Its ALIVE!!!! ALIVE!!!!

Such a sweet sound steppers spinning. Thank you very much Robert you totally unstuck me on that one. Most appreciated. This solution works using Xloader to flash latest release of grbl hex file on to an Arduino Uno with a ATMEGA328P (Duemilanove).

Thanks again sir. I can't stop playing with the jog now.

So, I have my X and Y moving fairly smoothly but my z axis is causing me trouble. I went out and replaced the cheaper Pololu DRV8825's that I bought from China with the real thing from Pololu. The major difference is that the real thing has stops in the potentiometers while the cheap ones just keep spinning. With that fixed things have worked much smoother and the adjustment has been significantly easier.

My problem now is that my z-axis makes a short grinding noise upon starting to move and at the end of the movement. Additionally, it sometimes moves in the wrong direction. Adjusting the potentiometer doesn't make much in the way of difference. I adjusted the acceleration setting in GRBL but counterintuitively it gets worse the lower number I put for the acceleration. I've played with the step rate and that also doesn't seem to make too much difference.

Any advice? From googling I've discovered that I might need to loosen things up to try to reduce the initial load so I'll give that I try while I see if any other advice surfaces.

Can't watch your video ... says it is "private".
What are you using for screw and nut? making sure they are in line and that nothing is rubbing sounds like good first step. I used a nut made for the screw I used and they work well together, no grinding problems ...

Sorry about the privacy setting. It should be visible now. I bought the delrin nut and screw from the same guy. I haven't tried adjusting the nut yet. Perhaps that is the next step.

Dude, I have the same motors and mine can produce enough force to bend the gantry, strip the belts, etc. I had a nightmare cutting aluminum because my spindle mount was weak and there was play in my v-wheels. Once that was fixed it does just fine. I'd be looking at your dremel for runout, a dull bit, play in the wheels, etc. Maybe your mount is weak too.

My motors run at about 0.85 A on 12V

I should note that I have also tried various feed rates and there doesn't appear to be much difference between the default feed/seek rate of 200 and 500 mm/min on the z-axis issue. I've checked the backlash nut and it doesn't seem to be binding.

Turning the leadscrew by hand take a bit more effort than turning the pulleys on the other axis. I've largely run out of ideas. I may solder together my extra driver to see if that will make a difference.

Ok, so upon further review, I'll blame this one on my shoddy soldering Upon closer inspection on of the header pins wasn't well soldered. Once that was remedied the z-axis moves smoothly in the correct direction. How to put a spoiler board in place, strap my dremel on and cut something...

I still have yet to cut anything as well. I keep tuning my machine and since baby is asleep at night I don't want to stand the chance of waking her up.

I have started doing some dry runs with my machine, I too do not even have a spoiler down yet and I noticed that circles do not trace well. With the stock settings in sketchup you will end up with a circle with 24 segments. Indeed if you try and cut it SketchUCam will segment your circle (this was discussed earlier). I found a nice way to generate circles without all the segments and that is by increasing the segments from 24 to say 64 using Window->Entity Info under sketchup.

The resulting gcode looks good enough, seems like it would make a nice circle but when I run it the machine does not do anything smoothly at all. It is very jerky when it starts preforming the tool path. It is like it is starting and stopping a lot for some reason. Anyone have any suggestions on how to smooth this out to make a nice smooth circular cut without all the starting / stopping?

Also this starting / stopping only seems to happen when I start cutting anything with a radius to it. Linear stuff works nice and smooth. Its almost as if its just doing segments and the look ahead that the grbl shield is supposed to have doesn't seem like its doing its job.

I would suggest downloading a free trial of a 'real' CAM program such as CamBam. Draw a simple circle in that and generate the GCode. If that does the same thing, then it's probably just the best you can do with your setup. If it is different, you can inspect the GCode to see what is different, or consider shelling out for the program (I hear it is really good).

David, Thanks for the tip. First thing I did after getting my spoiler in place today was to draw some text. Then I read your post and followed your suggestion. Looks like my machine is not quite calibrated correctly (see attached image). The Y length is spot on but the X is all outta whack by a little under half. Actual line on the x measured 47mm. I'll go over the settings and see if I can figure out where I went wrong but thanks for the help guys most appreciated, I'll let you all know how it turns out and what the deal was.

That was fast! It was the motors that I used. A friend of mine happened to have 4 stepper motors at work that he gave to me and they don't all match. This made sense at the time to just get started since the store was out of stock. 2 steppers are 0.9 degree steps where the other 2 are 1.8 degree steps. The 2 on my X and Z axis are both 0.9 degree steps so mystery solved. When I doubled the step/mm on the X from 40 to 80 it works like a top and the X is now drawing 100mm lines.

