CNC Mini-Mill User`s Guide

CNC Mini-Mill
User’s Guide
Minitech Machinery Corporation
6050 Peachtree Parkway
Suite 240-205
Norcross, GA 30092
P: 1-800-662-1760 P: 770-441-8525
F: 770-441-8526
www.minitech.com
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TABLE OF CONTENTS
Preface
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Copyright
Warranty
FCC Statement
Safety
System Requirements
Installation
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Shipment Review
Mounting the Machine
Computer Interface Connection
Controller/DCPower Supply Connections
Stepper Motor Connection
Spindle Assembly
Milling Basics
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Types of Work
Spindle Mechanism
Cutting Tools and Standard Accessories
Operating Instructions
The CNC Milling Machine
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Parts of the machine
Aligning the machine tool
Maintenance
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Worksite
Cleaning
Coupler Adjustment
Lubrication
Service and Support
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Preface
Copyright
All Rights reserved. No part of this manual may be reproduced in any form, electronic or mechanical,
including photocopy, recording, or any information retrieval system, without the permission from the
publisher. No patent liability is assumed with respect to the use of the information contained herein. While
every precaution has been taken in the preparation of this guide, the publisher and author assume no
responsibilities for errors or omissions. Neither is any liability assumed for damages resulting from the use
of information contained herein.
All terms mentioned in this guide are known to be trademarks or device marks are listed below. Minitech
cannot attest to the accuracy of this information. Use of a term in this book should not be regarded as
affecting the validity of any trademark or service mark.
IBM is a registered trademark of International Business Machines Corporation.
Minitech is a registered trademark of Minitech Machinery Corporation.
Mini-Mill/Pro, Mini-Mill/3, Mini-Mill, Mini-Mill/2, Mini-Mill/Classic are registered trademarks of Minitech
Machinery Corporation.
Copyright 2005 Minitech Machinery Corporation.
Warranty
Minitech Machinery Corporation warrants the Mini-Mill Desktop Manufacturing System to be in good
working order for a period of one year from the date of purchase from Minitech or an authorized dealer.
Should this product fail to be in "good working order" at any time during the warranty period, Minitech will,
at its option, repair or replace the product at no additional charge except as set forth below. This limited
warranty does not include service to repair the product resulting from misuse, abuse, or non-Minitech
modifications to the product.
Limited warranty service may be obtained by registered owners by delivering the product to an authorized
dealer or Minitech with documentation of purchase date. If this product is shipped, the owner agrees to
assume full risk of loss or damage in transit and prepay shipping charges to the warranty service location.
For service, contact and authorized dealer or write to Minitech at 6050 Peachtree Pky Ste. 240-205 Norcross,
Georgia 30092.
All expresses and implied warranties for this product, including warranties of merchantability and fitness for
a particular purpose, are limited in duration to one year from the date of purchase, and no warranties,
whether expressed or implied will apply after the this period.
If this product is not in "good working order" as warranted above, the sole remedy shall be repair or
replacement as provided above. In no event will Minitech be liable for any damages, including lost profits,
lost savings or incidental or consequential damages arising out of the use, or inability to use such product,
even if Minitech, or any authorized dealer has been advised of the possibility of such damages, or for any
claim by any party other than the original purchaser.
The foregoing warranty is in lieu of all other warranties, expressed or implied, including but not limited to
any implied warranty of merchantability, fitness, or adequacy for any particular purpose or use. Minitech
shall not be liable for any special, incidental, or consequential damages, whether in contract, tort, or
otherwise. In no event shall Minitech be liable for incidental, consequential or special damages. Liability to
third parties for bodily injury including death relating to our performance or products delivered hereunder
shall be determined in accordance with applicable law and shall not exceed the payment, if any, received by
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us for the product or service furnished. This warranty gives you specific legal rights, and you may also have
other rights which vary from state to state.
Minitech warrants the product to function properly only when used with the International Business Machines
IBM Corporation IBM Personal Computer product line with 100% IBM ROM BIOS. Minitech does not
warrant the product to function properly in every hardware/software environment. Furthermore Minitech
does not guarantee or warrant that the Mini-Mill will make or produce any specific part.
This warranty provides specific legal rights, other rights may exist due to the varying State laws.
Federal Communications Commission Statement
This equipment complies with the requirements in part 15.103(c) of FCC Rules for Test Equipment.
Operation of this equipment in a residential area may cause interference to radio and TV reception requiring
the operator to take whatever steps are necessary to correct the interference. This unit is not for resale to the
general public.
There is no guarantee that interference will not occur in a particular installation. If this equipment does
cause interference to radio of television reception, which can be determined by turning the equipment off and
on, the user is encouraged to try and correct the interference by one or more of the following measures:
Reorient the receiving antenna.
Relocate the computer with respect to the receiver.
Move the computer away from the receiver.
Ensure that the expansion slot covers are in place when no board is installed.
Use properly shielded cables and connectors.
Plug the computer into a different outlet so that the computer and the receiver are on
different branch circuits.
If necessary, the user should consult the dealer or an experienced radio/television technician for additional
suggestions. The user may find the following booklet prepared by the Federal Communication Commission
helpful: “How to Identify and Resolve Radio-TV Interference Problems.” This booklet is available from the
US Government Printing Office, Washington, DC, Stock no. 004-000-00345-4.
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Safety
The most important lesson to learn is that of safety. Caution and safety must be considered at all times when
using the Mini-Mill, as well as any machine tool. Although the Mini-Mill posses only limited possibilities of
creating injury, users should learn and follow all safety rules any time they operate the Mini-Mill.
