Welcome to the SeeMeCNC Community

I'd like to be prepared for when something goes wrong and I need a replacement part. So I want to stock up on some parts now - before I need them - for my rostock roadside repair kit:

- 1 hot end thermistor
- 1 heated bed thermistor
- timing belts (enough to replace them all = approx. 225 inches?)
- 2 hot end resistors
- Should I get a spare Teflon tube (I ordered the new no22le last week)?
- fuses for the Rambo (described on this forum someplace)

What else do you think I should have around? Imagine having a 4 day weekend and then something breaking on day 1. I want to be ready.

I'd just deal with it when it happens, building and tuning the printer isn't something that happens quickly anyway. I built mine over XMas, and I did blow a fuse on my RAMBO board, I happened to have a spare RAMPS board which I used to get up and running during the 2 weeks I had off of work, but I got the replacement fuse from digikey inside 5 days.

The hotend and heatedbed thermisters are identical, and I've never had one fail, people occasionally break the legs off them during assembly.
Belts - mine are fine, I might order spares at some point though
Hotend resistors, IMO you are much more likely to destroy the entire hotend (by overheating it) than you are to blow a resistor.
Can't see how you'd destroy the bowden teflon tube, I actually have spare, but only because it's the same tube used on the inside of the original Steve's extruder, and I kept jamming mine requiring replacement so I ordered 10 ft of the stuff so I never had to worry about it. I've never had a jam since I received the tube.
RAMBO Fuses - I now have lots because I hate ordering 1 of anything.

All of this stuff can be gotten in < 1week from various online stores.

Definitely get spare teflon tubing for the hot end - both sizes.
A spare nozzle is a good idea too. I've also heard that the mechanical end stop switches can sometimes fail.

I've had my original printer for over a year with no need to replace anything electrical on it. I'd just wait until if/when you need these items.

cheers,
Michael

Thanks for this info.

If the hot end & heated bed thermistors are identical I'll probably just get one as a backup.

I think I read on this forum about 2 different people needing a new resistor, so I'll probably get those. Also, I'm wondering if I might already need one because since Sunday afternoon, my hot end is taking about twice as long to heat up (maybe 15 min from room temp to 235C). I didn't rerun the PID autotune yet, but I will try it. I've only printed a few things (designed by my kids and their friends) since then and they came out fine. But they were small and simple.

I have one backup belt now, but I'd like a whole set. I can imagine something going wrong when I'm not in the room to notice and all the belts getting chewed up.

When you say "both sizes" of teflon tube, does that mean one for the no22le and one for the standard nozzle I have now?

And I'm worried that if I blow a Rambo fuse, I won't remember how to find the post with the info about which one to get, and maybe the vendor won't have any or whatever. It will be comforting to me to have them in my little kit.

Endstops are a good addition, thanks. I actually had one DOA endstop with my Rostock kit (or maybe it was damaged when my kids were "examining" it). I got one from a local electronics shop, but I'll probably get another just to be ready.

On the spare nozzle, I'd like to see whether I prefer the std nozzle I have now or the new no22le when mine arrives. How would I damage those brass nozzles anyway? Clogs?

I know you guys are both suggesting that I just deal with it when a problem happens. But this is all still quite new to me and I don't consider myself to be particularly handy. The Rostock Max was kind of an ambitious project for me, and I'm very glad it's worked out so well (so far). Also, I don't get a lot of time to use it, so I'd be extra disappointed if I had a window of time that I couldn't use because I was waiting for parts. Maybe I'll feel differently after I've had it for a year.

There is something wrong if your hotend is taking 15 minutes to get to temperature mine takes more like 3.

Yeah I agree something is wrong. Up until Sunday mine was about 3 min too. Would you suspect one resistor not working?

It will be next week before I can get to it... should I order resistors now?

By both sizes of teflon I meant that inside the nozzle there is a 4mm OD tube and a 3mm OD inside it. The smaller 3mmOD is for 1.75mm filament. If you are only running 3mm filament you only need the 4mm tube. If you are running 1.75mm you need the 3mm OD tube and it doesn't hurt to have a bit of spare 4mm.

Question on your nozzle heater - have you checked all of the wiring to the controller? It really sounds like you are not getting enough juice. Last year when I was running a lot of PLA I actually removed one of the resistors in my hotend. It increased the heatup time by maybe a minute, maybe. The popular J Head has a single resistor.

You don't damage the nozzle really but depending on how you remove clogs, that might take a lot of time. If I'm in a hurry, I burn out the plastic with a torch. Not in a hurry I soak in acetone. In both cases, with a spare nozzle I can be printing while I clean a clogged nozzle!

Barnett - If I remember correctly, I didn't wrap the resistors with aluminum foil when we first assembled the printer (no manual at the time.....number six shipped!). The resistors could be slowly burning out due to this???? Any one know why it's important to foil wrap the resistors, beside the obvious transfer of heat to hotend?? We've been lucky with the Rostock besides this for months though....

good info again thx.

