CompUCut
CompUGuide
Universal, programmable, 4-axis, diy, full PC screen DRO system. Developing on the theme of the 'Rodent Rules' for an inexpensive DIY DRO system (MEWs 86, 87 & 88), CompUGuide offers the additional feature of being programmable.
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CompUGuide displays positional information for up to FOUR axes. These can be any mix of LINEAR or ROTARY movements. The inputting transducers can be based on the electronic circuitry taken from serial mice (RODENTS) or the imported Chinese LINEAR SCALES sold by most dealers who cater for amateur engineers. The displayed angular resolution of the rodents will be set by the users design but 0.02 degrees would be easily achievable using a 75 slot encoder and 60T worm wheel. The displayed resolution of the scales is 0.001 inches or 0.01mm and my four scales are accurate to this. Note, the CompUGuide hardware/software system is inherently accurate, it simply relays the data from scale to PC. The four line display fills the screen of a PC so can be easily viewed when placed at a considerable distance from the machine. The input devices can have units of mm, inches, degrees or rpm. The 'tacho' function requires a separate TTL level pickup from the spindle which can be fed into the COM port along with Rodent data. Feed this signal into pin 9. MODE 1: In the default DRO mode the display shows the current position in ABSOLUTE format. This position will usually be zeroed at the machine datum points. |
PCB drilling with CompUGuide (using airbine cutter head) |
| The inputs are all scaleable and reversible to allow for different methods of deriving the data to give a true display, this is especially important for rotary axes using different worm/wheel combinations. In DRO mode the advantage of the CompUGuide system is that it allows the transducers to be mounted out of the way of suds and swarf which usually means out of sight, and since the interface unit powers the scales they don't even have to be disturbed for battery changes. MODE 2: In RELative DRO mode the display can be zeroed and the scale parameters changed in the edit window without affecting the ABSolute co-ordinate system. | |
| Example, When the system is installed on a lathe, mode 2
can allow the Y-axis to display DIAMETRAL units and the polarity can be
changed to allow an incrementing display when turning both external and
internal diameters. Since my machine datum is usually the lower left hand
corner of the XY envelope (saddle wound right up to chuck end of bed,
cross slide retracted fully from axial centre line) it is also convenient
to reverse the X-axis polarity to show an incrementing display as the
boring tool enters the work. To turn an external diameter, face the end
of the work and zero the X-axis display. Take a measuring cut along the
Y-axis and measure the diameter at say, 67.35mm. Type y67.35 in the Edit
window, zero the Y-axis and click STEP to display 67.35 mm. Thereafter
the Y-axis display will show the diameter which will be turned for any
setting of the cross slide. Simply set the cross slide to display the
diameter required and feed in X until the X-axis display shows the required
length. To turn an internal diameter, face the end of the work and zero
the X-axis display. Take a measuring cut along the drilled bore at say,
32.56mm. Type yR32.56 mm in the Edit window, zero the Y-axis and click
STEP to display 32.56 mm. Note, the 'R' in the input line signifies 'Use
reverse Y-axis polarity' At this point the Y-axis display will show the
size of bore which will be produced for any setting of the cross slide.
Move the cross slide to display the diameter of the bore on the Y-axis
display and feed in X until the X-axis display shows the required depth.
This 'It turns the diameter that's shown on the display' structure is
very convenient. MODE 3: In programmable 'GUIDER' mode the system uses
stored data in RELative co-ordinates and can be used as a 'virtual jig'
to guide the cutter to the correct location using a large clear display
that will always show the final 'TARGET' position as ZERO.
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| The user inputs a program in the form of a list of co-ordinates which can be typed straight into the inbuilt text editor or loaded in as a disk file. Either way, the format will be: x20, y65, z43, r75 It is not essential to order the axes as x , y, z, r and it is not necessary to specify values for axes that have not changed, so x35, r50 is acceptable, the file ends with the statement END; Example: BART.rod could be a file which when loaded might display at the bottom of the screen as: S Scale options are x1, y1, z1, and r1 S Set 5mm drill to datum 0,0 x20, y50 x30, y40 x60, y70 x95, y100 END; To execute this series of XY moves we 'left click' on the START button or press Cntrl & T on the keyboard. |
Assembled CompUGuide PCB |
| This displays a message with which we comply by setting to X0,Y0 then pressing Enter. The display is now zeroed by Ctrl plus the axis letter ie Cntrl X, then Cntrl Y, then Cntrl Z, and Cntrl R. Left clicking on STEP or Cntrl S on the keyboard will step through to the next program line. This will display X -20 and Y -50, which signifies that in your own time you will wind the table +20 in X and +50 in Y to give zero on the displays. Drill the 5mm hole, then press SPACE bar or press Enter or click STEP and proceed through the program moving to each successive pair of ordinates, drilling and pressing the SPACE bar for the next target to appear. 'S' screen message lines can be inserted as required at the job planning stage to make sure that you use the right drill or mill and that the job is correctly oriented in the vice etc. The program can be aborted at any time by clicking STOP or Cntrl T. These program lists are saved with a .rod extension to allow them to be identified as 'rodent' files | |
The computer display 'Guides' the user by displaying the 'ERROR' in the position of that axis relative to the current 'TARGET' position. For example, if the X-axis display changes to -200 mm, then the user moves the table +200mm in X which will cause the display to increment to zero. Note, the computer is NOT in control, the user turns the feed screws as usual but is guided by his own program to move just the correct amount including the allowance for backlash. Applications are obvious, when gear cutting or drilling with angular displacements or indeed making any movement involving several turns of a handwheel there is always the chance of a mis-cut due to an error of one whole turn or other miscalculation, this cannot happen with a non-cyclic display which simply has to be DRIVEN DOWN TO ZERO. CompUGuide'd orthogonal milling is useful as when making rectangular cutouts in small diecast boxes / front panels for electronic projects. Previously, when faced with the prospect of cutting several 9-way sub D connectors in each of a batch of small die cast boxes, I would start to lose the will to live. I won't claim that the following procedure makes it into a 'plum' job but it is bearable.