Safety Rules:
1. Never Run A CNC Machine Unattended - CNC machines are potentially dangerous. Untrained people
must not operate the CNC machine. CNC machines are not toys. Keep kids away. Never let the machine run
unattended. Always wear safety goggles. Unexpected machine movement can occur at any time. You are
responsible for the safety of yourself and others. You are working at your own risk.
2. Always Wear Safety Glasses - foresight is better than no sight! The Operation of any power tool can result
in foreign objects being thrown into the eyes, which can result in severe eye damage. Always wear safety
glasses or eye shields before commencing power tool operation. For the best protection we recommend wide
vision safety mask. and standard safety glasses.
3. Know Your Mini-Mill Machine - Read the owner's manual carefully. Learn its application and limitations
as well as the specific potential hazards.
4. Ground All Power Connections - All the AC plugs are equipped with a three pronged plug. Make certain
the receptacle is properly grounded.
5. Keep Guards In Place - Never remove the safety shield. Use it for the protection of flying debris.
6. Remove Adjusting Keys And Wrenches - Form a habit of checking to see that keys and adjusting wrenches
are removed from the spindle and machine prior to turning the machine on.
7. Keep Work Area Clean - Cluttered areas and benches invite accidents.
8. Avoid Dangerous Environments - Do not use power tools in damp or wet areas. Keep area well
illuminated.
9. Keep Children Away - All visitors should be kept a safe distance from the machine area.
10. Make Work Area Child Proof - with locks, master cutoff switches.
11. Do Not Force Tool - Do not force tool or attachment to do a job it was not designed for.
12. Use The Right Tools - Do not force tool or attachment to do a job it was not designed for.
13. Wear Proper Apparel - Avoid loose clothing or jewelry that could get caught in the moving parts of the
machine and spindle mechanism. Wear protective head gear to keep long hair away from moving parts.
14. Use Safety Glasses - Also use a dust mask if cutting operation is dusty
15. Secure Work - Use clamps or a vise to hold work. Do not you your hands to hold work down.
16. Do Not Touch Machine When It Is On - Avoid touching any part of the machine while it is operating. If
the proper settings are made, and the work is fastened properly, there is no need to touch the machine.
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17. Maintain Tools In Top Condition - Keep tools sharp and clean for best results and safest performance.
Follow instructions for lubricating and changing accessories.
18. Disconnect Tools - before servicing and when changing accessories such as end mills, and cutters.
19. Avoid Accidental Starting - Make sure spindle switch is off before plugging in power cord.
20. Use Recommended Accessories - Consult the instruction guide. Use of improper accessories may be
hazardous.
21. Check That All Holding, Locking, And Driving Devices Are Tightened - At the same time, be careful not
to over-tighten these adjustments. They should be just tight enough to do the job. Over-tightening may
damage threads or wrap parts thereby reducing accuracy and effectiveness.
21. Be Aware Of These Safety Precautions - and use these as a basis for your safety protection. Implement
your own safety rules in conjunction with these.
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System Requirements
Prior to setting up your Mini-Mill make sure you have the proper requirements for the
system. It is also recommended that you first setup your computer system and software prior to
installing the machine. The minimum requirements for the Mini-Mill are:
1. PC Computer, IBM or compatible with a minimum of 512 KB RAM
2. Windows 2000 or XP
3. CD drive and 30 Meg Hard Drive
4. Color Monitor with color graphics card, keyboard, mouse
5. Parallel port - LPT1 or LPT2, Open PCI slot, or Serial Com1 (depends on the control software that came
with your machine)
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Installation
Shipment Review
You should review your Minitech shipment to see how many packages you received. To do this, check first
with the Ship List located on the outside of box number one. If there is only one box, then it will be marked
as 1/1, or 1 of 1 box.
Review the ship list carefully. The ship list provides you with the contents of each box and the items
ordered. Although you may not be completely familiar with all the items, it is important that you become
introduced to items as they become unpacked.
If you are uncertain of what some of the items are, do not worry. Simply call Minitech on our toll-fee
telephone number, if you need any assistance or would like further information on setting-up your system.
We are happy to assist you.
To open the shipment follow the instructions below.
1. Carefully open the crate containing your Mini-Mill machine. This should be a large wooden crate. To
open the crate, use a power drill with Phillips head to unscrew all the screws from the top.
2. As you open the box, notice the four mounting screws that attach the mill to the plywood base. This
secures the machine during shipping and is not need for operating the machine. Therefore, remove the
four mounting screws from the base, prior to attempting to remove the machine from the box. Note:
Some Mini-Mills have only mounting straps that need to be removed.
3. Once the machine is unsecured from the plywood base, it can then be pulled-out of the box and placed on
a bench or desktop. Do not lift machine by the stepper motors. This should be within a five-foot
distance from the computer system you want to control your new Mini-Mill. Remove any items from
your bench that may interfere with the operations of the mill, or items that may become entangled with
the spindle mechanism.
4. Open all other boxes (if any) and inspect their contents with the ship list provided.
Mounting the Machine
Use your discretion to mount the machine to a solid surface. We recommend mounting the Mini-Mill to a
table surface for maximum stability and machining accuracy. The four mounting holes in the chip tray
provide an excellent way to bolt the machine to a mounting surface. The Mini-Mill can be mounted to a
machined surface, or pre-finished board using four machine bolts and rubber washers, and nuts available
through local hardware stores.
This arrangement will give the Mini-Mill a stable and secure platform for operating the machine. The rubber
washers will help in reducing noise created by the spindle motor, spindle, and cutting surface. The better the
foundation, the less vibration will occur and the better the machine will perform.
