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Upgrading to a much bigger CNC mill
00:16 17/11/2004 |
In 2004 I bought a milling machine
from Chester UK. Up until then I'd been using a Sherline
CNC milling machine. The Sherline was a fantastically good little machine, but had one flaw (or perhaps it was just me). The Sherline
is very good for small, but having caught the machining bug, I wanted bigger, more powerful! Unlike the Sherline, the Eagle-25
milling machine I bought was not CNC-ready. A CNC-Ready machine has all of the mountings needed for converting to CNC (computer
numeric control) all you need to do is add motors and go, but on a manual milling machine you're stuck with 3 handles: X, Y and Z.
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| This meant I had to do quite a bit of work to convert it to run CNC! This included building enclosures, making electronic safety
circuits, adding motors, machining pulleys and brackets and hooking it all up together.
About a year later it was all done
but not incredibly accurate: the mill was still using it's original leadscrews, which are basically just a screw thread that converts
the rotation of the motor into the linear movement of the mill table. Since these are nothing much more than a fancy nut and bolt
they tend to be as accurate! The problem is that there is a massive contact area (the threads interfering with each other) and the
very necessary oil/grease that keeps it moving causes a type of hydrostatic pressure. The result: it's okay for big chunky bits
where you don't really care about accuracy, but as soon as you want to get detailed it's sloppy and all over the place.
Finally in late 2005 I moved house, to a much newer, nicer, place. Unlike the industrial wasteland that my prior flat was, my
new home is rather comfy and tidy. As I live in London, I don't have a massive place, so my milling machine sits in my lounge! At
my old, very-studenty abode, this was not a problem, but in my new home, this sets me a challenge: Build the mill into a very nice
stealth cabinet, so I can go from drinking tea with the landlady to milling titanium in 25 seconds! (and she won't know!)
It also means I can finally install ballscrews, improve the accuracy and fix all the "bugs" of the old system. |
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Mission 1: Delivery and unpacking of a Mill
11:21 17/11/2004 |
So, you save up the money (or more likely make excuses to yourself until you put it on your credit card - "it's okay: it'll pay
for itself in no time!" ;) We've heard that one before - Ed ) and finally order the machine. Your worries may not end right there: in my case the problem began at
my drive. The machine (only weighing 170Kgs) arrived on a pallet but my drive was a gravel one, so the little dolly that took it
from the truck basically ground to a halt, and the driver left the crate blocking my drive half in the street! It seems ludicrous
to me now, but I was stressed to tears that my new baby was lying out on the London road. Of course, it's not like someone could
have just picked it up and ran off with it. In the end I managed to work out a half-compromise and used my car (parked inside) to tow the crate along the gravel into my front garden. This worked quite well with little friction as the gravel acted kinda like
ballbearings.
When I got the crate open I realized how big the thing actually was (these pics don't do it justice) There
really was no way someone was going to just run off with it. A thing I learnt when moving a big old lathe is that with a lot
of machinery like this the best way to move it is to take it to pieces. So (using my camera phone to take a picture of the
electrical connections) I removed the motor, then had some help from a neighbour in taking off the head. Took the table off,
and finally managed to carrry the base through.
A lesson to be learnt here: don't expect the drivers to help you
move anything like this. They're not UPS. They're a palette company and they'll only take it as far as the dolly goes. Make sure
to have a good friend ( multiple friends is better ) handy, and some beer. :)
Taking it apart was a good lesson on the
workings of the machine, and I was very impressed with the build quality. The night before I'd heavily reinforced a pine
table with thick oak and shortened all the legs, as it was both a cheaper and more sturdy option than the stand from the supplier. |
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