage was mounted inside a very large and very heavy steel vacuum chamber. The whole unit was sitting in the Machine shop (lab) where I worked for a month or so. I had my eye on it and after a while I had to ask what they were doing with it.

It was earmarked for another lab on campus that wanted it for something silly and had no idea how to use the stages. It sat around long enough, and the shop manager got tired of looking at it and they lost their chance..... I spent a day dismantling the vacuum chamber, extracting the stage, and then brought the steel to the scrap yard. All-in all, The $ I got for scrap has paid for everything except the spindle so far.

Everything, with the exception of the linear bearings and ball screws, in the machine is nickel plated. I believe the frame is aluminum (mostly), but the whole thing weighs at least 125lbs. The Nickel plating is to reduce outgassing of the material under vacuum which will ruin silicon wafers with micro-e on them.

The stepper motors are Superior Electric slo-syn brand, but they are not a standard part number. It took me a lot of searching to get any info, and the manufacturer was no help. They are a custom unit and without an NDA they would not release ANY info. Funny enough, I found a website made by a guy that used to work for Superior Electric that had a database of nearly every motor they ever made. I was able to find datasheets for both the single stack and double stack motors I found. They are 1.25V 3.8A motors, and I am driving them with 24V at about 3.5A right now.

If you have any other specific questions feel free to ask.

[blinkenlight]

Very nice piece of kit, I'm curious to see how exactly you plan to implement the Z-axis. My only concern is that the axes seem to be rather exposed (original application obviously had no issues with that); the second you start milling something eeeeeverything will be full of swarf.

[lapoltba]

The z axis is there. If you watch the video I show it quickly. It is a wedge setup which limits the travel to about 2-3". The spindle will be attached to a length of 1.5x3" 80-20 via a steel bracket with gib/keyway arrangement for quickly adjusting working height. The gantry will be attached to the existing side frames which are stationary. They already have 4x10-32 tapped holes, but I will probably drill them out for 1/4-20 to attach the brackets for the 80-20 gantry.

The tilt axis of the table will be locked in place and will serve as an easy way to tram the table in the y-axis direction. The x-axis will be trammed by loosening the spindle mounting plate on the gantry and tweaking it. Once the table is trammed, the gib arrangement will allow me to quickly adjust the spindle height to put whatever I am working on into the z travel range.

The open bearings/screws aren't exactly ideal and I had looked into some sort of covers for them. Space is at a premium around those components and I was unable to find something suitable and gave up. The x-axis is farily well protected under the main table, but the y-axis screw is wide open. I plan on putting a 9"x9" plate on it for a table surface which will overhang the existing table some. That will give quite a bit of protection to the y-axis bearings and some to the y-axis screw.

I also plan to have a vacuum attachment at the spindle nose to suck up the majority of the dust/chips as I am cutting. In order to be able to cut metals I will have to build some sort of shield/wall/tub to contain the chips and keep them from going everywhere.