Computer Interface Connection
The Mini-Mill is controlled by a PC based computer. This means that the signals used to control the table
movements and other operations are all controlled by the computer. The Mini-Mill system is supplied with a
standard DB25 pin cable with the same type of connector at each end. It is a standard cable which can be
purchased at any computer outlet, if you should misplace this item. No internal wires are switched, and all
wires are 1 to 1, 2 to 2, etc.
The Mini-Mill system operates from a parallel port of a PC based computer. This allows for multi-signals to
be transferred to the mill without having to set com settings and other internal settings of the computer. No
internal settings of the computer are required to operate the Mini-Mill.
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Do not attempt to connect the interface cable while either the computer or Mini-Mill is powered on. This
may cause electronic failure to These electronic components. For your safety and the integrity of the
equipment, turn all devices off prior to making any interface connection.
1. Setup the computer to be used with the machine and install the controller software. Refer to your software
manual for installation instructions.
If at anytime you experience inconsistent table motions, or no table motions at all, check this cable to make
sure it is properly installed.
Controller Connections
The Mini-Mill's stepper three motors and interface card are supplied by DC current. Therefore, it is
necessary to properly install the controller/power supply that comes with your Mini-Mill system. It is
packaged in a separate box that came with your Minitech shipment.
The controller outputs DC current, and is supplied by AC current coming in from a 110 outlet (international
220 VAC). The power cord is equipped with a 3-prong ground plug that must be connected to a properly
grounded receptacle for your safety. If an electrical failure occurs, the grounded plug and receptacle will
help protect the user from electrical shock. Only use a properly grounded outlet when running your MiniMill.
NOTE: The power supply must be connected to a properly grounded receptacle for your safety
NOTE: Do not attempt to make any connections to the controller while the power supply is plugged in, or
turned on. Unplug the power supply, and make sure the power switch is in the off (down) position.
1. Connect the interface cable from the computer's parallel port to the back of the Mini-Mill
controller. Secure the cable at each end with the screw-down connectors.
Problem Solving:To check to see if AC power is getting to the power supply, turn it on and the red
light switch should come on. If it does not, check the fuse on the back side of the power supply. If
it is blown, replace it with the same power rating. Do not attempt to operate the power supply with
out the properly installed fuse.
Problem Solving:Check DC power. There are two ways to see if DC power is getting to your Mini-
Mill. One, you will hear and feel a fan come on, when the power supply is turned on. If no fan,
check connections and retry. Second, when the power is turned on, the motors should be torqued
and it becomes difficult to turn the lead screws by hand. If the lead screws are easy to turn (with the
power on) you are not getting power to the interface card and the stepper motors.
FRONT
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Power Switch - This is on the right side of the controller box. On is in the up position, off is down.
A light illuminates when power is on.
Emergency Stop - This cuts the power to the stepper motors in case of a failure. Press this when
you want the stepper motors to shut off.
BACK
AC IN - Connect the power cord from your wall outlet into this connector. It supplies the AC
power for the controller.
Computer Interface - Connect the parallel cable from your computer into this connections
Stepper Motor Connections
Stepper Motor Cables - These get connected to each one of the stepper motors. Each cable
corresponds to a motor; match the X to the X motor, Y to Y, etc.
The Mini-Mill has three stepper motors that control the movements of each table. Each
stepper motor has a cable that leads from the motor's case to the controller box.
NOTE: Make sure all power devices including the computer, controller and spindle are turned off prior to
making the stepper motor connections.
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1. Take the lead of each motor and find the corresponding outlet. Snap the connector into the
corresponding connector.
NOTE: The stepper motor connections are important. To assure you have made the right
connections review the following diagram. Make sure the correct axis is connected to the
corresponding axis port on the controller box.
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Spindle System
Skip this section if you do not have this spindle.
The spindle mechanism is the only component that needs assembling. It is not assembled due to the
possibilities of it becoming damaged during the shipment to your location. If you need to ship the Mini-Mill
to another location, make sure the spindle is taken off the mill prior to shipping.
NOTE: Prior to plugging in the spindle's power cord into any power source, make certain the switch (located
on the speed control) is turned off. Do not attempt to plug in spindle plug before properly
assembling it to the Mini-Mill. Do not attempt to install any cutting device prior to proper
installation. Do follow these instructions for proper assembly.
Un-packaging Spindle Mechanism
The spindle mechanism is detached from the machine prior to shipping. It is in a separate package
within one of the boxes you received. Open the box with the spindle motor, bracket and belt.
Mounting the Motor and Speed Control Unit to the Headstock
1. Remove the motor pulley from the motor shaft. Mount the inner belt guard to the motor using the
two standoffs. Next, install the motor pulley (P/N 4336) to the motor shaft and tighten the set
screw. The end of the pulley should be just about even with the end of the motor shaft, with the
smaller pulley toward the end of the shaft.
2. Place the drive belt over the motor pulley.
3. Place the round post (A) on the speed control hinge plate in the hole on the inner belt buard (B).
4. Set the outer belt guard in place, locating the other post of the hinge plate (C) in its pivot hole
(D). The motor standoff ends will register in holes in the outer belt guard. Make sure the drive belt
is routed properly, then secure the cover with the two 1-3/8" pan head screws that go into nuts
pressed into the back of the inner belt guard.
5. Attach the motor mounting bracket to the rear of
the headstock with two 10-32 x 3/8" socket head
screws. (These screws are shipped threaded into the
headstock rather than in the parts bag.) There is
enough “play” in the mounting holes to allow you to
ensure the motor is visually mounted parallel with
the spindle axis. (Note: If a chip guard is to be
mounted, its attachment screw replaces one of these
mounting screws. It can be mounted at this time or
after the headstock is in place.
