Category: Machine Shop

Mechanical widgetry

Sherline EMC2 CNC Mill: Configuration Files

This is a stick in the ground for the current config files I’m using with EMC 2.4.5. Even the automagically generated files may have some tweakage, which is why I’m putting them here…

[Update: this is for a Dell Dimension 4550 with a latency around 10 µs, occasional glitches to 20 µs, and a very rare burp to 80 µs. Worked fine, but those rare burps were disturbing.]

Sherline.ini

# Ed Nisley - KE4ZNU
# Just don't run stepconf ever again...

[EMC]
MACHINE = Sherline-XYZA
DEBUG = 0
RS274NGC_STARTUP_CODE = G21 G40 G49 G54 G80 G90 G92.1 G94 G97 G98

[DISPLAY]
DISPLAY = axis
EDITOR = gedit
GEOMETRY = AXYZ
POSITION_OFFSET = RELATIVE
POSITION_FEEDBACK = ACTUAL
MAX_FEED_OVERRIDE = 3.0
INTRO_GRAPHIC = Sherline.gif
INTRO_TIME = 3
PROGRAM_PREFIX = /mnt/bulkdata/
#PROGRAM_PREFIX = /home/ed/
#INCREMENTS = .1in .05in .01in .005in .001in .0005in .0001in
INCREMENTS = 10 mm, 1 mm, 0.1 mm, 90 deg, 45 deg, 10 deg

[FILTER]
PROGRAM_EXTENSION = .py Python Script
py = python

[TASK]
TASK = milltask
CYCLE_TIME = 0.010

[RS274NGC]
PARAMETER_FILE = emc.var

[EMCMOT]
EMCMOT = motmod
SHMEM_KEY = 111
COMM_TIMEOUT = 1.0
COMM_WAIT = 0.010
BASE_PERIOD = 100000
SERVO_PERIOD = 1000000

[HAL]
HALUI=halui
HALFILE = Sherline.hal
HALFILE = custom.hal
HALFILE = Logitech_Gamepad.hal
POSTGUI_HALFILE = custom_postgui.hal

[TRAJ]
AXES = 4
COORDINATES = X Y Z A
MAX_ANGULAR_VELOCITY = 45.00
DEFAULT_ANGULAR_VELOCITY = 36.0
LINEAR_UNITS = inch
ANGULAR_UNITS = degree
CYCLE_TIME = 0.010
#DEFAULT_VELOCITY = 0.333
DEFAULT_VELOCITY = 0.475
#MAX_LINEAR_VELOCITY = 0.400
MAX_LINEAR_VELOCITY = 0.500
POSITION_FILE =	lastposition.txt
NO_FORCE_HOMING = 1

[EMCIO]
EMCIO = io
CYCLE_TIME = 0.100
TOOL_TABLE = Sherline.tbl
TOOL_CHANGE_AT_G30 = 1

[AXIS_0]
TYPE = LINEAR
#MAX_VELOCITY = 0.400
MAX_VELOCITY = 0.475
#MAX_ACCELERATION = 1.5
MAX_ACCELERATION = 5.0
#STEPGEN_MAXACCEL = 1.7
STEPGEN_MAXACCEL = 10.0
SCALE = 16000.0
FERROR = 0.05
MIN_FERROR = 0.01
MIN_LIMIT = -1.0
MAX_LIMIT = 9.5
BACKLASH = 0.003
HOME_IS_SHARED = 1
HOME_SEQUENCE = 2
HOME_SEARCH_VEL = 0.3
HOME_LATCH_VEL = 0.016
HOME_FINAL_VEL = 0.4
HOME_OFFSET = 9.1
HOME = 4.5

[AXIS_1]
TYPE = LINEAR
#MAX_VELOCITY = 0.400
MAX_VELOCITY = 0.475
#MAX_ACCELERATION = 1.5
MAX_ACCELERATION = 5.0
#STEPGEN_MAXACCEL = 1.7
STEPGEN_MAXACCEL = 10.0
SCALE = 16000.0
FERROR = 0.05
MIN_FERROR = 0.01
MIN_LIMIT = -0.5
MAX_LIMIT = 4.90
BACKLASH = 0.003
HOME_IS_SHARED = 1
HOME_SEQUENCE = 1
HOME_SEARCH_VEL = -0.3
HOME_LATCH_VEL = -0.016
HOME_FINAL_VEL = 0.4
HOME_OFFSET = 0.0
HOME = 4.0

