The first one is ttt2ngc which simply demonstrates my C++ port of Chris Radek's truetype-tracer. The original code is a rather monolithic C-program while my C++ port is divided into smaller files and offers python-bindings and more options (for example arc, cubic, conic output can be turned on/off independently).

The seconds script is ttt2offset which takes ttt-geometry, builds a VD, and produces offsets. By reversing the list of points from ttt either inwards or outwards offsets can be produced. Currently the toolpaths are machined in the order they are produced, i.e. in order of increasing offset value. An improvement would be to order the loops so that for e.g. pocketing the innermost loop is machined first, and rapid-traverses are minimized.

The third script is ttt2medial. Here the VD is filtered down to an (approximate) medial-axis, and the edges of the medial axis are chained together into a toolpath. The chaining-algorithm could probably be improved much, again to minimize rapid-traverses.

If this is run with a V-shaped cutter with a 90-degree angle we can push the cutter into the material by an amount equal to the clearance-disk radius of the edge. This is a "V-carving" toolpath which should produce a cut-out very similar to the outline of the font. For added effect choose a material with  contrasting surface and interior colors.

It would be interesting to know if this v-carving g-code is anywhere near to correct. If someone has a cutting-simulator, or is adventurous enough to run this on an actual machine, I'd be very interested in the results! (here is the g-code: emc2_vcarve.ngc)

Here is a metric version. The max depth is around -3mm, so a 10mm diameter 90-degree V-cutter should be OK. The text should be roughly 100mm long: emc2_vcarve_mm_ver2.ngc

Disclaimer: This is experimental code. Warnings, Errors, and Segfaults are common.

By popular demand a simple example of how to modify the stepper_mm sample configuration to output phase-A/phase-B quadrature signals (stepgen type=2).

In core_stepper.hal we specify step type 2, and re-name/wire the stepgen output:

loadrt stepgen step_type=2,2,2

net XA <= stepgen.0.phase-A
net XB <= stepgen.0.phase-B
net YA <= stepgen.1.phase-A
net YB <= stepgen.1.phase-B
net ZA <= stepgen.2.phase-A
net ZB <= stepgen.2.phase-B


Then in standard_pinout.hal we wire the phases to the parport:

net XA => parport.0.pin-03-out
net XB => parport.0.pin-02-out
net YA => parport.0.pin-05-out
net YB => parport.0.pin-04-out
net ZA => parport.0.pin-07-out
net ZB => parport.0.pin-06-out


Since I have neither a parport nor an oscilloscope at hand right now I'm using some pyvcp LEDs to look at the A/B signals. These are set up with two changes to the INI-file:

[DISPLAY]
PYVCP = phaseleds.xml

and

[HAL]
POSTGUI_HALFILE = pyvcp_phaseleds.hal

The files I'm using are here: phaseleds.tar

Now it is possible to look at the blinking of the LEDs when the machine moves and see the 90-degree out-of-phase square waveform (see also image here).

Then install all the required packages with "sudo apt-get install". dpkg-checkbuilddeps suggests installing tk8.4 and tcl8.4 but I found that in ordet to get the configure-script to run without errors I needed tk8.5, tk8.5-dev, tcl8.5 and tcl8.5-dev, and I removed all the 8.4 packages of tk and tcl. That makes configure run without errors. Then try building:


$ cd src
$ ./autogen.sh
$ ./configure --enable-simulator
$ make


However that produces a number of linking errors. Don't ask me exactly why but this patch: 0001-changes-to-make-sim-build-on-ubuntu-11.10.patch.tar (updated corrected version!) seems to fix things, and I get emc2 sim built and running. Just in case anyone else wants to build on 64-bit Ubuntu 11.10.

A recent post on the dev-list has asked why the math I wrote down in 2006 isn't what's in the code, so here we go:

I will use the same shorthand symbols as used on the wiki page. We are at coordinate P ("progress") we want to get to T ("target") we are currently travelling at vc ("current velocity"), the next velocity suggestion we want to calculate is vs ("suggested velocity), maximum allowed acceleration is am ("max accel") and the move takes tm ("move time") to complete. The cycle-time is ts ("sampling time"). The new addition compared to my 2006 notes is that now the current velocity vc as well as the cycle time ts is taken into account.

