Hey again! I’ve made a lot of progress on my machine! Successful crown test and starting to cut foam! One issue I’m seeing however is with one side of the Z axis missing steps when the router is near it (but works fine when it’s more in the center and the motors are sharing the load). Im currently using a Porter Cable 6902 router that I had laying around (had to modify the mounting plate a fair amount). A quick Google search shows that this router is around 7.5 lbs while the recommended DeWalt 611 is around 5.5. Does this sound like expected behavior due to the additional 2 lbs or do I have something else (binding maybe?) going on?
DeWalt lists the weight of the DWP611 at 4.6 pounds. Amazon lists it as 5.5, which is probably the shipping weight for the whole kit. So, the weight difference might be more substantial than you think.
Try just loosening the screws holding the Z leadscrew nut a fraction, sometimes the nut doesn’t sit perfectly flat which causes binding on the leadscrew.
So went to do my first through cuts and it looks like loosening those nuts wasn’t quite the end-all fix it looked like it was. The router seems to do okay for a short amount of time, but ends up slowly dropping over time until it takes a final plunge of death into the material. I think the router is definitely too heavy.
I did a quick test where I took the router off and put some weights on the router plate to test its capabilities. Turns out the only known weights I had in my house were cans of beans. Looks like I can lift 5 cans of beans (around 5lbs) but start missing steps at 6 cans. This is with the router in the extreme positions.
Does this sound like expected behavior? I’m using 1/16 stepping and my drivers are old and from a cheap 3D printer kit…any chance these could be the root of my problems?
Oh wow. Yeah I definitely have something going on. That looks like it would lift an entire pantry of canned beans! The 5 I was lifting was without a router or mount even on the thing.
I’m thinking the issue may be stepper driver related. The motors are brand new and high torque and the arduino mega is genuine. My ramps 1.4 board and A4988 drivers are recycled from an old 3D printer kit (and based on what I paid at the time almost definitely counterfeit). Think it’s worth swapping the drivers for new DRV8825s? Maybe I just get a new ramps board too?
Anyone have tips or tricks on honing in on the issue? The electronics and firmware are only slightly clearer than mud to me…
Have you set/verified the vref? Old 3d printer kit doesn’t need the torque, so maybe they are set way low. I skipped through this video pretty quick, but it looks OK. I didn’t catch the calculation for a starting point, but I think it’s 0.45V for the 4988. Either verify that with the internet or wait for a pro here to confirm or deny. I use the DRV8825, and I think the calc is different.
Thanks for the video Tony. I had messed with those previously and they are set correctly. I’d since messed with them a bit in hopes that more current might help fix some problems, but even then I’m having issues.
It has to be either a lack of ‘oomph’ from the motors or too much friction. Having had a go at the ‘too much friction’ side of things lets have a go at ‘not enough oomph’.
When you say you have adjusted the Vref correctly what value have you set them to?
I set my DRV8825 drivers at 1.1V Vref. But a word of warning here, I force cool the stepper drivers with two 40mm flushing fans. A genuine polopu DRV8825 utilises a 0.1ohm sensing resistor and has a working formula of -
Current Limit = VREF × 2
so a Vref of 1.1v for me represents a coil current of 2.2Amps…the maximum for the motors. Stuff is going to get hot! I keep a check on the motor temperature during a job run. I have not yet had a long enough job that caused me problems but it could be an issue in the future. Additional 40x40 heatsinks are available for the bottom/side of the motors to mitigate some of the heat.
To check you have the correct value sensing resistor on your drivers check the markings on your boards. The sensing resistors (there are actually two of them) are located next to the trimmer pot on the pcb, they are labelled R100.
Assuming yours are 0.1ohm sensing resistors and assuming you have the correct stepper motors (that Ryan supplies…their dimensions should be 42x42x52) they have a max current rating of 2.2Amps.
Ah…re-reading your earlier posts I note you have A4988 drivers so forget all that then…
sold my old Porter Cable router and upgraded to the dewalt 611.
replaced all 5 stepper drivers with DRV8825s.
The steppers were undoubtedly the main problem, it’s night and day difference how much more torque I’m getting, but the new router isn’t hurting a bit either–it’s much lighter and the spindle speed adjustability is a big plus.
In conclusion, I made my first successful cut without issue (the 611 plate). Super excited to see what this thing can do!
Looks like I can lift 5 cans of beans (around 5lbs) but start missing steps at 6 cans. This is with the router in the extreme positions.