[AXIS_2]
TYPE = LINEAR
MAX_VELOCITY = 0.333
#MAX_VELOCITY = 0.400
#MAX_ACCELERATION = 1.0
MAX_ACCELERATION = 3.0
#STEPGEN_MAXACCEL = 1.2
STEPGEN_MAXACCEL = 6.0
SCALE = 16000.0
FERROR = 0.05
MIN_FERROR = 0.01
MIN_LIMIT = 0.0
MAX_LIMIT = 6.930
BACKLASH = 0.005
HOME_IS_SHARED = 1
HOME_SEQUENCE = 0
HOME_SEARCH_VEL = 0.200
HOME_LATCH_VEL = 0.016
HOME_FINAL_VEL = 0.3
HOME_OFFSET = 6.93
HOME = 6.5

[AXIS_3]
TYPE = ANGULAR
###WRAPPED_ROTARY = 1
MAX_VELOCITY = 40.0
MAX_ACCELERATION = 250.0
STEPGEN_MAXACCEL = 275.0
SCALE = 160.0
FERROR = 1
MIN_FERROR = .25
MIN_LIMIT = -999999999.9
MAX_LIMIT =  999999999.9
HOME_SEARCH_VEL = 0
HOME_LATCH_VEL = 0
HOME = 0.0

Sherline.tbl

;common end mills
T1 P1 Z1 D0.1225 ; 1/8
T2 P2 Z1 D0.1535 ; 5/32
T3 P3 Z1 D0.1870 ; 3/16
T4 P4 Z1 D0.2500 ; 1/4
T5 P5 Z1 D0.3122 ; 5/16
T6 P6 Z1 D0.3755 ; 3/8 - 4 flute long
T7 P7 Z1 D0.4374 ; 7/16
T8 P8 Z1 D0.4720 ; 1/2
;random metric equivalents
T20 P20 Z1 D0.09787 ; 2 mm
;number drills 1xx = xx
T107 P107 Z1 D0.201 ;  7	 5.11	10-32 clear
T109 P109 Z1 D0.196 ;  9	 4.98	10-32 clear
T118 P118 Z1 D0.170 ; 18	 4.32	 8-32 clear
T121 P121 Z1 D0.159 ; 21	 4.04	10-32 tap
T127 P127 Z1 D0.144 ; 27	 3.66	 6-32 clear
T129 P129 Z1 D0.136 ; 29	 3.45	 8-32 tap
T136 P136 Z1 D0.107 ; 36	 2.72	 6-32 tap
T132 P132 Z1 D0.116 ; 32	 2.95	 4-40 clear
T143 P143 Z1 D0.089 ; 43	 2.26	 4-40 tap
T141 P141 Z1 D0.096 ; 41	 2.44	 2-56 clear
T146 P146 Z1 D0.081 ; 46	 2.06	 good for 2 mm pin
T148 P148 Z1 D0.076 ; 48	 1.93	 1-72 clear
T150 P150 Z1 D0.070 ; 50	 1.78	 2-56 tap 0-80 clear
T152 P152 Z1 D0.064 ; 52	 1.63	 0-80 clear
T153 P153 Z1 D0.060 ; 53	 1.52	 1-72 tap
;fraction drills 2xx = xx/64
T203 P203 Z1 D0.047 ; 3/64	 1.2	 0-80 tap
;inch decimal drills for eagle drilling
; 1xxx = xxx/1000
T1000 P1000 Z1 D0.000	; center drill
T1024 P1024 Z1 D0.024
T1025 P1025 Z1 D0.025
T1032 P1032 Z1 D0.032
T1039 P1039 Z1 D0.039
T1040 P1040 Z1 D0.040
T1045 P1045 Z1 D0.045
T1047 P1047 Z1 D0.047
T1052 P1052 Z1 D0.052
T1067 P1067 Z1 D0.067
T1125 P1125 Z1 D0.125
T1140 P1140 Z1 D0.140
T1150 P1150 Z1 D0.150

custom.hal

# Include your customized HAL commands here
# This file will not be overwritten when you run stepconf again

#--------------
# Get buttons and joysticks from Logitech Dual Action gamepad

loadusr -W hal_input -KA Dual

#--------------
# Home switches are all in parallel, active low

net homeswitches <= parport.0.pin-10-in-not
net homeswitches => axis.0.home-sw-in
net homeswitches => axis.1.home-sw-in
net homeswitches => axis.2.home-sw-in