Try drawing in CAD with a cutter radius allowance and placing circles along the inner sloping edges of the cutout as 50% overlapping chain drilling, or tracing the cutout for a single connector using a cutter sized stylus on a tablet then save the cutter ' centre-path' details referenced from the left side fixing hole. This small 'software jig' can be executed as many times as needed simply by lining up a small 3-flute end-cutting mill with the reference hole and run your program. Use 'S' messages to remind you when to leave the cutter down for orthogonal piercing cuts and when to chain drill the awkward shapes. Don't bother with Z-axis data for this class of work, just advance the mill into the work to cut close to the top of the flutes for max stiffness and to save wear at the bottom. Hint; use several layers in the CAD file to make it clear where the piercing and chain drilling data is delineated. These .plt files then require editing into your program list. Hint; Chop off some pieces of 3*2 or whatever timber is slightly larger than your boxes to prove the program. You only need to skim the faces when profiling. What is required: The PC needs to be 300MHz or faster as it is quite busy in this application.
The operating system needs to be Windows 2000 or later with Microsoft Internet Explorer Ver 5.01 or later. The program prompts you to download a free update of this program if needed. A single serial port will support up to FOUR scales or TWO rodent devices. I consider a very useful configuration to be two COM ports with XY&Z scales sitting on COM1 and a Rodent rotary encoder for the headstock or dividing head sitting on COM2. The software comes on one CD which also contains the Microsoft dotNET Framework 1.1 which is easily installed if you haven't already got it. The dotnetfx.exe file is also available as a free download from Microsoft. The hardware will include whatever scales or rodents you need for your application. The mouse brained Rodents with their new encoder wheels are plugged straight into a COM port. The scales which are UNmodified except for removing the watch type cells are plugged into the interface unit which in turn plugs into a second COM port. A small 9-12v power supply is needed to power up the interface. Since a 12v machine lamp supply will easily power this device in addition to its halogen bulb there is scope to build the interface into the lamp base and share the mains input keeping the trailing wires to a minimum. That's it, mount your scales / rodents and allow them to guide you around the work, but do remember that it is your map that they are following.
Over 1,800 folk have downloaded the 'Rodent Rules' program from our website, so there ought to be a few dismembered mice around with 'big wheels and no balls' ready to get guiding. The CompUGuide program has several 'macro' commands which are called by a single letter and, in some cases by parameters. These are short routines which are dedicated to common situations. They include: C; The 'MOVE TO THE CENTRE OF A CIRCLE' command. The user chucks a short dowel to act as a probe and positions it within the bore of the work (Imagine chapter rings of clocks or rear sprockets for motor bikes) The screen prompts the user to set the probe against the bore in three places, the program then calculates the XY co-ordinates to display allowing the user to wind to X0,Y0 and be at the centre of the bore. Can also be applied to the external perimeter of a circular component. B p200, h7, a25; The command to drill any number of equispaced holes on any Pitch Circle Diameter. The example parameters show 7 holes around a PCD of 200 starting at 25 degrees. (It's often useful to run the C command prior to the B command.) Mx; (alternatively My; or Mz; or Mr; ) The 'Midpoint' command. The user chucks a short dowel to use as a probe and positions it, for example between the jaws of a vice which clamps a horizontal bar. The program prompts to set the probe against first one limit (jaw) then the other, it then calculates the ordinates to display to allow driving down to display zero when exactly mid way between the jaws. G t74; The angular dividing routine. The user is presented with displayed R-axis ordinates which are driven down to zero for each successive tooth of a gear wheel. S Type any message here; The Screen command puts a message on the screen to elicit a user response such as change tools, check size, relocate work etc. User must press Enter to acknowledge message before stepping on.
Building the CompUGuide System
BASIC KIT Includes:
The user buys the 30 or so electronic components to be soldered into the PCB from Maplin, RS Components or Farnell etc.
Click here for the price guide.
