Repair a Broken Tip For A Tormach PCNC Touch Off Probe

If you have a Tormach PCNC machine with their passive touch off probe you’re bound to break the tiny ceramic tip at some point. There’s two strategies, one is to buy a new one with a carbide or stainless steel tip but then if you crash it you might damage the probe itself – the alternative is to upgrade to a thicker boss by purchasing a non-Tormach replacement. Either of those doesn’t help you with your current problem – finishing the job you started with a non-broken tip!

I ended up trying to drill out the broken off chunk of ceramic with carbide tooling but to no avail. What did work great was heating up the probe tip with the broken ceramic stuck in it with a propane torch, the glue burns off and the broken ceramic chunk will fall out. You can then superglue whatever you’ve got left of the tip back in. Of course you’d think this would mess up the precision of the tool but that’s why you have to calibrate the probe in the first place, because it’s not glued in precisely initially.

Once your probe breaks off:

Add heat with a propane/butane torch:

Reglue the remaining tip into the socket with some super glue:


Slightly shorter and the stainless steel is a little crispy looking – but it works fine!

Go forth and save your $90 on the replacement, at least for the first time until it ends up too short!

RepRap gcode using MeshCAM

Warning – this post was sitting in the drafts, I don’t know how helpful it’ll be but it’s been sitting for 5 years – may as well release the information and hope it helps someone.


If anyone out there is running the RepRap / Makerbot gcode intrepreter for a CNC dremel / router / etc and is trying to use MeshCAM here’s some instructions:

Use MeshCAM as usual, but you’ll want to use this post script (you probably don’t actually need to print all of the XYZ commands when you’re not moving them, but it doesn’t hurt to do it, hence the @ rather than #):
; MeshCAM config
; This config is the basis for the minimum
; gcode output. If you're looking for
; the shortest output file then this is the config
; to start with. Also show how to integrate CutViewer config into
; the output.
; 2/29/04 Changed comments to be enclosed by () rather than start with ;
; Added CutViewer config output
; 5/13/04 Added toolchange gcode
; 2/12/05 Changed name and added units
; 3/17/05 Changed stock definition to use CUTVIEWERSTOCK variable
; 5/19/05 Removed feedrate command for rapid moves
; 5/25/05 Added dummy tool for CutViewer
; 6/27/05 Changed the formats to 1.4 to get 4 decimal places of accuracy
DESCRIPTION = "RepRap GCode-MM(*.nc)"
FORMAT = [F|@|F|1.1]
FORMAT = [X|@|X|1.4]
FORMAT = [Y|@|Y|1.4]
FORMAT = [Z|@|Z|1.4]
START = "%"
; The following is a dummy tool to keep CutViewer from generating an error when G20 is called without a tool
START = "(TOOL/MILL,0.1,0.05,0.000,0)"
START = "G21 ;Metric is good"
START = "G90 ;Absolute Positioning"
RAPID_RATE_MOVE = "G0 [X] [Y] [Z]"
FEED_RATE_MOVE = "G1 [X] [Y] [Z]"
END = "(END)"

Here’s a text version, make sure to rename the extension to .con and put it in your posts folder in the MeshCAM installation directory

RepRap gcode-MM

Next up, open your STL/etc file, set up your tooling, and then the important part:

Your RepRap will not allow you to cross the Z axis, so when MeshCAM creates the gcode and moves the position to positive Z to clear the work surface, your RepRap will toss this command and destruction will ensue. . .  Figure out your retract height, in my case I set it to 2.5mm so I can easily remember it.  You want to take this number, then set your stock size to fit geometry (or as needed), but make sure you add your retract height to the stock height and put it in the Z Position.

For example, I have a 5.08mm block I’m machining, with a 2.5mm retract height.  So I would define my Z Position as 5.08+2.50 or 7.58mm  This will result in your retraction remaining less than 0mm and the machine will actually retract away from the workpiece.

