Jim,
At some point I would like to do a retrofit, I know it would be the most
ecomical way to go if frames are available.
Howeverthe purpose of my project is a bit more complicated. I am trying to
seeif through innovative sourcing and design the price of VMC of HMC couldbe
brought down. Way down. The over all objective is to try and createopen source
hardware designs. I am not doing this on my own I am beingsponsored by my
company MFG.comto try and get this off the ground. I've never build a CNC
machinebefore, however I like the challenge of reducing the price ofproprietary
hardware.
Now you may be thinking Open SourceHardware? What am I smoking, Well projects
like EMC have createdexpectation that perhaps this would be possible. If
software can beopen source why not hardware? Well I've been giving this lots
ofthought. And although there are projects out there like OSCAR (opensource
car) and a number of machine designs (mostly pictures), I am outto create a
full set of detail drawings and a detail BOM, together witha site for
collaborative engineering that works. I am also looking toget off the bench top
into something in 2-4 ton range. I like some of the project on Instrutable but
I want to go bigger.
Collaborativework is a piece of the puzzle and the tools for collaborative
softwaredevelopment have been here for a long time (with low cost to
entree).For hardware we have not been so lucky but with the right tools and
bythis I mean engineering and sourcing perhaps this can be cracked. AlsoI know
there is more work here than I can handle so perhaps this is agood time see who
out there may be interested in collaborating on thisidea.
Rayh, thanks for the info. We where suspecting that thelinear encoder could
present an problem with the back slash and we havegiven it some thought. So far
we only tested the scale-motor setup onthe benchtop it worked very nicely but
it was not under load. Thanks for the link on the dual PID look rehenry
I amabout two weeks way from having all three axis running, I am waiting ona
casting that houses the cartridge spindle, one out of four thatthe machine has.
It has come out bad twice now, Tomorrow I'll knowagain, if not I am off to
finding a new foundry, I made the mold myselfso I'll just take it to some else.
Jorge
----- Original Message ----
From: Jim Fleig - CNC Services <[EMAIL PROTECTED]>
To: [EMAIL PROTECTED]
Sent: Saturday, March 15, 2008 6:08:37 PM
Subject: 800mmx500mmx500mm vertial machine
Hi Jorge,
I saw your email on the EMC forum. What will be the
benefit of building an approximately 30 inch bed mill rather than retrofitting
an existing frame with spindle motor, spindle drive, servo amplifiers and servo
motors? Would you like a tool changer too? These are often available
on bed mill frames.
I have one for sale.
----- Original Message ----
From: "[EMAIL PROTECTED]" <[EMAIL PROTECTED]>
To: Enhanced Machine Controller (EMC) <emc-users@lists.sourceforge.net>
Sent: Saturday, March 15, 2008 9:36:41 AM
Subject: Re: [Emc-users] home-mad CNC machine project.
Couple of thoughts Jorge. First is how to manage building the machine base.
I'm sure that you know that the parts of the machine that hold it together and
allow it to move are what absorb the cutting forces and harmonics and allow it
to cut accurately. The K&T company built quite a business with large machines
using welded bases rather than cast. You might look at some of their
designs. The concrete floor provided quite a bit of the rigidity of the
assembled machine. You might also consider concrete castings for some of the
base. Portable concrete step manufacturing companies do some great work with
small aggregates and fiber mixes.
The second thought is EMC2 related. The linear scales, while very accurate in
themselves have not proven to be very good for use with EMC2 control. The
problem has to do with backlash in the drive components. Our backlash
compensation counts encoder pulses to find the other edge of the lash whenever
the direction reverses. Since the linear scale is connected on the work piece
side of the lash EMC will not see pulses until the lash has been taken up.
Even small amounts of lash will cause a well controlled servo system to hunt
and overshoot. We've talked about using a motor driven encoder connected to
one PID loop in our software to handle this lash problem and another PID
connected to the linear scale to handle final positioning. I don't know that
any real tests of such a system have been reported.
HTH
Rayh
--- [EMAIL PROTECTED] wrote:
From: Jorge Barrera <[EMAIL PROTECTED]>
To: "Enhanced Machine Controller (EMC)" <emc-users@lists.sourceforge.net>
Subject: Re: [Emc-users] home-mad CNC machine project.