Once I corrected that I layed down a 64 segment circle and drew it. The machine preformed much smoother than last night by a long shot and you can't even tell the circle is segmented by looking at it. However you can hear that it is segmented as the machine is drawing it . There is still that starting and stopping but it is less jerky than before. Not the smooth motion that I would have expected, but in all honesty I wouldn't be able to tell the difference by looking at it so I'm ok with it grunting through circles and arcs a little.

The real funny thing was the curves for the text sounded great when it was drawing those even with wonky settings. The 'O' was a very fluid motion unlike the circle. I'll have to take apart the G-code maybe that can tell me why.

I am using the grbl controller version 3.5. I grabbed the source code my version is using and also the 3.51 version to have a look and G64 is not supported unfortunately.

I guess SketchUCam exploded my circle because I didn't see any Rxxx terms in any of the generated gcode of sketchUCam when drawing the circle in sketchup (I did not scale it or use a transform in any way). I do not know how to make a complete arc with sketchup beside just using the circle tool. When you say complete arc I'm assuming you mean a circle. A few questions came to mind as I was writing this:

Is there any sort of tutorial on phlatboyz SketchUCam and what all the buttons do etc? I still don't understand what the majority of controls do, for instance, I still have no idea what a phlatbone is or what it is used for.

I need to learn more about these gcodes. Does anyone know of a good site that explains in detail each one?

David, what controller is your friend using?

David, Thanks for all the info will have plenty of reading to do now.

I'm getting ready for my first cut and I will be cutting foam first to test out the gcode and then acrylic. Do you guys have any recommendations for a dremel drill bit that cuts acrylic nicely? Something that doesn't melt it and gum it all up.

The thought never occurred to me until I started planning to cut something real but how are you guys clamping down your work pieces to the bed of your CNC's? There doesn't seem to be any good spots to use a clamp or such.

I had a look at it today, going to hold off on buying software until I know for sure this is something I want to invest a lot into. I don't want to use it quite yet because I'm afraid I will spoil myself with it and not want to go back

Acrylic is harder than wood. I use a 2 flute solid carbide 1/4" bit. At first I cut some foam but it sucked. Then I did wood and it looked great. Next I milled my spoilboard flat and that went well. Now I'm milling acrylic and I hold it down with double-sided tape. I'm finding that some belts need tightening, screws need tightening, etc when I cut the acrylic. It isn't melting at 10,000 rpm but it takes a lot of torque to move at the feed rate I'm using (200mm/min).

EDIT: Shortly after writing this I went out to check on my piece and the tape had come loose and the part was ruined. Now I'm drilling holes in the material and screwing it down to the spoil board.

Funny, my feedrate is set to 500mm/min(20ipm) and my cut depth is 1mm(0.04in). They suggest 0.003"(0.0762mm). I think my leadscrew pitch is wrong so it was cutting half that amount(0.02in) but that's still way too much, I guess. I did notice it jerking around as the gantry flexed. Maybe I'll fix the leadscrew pitch and try again at a much smaller cut depth.

Let me know how that goes for you. I would be very interested in the settings you used for acrylic if your planning on cutting that. I had a look at the chart but I'm sure I have calculated something incorrectly. I was going to make a metric version of that chart that kram posted but some of the math is wonky trying to sort it out now.

Not quite sure how to interpret this chart. It's not likely that any of us have a machine that will travel 600-1200 feet per minute or am I misunderstanding SFM? And if dividing that rate by 50 does that mean we can increase the depth of cut 50x?

In case you don't have a network connection attached close to your mill like me, I created a little xls file with Krams info in it. There are 2 sheets one for imperial (Direct copy of sites info) and one for a metric conversions of the imperial chart.

Thx. Makes a lot more sense now.

It's working with 200mm/min, 20% plunge rate, 0.0762mm cut depth. This is 1/2" plexiglass, so it's probably the "plastic with glass" type listed in the chart. The cuts are wicked clean, edges sharp, and there's a lot smaller chips coming off which can go airbourne.

Very nice, thanks for the info. Glad to hear you have had good success with those settings. When the time comes I will use them, hopefully this weekend. I'm still trying to fashion myself a holder for my Dremel tool. I first tried to use zip ties to hold the dremel to cut some leftover MDF to make some brackets to hold it in place. After that failed, I decided just to let the machine draw it and I will cut it out with the dremel. My hands work better than zip ties any day of the week and even in the mornings.

I have the same tool that Forest has and I downloaded his designs. Had to make a slight modification though because my machine is certainly not a standard one. (I went by the parts list ). I ended up with a piece of 20x80 and not 20x40 on the Z to mount the spindle/tool so I took the liberty of modifying your design a little Forest. I also increased the thickness of the holder a little. I was worried about the MDF not holding up so its thicker now. The holder should buy me enough time to make a better one later... I hope. Attaching the skp file as well if anyone needs/wants it.

Better brackets just arrived . Anyone cut 3/4 in MDF before? If so what were your settings. Settings on todays cut were the acrylic settings The Dude posted. My god it was slow... 3 hours about. Wife banned me from ever using it in the house again.