6. Place the drive belt over the spindle pulley and
insert two 10-32 x 3/4" socket head screws (with 2
washers on each) through the motor mount slot and
into holes in the ends of the motor standoffs. (These
standoff ends should be exposed through locating
holes in the outer belt guard.) NOTE: The normal
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operating position for the drive belt is on the large diameter groove on the motor pulley and the
small diameter groove on the spindle pulley.
7. Tighten the motor mount screws, tilt the speed control unit out of the way and check the
alignment of the drive belt. It should be perpendicular to the drive pulleys. If it is not, loosen the set
screw on the motor pulley and adjust it in or out on its shaft until the drive belt is square with the
motor.
8. Pull the desired tension into the drive belt by sliding the motor unit outward in the bracket slot.
Tighten the mounting screws to hold the motor and control unit in place. NOTE: Do not overtension the drive belt. Just make sure it has enough tension to drive the spindle pulley without
slipping under normal load. By not over tightening the belt you will not only extend its life, but will
also provide a margin of safety for belt slippage should a tool jam in a part or an accident occur.
The belt must be a little tighter when used in the low speed range because small diameter pulleys
are not as efficient.
9. Set the mounting plate into the top of the belt guard housing so it rests on the rails molded onto
the inside surfaces of the housing. (The pressed-in nut goes down and to the outside.) Slide the plate
toward the outside (toward the spindle pulley) until it stops. NOTE: The mounting plate was
designed to be easily removable so it is out of the way when changing the drive belt position.
10. Rotate the speed control unit down into place and insert the single 10-32 x 3/8" socket head
screw through the hole in the speed control housing and into the nut in the mounting plate. Tighten
enough to hold it in place. Do not over tighten. NOTE: If you machine a lot of wood or brass, you
may want to purchase and install a switch cover (P/N 3015) to keep the fine dust out of the power
switch. The wood dust can gum up the switch causing intermittent operation. Brass dust can short
out the switch or cause a risk of electric shock to the operator.
Mounting the Headstock to the Machine
You may notice that the post onto which the headstock mounts is a loose fit where it projects from the lathe
bed or column saddle. This is normal. The screw in the front center of the headstock has a cone point. The
pivot pin has a tapered slot with a corresponding angle. When the screw is tightened, its angled face engages
the groove, and, because the pivot pin can not come up, it draws the headstock down into position, clamping
it into place. If the pin were rigid, it could keep the headstock from pulling down squarely. The headstock is
aligned with the lathe bed or column saddle by means of a precision ground key that fits into key ways in
both parts. It is not square in cross section so it will fit in only one direction. Push the headstock firmly
against it as you tighten the hold-down screw. The mill column saddle has two key ways milled into it so the
headstock can be mounted in conventional fashion or at a 90° angle for horizontal milling. Additional
information about mounting the spindle is under the aligning the machine section.
Power Connection
Although the spindle motor operates on DC current, it is supplied by AC current coming into its own
converter. Therefore, it uses AC current from a 110 outlet (international 220 VAC).
The power cord is equipped with a 3-prong ground plug that must be connected to a properly grounded
receptacle for your safety. If an electrical failure occur, the grounded plug and receptacle will protect the
user from electrical shock. Only use a properly grounded outlet when running your Mini-Mill.
The power cord can be plugged directly into a properly grounded (110VAC) wall outlet and controlled on/off
manually by the power switch located on the variable speed control panel . If you are just being introduced
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to the Mini-Mill, it is recommended that you plug the spindle's power plug directly into a properly grounded
(110VAC) wall outlet.
For advanced users, the Mini-Mill has two AC power outlets on the back of the mill. These are both used for
supplying AC power to the spindle. The top outlet is for users who want to control the on/off of the spindle
by the computer. This is only for advanced users who are using CIM (computer integrated manufacturing),
and need to have the spindle switched on/off automatically by the software controls. When AC is first
properly supplied to the mill, the bottom AC outlet can be used as a regular AC outlet, and is not switchable
by software control.
3. Automatic on/off Spindle Connection. To have the software control the on/off switch, first insert
the supplied power patch cable from a properly grounded wall outlet to the AC-in connector on the
back (bottom center) of the Mini-Mill. The AC-in connector is supplied with a 10 amp fuse in case
of a electrical failure.
NOTE: If you have difficulty in the AC system, check the fuse to see if it is blown. If it is, check
the AC connections and replace the fuse with a 10 amp rating. Do not attempt to operate the
Mini-Mill without a fuse.
Next, insert the spindle power plug into the top AC outlet on the back of the Mini-Mill controller.
When you have completed your part program and are ready to run it, make sure the power switch is
"ON". This way, when the software makes the switch on the interface card, it is able to supply
current to the spindle motor.
The second (lower of the 2 AC outlets) AC outlet on the back of the Mini-Mill controller is
just an additional source, or auxiliary patch for AC current.
Additional Information on the Sherline Spindle
THE ADVANTAGES OF SHERLINE’S DC MOTOR AND ELECTRONIC SPEED CONTROL
Sherline’s 90-volt DC motor is very smooth and powerful, particularly at low RPM. The specially designed
electronics package also provides some unique advantages in addition to smooth speed control with a usable
speed range of 70 to 2800 RPM. A special circuit compensates for load, helping to keep RPM constant. The
machines can also be used on any current worldwide from 100 VAC to 240 VAC, 50 or 60 Hz without any
further adjustment other than seeing that the proper wall plug is used. The control reads the incoming current
and automatically adjusts to the proper settings.
CAUTION—MOTOR IS THERMALLY PROTECTED
Thermal protection means there is a built-in circuit breaker that will shut down the motor if it gets too hot.