#--------------
# Probe input is active low

net probe-in <== parport.0.pin-15-in-not
net probe-in ==> motion.probe-input

custom_postgui.hal

#-- empty

Logitech_Gamepad.hal

# HAL config file automatically generated by Eagle-CAD ULP:
# [/mnt/bulkdata/Project Files/eagle/ulp/hal-write-array.ulp]
# (C) Martin Schoeneck.de 2008
# Mods Ed Nisley 2010
# Path        [/mnt/bulkdata/Project Files/eagle/projects/EMC2 HAL Configuration/]
# ProjectName [Logitech Gamepad]
# File name   [/mnt/bulkdata/Project Files/eagle/projects/EMC2 HAL Configuration/Logitech_Gamepad.hal]
# Created     [11:51:27 10-Nov-2010]

####################################################
# Load realtime and userspace modules
loadrt constant		count=16
loadrt and2		count=17
loadrt flipflop		count=4
loadrt mux2		count=5
loadrt mux4		count=1
loadrt not		count=8
loadrt or2		count=10
loadrt scale		count=7
loadrt timedelay		count=1
loadrt toggle		count=1
loadrt wcomp		count=6

####################################################
# Hook functions into threads
addf toggle.0		servo-thread
addf wcomp.1		servo-thread
addf wcomp.2		servo-thread
addf wcomp.3		servo-thread
addf and2.0		servo-thread
addf and2.4		servo-thread
addf and2.3		servo-thread
addf and2.2		servo-thread
addf and2.1		servo-thread
addf constant.6		servo-thread
addf constant.5		servo-thread
addf constant.4		servo-thread
addf constant.3		servo-thread
addf constant.2		servo-thread
addf constant.1		servo-thread
addf constant.0		servo-thread
addf constant.7		servo-thread
addf constant.8		servo-thread
addf scale.1		servo-thread
addf scale.2		servo-thread
addf scale.3		servo-thread
addf mux4.0		servo-thread
addf mux2.0		servo-thread
addf scale.4		servo-thread
addf scale.0		servo-thread
addf wcomp.5		servo-thread
addf wcomp.4		servo-thread
addf wcomp.0		servo-thread
addf flipflop.1		servo-thread
addf flipflop.0		servo-thread
addf and2.5		servo-thread
addf and2.6		servo-thread
addf and2.7		servo-thread
addf and2.8		servo-thread
addf flipflop.2		servo-thread
addf flipflop.3		servo-thread
addf or2.4		servo-thread
addf or2.8		servo-thread
addf or2.7		servo-thread
addf or2.6		servo-thread
addf or2.5		servo-thread
addf or2.3		servo-thread
addf or2.2		servo-thread
addf or2.1		servo-thread
addf or2.0		servo-thread
addf not.1		servo-thread
addf not.2		servo-thread
addf not.3		servo-thread
addf not.4		servo-thread
addf not.5		servo-thread
addf not.6		servo-thread
addf not.7		servo-thread
addf not.0		servo-thread
addf constant.9		servo-thread
addf mux2.1		servo-thread
addf mux2.2		servo-thread
addf mux2.3		servo-thread
addf mux2.4		servo-thread
addf constant.10		servo-thread
addf constant.11		servo-thread
addf scale.5		servo-thread
addf scale.6		servo-thread
addf constant.12		servo-thread
addf constant.13		servo-thread
addf timedelay.0		servo-thread
addf constant.14		servo-thread
addf constant.15		servo-thread
addf and2.16		servo-thread
addf and2.15		servo-thread
addf and2.14		servo-thread
addf and2.13		servo-thread
addf and2.12		servo-thread
addf and2.11		servo-thread
addf and2.10		servo-thread
addf and2.9		servo-thread
addf or2.9		servo-thread

####################################################
# Set parameters

####################################################
# Set constants
setp constant.0.value	+0.02
setp constant.1.value	-0.02
setp constant.2.value	60
setp constant.3.value	1.00
setp constant.4.value	0.10
setp constant.5.value	0.50
setp constant.6.value	0.10
setp constant.7.value	+0.5
setp constant.8.value	-0.5
setp constant.9.value	0.0
setp constant.10.value	[TRAJ]MAX_LINEAR_VELOCITY
setp constant.11.value	[TRAJ]MAX_ANGULAR_VELOCITY
setp constant.12.value	-1.0
setp constant.13.value	0.1
setp constant.14.value	0.020
setp constant.15.value	0.000