Jake is correct - I had forgotten the resistors are not wrapped in foil because we didn't know to do that.

I have not checked wiring, but will give that a shot. Sunday I printed about 10 small items and I didn't notice this problem until near the end of the day. But as of this morning it was still slow. The print went fine, but I had time to brush my teeth, make coffee and toast before it was ready to start.

The foil wrapping is to transfer heat to the hot end. This is identical to the H-1 and H-1.1 hotend (I wrote the manual for the H-1 in the Official Docs thread). If you didn't do this it shouldn't cause a premature resistor failure. It might result in taking longer to heat your hotend though, depending on how loose the resistor is.

OK maybe one came loose somehow, but I'm still going to check the wiring per your suggestion. If that all looks fine and the problem remains, then the next step would be dig out the resistors, wrap in foil, reseal them and try again?

I'd check wiring at the RAMBo and also make sure the leads at the resistor/hotend end are connected properly. If that isn't it, then I would measure the resistance at the hotend. You should be able to do this by disconnecting the wiring at the RAMBo and measuring the resistance across the wires. Since you have two 6.8 Ω resistors in parallel, you calculate the resistance as:

R(total) = 1 / (1/R1 + 1/R2) = 1/ (1/6.8 + 1/6.8) = 3.4 Ω

The resistance from the wires is minimal.

If your measurement is closer to 6.8Ω then a resistor is not connected or has failed. If it measures close to 3.4Ω then you are not getting the voltage to the hotend that you were getting earlier.

That's an answer from someone who knows what they're doing. I will try that tonight if I can, otherwise it will be next week.
thank you!

Hey...I put those resistors in tight. No sure about your connections though....HaHa, just kidding.
Great info, thanks..!!

I am not very experienced at the multimeter, but I'm getting 8.8 ohms measured right at the hot end and also if I do it at the plug where the wires connect to the Rambo (but with the wire unplugged from the board for measuring).

An inspection reveals a place where the sealant has come open around one of the resistors. The photo is kind of gnarly.

Am I going to be putting in another resistor?

[img]http://farm9.staticflickr.com/8228/8475 ... 2c88_b.jpg[/img]

Now you are starting to get somewhere. It's still possible that the leads to the resistors are not connected tightly. Did you solder them or use a crimp fitting? It's possible you have a bad connection at the hot end.

Connections are soldered and look okay to me (image below; my shot of the other side isn't as good). I could undo the connections and test the resistors separately, but it sounds like I'll be taking this apart next week either way.

Would seemecnc send me new resistors or should I get them someplace else? You mentioned 6.8ohm... is there a wattage spec on them?

[img]http://farm9.staticflickr.com/8104/8476 ... 16cd_b.jpg[/img]

That does look like a good connection. It would be good (for us to learn from as well) to measure them individually when you get the chance.

You do need resistors rated for 3 watts or more - the little 1/2 Watt resistors won't cut it! SeeMeCNC carries them and you should check in with them first. Resistors have a lot of variation in dimensions across brands, etc and the ones SeeMeCNC carry are known to be the right size!

I will post further testing results next week. Thanks for your help.

I think I found this link through mhackney; a pretty good tutorial for using your mutlimeter..?!?

http://www.sparkfun.com/tutorials/202

For your spare list:
Add also 1 or 2 of the push in fittings for the bowden tube.
Mine broke last night, resulting in 5 meters of filament in the workshop. When it breaks, it is non repairable, you need a new one.

Does anyone have data for this component, as I would prefer to purchase them locally here in europe?

/Poul

For your spare list:
Add also 1 or 2 of the push in fittings for the bowden tube.
Mine broke last night, resulting in 5 meters of filament in the workshop. When it breaks, it is non repairable, you need a new one.

Does anyone have data for this component, as I would prefer to purchase them locally here in europe?

/Poul

kometen: thanks I'll add the push to connect fittings to my kit ... I already have two extra ones.

On my hot end resistor trouble, I installed two new ones this morning. The RTV is still curing.

The original ones were both cracked. One resistor was dead, no connectivity through it:
[img]http://farm9.staticflickr.com/8369/8501 ... f85c_b.jpg[/img]

The other one scored 8.8 ohms on the multimeter.
[img]http://farm9.staticflickr.com/8388/8501 ... fb03_b.jpg[/img]

They were not wrapped in tin foil because I didn't know to do that at the time. But other than that, not sure what I did to kill them? I did not leave them sitting there hot for more than maybe 20 min at a time. I tried to avoid even that because my orange ABS would cook in there and come out brownish and/or crusty/brittle almost to the point of causing a clog.

Thanks for the update barnett! It was great meeting you the other day.

Well, at least we now know the problem! After seeing the cracked resistors and knowing the history, I suppose there is reason to suspect that without the resistors in good thermal contact (i.e. no aluminum foil wrap) to the hot end, they were being over powered to get hot enough to transmit the heat through the air envelope surrounding them. I would not have thought that small gap would make that big of difference but the evidence doesn't lie!

cheers,
Michael