tag:blogger.com,1999:blog-12223283.post7490162262072676883..comments2009-06-03T08:46:18.462+01:00Adrian Bowyerhttp://www.blogger.com/profile/17595509188999219420noreply@blogger.comBlogger13125tag:blogger.com,1999:blog-12223283.post-80526764762469543792009-05-27T23:41:20.255+01:002009-05-27T23:41:20.255+01:00...<br /><br />Err, why are you extending G-code with an E keyword like it were a new axis? The extruder only goes one direction, right? (And even if you do need an axis, why not use one of the ones G-code already has defined, like C or B?)<br /><br />It seems more elegant to me if you used the S keyword to set the spindle speed, then tie the extruder feed rate (spindle speed) to the XYZ axis motion. For example, with S75 (75% rate), the extruder could extrude 75 mm of plastic for every 100 mm of motion on the XYZ axes. This would let you handle acceleration as well, since you can make extrusion match the instantaneous speed of the motion while accelerating, while not having to independently calculate out a distance to move on the E axis like you have now.<br /><br />When folks want to hand-tweak the G-code later for optimization, (and they eventually will), they'll thank you for the ease of use, and consistency with standard G-code.Revar Desmerahttp://www.blogger.com/profile/05536179239120721950noreply@blogger.comtag:blogger.com,1999:blog-12223283.post-33281873474231275082009-05-27T23:38:47.414+01:002009-05-27T23:38:47.414+01:00...<br /><br />Err, why are you extending G-code with an E keyword like it were a new axis? The extruder only goes one direction, right? (And even if you do need an axis, why not use one of the ones G-code already has defined, like C or B?)<br /><br />It seems more elegant to me if you used the S keyword to set the spindle speed, then tie the extruder feed rate (spindle speed) to the XYZ axis motion. For example, with S75 (75% rate), the extruder could extrude 75 mm of plastic for every 100 mm of motion on the XYZ axes. This would let you handle acceleration as well, since you can make extrusion match the instantaneous speed of the motion while accelerating, while not having to independently calculate out a distance to move on the E axis like you have now.<br /><br />When folks want to hand-tweak the G-code later for optimization, (and they eventually will), they'll thank you for the ease of use, and consistency with standard G-code.Revar Desmerahttp://www.blogger.com/profile/05536179239120721950noreply@blogger.comtag:blogger.com,1999:blog-12223283.post-13680235406414209742009-05-11T19:49:00.000+01:002009-05-11T19:49:00.000+01:00aka47,<br /> Bizarre, I had the same idea while out walking this weekend. I.e. using green ABS as a support for white.<br /><br />I have no idea if i will work, but worth a try when I have two extruders working.nopheadhttp://www.blogger.com/profile/12801535866788103677noreply@blogger.comtag:blogger.com,1999:blog-12223283.post-35341988087213011842009-05-10T08:30:00.000+01:002009-05-10T08:30:00.000+01:00Catty<br /><br />Less of a problem than it might first appear fortunately. But well observed.<br /><br />Both nozzles have to be adjusted to be exactly level.<br /><br />Even printing with one nozzle the nozzle is spaced from the work piece by at least the thickness you want to print. This is how one nozzle printing avoids smudging and colliding with what it has already printed.<br /><br />If the two nozzles are exactly level the second nozzle has the same clearance as the first and is no more likely to collide and smudge the print than was the first.<br /><br />Nophead also had a strategically placed brush to occasionally wipe the nozzle and get rid of Klingons.<br /><br />Hope this helps.<br /><br />Cheers<br /><br />aka47aka47http://www.blogger.com/profile/04272439579353956235noreply@blogger.comtag:blogger.com,1999:blog-12223283.post-2659282515971476472009-05-10T06:55:00.000+01:002009-05-10T06:55:00.000+01:00i see a potential problem with the two print heads, the second head might go over a section that has already been printed ans so is slightly higher.<br /><br />not sure how common those collisions would be, or if they can even happen, but it is a potential soure of problems. What is the clearance between the printed plastic and the print-head? what happens if one of the two nozzels is half a millimeter higher or lower?Catty Nebularthttp://www.blogger.com/profile/06150999371535640037noreply@blogger.comtag:blogger.com,1999:blog-12223283.post-4279908248308359812009-05-09T23:19:00.000+01:002009-05-09T23:19:00.000+01:00Much as I like your suggestion of mixing on the fly it wasn't quite what I was thinking of.