####################################################
# Connect Modules with nets
net a-button-minus input.0.btn-trigger or2.2.in0 and2.15.in0
net a-button-plus input.0.btn-thumb2 or2.2.in1 and2.16.in0
net a-buttons-active or2.2.out or2.3.in0 or2.4.in1
net a-disable not.7.out and2.5.in1
net a-enable or2.4.in0 flipflop.3.out not.7.in mux2.4.sel
net a-jog wcomp.2.in input.0.abs-z-position mux2.4.in1
net a-knob-active not.2.out and2.7.in1
net a-knob-inactive wcomp.2.out not.2.in and2.6.in1
net a-select and2.8.in0 and2.7.out
net a-set flipflop.3.set and2.8.out
net angular_motion or2.4.out mux2.0.sel
net any-buttons-active mux4.0.sel0 or2.8.out
net az-buttons-active or2.3.out or2.8.in1 or2.9.in0
net az-reset flipflop.2.reset and2.6.out flipflop.3.reset
net button-crawl scale.4.out mux4.0.in3
net button-fast scale.2.out mux4.0.in1 scale.4.in
net jog-crawl toggle.0.out mux4.0.sel1
net jog-speed halui.jog-speed mux4.0.out
net knob-crawl mux4.0.in2 scale.3.out
net knob-fast mux4.0.in0 scale.1.out scale.3.in
net n_1 constant.10.out mux2.0.in0
net n_2 and2.0.in0 input.0.btn-top2
net n_3 and2.0.in1 input.0.btn-base
net n_4 and2.0.out halui.abort
net n_5 halui.mode.manual input.0.btn-base3
net n_6 wcomp.0.max wcomp.1.max wcomp.2.max wcomp.3.max constant.0.out
net n_7 halui.program.resume input.0.btn-base4
net n_8 wcomp.0.min wcomp.1.min wcomp.2.min wcomp.3.min constant.1.out
net n_9 mux2.0.in1 constant.11.out
net n_10 constant.12.out scale.5.gain scale.6.gain
net n_11 input.0.btn-base5 or2.0.in0
net n_12 input.0.btn-base6 or2.0.in1
net n_13 constant.9.out mux2.1.in0 mux2.2.in0 mux2.3.in0 mux2.4.in0
net n_14 mux2.1.out halui.jog.0.analog
net n_15 toggle.0.in or2.0.out
net n_16 constant.2.out scale.0.gain
net n_17 constant.5.out scale.1.gain
net n_18 constant.3.out scale.2.gain
net n_19 constant.4.out scale.3.gain
net n_20 scale.4.gain constant.6.out
net n_21 halui.jog.1.analog mux2.2.out
net n_22 mux2.2.in1 scale.5.out
net n_23 scale.6.out mux2.3.in1
net n_24 constant.13.out halui.jog-deadband
net n_25 wcomp.4.max constant.7.out wcomp.5.max
net n_26 constant.8.out wcomp.4.min wcomp.5.min
net n_27 mux2.3.out halui.jog.2.analog
net n_28 halui.jog.3.analog mux2.4.out
net n_29 timedelay.0.out and2.9.in1 and2.10.in1 and2.12.in1 and2.11.in1 and2.13.in1 and2.14.in1 and2.16.in1 and2.15.in1
net n_30 and2.9.out halui.jog.0.minus
net n_31 or2.9.out timedelay.0.in
net n_32 constant.14.out timedelay.0.on-delay
net n_33 constant.15.out timedelay.0.off-delay
net n_34 and2.10.out halui.jog.0.plus
net n_35 and2.11.out halui.jog.1.minus
net n_36 halui.jog.1.plus and2.12.out
net n_37 and2.13.out halui.jog.2.minus
net n_38 and2.14.out halui.jog.2.plus
net n_39 and2.15.out halui.jog.3.minus
net n_40 and2.16.out halui.jog.3.plus
net vel-per-minute scale.0.out scale.1.in scale.2.in
net vel-per-second mux2.0.out scale.0.in
net x-buttons-active or2.7.in0 or2.5.out
net x-disable not.4.out and2.4.in1
net x-enable not.4.in flipflop.0.out mux2.1.sel
net x-hat-jog wcomp.4.in input.0.abs-hat0x-position
net x-hat-minus wcomp.4.under or2.5.in1 and2.9.in0
net x-hat-plus or2.5.in0 wcomp.4.over and2.10.in0
net x-jog wcomp.0.in input.0.abs-x-position mux2.1.in1
net x-knob-active not.0.out and2.1.in0
net x-knob-inactive wcomp.0.out not.0.in and2.2.in0 and2.3.in0
net x-set and2.1.out flipflop.0.set
net xy-buttons-active or2.7.out or2.8.in0 or2.9.in1
net xy-reset flipflop.0.reset and2.2.out flipflop.1.reset
net y-buttons-active or2.6.out or2.7.in1
net y-disable not.5.out and2.1.in1
net y-enable flipflop.1.out not.5.in mux2.2.sel
net y-hat-jog input.0.abs-hat0y-position wcomp.5.in
net y-hat-minus wcomp.5.under or2.6.in1 and2.12.in0
net y-hat-plus or2.6.in0 wcomp.5.over and2.11.in0
net y-jog wcomp.1.in input.0.abs-y-position scale.5.in
net y-knob-active not.1.out and2.3.in1
net y-knob-inactive not.1.in wcomp.1.out and2.2.in1
net y-select and2.4.in0 and2.3.out
net y-set flipflop.1.set and2.4.out
net z-button-minus input.0.btn-thumb or2.1.in0 and2.13.in0
net z-button-plus or2.1.in1 input.0.btn-top and2.14.in0
net z-buttons-active or2.1.out or2.3.in1
net z-disable not.6.out and2.8.in1
net z-enable not.6.in flipflop.2.out mux2.3.sel
net z-jog wcomp.3.in input.0.abs-rz-position scale.6.in
net z-knob-active not.3.out and2.5.in0
net z-knob-inactive not.3.in wcomp.3.out and2.7.in0 and2.6.in0
net z-set and2.5.out flipflop.2.set