As before, the area under the velocity curve is the distance we will travel, and that needs to be equal to the distance we have left, i.e. (T-P). (now trying new latex-plugin for math:) (EQ1)

$$T-P = {1 \over 2} t_s v_c + {1 \over 2} t_m v_s$$

Note how the first term is the area of the red triangle and the second therm is the area of the green triangle. Now we want to calculate a new suggested velocity vs so that using the maximum deceleration our move will come to a halt at time tm, so(EQ2):

$$v_s = a_m (t_m - t_s)$$

$$T-P = {1 \over 2} t_s v_c + {1 \over 2} t_m a_m (t_m - t_s)$$

$${1 \over 2} a_m t_m^2 - {1 \over 2} a_m t_s t_m + {1 \over 2} t_s v_c - (T-P) = 0$$

$$t_m = {1 \over 2}t_s + \sqrt{ {t_s^2 \over 4} - {t_s v_c - 2(T-P) \over a_m} }$$

$$v_s = a_m (t_m - t_s) = -{1 \over 2 }a_m t_s + a_m \sqrt{ {t_s^2 \over 4} - {t_s v_c - 2(T-P) \over a_m} }$$

discr = 0.5 * tc->cycle_time * tc->currentvel - (tc->target - tc->progress);
discr = 0.25 * pmSq(tc->cycle_time) - 2.0 / tc->maxaccel * discr;
newvel = maxnewvel = -0.5 * tc->maxaccel * tc->cycle_time +tc->maxaccel * pmSqrt(discr);

over and out.

We printed the same geometry three times, here is the second try (in the first try the base/bed wasn't staying very fixed, so the print resembles the leaning tower of Pisa...)

Here is the third try. Now we are moving the Z-axis +0.5 mm during the last Y-axis move. This is at 600mm/min.

We were pretty happy with the print-quality so far, considering this is the first ever test of our extruder/xyz-table setup. Some tuning of how much plastic is extruded for each mm of xyz-feed, and perhaps a heated printing-bed, should improve the quality further. Next is learning to use one of the many STL to G-code CAM programs and filtering the G-code output so it is suitable for our EMC2 setup (the extruder is the A-axis, in absolute mode).

Update: Risto has more on this in his blog: ?http://risto.kurppa.fi/blog/2010/12/first-prints-with-reprap-the-open-source-3d-printer/

The slider is used to set the jog speed in units of mm/min and the buttons jog the axes in the + and - directions.

HAL and XML files: halui_jog_example

We hooked up the temperature measurement circuit and the PWM-amplifier to EMC today and tested PID-control of the extruder head temperature. The ini, hal, and xml files for this are here: temp_control_pid.tar

It's probably much easier to figure out the connections from the diagram below than to browse the text files. The square wave, which has a frequency proportional to the temperature, comes in on parallel port pin-13, and is connected to an encoder. The encoder has a velocity output which will be equal to the frequency of the square wave in Hz. This frequency is used as the feedback for a PID-component which compares the measured frequency against a set-point which is taken from a pyvcp slider. The pid output is used as an input to a pwm-generator, whose output needs an inverter, since the pwm-amplifier is active-low. The PWM is output on parallel port pin 9.

I wish there was a tool which would draw these HAL/pyVCP diagrams automagically from the source files. There is some work in that direction already: crapahalic and HAL with gschem.

Here are some selected screenshots:

Next stop is getting the X and Z servos moving, as well as the hefty 2 kW spindle servo.

The xml and hal files are here: pyvcp_pause_resume_button.tar

The wikipedia-police have immediately put it on the list of pages to be deleted ("unremarkable", "no third party references", "borderline advert", etc.). So I decided to collect some references. It is best to archive them here also, in case the wikipedia page does get deleted.

There should be a report by Rogier Blom called roughly "Design and development of a real time trajectory planner for the Enhanced Machine Controller", but I wasn't able to find that. It's probably the same document as this one (the pdf has chapter 4->): http://emc.cvs.sourceforge.net/viewvc/emc/emc/doc/segmentqueue.pdf?view=log

Please comment below and/or enhance the wikipedia article if you find more references!

• Proctor, F. M., and Michaloski, J., "Enhanced Machine Controller Architecture Overview," NIST Internal Report 5331, December 1993. Available online at ftp://129.6.13.104/pub/NISTIR_5331.pdf

• Albus, J.S., Lumia, R., “The Enhanced Machine Controller (EMC): An Open Architecture Controller for Machine Tools,” Journal of Manufacturing Review, Vol. 7, No. 3, pp. 278-280, September 1994.