<br /><br />Nophead has done some great work with different polymers. But most striking was that when he was working with the same polymer but different colours the physical properties ie melt temperature and adhesion were different. They were affected marginally by the pigment added to colour the base polymer. The pigment was acting as a dopeant.<br /><br />Theoretically if you have two independent extruders and nozzles sharing a single heater assembly with the common heater block set up for the temperature of the polymer to be used as the build material. If the second material is doped (coloured) to be less sticky at the same temperature it can be used as a detachable support material.<br /><br />By keeping the nozzles close together the amount of head travel needed when switching between materials will be minimised. As each layer is printed.<br /><br />Because you are relying on the differing properties of the two polymers you will not need to change the heater temperature from it's set value during the run. This means you will not be waiting for the temperature change when you switch materials.<br /><br />Eh voilà detachable support material.<br /><br />Thoughts for that they are worth.<br /><br />Cheers<br /><br />aka47aka47http://www.blogger.com/profile/04272439579353956235noreply@blogger.comtag:blogger.com,1999:blog-12223283.post-15735126508411609752009-05-09T10:42:00.000+01:002009-05-09T10:42:00.000+01:00I like the scary idea of running a number of extruders simultaneously to mix resins or colours or whatever. I won't make that addition for a while; I just want to add an accelerate/decelerate option, then we'll leave it to bed in for a bit. But we should definitely bear that in mind for the future.<br /><br />Calling RepRap "4D" - great for geeks; off-putting for keegs*, whom ultimately we want to be our main users, I think :-)<br /><br />*According to this new-fangled world-wide-cobweb thing, there is no antonym for the word "geek". The nearest is e-tarded, which doesn't quite cut the mustard. So I just coined that neologism. Remember, you saw it here first...Adrian Bowyerhttp://www.blogger.com/profile/17595509188999219420noreply@blogger.comtag:blogger.com,1999:blog-12223283.post-56175735514923544162009-05-08T23:21:00.000+01:002009-05-08T23:21:00.000+01:00That's really neat Adrian.<br /><br />Should we now be describing the RepRap as a 4D printer?<br /><br />Vik :v)Vik Olliverhttp://www.blogger.com/profile/14574212494833831824noreply@blogger.comtag:blogger.com,1999:blog-12223283.post-65965275655792793672009-05-08T16:59:00.000+01:002009-05-08T16:59:00.000+01:00Thoughts for what they are worth.<br /><br />Is it worth having an E1 to En so as to be able to run more than one extruder at once say for example two extruders at once. I am thinking here of running two feed stocks through independent barrels and nozzles set in a common heater block. One as the build material the second as a support material.<br /><br />Sort of a 2 in 1 extruder......aka47http://www.blogger.com/profile/04272439579353956235noreply@blogger.comtag:blogger.com,1999:blog-12223283.post-12252683224967394072009-05-08T10:32:00.000+01:002009-05-08T10:32:00.000+01:00&gt; incremental distance<br /><br />Yes - you get that automatically, as there&#39;s a G-code to switch from absolute to incremental positioning, and another to switch back. Now it does that for all four axes, of course.Adrian Bowyerhttp://www.blogger.com/profile/17595509188999219420noreply@blogger.comtag:blogger.com,1999:blog-12223283.post-32963835551025936662009-05-08T06:24:00.000+01:002009-05-08T06:24:00.000+01:00VERY nice! :-DForrest Higgshttp://www.blogger.com/profile/17208965471464716174noreply@blogger.comtag:blogger.com,1999:blog-12223283.post-32252203988072273992009-05-08T01:43:00.000+01:002009-05-08T01:43:00.000+01:00Could the incremental distance be used instead of the total distance? Using the incremental distance would mean a smaller distance variable and probably less calculation time on the Sanguino.Enriquehttp://www.blogger.com/profile/09426013757234244524noreply@blogger.comtag:blogger.com,1999:blog-12223283.post-33390235939363711262009-05-08T01:09:00.000+01:002009-05-08T01:09:00.000+01:00Adrian, I love this approach-- i have taken the same approach on my extruder.<br /><br />This approach appealed to me because when the extruder is the 4th axis, it should make it possible to do melt-flow compensation by using the 'position' and speec of the 4th axis.<br /><br />in my case i switched to incremental units to avoid a potential size issue with the ever-growing value of the axis.<br /><br />is that what you did?Davehttp://www.blogger.com/profile/11987514110079695313noreply@blogger.com