This keeps the motor from burning out. The breaker will automatically reset as soon as the motor cools and
you can go back to cutting, but you should be aware of how it works and what to do if the machine suddenly
shuts itself down. If your motor is shutting down from overheating on a regular basis, it means you are taking
cuts that are too heavy or operating at too high an RPM for long periods. Slow your speed down, reduce your
cut or feed rate, and you should have no further problems.
Due to the nature of miniature machining, overloading the machine is a common problem. It is often
tempting to try to speed up the process by working faster. Keep in mind this is a small machine, and work
with patience and precision— don’t be in a hurry. Your parts will come out better, and your machine will last
much longer if it is not over stressed.
WHAT TO DO IF THE MOTOR SUDDENLY SHUTS DOWN
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If your thermal protection circuit shuts down the motor while work is in progress, immediately shut off the
power switch and then back the tool out of the work. It should only take 10 seconds or less for the circuit
breaker to reset, then you can turn the motor on and start the cut again, this time putting a little less stress on
the motor. If you leave the tool engaged in the part and the power on, when the circuit breaker kicks back on,
the motor must start under load. This can be very hard on your motor. Remember that the circuit breaker
turns the speed control off, which turns off the motor. If power were to be applied to the speed control with
the motor disconnected, it could damage the speed control. Thermal protection is built into your motor to
insure it is not damaged by overloading. Use good common sense when operating the motor for years of
trouble-free operation.
OPERATION OF THE MOTOR AND ELECTRONIC SPEED CONTROL
The lathe is supplied with an electronic speed control that produces a comprehensive range of speeds suitable
for all operations. Special circuitry designed into the DC motor speed control automatically compensates for
speed changes due to increased load. If the spindle RPM drops noticeably when cutting, you are taking too
heavy a cut. The speed range of the spindle using the speed control is from 70 to 2800 RPM. This is achieved
without the inconvenience of changing belt positions or gear ratios as is often the case with other designs. A
second belt position is offered as an additional feature to provide extra torque at low RPM for larger diameter
parts should your job require it. To operate the motor, turn the speed control knob counterclockwise as far as
it will go. Then turn the toggle switch to “ON” and select the speed by turning the speed control knob
clockwise.
Motors are Pre-tested at the Factory
Your new motor should run smoothly the first time you use it, as it has been “run in” for about an hour
before being shipped to you. Despite our secure packaging, there have been cases where extremely rough
handling by a shipper has damaged the magnets in the motor. If the motor does not run when plugged in, turn
the motor by hand. If it does not turn smoothly, it may have been damaged in shipment. Call Minitech for
instructions on making a damage claim with the shipper. Do not attempt to repair the motor yourself.
HIGH SPEED SPINDLE OPERATION
A special pulley set is available that turns the spindle at up to its maximum rated capacity of 10,000 RPM.
See P/N 4335.
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Milling Basics
The Mini-Mill's three table motions are classified as X, Y and Z axes, and are standard to most industrial
operations. Additional CNC programming terminology is explained in the CNC User's Guide. If you are not
familiar with CNC program and controls, it is recommended that you study this prior to using the Mini-Mill
system.
Types of Work
There are three basic types of work the Mini-Mill can perform; milling, drilling, and boring. Additional
work with accessory items such as our Mini-Rotary Table is available for attaining machining of cylindrical
objects. Milling on the CNC Mini-Mill is usually accomplished with end-mills. These are the cutters
designed to cut with both the sides and the end. Drilling is accomplished by special CNC commands given
to the mill. It is also recommended that center drills be used prior to drilling to achieve the maximum degree
of accuracy. Boring is a method of making accurate holes by rotating a tool within a single cutting edge,
usually in a boring head. Another type of milling is performed with an adjustable fly cutter, which may be
used for surfacing. For maximum safety and rigidity, the cutter bit should project from the holder no more
than necessary. Be certain that the RPM is appropriate before attempting to remove any metal. An end mill
can be instantly damaged if a cut is attempted at excessive RPM.
Spindle Mechanism
It is important to note that you can overload the spindle motor. The many variables involved in machining,
such as materials being machined, size and shape of end mill, sharpness, can lead only to one rule to
follow .... Common Sense!
Heavy cuts at low RPM will make the motor run hotter than light cuts at high RPMs. In normal operations
the spindle motor will run warm to the touch, but not hot. This does not mean your machine can not run
at low RPMs, but only that the load put on the motor must be considered in each setup and
operation of the machine.
Cutting Tools and Standard Accessories
End Mills
End mills are the standard vertical mill cutting tools. Your Mini-Mill was designed to employ miniature
series end mills, having 1/8", 3/16", or 1/4" shank sizes. A 3/8" end mill holder is also available. We
recommend using 2-flute, single-end, high speed steel end mills. The solid carbide tools are more expensive,
and the cutting edges will chip unless used properly. End mills may be purchased from industrial machine
shop outlets or catalogs.
As smaller diameter cutters (less than 1/8") are quite fragile, the largest diameter cutter possible for the job
requirements should be employed. Be certain that the RPM is appropriate before attempting to remove any
material. An end mill can be instantly damaged if a cut is attempted at excessive RPM.
There are no firm rules other than common sense in determining the depth of cut. Commence with very light
cuts, and increase depth of cut until satisfactory cuts are achieved.
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Note that end mills should not be used for drilling; however, they may be employed to enlarge an
existing hole.
Collet Set
The main purpose of the collet set is to hold end mills securely. The spindle nose has an internal Morse No.
1 taper, which closes the collet as the Draw bolt is tightened. Morse tapers are approximately 5/8" per foot
and are self locking. Therefore, to loosen a collet, the draw bolt must be loosened a few turns, and taped
with a hammer to release.
