Re: Please take a look over my shoulder – CAD CAM CNC Bench Mill System

Fred thank you very much for both your replies.

I just received them and read them over. I appreciate you taking the
time to answer each of of my endless questions. You have taught me a
lot. This subject is overwhelming no matter how much searching I
do. It is people like you on this forum that taught me the most, and
in such a short time. Again thank you.

Whelen

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Fred Smith" <imserv@v...>
wrote:

> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "whelenremington"
> <wperun1@r...> wrote:
> > I've been researching the web for three weeks to figure out how
> > to
> > select the software, electronics, motors, and mechanicals to put
> > together a bench mill system.
>
>
> > My present system contains a MicroLux Milling Machine #82573
> > purchased from Micro Mark. I also have a MicroLux 7x14 Lathe
> #82710,
> > so I can do fabrication to mount servo motors, and or build new
> x,
> > and y axis slides. I'll start with the lead screws that came with
> > the
> > milling machine. Need information about, do I need to modify the
> lead
> > screw nuts, as an example. I plan to measure backlash.
>
> This is what is called a micro mill. It is light duty and should

be

> fine for the size and types of parts you describe.
>
> In order to convert any machine to CNC, you need to make it "CNC-
> ready"
>
> Here is how I define CNC ready:
>
> 1) Thrust bearings to prevent end play on all axes
> 2) Anti-backlash nuts on the lead screws
> 3) Motor mounts
> 4) Flex couplings to adapt motor shafts to lead screws
>
> The X and y axis on a micro mill are relatively straightforward to
> accomplish, but the Z is more complicated because of the drill
> handle mechanism. Steve Stallings of PMDX has a ball screw Z axis
> that he has built on his machine. It avoids the drill handle mess
> and substitutes a precision leadscrew. A similar device with an
> Acme screw would be sufficient for a micro-mill.
>
>
> > I guess I want to output .stl files from my CAD software. There
> is
> > also .dxf, but I don't understand why I would prefer .stl over
> > .dxf
> > output files.
>
> .stl is for 3D surfaces only, this includes carved and sculpted

forms

> .DXF can be used for 3d surfaces or prismatic shapes, contours, and
> engraving.
>
>
> > Again what would you suggest for the CAD and CAM software for my
> > application? Where do I specify the .stl mesh size? In the CAD
> or
> > the CAM software?
>
> You specify the .stl mesh density in the Cad software and you
> specify the tool cutting pattern and density in the CAM software.
>
> > Next I guess I need translator software. The CAM output files

are

> G
> > code, I think (what is M code?). I find the translator software
> > confusing. What is it doing? Is it part of the motor drive
> > electronics package, which provides the CNC signals to the motor
> > drivers?
>
>
> See this link:
>
> Creating CNC parts: The software
>
> http://www.cadcamcadcam.com/hobby/creating_CNC_parts.htm
>
>
> > I might want a tool-path simulation software.
> >
> > Somewhere in all of this is the ability to set up the 0,0,0
> > coordinates to relate the cutter to the work-piece.
>
> Standard item
>
> > Limit switches
> > to control run away programs, and something to turn on coolant.
> Also
> > something must isolate the PC from feed back from the motor

driver

> > circuits and power supply.
>
> For a desktop machine, these may not be required. Programs do not
> run away, and coolant may not be required for your parts.
>
> > I am also aware of IMService SYS-3-4axis complete, ready to bolt
> on
> > closed loop, servo CNC system with brushed DC servo motors,
> cables,
> > enclosure, and software. Price approximately $1,424.
>
> This system includes new, USA servo motors with timing belt reducer
> assemblies.
>
> It also includes DeskCNC which has a CAM capability to produce G-

code

> to cut rings with a rotary axis( from .stl files), and Cam
> capability to produce pockets, contours, and drilled holes from DXF
> files, and text engraving.
>
> It can also probe a target surface directly to an .stl file for
> duplication
>
>
> > Next the Mill and attaching the servo motors
> > Will the LowCostCNCRetrofits , Hitachi 100oz.in Cont /500ppr.
> Servor
> > Motors and chopper driver electronics (motor current and voltage)
> > have enough torque for my MicroLux Milling Machine acme lead
> screws
> > (#82573 purchased from Micro Mark)?
>
> yes, but they may be too big. 100 oz-in on a servo motor is a lot
> for a micro mill. You need to know the rpm that they have at the
> power supply voltage to determine if they will work well.
>
> > What will be the approximate maximum inches per minute feed rate,
> > cutting brass, with a 1/8" dia end mill, cutting 0.040" deep?
> > Should
> > I connect the servos directly to the lead screws (with flexible
> > couplings) or should I provide a timing belt reduction? What
> should
> > the reduction ratio be, and what is the technical reason for the
> > reduction and the ratio (other than more torque)?
>
> You need to reduce the RPM of a servo motor to balance the high
> motor shaft rpm to the desired cutting speed and rapids on the
> milling machine.
>
> Belt reduction is usually needed for these type of servos.
>
> >What do I tell the
> > CAM program about the servo motors, the reduction, and encoder
> > frequency? I'll be measuring the backlash in the acme lead
> > screws.
>
> Tell the Cam none of this. You will set axis resolution, backlash,
> acceleration and speed in your controller.
>
> > Should I replace the lead screw nuts? Do I loosen up the gibs on
> the
> > slides? Should I lap the ways? What else should I be doing?
>
> You need physical backlash control for CNC. The less backlash, the
> better parts you can make. The gibs should be adjusted so the axis
> can slide freely. Way lapping may not be too useful if your

machine

> is already fairly accurate. The quality of these machines varies
> quite a bit and yours may be fit well enough as it stands, that no
> rework is required.
>
> Fred Smith - IMService
> http://www.cadcamcadcam.com/hobby