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About Ajohn

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  1. Nigel gave you some good advice Rick. Hope I have the right one but fringexp will allow you to play with the mirror rad and put errors where you want them to be or put another way allow you to minimise the work that needs to be done. The only catch really is the need at some point to but the knife edge pretty precisely on the mirror rad. John -
  2. I'm pretty happy about microstepping now and it's effects. Google comes up with a truth about microstepping web page at the top but I think it misses several important aspects and am more inclined to follow the comments in the links I posted. What I am still asking about is the steps per mm set in the software. Typical 3d printers might use a 2.5mm pitch belt and either 16 or 20T pulleys. along with 16x microstepping This results in either 40 or 32 steps per mm being set into the software. They are exact numbers. 8x microstepping would result in 20 or 16 and so on. Belt stretch might resu
  3. I had hoped some one would answer the steps per mm from the software end. I've read that too high a number can give the micro too much work to do. Looks to be dated info but leaves me wondering. I thought stinking fish when the power drop of with micro stepping was mentioned and thought that doesn't make much sense when the motor is rotating at some speed to produce a torque to drive something. The holding torque will drop off but that isn't what matters. The rotational torque does. 2 view on the subject http://www.designnews.com/document.asp?doc_id=221386 a pdf to download on
  4. There seems to be a number of extruder like the one I posted fitted to a number of printers, usually in Bowden mode. No gearing and the gear that drives the filament through is larger diameter than the usual ones in the geared extruders. It is shaped like a gear as well. I'd guess it can't handle more than 1.75mm but I suspect that will suite me. It's fitted with a 1.8amp nema 17. I can give it a try anyway. A while to go yet as some bits have to come from far away to keep the prices down - angle brackets for the frame material I will be using. I should have asked the question in another
  5. A question I hope some one can answer. How effective is microstepping on the extruder and axis. What sort of level is usually set? I've got to the point where I need to tie down feed rates on all of the steppers so wonder how far microstepping can be reliably pushed? The extruder arrived today. Some other bits have to come from far away but at least it's a start. This one could be converted to boden if needed. It appears to be the latest greatest. Doh I seem to have attached the image and can't add it to the thread. John -
  6. Not sure I have looked at the right parts Neil - 8bit 20mHz and a lot of variants? John -
  7. I was thinking in terms of using a shelf going back into the case to support the horizontal gears Gina. Backing paper running down from that an also in the "pocket" formed by the shelf leaving all of the gearing visible. I suggested making the clock face a bit smaller to get round the lack of visibility in the area you indicated with arrow A. That might mean changes to the size of the case or it might not. As it's a visual thing hard to say. The shelf gets around having a slot and leaves everything visible. I'm no artist though. Just a humble engineer. Mmmm you would ha
  8. I thought the volcano site might give more info on extruders but apart from offering up to 1.2mm even for 1.75mm filament little else. They do a 5:1 geared stepper but is seems to have rather low power for that sort of ratio. I wondered if it might be possible to use a screw feed to get more contact area. Length of bolt pressing on the filament but it would need a seriously long drive shaft to avoid having a sharp bend in the filament. Might be an idea for a bowden type as might a rubber wheel. I looked at the data on the other driver I mentioned. It's 2.5a peak, 1.8a rms but a lot
  9. I'm pretty sure that the stepper drivers are completely compatible with ramps. They are offered as an alternative. The spec might be a bit misleading as the part they use is rated at 1.8 amps rms. The 2.5 amps is peak and they might best be limited to 24v even though they will go higher. I managed to find a little bit more on the stepper motor ratings, from an RS data sheet. The 80C temperature rise is correct and it seems they are ok with an ambient temperature of -20 to 50C, I wouldn't want to touch one running at 130C though and would probably pass out if the ambient was 50C. I'v
  10. That's interesting Gina. When I looked at steppers the 12v ones didn't show up. I need more details on the electronics but my impression is that the stepper drivers are plugged into ramps so it's possible to use drivers such as these which allow the drive voltage to be increased which will also increase the speed the motors can switch at. http://ooznest.co.uk/3D-Printer-Electronic-Parts/Boards/DRV8825-Stepper-Motor-Driver These could be used for instance to switch 36 or 40v into the 12v parts which in principle will speed up the switching. I tried to find an online calculator th
  11. Thank's Gina The reason for thinking 23's one X and Y is that the X will be carrying 2 steppers and the guide and bearings for the X axis. Also in my view the same unit should from a reasonable basis for an engraver / super light router/miller. When ever this is mentioned on the web people compare it with cnc millers driven by mach 3 which in my view constitutes missing the point. They also mention missing G codes. At the moment there is a lot of work going on in various places using Arduino for cnc on lathes so why not mills. Initially I thought drive current to the steppers might be a
  12. Maybe a smaller dial just showing the teeth of the larger gear and the rest of the drive sitting on a shelf hidden by the background. The case would probably look better oblong then rather than square. I nearly suggested larger gears to keep the dial the same but the case would still probably look better oblong. John -
  13. For some reason I can get rid of the quote. Took 3 days to read the long one. Interesting again. From this and the other my vision looks like it will involve a sturdy frame. Not sure which aluminium section to use yet. Comparing prices may as well be the V guide type but not sure yet. Expensive option but I had a weird Ebay refund recently and they didn't want the item returned and I managed to sell it. Be good to spend it on something useful. So it's looking like a 500mm cubic frame with space for bits at the bottom and a 300x200 build area and what happens to be left or less for Z.
  14. I'm bleary eyed from reading the Pilot thread. A useful thread Gina. I'm worried. I now know I can buy some things such as borosilicate sheet etc. The braid is very abrasive so can understand why you switched to the V groove bearings. One of the interesting aspects was different masses on the x and y axis. I wonder if different motor powers might help - crazy thought. Good thoughts on the reasons for problems as well. I had forgot something that I actually spent some time using long ago. A drawing board. My excuse is that it was a different type but the x arrangement might prove usef
  15. Thanks Gina. I didn't think to search extrusion. I think I am going to have a vision. I've looked at various kits and it seems to be a good frame and by the look of it missing parts on the electronic side, and may not be in the uk really or so so simple flat aluminium plate frame with everything that looks like it may be made by a UK company with all of the fittings printed. So in some ways making one up appeals. I found some details on how the braid is handled - clockwise and anticlockwise around a drum. I sea fish a lot at times so am bound to have some braid about. I've seen com
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