Hold Down Provisions
Some CNC Mini-Mills are supplied with a set of V-block clamps. This secures most materials to the surface
of the mill's table top. The table top supports several 1/4-20 tapped holes separated at one inch centers for
modular placement of parts.
For additional hold-downs, it may be necessary to purchase a small manual vise. This can be fitted
with bolts to secure it to the table.
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Mini-Mill Operating Instructions
Minitech machines are among the finest tools that can be purchased for the price, and although not offering
the degree of precision found in machines costing several times more, they are capable of very precise and
exacting work when properly employed. In short, we feel that this is the best possible product in its price
range on the market today.
Follow these guidelines prior to operating your Mini-Mill:
1. The Mini-Mill is a small, light duty machine which should not be used for removing large amounts of
material. For efficiency, select a piece of stock that is close to the finished size as possible.
2. Stresses on any mill are high when cutting most materials. These stresses cause most machines to be
constantly adjusted for gib tightness and backlash. The Mini-Mill does not have these adjustments to make,
because of its dual linear shaft design. It also supports a zero-backlash lead screw nut that does not need
adjusting.
3. End mills must be true and be sharp. Holding end mills in a drill chuck is a poor practice. Use collets
instead.
4. Fly cutting is an excellent way of cutting stock from flat surfaces
5. For accurate setup, you should have and know how to use a dial indicator. The trueness of the spindle can
be more accurately attained, which results in more accurate work.
6. Often, more time is spent on designing part programs and setup, than on actual machine time.
7. Always plan on having a start reference point from which to begin the job.
8. A good rule to follow is: if the tool chatters, reduce the spindle speed and increase the feed rate.
9. It takes a long time to accumulate the knowledge, tools and fixtures required for many different types of
applications. Try not to become discouraged by starting with a job that is too complex or by using materials
that are extremely difficult to machine.
10. Test your part programs and work in prototyping material first. This will reduce the cost of materials and
allow you to practice machining. You can even test your programs without cutting anything, just let the
machine go through the motions - cutting air.
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The CNC Milling Machine
Parts of the Machine
Figure 6 is a photograph of the Minitech Mini-Mill 3. This particular model is a 4-axis vertical CNC milling
machine. There are three linear axis; X,Y, and Z; and one is rotational, A. The figure illustrates the machine
axis and their direction of movement.
Figure 6: Mini-Mill 3
Aligning the Machine Tool
The following processes are recommended for advanced users only. If these adjustments need to be made
please contact your authorized dealer and a qualified service technician can perform this service. These
machines go through a quality control process before delivery and these tests have already been performed.
Minitech nor its affiliates will be responsible for damage or injury done from use of these processes or use of
the machine.
Alignment Tools
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Ideally all parts of a machine are perfectly uniform, square, flat, and perpendicular or parallel to one another.
The reality is that there are tolerances to which the machine is true. A machine can not create parts anymore
accurate or precise than the accuracy or precision of the machine itself. So it is important that the machine
be adjusted properly to obtain dimensionally accurate parts repeatedly. In order to do these adjustments and
understand the nuances of your machine you will need a set of tools. The list of recommended tools is
below.
Dial test indicator with 0.0005” increments
A steel parallel bar that is accurate and uniform
A steel round bar with center drill hole in end that is accurate and uniform
Hex key set
Shim material (rolling papers)
A micrometer with 0.0005” increments
With careful attention to detail and the processes illustrated below you will be able to use the mill to produce
parts to tolerances of ~0.001”.
X/Y Table Alignment
Flatness
The first step is to test the flatness of the machine table. The table is not perfectly flat. It is good to know
how flat it is so when mounting parts on the table you can make adjustments. This will become important
when mounting material or a fixture like a tailstock or rotary axis on the table. In the pictures the red arrows
indicate the direction the tool is moving relative to the table. Understand that the tool never moves except up
and down, but the position of the machine is always referred to by the position of the tool tip. To test the
flatness of the table the process is as follows.
1. Mount the dial test indicator in the spindle.
2. Jog the machine so the indicator is at the end of the table and lower the Z-axis so that the lever of the
dial test indicator touches the table.
3. Once the ball of the lever touches the table, make sure the needle moves at least a few thousands.
Then zero the indicator.
4. Jog the X-axis to the left.
5. As the table moves underneath the indicator note the change in height on the indicator.
6. You will see that the table is pretty flat but not perfect.
7. Move the Y-axis so that the tool is at the front of table, set the indicator then move the Y-axis and
note changes in height.
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Figure 8: Measuring table flatness across x and y
Alignment
There are six degrees of freedom that need to be accounted for in aligning
the machine table. They are the pitch, roll, and yaw. Pitch is the how
perpendicular the machine bed is along the X-axis relative to the Z-axis.
Roll is how perpendicular the machine bed is along the Y-axis relative to
the z axis. Yaw is how perpendicular the machine bed is along the x-axis
relative to the y-axis.
Adjusting the pitch and roll is possible by screw tightening methods and
shimming. Adjusting the yaw of the machine is not necessary and beyond the scope of the manual. The
methods of measuring the pitch and roll are described below.
1. Place a precision parallel bar on the table. (pictured bar is flat/parallel to .0001”over 6”)
2. Run the dial test indicator along the parallel bar noting the change in pitch.
3. Do the same for the roll.
Figure 9: Measuring pitch and roll of table.
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4. If for any reason the table must be
removed or replaced it is important the
table is properly installed to insure
accuracy. This will require the loosening
and/or removal of sixteen slide screws and
the four screws which attach the table to
the lead nut. Figure 10a shows the lead nut
screws. Figure 10b shows the area to
place the shim.
