Sorry for being gone for so long. I see Jeffeb3 is still prolific! Amazing. I moved, so my LR2 is now more conveniently located in my basement than my overstuffed and cold garage and I’m trying to get back into the swing of things. Questions in order by my need and curiosity.
Occasionally my Y axis steppers rotate then seem to give up, unable to move the gantry (I hope I’m using that word right), trying, giving up and seeming to snap back, then trying again - over and over. I had this problem before moving my table, occasionally, on long moves (like 4 feet). I thought it was belt tension but I think I have them tensioned well now. I don’t think it’s binding against the material I’m cutting since it seems to cut smoothly for a good length and then just stop dead. I know I’m not giving much information but anyone know where to start? Could there be a problem with power? Maybe wiring? Maybe the board? I have a multi-meter and sort of know how to use it but if you can ELI5 that would help.
What’s this I hear about an LR3? Any links handy?
I noticed my wheels are looking a bit saggy, like sometimes slanting from the weight of the gantry. I think the tension on them is mostly right as if I tighten them more there is a lot of friction when moving - maybe a spacer could help? I don’t know if this sag is causing any problems, I just noticed it and I’m curious if anyone has any insights.
Glad to be back! I am planning on getting Jeffeb3’s v1pi running and can’t remember if I ever did since my memory is crap in my old age. I have a spare pi ready to go, just need to dig around for a microsd. Going to work on this now.
Thank you for any help you can offer and I’m really looking forward to hearing more about this LR3 and any other notable news!
How long are they stopped? Skipping steps is momentary, and there may be a few reasons. If it is at least several seconds, then something may be overheating. Which controller do you have?
I’m interested too. But right now, Ryan is in the design phase and is keeping it pretty secret. I wouldn’t count on it being done soon. But I would bet it is before any updates to other machines.
Maybe a picture would help? I am not understanding where it is moving.
There are also quite a few prolific posters here. Lots of great help. But I got here first
It’s like they are trying to move then give up and immediately try again. So it’s like a tic, tic, tic, sort of sound under a second each cycle. I think I have the Rambo v1.3.
Oh OK. I guess it won’t be in time for the project I’m working on.
I think it might be that the 1/2" ultra-light MDF has gotten a bit flexible plus maybe that the bolt isn’t tightened very tight. But I remember having to back off because of too much friction. Also, my gantry is over 5’ wide so maybe it’s more heavy than most?.?
That’s going to **** with the alignment for the Z screw, which is going to make turning the screw rather difficult. The bearings on the top part of the Z rails are going to be aligned funny, too.
Yeah… That looks like it’s the case.
For the weight, I just put my LR2 through some weightlifting, and it doesn’t seem to struggle too bad with a couple of boxes of books on it, so I doubt that a foot of steel is enough to stall the motors. That does sound like skipping steps. I’m not aware of any stall detection available on the RAMBo, so it won’t try and then give up, because the board doesn’t know that it’s stalling.
Cutting new plates should probably be priority 1. Those are looking a bit bowed. If you’re currently out of commission, maybe making a brace with some other tools could help get you limping along until you have new plates.
Skipped steps sounds kind of like grinding gears. Steppers have 4 phases. The motors can only try to force the movement towards a specific phase (1-2-3-4-1-2-3-4-1-2-3-4). If they get a lot of force, or they aren’t holding on very strong, they will move backwards to find that phase (instead of moving to the next phase 2, they will move backwards to the previous phase 2). The drivers and microcontroller have no idea they didn’t get the rotation they wanted.
Some things to look for:
Make sure your grub screws are tight. The coupler can spin on the motor shaft.
Make sure your drivers have the current set correctly. If you are using a Rambo, then it is set in the firmware.
If your Y axis is one with two motors on one driver, then make sure they are wired in series and not parallel.
Look for intermittent wiring issues.
With the machine unpowered, look for tough spots. If the machine hits a lot more friction, no amount of electrical fixes will help.
Make sure your CAM settings aren’t too aggressive.
I had the same problem with mine (not to the same degree as yours though) and ended up replacing it with some nice plywood drops from a cabinet maker. People say MDF doesn’t absorb moisture but I’m not so sure that’s true. Maybe high grade stuff doesn’t but you’re not gonna get that at a big box store. Mine was squishy after awhile.
Using a good plywood might add a lot more rigidity to your machine too. At least in my case it did.
I have only heard the opposite. In my experience, it definitely does absorb a lot of moisture. There is marine grade stuff that probably doesn’t, but regular MDF is a sponge.
Even the marine grade stuff absorbs moisture eventually. You really have to seal the stuff good, but if it ever gets cut or scratched, all bets are off.
Oh yeah, maybe it’s allowing the belt to slip. I’ll have to reproduce it and take a closer look. Maybe I’ll hit the gear with a little sharpie so I can see more clearly.
Good points about the Z screw. I’ll get some plywood and cut myself some replacements.
This is my experience too. Guess you can’t believe what people tell you sometimes. I’ve all but banned the stuff from from my shop. The dust it creates is a nightmare. It will get in anything and everything. Truly awful stuff.
I’ll create a separate topic for this but I’d like to know if anyone uses an alternate spoil board material instead of MDF. Once mine needs replaced it’s not going to be MDF.
Ooh, these are good ideas. I’ll have to fumble my way through verifying the series vs. parallel. It is only using one driver - I’ll take a look.
I can currently cut things but they have to be on the smaller side. I’ll probably be able to nurse it, but the clamping is a good idea. I will have to try that.
This is a great way to test and something I recently learned from you and Dan.
I have a post somewhere around here where I just troubleshot this same thing over the weekend. Mine was on a MPCNC that I decided to re-wire when I upgraded from a Burly to a Primo. Silly me wired it in parallel instead of series.
Like others said, cut new plates, from the picture looks like the Z tube is rubbing at the table creating enough friction to make the stepper lose steps.
MDF is still a good spoil board. It’s relatively cheap and can be resurfaced. You can’t really resurface plywood. Well you can, you’ll just not like the results.
Agreed. The last project I ran was s new MDF spoilboard. Which also reminded me how much I hate this stuff! Spent more time blowing out the machine than cutting the board.
Is there a specific bit that is designed to peel chips off of MDF instead of pulverize it? That would be ideal.