Sherline.hal

# Generated by stepconf at Sat Aug 23 12:10:22 2008
# If you make changes to this file, they will be
# overwritten when you run stepconf again
loadrt trivkins
loadrt [EMCMOT]EMCMOT base_period_nsec=[EMCMOT]BASE_PERIOD servo_period_nsec=[EMCMOT]SERVO_PERIOD traj_period_nsec=[EMCMOT]SERVO_PERIOD key=[EMCMOT]SHMEM_KEY num_joints=[TRAJ]AXES
loadrt probe_parport
loadrt hal_parport cfg=0xecd8
setp parport.0.reset-time 60000
loadrt stepgen step_type=0,0,0,0
loadrt pwmgen output_type=0

addf parport.0.read base-thread
addf stepgen.make-pulses base-thread
addf pwmgen.make-pulses base-thread
addf parport.0.write base-thread
addf parport.0.reset base-thread

addf stepgen.capture-position servo-thread
addf motion-command-handler servo-thread
addf motion-controller servo-thread
addf stepgen.update-freq servo-thread
addf pwmgen.update servo-thread

net spindle-cmd <= motion.spindle-speed-out => pwmgen.0.value
net spindle-enable <= motion.spindle-on => pwmgen.0.enable
net spindle-pwm <= pwmgen.0.pwm
setp pwmgen.0.pwm-freq 100.0
setp pwmgen.0.scale 1166.66666667
setp pwmgen.0.offset 0.114285714286
setp pwmgen.0.dither-pwm true
net spindle-cw <= motion.spindle-forward

net estop-out => parport.0.pin-01-out
net xdir => parport.0.pin-02-out
net xstep => parport.0.pin-03-out
setp parport.0.pin-03-out-reset 1
setp parport.0.pin-04-out-invert 1
net ydir => parport.0.pin-04-out
net ystep => parport.0.pin-05-out
setp parport.0.pin-05-out-reset 1
setp parport.0.pin-06-out-invert 1
net zdir => parport.0.pin-06-out
net zstep => parport.0.pin-07-out
setp parport.0.pin-07-out-reset 1
net adir => parport.0.pin-08-out
net astep => parport.0.pin-09-out
setp parport.0.pin-09-out-reset 1
net spindle-cw => parport.0.pin-14-out
net spindle-pwm => parport.0.pin-16-out
net xenable => parport.0.pin-17-out

setp stepgen.0.position-scale [AXIS_0]SCALE
setp stepgen.0.steplen 1
setp stepgen.0.stepspace 0
setp stepgen.0.dirhold 60000
setp stepgen.0.dirsetup 60000
setp stepgen.0.maxaccel [AXIS_0]STEPGEN_MAXACCEL
net xpos-cmd axis.0.motor-pos-cmd => stepgen.0.position-cmd
net xpos-fb stepgen.0.position-fb => axis.0.motor-pos-fb
net xstep <= stepgen.0.step
net xdir <= stepgen.0.dir
net xenable axis.0.amp-enable-out => stepgen.0.enable