Dreamhost How to Use Cronjobs to Email Backup MySQL Databases

I’ve been using Dreamhost for a while (works great btw), I had been backing things up manually but I thought it was about time to start automated mysql backups. Looking around online I found these instructions but they simply say to modify the instructions and add this mutt command

mutt -a /home/username/backups/archives/mysql_backup.$suffix.tar -s "MySQL Backup"

to get e-mail backups working. In reality, this command will merely open up mutt and create a new message but it will not automatically send it without additional input. Buried online I found someone else who said to simply:

mutt -s "MySQL Backup" < /home/username/backups/archives/mysql_backup.$suffix.tar

which does automatically e-mail you, but it just dumps the file into the e-mail body without attaching it as a document. What that statement is really doing is piping in body text and completing the e-mail prompts magically, which isn’t what I wanted to do. The solution is to:

mutt -a /home/username/backups/archives/mysql_backup.$suffix.tar -s "MySQL Backup" < emailbody.txt

What this gives you is an attachment of your file, and then it pipes in an e-mail body (put it in the same location that this script is running from) and sends the message. You would also use echo statements to “type” whatever additional input you wanted in mutt and script the rest of the message completion [untested but it conceptually should work, YMMV]

Full Script:

cd /home/username/backups/
mkdir mysql
suffix=$(date +%y%m%d)
mysqldump --opt -uUser -ppass -h db_nameA > mysql/db_nameA.$suffix.sql
mysqldump --opt -uUser -ppass -h db_nameB > mysql/db_nameB.$suffix.sql
tar -cf archives/mysql_backup.$suffix.tar mysql/*
mutt -a /home/username/backups/archives/mysql_backup.$suffix.tar -s "MySQL Backup" < emailbody.txt
rm -r mysql/

RepRap is Alive!

I’ve been wrenching for a few weeks to machine enough pieces to create a CNC plastic extruder (RepRap / Makerbot). I’ve got the CNC part done, now I have to get the extruder and heated bed up and running so I can start RPing parts.

Sector67 Forum Thread

I’ve gotten a few questions as to what you’re looking at, if you’re completely unfamiliar a visit to Wikipedia should clear things up.

It’s made out of 2″ x 2″ extruded aluminum channel, the railed looking stuff that makes up the top of the arm and the drop for the spindle (dremel) is called 80/20, it’s fairly expensive but is very precise and saves a lot of time for some projects.

The Z axis is the classic over constrained parallel rods, I pulled the rods out of a pair of identical printers and then drilled and reamed to size the end blocks and the slider block, which is just a chunk of delrin plastic. The bad part about using a plastic block for a sliding surface is that you have a drill/ream it over significantly to get it the right size, which in my case just means it’s sloppy and will be replaced by linear bearing when it becomes the weakest link in the machine for precision or stiffness.

The bottom end X-Y axes are THK precision linear bearing. I picked this out of discarded equipment at the university, which I understand it not available to “normal people”. I found out a few years after I picked it up that it’s $0.43/millimeter (yep, that’s a half of a dollar per the thickness of your fingernail, it’s expensive). The bearing carriages are ~$130/each. I was fortunate enough to find a pair of 18″ linear track and a pair of bearings still in their well oiled bags! They do have lash in them and should certainly be run in parallel or with a precision guide track for stiffness/rigidity but for my application (milling light plastics and depositing plastic in an additive process) it’s not a major concern this early in the project.

The other common question is how much does this thing cost. So far I have $199 for the full generation 3 Makerbot electronics (thanks Zach et al., they work great!) and $4.11 for 3 x 1″ long 1/4-20 nuts that are used on each of the axes (True Value). The rest has been collected or given to me by others.

These are a few of my favorite stores. . .

I’ve been meaning to post this for a while now 🙂

Electronics vendors:
Digikey (Excellent search function, expensive but very good pictures, lots of products too)
Mouser (lots of what digikey has but no pictures! Great for Delphi / Amphenol connectors)
Newark (bigger weirder stuff, careful some stuff ships from Farnell in the UK)
Jameco (Search is terrible, but if you can’t find it anywhere else. . .)
Allied Electronics (Cheap amphenol. . .)
Waytek (cheap for bulk connectors and wire, next day shipping)

Adafruit (cheap and usually has what I need, I’d rather pay a little more to support a still growing startup)
Sparkfun (expensive but a good one-stop-shop)

Electronics Surplus:
All Electronics

China Direct Electronics:
Futurlec (Cheap, good customer support, responsive, shipping takes a while – as indicated up front)
Deal Extreme (holy cheap, lots of people on eBay/discount stores are buying and drop shipping from them)
Sure Electronics (Lots of great cheap parts, you have to add them to your cart and check shipping after each item though, they’re making up some of their costs by charging shipping for each item – I received everything 3rd day after I ordered it though, which is amazing)
MPJA Ships from Florida, cheapest breadboard prices I’ve ever seen, not sure about anything else.