Figure 10a: Lead nut screws
The screw tightening pattern is the most important process in making this adjustment. The pattern illustrated
in figure 11 will bring the table down evenly so it sits as flat as possible. The process is as follows:
1. Tighten all screws by number only using two fingers on the hex key. Do not crank them down real tight, it
should be a soft snug. Figure 12 shows the pattern.
2. Make a second tightening pass to snug the screws down tight. Exclude the lead nut screws from final
tightening (screws 1-4). They will be done in the following steps.
3. Once screws 5-20 are tight jog the table left and right a few times in the X direction. This will help to seat
everything before the lead nut is tightened. Once done make final tightening of the lead nut screws in order.
4. Do a final check on the table pitch and roll to make sure you have done it correctly.
Figure 11: Screw tightening pattern.
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Tramming the head
Tramming the head means to make the spindle perpendicular to the table. It is important that the table
already be aligned before you begin this process. There are two directions that the head must be adjusted.
The tramming process is illustrated below.
1. Mount the dial test indicator in the spindle. (if you like you can put your parallel bar on the table and indicate
off of it)
2. Orient your test indicator as shown in figure 12 and zero it.
3. Rotate the spindle in a half circle motion from left to right and check the indicator.
4. Adjust the spindle in a clockwise or counter-clockwise direction until the head is perpendicular, this is
shown in figure 13.
5. The indicator needle should give the same reading at each end of the half circle. To adjust the spindle you
will need to partially loosen the screws shown in figure 14.
Figure 12
Figure 14
Figure 13
6. Orient your indicator as shown in figure 15 and zero it.
7. Now rotate the spindle with indicator in a half circle motion from front to back.
8. To adjust for this (figure 16) you will need to shim between the spindle and the mounting plate as shown
in figure 17.
9. Once done spin the spindle in a complete circle and check the indicator ideally the needle should not
move, reshim or readjust as needed.
Figure 15
Figure 17
Figure 16
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Rotary Table and Tailstock
The rotary table and chuck are the 4th axis of the machine referred to as
the A-axis. This part is used for cutting round objects or indexing.
There are three alignments to be made to the 4th axis. It is normally
mounted vertically on the left or right of the table parallel to the x axis.
There are other orientations of the A axis which are useful, but the
setup process for other configurations is similar and should be obvious
if you can make it through this one.
Run Out
The properties of concern are the concentricity of the rotary table and chuck, and the parallelness to the X
axis. Setup the rotary table, chuck, and indicator with a straight round bar as shown in figure 20. To
measure concentricity of the rotary setup make sure the round bar is properly fixed in the chuck. Rotate the
A-axis 360 degrees, and note the change on the dial test indicator at the chuck and about an inch away from
the chuck. The run out on the pictured setup was about 0.002” at about two inches out. If your run out is
larger than you required part tolerances contact the manufacturer and this can possibly be adjusted.
Alignment
The next step is to mount the A-axis parallel with the X-axis. This means the pitch and yaw of the A-axis
will need to be adjusted properly. Follow the steps below to setup the
rotary axis.
Figure 20: Run out check
1. Mount the rotary table on the XY table as parallel as you can by eye.
Tighten the screws by starting with the front right, then back left, then
back right, and then front left. This will help to insure that the mounting
plate is level.
2. To check the A-axis pitch, indicate at the bar at the chuck face by
moving the indicator lever overtop of and in front of the bar. Then slowly
move the Y-axis toward the front of the machine and as the indicator
drags over the bar note the highest point on the indicator as in the figure
21.
3. Repeat this process an inch or two down the bar. Note the high point,
as in figure 22.
4. Compare the points. If the first point is higher than the second then the bar is sloping down. If the second
point is higher then the bar is sloping up.
5. You can do this test a few times by rotating the A-axis and
retesting. This way the run out can be considered.
6. To improve the alignment if your readings result in numbers
much larger than the run out of the A-axis you will need to place
a shim under the rotary table mounting plate. Place it on the right
if the bar is sloping down and on the left if it is sloping up as in
figure 23.
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After the pitch is adjusted the yaw of the
rotary table needs to be aligned. This is
done with the same setup and method but on
the side of the round bar rather than the top.
The method is described below.
1. To check the A-axis yaw, indicate at the
bar at the chuck face by moving the
indicator lever below and behind the bar. Then slowly move the Z-axis up and as the indicator drags over the
bar note the highest point on the indicator as in the figure 24.
3. Repeat this process an inch or two down the bar.
4. Compare the points. If the first point is higher than the second then the bar is sloping toward the front of
the machine. If the second point is higher then the bar is sloping away.
5. You can do this test a few times by rotating the A-axis and retesting. This way the run out can be
considered.
6. To improve the alignment if your readings result in numbers much
larger than the run out of the A-axis you will need to loosen the screws in the mounting plate and rotate the
table.
You will probably have to repeat the alignment processes a couple times if you want to make it very
accurate.
You will need the same setup to align the tailstock to the center of the rotary axis. This time you will make
use of the center hole drilled in the end of the round bar. The center hole is visible in figure 24. To align the
tailstock follow the steps below.
1. Move the tailstock tip into the center hole at the end of the round bar with the dial test indicator
set on the bar. Probably best even closer to the tailstock end of the bar than in figure 25.
2. Note the change in the dial test indicator. Adjust accordingly.
3. You will need to check with the dial test indicator on top of and behind or in front of the bar. This will
take into account the pitch and the yaw. Screws mounting the plate to the table will be loosened to adjust the
yaw. The screw attaching the tailstock to the mounting plate will be loosened to adjust the pitch.
Figure 25:
tailstock
alignment
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Setting Home and Probe Positions
The home switches and tool probe sensors are optional items used to Home the machine and check
to the position of the tool’s tip. This is an advanced feature for experienced operators.