setp stepgen.1.position-scale [AXIS_1]SCALE
setp stepgen.1.steplen 1
setp stepgen.1.stepspace 0
setp stepgen.1.dirhold 60000
setp stepgen.1.dirsetup 60000
setp stepgen.1.maxaccel [AXIS_1]STEPGEN_MAXACCEL
net ypos-cmd axis.1.motor-pos-cmd => stepgen.1.position-cmd
net ypos-fb stepgen.1.position-fb => axis.1.motor-pos-fb
net ystep <= stepgen.1.step
net ydir <= stepgen.1.dir
net yenable axis.1.amp-enable-out => stepgen.1.enable

setp stepgen.2.position-scale [AXIS_2]SCALE
setp stepgen.2.steplen 1
setp stepgen.2.stepspace 0
setp stepgen.2.dirhold 60000
setp stepgen.2.dirsetup 60000
setp stepgen.2.maxaccel [AXIS_2]STEPGEN_MAXACCEL
net zpos-cmd axis.2.motor-pos-cmd => stepgen.2.position-cmd
net zpos-fb stepgen.2.position-fb => axis.2.motor-pos-fb
net zstep <= stepgen.2.step
net zdir <= stepgen.2.dir
net zenable axis.2.amp-enable-out => stepgen.2.enable

setp stepgen.3.position-scale [AXIS_3]SCALE
setp stepgen.3.steplen 1
setp stepgen.3.stepspace 0
setp stepgen.3.dirhold 60000
setp stepgen.3.dirsetup 60000
setp stepgen.3.maxaccel [AXIS_3]STEPGEN_MAXACCEL
net apos-cmd axis.3.motor-pos-cmd => stepgen.3.position-cmd
net apos-fb stepgen.3.position-fb => axis.3.motor-pos-fb
net astep <= stepgen.3.step
net adir <= stepgen.3.dir
net aenable axis.3.amp-enable-out => stepgen.3.enable

net estop-out <= iocontrol.0.user-enable-out
net estop-out => iocontrol.0.emc-enable-in

loadusr -W hal_manualtoolchange
net tool-change iocontrol.0.tool-change => hal_manualtoolchange.change
net tool-changed iocontrol.0.tool-changed <= hal_manualtoolchange.changed
net tool-number iocontrol.0.tool-prep-number => hal_manualtoolchange.number
net tool-prepare-loopback iocontrol.0.tool-prepare => iocontrol.0.tool-prepared

2010-11-29

Clearing the Shower Drain

Clearing a clog

My shop assistant bears most of the hair in the household, so it seemed entirely appropriate that she clear the clog from the shower drain. She says she’s going to take a picture of the hairball and show her friends what her parents make her do…

I pointed out that plumbers are ecstatic when they get a call for this sort of problem and will charge maybe 150 bucks to make the clog Go Away. When she’s writing the check, she can make whatever choice she wants.

For now, this is how it gets done; the snake hangs on the garage wall.

2010-11-28
Ruler Edge Straightening

While shoveling things off the workbench, I encountered a old wooden ruler with brass-colored metal edges, one of which had popped out of its groove. No wonder: the poor thing was bent into an arc the hard way. I have no idea how that happened, honest.

Distorted ruler edge

Anyhow, I figured I could fix it with the same technique I apply to straighten copper wire: grab one end in the bench vise, the other in a Vise-Grip, and whack the pliers with a hammer to stretch the wire a percent or two. So I did that and failed completely: the metal strip is actually copper / brass plating on steel.

But it was straight enough to tuck back into the groove, where friction seems to be holding it in place, and all is well.

(If I’d found it before I put a dot of epoxy into the sunglasses hinge, I’d have dabbed some dots along the groove and secured it in place forever. No such luck… the workbench is really buried this time.)

2010-11-27
Needle-nose Tweezers: Matching the Jaws

While excavating the top of my workbench and putting things away, I managed to drop my favorite needle-nose tweezers… which, of course, landed point-down on the concrete floor:

Mismatched tweezer jaw

Well, that gave me an excuse to match up the jaws. If you take a close look at most of your tweezers, they’ll have jaws that don’t quite come together evenly, so you’re trying to grab things with a single point instead of between two flat surfaces.

A brief session with coarse and medium diamond files produced this pleasing result (with a mm scale for size):

Matching tweezer jaws

Much better!

