On Mon, Jun 14, 2021 at 9:43 AM John Dammeyer <jo...@autoartisans.com> wrote:
> Have you any photos of the 3D printed motor mounts etc? Direct drive or > belt driven? The 3Nm implies size 23 so I'll guess direct drive. > John > THis shows X and Y. https://youtu.be/wupYP2NNsXI?t=33 This shows the Z axis. On this machine the nut spins on a non-rotating ball scew https://youtu.be/tlMTksuOuZQ?t=27 This is a render of some z-axis parts https://a360.co/3zrzIwB Note that in the two above videos I am used 3D printed timing belts. At first I did this as a joke but they actally work for almost an hour with is long enough for testing to see if you have the right size belt. It is just plane old PLA printed 100% solid. All the timing pulleys are printed but have steel hubs and steel set screws. Here is an interactive 3D model you can look at. This versionhas some alignment issues but by using the "eplode" button and slider you can look at the parts and rotate them to see all sides https://a360.co/2TxOscU "Universal PWM spindle speed control device" (don't laugh, it works.) https://a360.co/2N95AiL > > > > -----Original Message----- > > From: Chris Albertson [mailto:albertson.ch...@gmail.com] > > Sent: June-14-21 8:41 AM > > To: Enhanced Machine Controller (EMC) > > Subject: Re: [Emc-users] Spindle Control > > > > Yes, I thought about reverse engineering the spindle motor controller and > > fitting it with a conector for external PWM input but my goal with this > CNC > > conversion was to try and do the lowest cost and easiest possible > > conversion and document it. So at every decision point I take the > simplest > > route that costs the least and most importantly, they anyone reading my > > instructions could follow. As soon as I suggest modifying a controller > > board, I've lost 90% of the machinists who might be following my > > instructions. > > > > To that end I've 3D printed almost all the parts needed for CNC > conversion. > > People usually use metal but the stepper motors I use only only > produce > > less them 3 Newton meters of torque. The the maxim force the motor > mounts > > will ever see is 3 Newton meters. I don't need cast iron for that, > plastic > > works. My goal is to do the complete conversion including motors and a > > ball screw all for under $400 with an assembly time of no more then one > day > > of work, not counting the time needed to print the parts. I looks like > > I'll meet these goals. > > > > I use a dial indictor to measure deflection under load of the plastic > parts > > and there is one part on they-axis that needs to be redesigned into the > > more organic-looking shape with compound curves. I find this is the > > "secret" for making strong 3D printed parts, It is the same reason car > > fenders don't bend, even though that are made with thin sheet metal, It > is > > the compound shape. Printed parts are like that, they are made of a > thinn > > skin of solid plastic over a light foam-like core and all the strength is > > in the skin. Flat slabs of printed plastic are not very strong or > ridgid. > > > > I does not impress me much that someone can build a CNC milling machine > for > > $10,000 and 6 months of work. Anyone can do that. What I want is "under > > $400 and one day". After about three attemps I'm getting closer to > that. > > When I get there I'll write it up on the web and publish the design > files. > > > > So, back to my spindle speed controller. This device will literally > > replace the knob on the pot and cost about $6 to make. > > > > > > > > On Sun, Jun 13, 2021 at 11:09 PM Gregg Eshelman via Emc-users < > > emc-users@lists.sourceforge.net> wrote: > > > > > How old is that mill? Those Chinese mini mills and lathes have had PWM > > > spindle motor controllers for many years. I used to have a Grizzly mini > > > lathe with a low 3 digit serial number, probably from the first batch > they > > > imported. I was at least the 3rd owner and I had to fix a lot of > issues, > > > both original and from prior owner abuse. One fix was resoldering one > end > > > of a big resistor on the primitive and very noisy motor controller. > > > You can buy a new PWM motor controller and potentiometer to upgrade. > > > > http://benchtopmachineshop.blogspot.com/2017/01/mill-speed-controller.html > > > On Sunday, June 13, 2021, 2:30:15 PM MDT, Chris Albertson < > > > albertson.ch...@gmail.com> wrote: > > > I have a Harbor freight mini mill with the dumbest possible spindle > > > control. The mill comes from the factory with a variable resistor to > > > control speed. My idea was to connect a variable resistor to a $5 > model > > > airplane servo. So the PWM output from LinuxCNC drives the servo and > the > > > servo turns the pot which controls the spindle motor. I would never be > > > able to do rigid tapping with this setup. > > > _______________________________________________ > > > Emc-users mailing list > > > Emc-users@lists.sourceforge.net > > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > > > > > > > -- > > > > Chris Albertson > > Redondo Beach, California > > > > _______________________________________________ > > Emc-users mailing list > > Emc-users@lists.sourceforge.net > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > -- Chris Albertson Redondo Beach, California _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