McMaster-Carr (Expensive, ships quick, stocks a lot, great pictures/details on products, search rocks)
Grainger (Search sucks, plumbing stuff/etc much cheaper than McMaster, if you can find anything. . .)
MSC Direct (Tooling, industrial consumables)

Harbor Freight (If you’re on a budget you can’t get better than HF tools, but make sure you read the reviews)

How to Program Sparkfun Arduino Pro Mini

I just picked up a Sparkfun Arduino Pro Mini board for a project.  It’s a really nice really compact board with almost all of the pins broken out on it.  If you already own a Duemilanove you can easily program it using the Arduino software, just pull the Atmega chip off the Duemilanove and then using the shortest side of the board’s contacts, wire:

reset – grn
blank – blk

The words grn and blk are silkscreened on the board to denote which pins are which.  You could of course use a RS232->TLL converter to program this as well, but using the Duemilanove is really convenient as it pulls the reset pin low for you.

On the topic of this Pro Mini board, I had a few e-mails back and forth with Sparkfun trying to figure out what the actual maximum input voltage for the board is, Sparkfun’s Website lists it at 12VDC max, the EagleCAD schematics list it as 16VDC, and the datasheet for the voltage regulator list it as operational maximum 16VDC, with an absolute maximum of +/-20VDC before damage occurs.

Also noted is that the oscillator on this board is absolute crap, I have a timing critical application that I intended to use this board on, using a stopwatch and a Duemilanove and this board, both running identical software and hardware configurations:

15hours 37 minutes elapses, the Duemilanove is exactly in sync with the stopwatch still, the Pro Mini has gained 1 minute and 1 second. I ran this test several more times with identical results, the stop watch and the Duemilanove are in sync, with the Pro Mini gaining time each time, always about 20 second per 5 hours elapsed time, which is not acceptable in my application.

I swapped the Sparkfun crystal/resonator for one of my own resonators and ended up with the same crappy timing. I finally switched out the resonator for a crystal and a pair of capacitors tied to ground and was able to clean up the timing mostly, it’s still gaining a second for every 40 minutes it runs for, it was previously 15 so it’s improved, but not ideal. I’m going to ditch using the Sparkfun board for my own layout on the next iteration.

National Instruments DIAdem Text @@ Commands

If you’ve ever used NI’s DIAdem for data analysis you know how useful it is for looking at and analyzing large datasets.  What you may or may not have discovered is the @@——@@ commands that can be used to display channel related texts anywhere in the program.

DIAdem helpfully gives you a list of available commands, but doesn’t tell you what they display or how to use them.
Program Command: @@ChnPropGet(No,Property name)@@
Formatting: @@ChnPropGet(1,”Description”)@@
Output: The 1st channel’s Description, other input could be Name, Unit, etc
Notes: Make sure to use quotes around the Property name and remember that the channels are counted from the very first channel onwards and found as “Number” in the channel information.

Command: @@CD()@@
Formatting: @@CD(1)@@
Output: The 1st channel’s Units

Command: @@ChD(Line,No)@@
Formatting: @@ChD(2,1)@@
Output: The 1st channel’s second data point value

Command: @@CL(No)@@
Formatting: @@CL(1)@@
Output: The 1st channel’s number of points (length)

Command: @@CNoXGet(Channel group number,No)@@
Formatting: @@CNoXGet(2,1)@@
Output: Finds the 2nd group’s first channel and returns it’s channel number (counting from the first channel.
Notes: Could be considered translating from relative position of a channel (in a group) to absolute position in the list of channels.

Couple of general notes, you can’t nest lookups (at least not in the text boxes, so it would be invalid to:


and turn it into a lookup:

Otherwise it’s pretty helpful to use these when labeling graphs/etc so you don’t have to constantly correct things.  DIAdem also builds in lots of string functions like trim/etc, so you can clean things up if necessary!

<Wordpress>  – I had all these formatted nicely in a table but WordPress ate itself trying to render it, hence the oddball list, sorry. </Wordpress>

MAX6675 Thermocouple Amplifier EagleCAD

I created a little SMT board for the MAX6675 thermocouple amplifier in EagleCAD if anyone out there is in need of a board.  It’s very simple layout but it is a bit noisy, definitely expect to average samples coming from this chip (/board?).  Other improvements would be adding a thermistor as the CJC (cold junction compensation) on the board so you can accurately offset the junctions at the board where you break the thermocouple wire and transition over to copper (which creates another TC junction unintentionally so you must compensate for it).

MAX6675 TC Amplifier Board and Schematic

MAX6675 TC Board Schematic and Board (and Panelized)