Another trick that works well: grab a piece of fine sandpaper in the tweezers, scrub sideways, and repeat for the other jaw. That’ll flatten out the jaws, make them reasonably parallel, and put the scratches in the direction that helps the most when you’re pulling something. Works best if the jaws are already pretty well aligned.

2010-11-26
Sunglasses Repair Redux

After the hinge repair described there, those old sunglasses have been working fine and I use them regularly. The screw recently worked its Loctite loose and was held in largely by blind faith.

It’s obvious why:

Sunglass hinge screw – loose

A tiny dab of JB KWIK should solve that problem for the foreseeable future:

Sunglass hinge screw – epoxy

In the highly unlikely event I must remove that screw, I’ll just refer to this picture and mill the epoxy out.

2010-11-25
Spectrometer: Quick and Dirty Camera Mount

This is a proof-of-concept lashup for a camera-mounted spectrometer; I wanted to find out if the image processing would work, but needed some images without devoting a lot of time to the hardware.

The general idea is that a direct-view spectrometer produces a focused-at-infinity image for your eye. Substitute a camera for your eye and you get an image with the spectral components laid out in a spatial array, suitable for measurement and calculation.

The trick is holding the spectrometer on the lens axis while blocking ambient light. I figured that I could mount the spectrometer in a disk that fit into the camera’s 58 mm filter threads, then hold it in place for the few pix I’d need to get started.

The end result was Good Enough for the purpose, although it’s definitely a kludge…

Spectrometer mounted on camera

The (admittedly cheap) prism-based direct-view spectrometer has a slide-to-focus mechanism that substitutes heavy grease for mechanical precision. A guide screw in a slot prevents the focusing tube from rotating in the body tube, so I decided to replace that with a locking screw to clamp the tubes together. It’s a very fine thread, undoubtedly metric, screw, but a bit of rummaging in my teeny-screw drawer turned up a match (those are mm divisions on the scale):

Spectrometer screw vs standard thread

I think the spectroscope makers filed down the head of an ordinary brass screw to fit the slot, rather than using an actual fillister screw. That’s a Torx T-6 head on the flat-head screw, which probably came from a scrapped hard drive. I eventually found a round-head crosspoint screw (requiring a P-1 bit) that worked better, with a brass washer underneath for neatness.

That got me to this stage:

Spectrometer with locking screw

Making the adapter disk involved, as usual, a bit of manual CNC to enlarge the center hole of a CD from 15 to 15.75 mm, then cut out a 57 mm cookie. A stack of CDs makes a perfectly good sacrificial work surface for this operation, with some fender washers clamping the pile to the tooling plate. Those homebrew clamps are smaller than the Official Sherline clamps and work better for large objects on the small table.

Milling outside diameter

I briefly considered milling a thread into the OD, but came to my senses… I still have that pile of 10-32 taps, but now is not the time!

While in the Machine Tool Wing of the Basement Laboratory, I bored a short plastic bushing to a tight slip fit on the focusing tube to clamp the disk to the eyepiece, with the intent of keeping the eyepiece from whacking the camera lens. That’s the small white cylinder in the first picture.

As it turned out, I had to mount the whole affair on a sunshade that screwed into the camera filter mount, because the eyepiece protruded far enough to just barely kiss the lens.

A liberal covering of black electrical tape killed off all the stray light. Hand-holding all the pieces together and aiming it at the CFL tube over the Electronics Workbench produced this First Light image:

First light – warm-white CFL – no adjustments

Believe it or not, that’s pretty much in focus. Much of the width in the red & green lines seems to come from the phosphors, as there’s a bar-sharp narrow blue line to the far right, beyond the obvious blue line.

Settings: manual focus at infinity, manual exposure 1/60 @ f/2.4, auto ISO = 100. Maybe 30 cm from the 27 W CFL tube: way more light than I’ll ever get through a liquid sample in a cuvette.

Now to fiddle with ImageMagick and Gnuplot…

2010-11-22
Bed Bugs: Hot Box Disinsector

Now, having seen what we’ve been living through, you might ask yourself

Wouldn’t It Be Nice If there was some way to be absolutely sure that mumble does not happen to me?

There isn’t, but you can stack the odds in your favor by disinsecting everything that enters your house. In particular, when you return from a trip, you must treat your luggage with the same casual regard as you apply to any lump of highly radioactive waste.

