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It was at this point that I first discovered Lithophanes and once seen, I had to be able to make them, they are really impressive. Yet another piece of software was required. I started with 'Bmp2Din' and later tried the trial version of 'Bmp2Cnc', both produced good results. This Handsome fella is a striking example of my fascination with lithophanes.
Another software is 'CamBam', this is capable of producing the depth maps necessary for lithophanes and just about anything else I would want to make. The down side is that I am finding it difficult to learn how to use it properly. According to its authors, 'CamBam' is still under development but it already has a large following with very active website, forums and people willing to help with problems. One such person is 'Yohudi' aka Danny at cnc4free.org.
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Initially there are decisions to be made which once you have decided are probably difficult to reverse. Stepper motors or servo motors, there are many arguments for each but I have chosen stepper motors. Operating language, there are many of these, I have chosen G-Code. Both of these decisions were based solely on popularity amongst 'hobby CNC builders' and the availability or otherwise of the software & hardware.
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Tweakie has been constructed using bipolar stepper motors as the driving force for each of the three axis. These stepper motors require a dedicated form of control electronics (which, fortunately, is readily available and is not expensive) this consists of one or more discreet p.c.b's. which require minimal wiring to get the whole thing working. An additional requirement is of course a PC. All that is required of this driving computer is to convert the source G-Code to Step and Direction pulses for each of the 3 axis and the software 'Mach3' takes care of this task perfectly. I originally tried a low priced laptop without much success as it appears that Mach3 derives its timing pulses directly from the microprocessor and if the processor has a high overhead (carrying out tasks in the background) it multi-tasks. This affects the timing pulses which become erratic, upsetting the speed and reliability of the stepper motor positioning. An old and very basic PC solved the problem, I can run the steppers at high speed and no steps or pulses are lost. Artsoft (owners of Mach3) do provide helpful tips on reducing background tasks and suggest ways of improving performance - the bottom line, of course, is that they provide the software on a 'try before you buy' basis. I wish all software was available like this.
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Now that Tweakie is operational, design software is required to create the G-Code in order to make things. There are of course many good (and free) programs out there and my first trial was with 'G-Simple'. This program let me design and profile cut the CNC cube. It was quite easy to get started by following the examples given and I had produced a perfect G-Code for my cube within a couple of hours. I was, and I still am, absolutely amazed at the accuracy to which these parts were cut. They were a little undersize (probably due to non-concentricity of the Jacobs chuck I am using) but each part was as identical to each other as I could measure with verneer callipers. To be fully proficient at using G-Simple, well, this would take some time. |
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For vinyl cutting, different design software is required but a fortunate thing is that pen plotters have been around for a long while now and there is a lot of freely available programs which produce HPGL Code (Hewlett-Packard Graphic Language) which has become the industry standard for plotters and guess what, HPGL is easily translated to G-Code. My first venture was downloading ready made HPGL graphic files (Company Logos), converting them to G-Code using 'Target2GCode' then feeding the result into 'Mach3'. Success first time ?, not quite, the vinyl cutter I had made and fitted to Tweakie needed setting up but I was soon making lovely decals. To create original artwork I used a trial (now sadly expired) version of 'SignGo' which again outputs HPGL which I converted to G-Code as before. Now I had to buy lots of different coloured vinyl (sticky backed plastic) and the low tack application tape and I was making signs.
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Wood routing. Tweakie was designed to take a 27000 rpm Bosch router but this was so incredibly noisy I tried the 3000 rpm, 3 phase motor I had used for profile cutting and with a 6mm, single flute milling cutter this routed softwoods, mdf and hardwoods perfectly (obviously the feed rates had to be reduced because of the lower rpm but the results were really good). I should say at this time I had a lot of failures along the way, not getting the cutting depth correct, starting at the wrong point on the work, getting the scale factor wrong, not zeroing the axis properly etc. etc. etc. and my photos only show the good stuff, not all the junk that went into the bin. |
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Software and Hardware issues. |