Date: Fri, 14 Mar 2008 20:09:24 -0700 (PDT)
I am curious about bigger machines, anybody tried making something with a 40
taper spindle. I am halfway done with my own design, using servos, linear
scales, linear bearings and ballscrews. I am trying to keep the BOM under 20k
and of course I am using EMC. Its work envelope is 800mmx500mmx500mm vertial
machine and I am trying to build it with simple tools and machines that are
smaller and less sophisticated than itself.
I would love to connect with anybody that has relevant experience
Jorge
----- Original Message ----
From: Doug Metzler <[EMAIL PROTECTED]>
To: Enhanced Machine Controller (EMC) <emc-users@lists.sourceforge.net>; [EMAIL
PROTECTED]
Sent: Friday, March 14, 2008 1:35:27 AM
Subject: Re: [Emc-users] home-mad CNC machine project.
I’m on my third rev of my home-built
CNC project. My best advice is to make it much more rigid than you think you
need to. I started out with small slider shafts and now I’m up to 7/8”
(which you can get surprisingly cheap at speedymetals). But in my case every
rev got considerably bigger. The first rev was a little 8*11 PCB cutter and it
had ¼” sliders, the second rev grew to 11*17 with 3/8’s and the
latest rev will be a whopping 20*34”, thus the need for the huge
sliders. But definitely err on the side of over-engineering for rigidity.
The other part that I couldn’t
afford that I wish I could have was good linear bearings. I tried many times
to come up with my own linear bearing surface but in the end most of the
available
torque was spent trying to overcome the sliders. I still can’t afford
good linear bearings but my latest home-brew setup uses small standard bearings
(some of which are spring-loaded). These are a bear to manufacture but will
dramatically
increase the quality of the machine.
I am using threaded rod but it makes for a
very slow machine. If anyone here has a line on good inexpensive ballscrews
please let me know.
As for electronics I am doing it all
myself because I want smart nodes. But I think the consensus here is probably
right – spend the money to save the time.
Drop me a note if you have specific questions.
DougM
From: [EMAIL PROTECTED]:[EMAIL PROTECTED] On Behalf Of seth wiley
Sent: Sunday, March 02, 2008 1:10PM
To: [EMAIL PROTECTED]; Enhanced Machine Controller (EMC)
Subject: Re: [Emc-users] home-madCNC machine project.
sean,
i'm slowly (in my very spare sparetime) working up a small(12"x12"x3") low
tolerance cnc machine for light wood andplastics. it is also serving as a
general teach-myself-cnc project. i chose togo with a pre-config'd electronics
/ servos package from keling inc.
(http://www.kelinginc.net/ThreeXCNCPackage2.html).after reading lots of cnczone
entries and doing lots of chipset / board /wiring research, i figured it's 329$
well spent by saving me time, and it's apretty complete set of items for a good
price. also, this site has some helpfulinfo on wiring
(http://www.robertguyser.com/).i am next building up the machine using basic
8020 or minitec extrusions andlinear accessories. lovejoy couplings will round
out the basic bom. i'll usewhatever i have as a cutter head - dremel, trim
router, etc. it should turn outto be a fairly cheap machine without eating up
too much time reinventing thewheel. cam environment: emc2 packaged with ubuntu.
it was a smooth install
andthe forums are great. so, i cannot say that this route is flawless and
workedout yet since i'm still in the process, but i can say that i've spent a
bunchof time running cnc machines, spent lots of time reading everything i
couldfind on the internet and printed about various diy cnc options. i think
thisroute seems like a pretty efficient and solid starting point. i'll let you
knowhow it comes out - if i ever get the time to complete it!
have fun regardless of which direction you choose. good luck.
-seth
On Fri, Feb 29, 2008 at 10:59 PM, <[EMAIL PROTECTED]> wrote:
I was wondering if anyonehas ever tried a do-it-yourself CNC project like
this.
http://www.instructables.com/id/Easy-to-build-CNC-Mill-Stepper-Motor-and-Driver-ci/and
this
http://www.instructables.com/id/Easy-to-Build-Desk-Top-3-Axis-CNC-Milling-Machine/.
If so, any pointers or words of knowledge before I dive in?
Also, I'm still looking for some stepper motors to use if anyone has a
goodsource.. I'm a college student, so I'm obviously broke andstarving. So,
inexpensive would be good. Thanks guys.
Sean
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