Because all bed bug stages die when exposed to temperatures over 45°C (113°F, which I round to 120°F), the simplest way to ensure that you’re not bringing any passengers home is to heat your luggage / packages / clothing / whatever to an internal temperature around 120°F, then let it soak for maybe an hour to ensure all the occupants get the message.

What you need is a box that gets hot on the inside, but not hot enough to set your luggage on fire. As with all things sold for bed bug problems, the commercial solution seems grossly overpriced for what looks like an uninsulated ripstop nylon bag containing a rack, a heater, and a fan.

It should come as no surprise that I built something that’s bigger, uglier, and harder to use… but it produces data and you can do science. And, with liberal use of my parts heap, the overall price is maybe 10 dB down from the commercial version…

Hot box exterior

I figured that this widget is going to be a major part of our lives from now on, so a foldable / storable heater wasn’t particularly useful. In point of fact, we’ve been using it heavily and I don’t expect that to stop any time soon.

It’s a rigid box made of Dow Tuff-R rigid polyisocyanurate foam insulating board, held together with 4-inch wide aluminum HVAC tape. The rim around the top is sealed with opposing strips of felt weatherstripping, held on with double-stick tape.

Inside, I used lengths of wire shelving to support the thing-to-be-baked. After we’ve used it a bit more, I’ll conjure up permanent supports for the second level shelving (stacked on the right of the exterior picture); right now, they’re supported on wood blocks as needed.

Hot box interior

Hot Box – Dimension sketch

The interior dimensions work out to 34x22x24 inches: it’s made from a single 4×8 foot sheet of insulating board. Here’s my working sketch showing how the parts lay out and fit together. (clicky the pic for more dots).

The only waste is the 1-inch strip along the right edge; the slab I bought came with a molding imperfection, so discarding that edge was OK.

I cut the sheet into four 2×4 foot strips, cut a 13-inch strip off each plank, then trimmed the 1 inch waste. That seemed less prone to catastrophic blundering than (trying to) make a pair of 8-foot cuts and whack each resulting strip in quarters. An ordinary razor utility knife worked fine, although I found that making two passes along each cut produced cleaner results than trying to do it all in one.

I assembled it with the heavy / shiny aluminum foil side inward, although I doubt it makes any difference. Cover all the edges with tape, tape all the joints both inside and outside, and it becomes a nice rigid box when you’re done. Pay attention to getting the sides at right angles; I used a framing square.

The board allegedly has an insulating mojo of:

R = 6.5 ft² • h • °F/Btu

Figuring a surface area of 32 ft² and a temperature differential of 120 – 60 = 60°F, the box should require 295 BTU/hr = 87 W to maintain that temperature.

Which, as it turns out, is pretty close to how it worked out:

Hot Box – Temp vs Time – First light

The lower curve shows a 60 W bulb with a 10 W 120 VAC fan heats the interior to a bit over 100°F in 100 minutes, where it looks to be stabilizing. That was the first test and showed that I was on the right track.

The second test, with a pair of 60 W bulbs and the fan produced the two upper curves: one for air, the other inside some cloth jammed inside a plastic bucket to simulate a (tiny) suitcase. The combined 130 W heats the box over 150°F in two hours, with the somewhat insulated bucket trailing neatly behind as you’d expect.

Without opening the box, I connected the bulbs and fan to a Variac plugged into my Kill-A-Watt meter and dialed it for 100 W total dissipation. The temperature fell to slightly over 130°F in 80 minutes and looks like it would stabilize near there.

Ambient temperature was 67°F, so

R = 32 ft² • 67°F / (341 BTU/hr) = 6.3

Close enough, I’d say. Given those few data points, it looks like the temperature sensitivity around 130°F is 0.7°F / W. [Update: typo in the equation. Doesn’t change the answer much at all.]

I swapped in a 100 W bulb, removed the Variac, and heated the cushions from my office chair.

Hot Box – Chair cushions

One thermocouple is hanging in mid-air, the other is wedged inside one of the cushions. After nearly 5 hours the cushion is up to killing temperature and I turned the heater off. The air temperature drops rapidly, but the cushion stays over 120°F for another two hours.

The light bulb is just a proof of concept, because it’s entirely too hot: if the fan fails, your luggage ignites. I plan to build a rather subdued heater with a surface temperature around 140°F and a controller that monitors several sensors to ensure the contents reach killing temperatures and stay there long enough.

But that’s a project for another day…

[Update: If you’re arriving from a link, start at the overview to get The Whole Story.]

2010-11-20