• Lumia, "The Enhanced Machine Controller Architecture", 5th International Symposium on Robotics and Manufacturing, Maui, HI, August 14-18, 1994, http://www.nist.gov/customcf/get_pdf.cfm?pub_id=820483

• Fred Proctor et al., "Simulation and Implementation of an Open Architecture Controller", Simulation, and Control Technologies for Manufacturing, Volume 2596, Proceedings of the SPIE, October 1995, http://www.isd.mel.nist.gov/documents/proctor/sim/sim.html

• Fred Proctor, John Michaloski, Will Shackleford, and Sandor Szabo, "Validation of Standard Interfaces for Machine Control", Intelligent Automation and Soft Computing: Trends in Research, Development, and Applications, Volume 2, TSI Press, Albuquerque, NM, 1996, http://www.isd.mel.nist.gov/documents/proctor/isram96/isram96.html

• Shackleford and Proctor, "Use of open source distribution for a Machine tool Controller", Sensors and controls for intelligent manufacturing. Conference, Boston MA , 2001 , vol. 4191, pp. 19-30, http://www.isd.mel.nist.gov/documents/shackleford/4191_05.pdf or http://dx.doi.org/10.1117/12.417244

• Morar et al., "ON THE POSSIBILITY OF IMPROVING THE WIND GENERATORS", International Conference on Economic Engineering and Manufacturing Systems, Brasov, 25-26 October 2007, http://www.recentonline.ro/021/Morar_L_01a.pdf

• Zhang et al., "Development of EMC2 CNC Based on Qt", Manufacturing Technology & Machine Tool, 2008, http://en.cnki.com.cn/Article_en/CJFDTOTAL-ZJYC200802046.htm

• Leto et al., "CAD/CAM INTEGRATION FOR NURBS PATH INTERPOLATION ON PC BASED REAL-TIME NUMERICAL CONTROL", 8th INTERNATIONAL CONFERENCE ON ADVANCED MANUFACTURING SYSTEMS AND TECHNOLOGY JUNE 12-13, 2008 UNIVERSITY OF UDINE - ITALY, http://158.110.28.100/amst08/papers/art837759.pdf

• Xu et al., "Mechanism and Application of HAL in the EMC2", Modern Manufacturing Technology and Equipment 2009-05, http://en.cnki.com.cn/Article_en/CJFDTOTAL-SDJI200905037.htm

• Zivanovic et al., "Methodology for Configuring Desktop 3-axis Parallel Kinematic Machine", FME Transactions (2009) 37, 107-115, http://www.simlab.mas.bg.ac.rs/istrazivanje/biblioteka/publikacije/Transactions_FME/Volume37/3/01_SZivanovic.pdf

• Glavonjic et al., "Desktop 3-axis parallel kinematic milling machine", The International Journal of Advanced Manufacturing Technology Volume 46, Numbers 1-4, 51-60 (2009), http://dx.doi.org/10.1007/s00170-009-2070-3

• Staroveski et al., "IMPLEMENTATION OF A LINUX-BASED CNC OPEN CONTROL SYSTEM", 12th INTERNATIONAL SCIENTIFIC CONFERENCE ON PRODUCTION ENGINEERING –CIM2009, Croatian Association of Production Engineering, Zagreb 2009, http://crosbi.znanstvenici.hr/datoteka/421305.209-Staroveski-Brezak-Udiljak-Majetic-CIM_2009.pdf

• Li et al., "Control system design and simulation of parallel kinematic machine based on EMC2", Machinery Design & Manufacture 2010-08, http://en.cnki.com.cn/Article_en/CJFDTOTAL-JSYZ201008074.htm

• Li et al., "Kinematics Analysis and Control System Design of 6-DOF Parallel Kinematic Machine with Matlab and EMC2" , Advanced Materials Research (Volumes 102 - 104): Digital Design and Manufacturing Technology, 2010, http://dx.doi.org/10.4028/www.scientific.net/AMR.102-104.363

• Klancnik et al., "Computer-Based Workpiece Detection on CNC Milling Machine Tools Using Optical Camera and Neural Networks", Advances in Production Engineering & Management 5 (2010) 1, 59-68, http://maja.uni-mb.si/files/apem/APEM5-1-view.pdf

• Milutinovic et al., "Reconfigurable robotic machining system controlled and programmed in a machine tool manner", The International Journal of Advanced Manufacturing Technology, 2010, http://dx.doi.org/10.1007/s00170-010-2888-8