1. Press Home All from the main screen near the Work Coordinates This brings the Z up to its
highest position and stops. Then Y moves back to the switch and stops. X will then moves
the table to the right, tool to the left and stops.
2. Use Jog to move the tool so it just presses the switch for the tool probe. A Green light will
come up on the screen in the Tool section. This is the lower right side of the Main Screen.
3. Select the Tools/Fixture bottom from the Main Screen and it will lead you to a new screen.
On the far right look for Tool Probe Position and press Set. This sets the position for the
probe.
4. Press the Page UP key on your key board and raise the tool about ¼” above the Probe. Make
sure the Green light goes Off. This is the Probing Start Position and you need to press Set
under the Probing Start Position.
5. Next use the Jog commands from the Main Screen to move the tool to your Fixture Home
coordinate. This is usually the center of the rotary table, or a known start location for your
part. Once in that position, press the Set button on the Fixture screen for Fixture1 This will
set XY and store a hidden Z value. Note that Z Probe to Fixture height did not change it will
be calculate by the software in the next step. You have 4 positions available for the Fixture
home. Most users will only use the Fixture 1 (G54).
6. The next step is to press Probe 1st Tool. This will home all axes, probe the tool, and
autocalculate the Z to probe Height Value.
7. From here on you will use Home and Probe and Probe for tool setting, the first when
starting up the machine the latter when changing tools during a machining operation.
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Maintenance
Proper maintenance and tool cleanliness are major requirements in all industrial environments, as
well as for anyone learning this type of equipment. The lessons practiced here with the Mini-Mill
are required in any future application. To ensure safety reliable service from the Mini-Mill, it is
important that you follow these recommended maintenance procedures.
Proper Work Site
The Mini-Mill and work site must be clean and free of obstructions before and after each use. The
computer must be cleaned of all debris by brushing-off or vacuuming.
Clean Mini-Mill
The key points on the Mini-Mill where foreign matter buildup occurs are in the operating mechanism of the
mill. These areas include the slide shafts and bearing sleeves, and the lead screws and lead screw nuts.
The user should brush, wipe or blow clear these areas, as well as all other areas where debris occurs.
You can also remove the table top by unscrewing the four bolts exposed at each ends of the table. This
allows you to gain access to the many places of debris accumulation, and the lead screw assemblies of the X
and Y axes.
Note: The table top, and spindle mount are the only parts you should remove without damaging or
misaligning the machine. Do not remove any other parts for cleaning.
Examine Couplers
Periodically examine the stepper motor to lead screw coupling device. This is the black component that
attaches the lead screw onto the shaft of the stepper motor. Two set screws are on each side of the coupler.
If these become loose, it will cause slipping of the table movements, and loss of motion. This will also cause
errors on parts you are attempting to machine.
The following are the recommended procedures for examining and reattaching a coupler.
1. Turn off and unplug all electronic devices such as the computer, spindle mechanism, and DC power
supply.
2. By hand turn each lead screw so that each axes is in the following positions. Lower the Z axis as far down
as possible, move the X and Y axes to approximate centers
3. Remove the table top by un-securing the bolts at each top-end of the table.
4. Complete the following procedures for all three couplers
5. Turn the coupler so that you can see the two set screws. Loosen the set screws with the proper Allen
wrench. You do not need to remove the set screws from their tapped holes - just one or two turns.
6. Remove the four socket cap head screws from that attach the stepper motor onto the frame of the MiniMill.
7. Carefully withdraw the stepper motor with the coupler attached to the motor from the lead screw. Pull in
through the hole opening without any sideways motion.
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8. Examine the coupler and its secures to the stepper motor shaft. Notice that between the coupler and the
motor face is a set of thrust bearings. Make sure the thrust bearings have no play in between the coupler and
the motor face.
9. If there is any spacing between the thrust bearings, loosen the coupler's set screws and push coupler onto
the motor so there is no spacing.
10. Re-tighten coupler by tightening both set screws a little at a time until both become tight. Do not tighten
one all the way and then the other.
11. Replace the motor onto the Mini-Mill.
12. Tighten the two set screws attaching the coupler to the threaded lead screw
Lubricating the Machine
Make sure to lubricate the machine. Lubrication frequency will depend on the environment and the use of
the machine. Lubrication directions are below.
1. Use lithium grease and/or 3and1 oil on the rails on the X,Y, and Z.
2. Use 3and1 oil on the ballscrews. It will be necessary to remove the way covers to gain access to the ball
screws.
3. Also use 3and1 oil on the rotary axis there is an oil port on the face of the rotary table.
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Service and Support
If the Minitech CNC Mini-Mill malfunctions in any way, be sure to check the system's hardware thoroughly
first. Then, you may call a Minitech service technician by telephoning 1-800-662-1760.
When you call, please include the following information:
1. The date of purchase and authorized dealer's name
2. The purchase invoice number
3. A full description of the problem as best described
4. Your mailing address and telephone number
The service technician may be able to determine the problem without the need for returning any parts. If the
return of a component is necessary, please include the above information in a note with the defective part.
Do not return any components, hardware or courseware without prior authorization from Minitech. This
authorization will take the form of a Return Merchandise Authorization (RMA) number issued by the
Minitech technical support representative.
When returning products to Minitech, write the RMA number clearly on the outside of the shipping carton,
in a conspicuous place. Ship the component in a suitable shipping carton prepaid and insured to the address
shown below. If you do not have a suitable carton, Minitech will provide you with one.
Minitech Machinery Corporation
Attn: Service Department RMA _______
6050 Peachtree Parkway Suite 240-205
Norcross, GA 30092
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