Waviness or not...That is the question

7.93mm is .3125 inch or 5/16" . .315 inch is 8mm so your rods are .0025 inch undersized. Better than my rods that were .311 inch at .004 inch undersize. My old rods were 7.90mm

 

.07mm can be disregarded as measurement error. Using the flat portion shows a more accurate measurement. You really need something like a micrometer to measure it with more detail.

 

Hi guys!
I've had rippling problems back and forth
The toy blocks were printed with stock KS robo3D a few months back at 0.2mm layer height. I have been printing with PLA/PHA at 210 first layer, 205 for the rest with extrusion multiplier of .95 and bed temp at 60C.

I have stock imperial z-screws and smooth rods.

Notice how the rippling is low in the lower part and then increases. Up to that level there is no infill behind the wall but when the infill comes the rippling increases alot.


Mods in above prints:
z-smooth rods top stabilizers. They didn't fit very well so I removed them later.
Fixed wooden printbed (12mm OSB instead of stock 6mm birchwood that got warped) + stock bed heater and boro glass.


In the second image I'm comparing the top drawer printed with repetier 0.95F at 0.2064 layer height with the lower one printed with MatterControl 1.1.0 at a 0.2mm layer height. (yeah, I know might not be fully comparable)



Mods in both cases above:
A filament guide removing lateral movement from the stock spool holder.
No z-axis stabilizer in place (it didn't fit very well so I removed it) I'll probably add an adjustable
new heated glassbed.

Since the robo3D inherits a lot of stuff from the reprap family of 3DPrinters I'd like to add this link about the antomy of z-axis artifacts in reprap family 3D printers: https://www.evernote.com/shard/s211...953d8924c71d/1ef992988295487c98c268dcdd2d687e

It's worth a read!

Regards, Daniel Hegner

 

Mike, I too have thought about a bracket containing a bearing for stabilizing the threaded rods but am currently running with the case off for easier access whilst perusing my upgrade to do list so brackets to stabilize the top are out of the question for me at the moment. I've been considering a boxed aluminum frame, like some other printers, to be mounted to the center sides and extend up and over the printer as a mounting rail (hope you can picture what I'm thinking). The base of the Robo would probably have to be made more rigid to mount these uprights though, maybe with a brim of aluminum boxing around the base, but then it's like building a new printer.

 

Yeah once you start integrating metal then it becomes a never ending chase towards perfection, and thus cost.

I personally bought the robo because of the aesthetic appeal. If I was gonna run it without the lid I'd have just build a Mendel90.

I'm just trying to optimize what I have available in the most cost effective way possible.

 

Great link, thanks! I'm going to look into a filament guide!

 

Daniel

If you can measure the step of each wave in your parts and they are the same as your screw pitch then it may be coming from runout of your couplers on the z motors. If you do not have any measuring tools to check it. Just use a bolt with the same pitch as your z axis screws as a gauge to check it. Stock z axis screws are 5/16-18

 

I have seen that link before. It is a great read! It helped me solve some of the ribbing problems I had with the screws. The screw pitch matched perfectly with the ribbing on my robo. I advise anyone to read it.

 

I found depending on the model and the way the model was made and orientated, that the print comes out nice and smooth. Other times the print is ruff on the exterior.



This was printed vertically. It looks smoother.

Try orienting your prints to print vertically rather than flat and see if that makes a difference. Here is an example



Rather than printing it horizontally




Sent from my iPhone using Tapatalk

 

Ziggy: I mean that's pretty bad, but within a decent margin of error. The harbor freight caliper has a .03mm error so 7.97+-.03 is basically 8mm.

Thing to remember about smooth rods is that its super critical to not be over the diameter, but below it slightly is fine. a 5/16" rod is 7.9375mm. Were it a 5/16" smooth rod you wouldn't see a value over this. A little under dimension is alright because the bearings press into the rod slightly to achieve grip, hence spin. Though the closer you are to accurate the better obviously. But a .1mm error is really not significant if it's even there.

Edit: They are in fact 5/16" rods

 

I kinda doubt it but if that's what your working hypothesis is it's worth a test.

 

Troubleshooting a printer is a science. You have a working hypothesis: The smooth rods are undersized causing instability in printing. You have a proposed solution: Replace the smooth rods with more perfectly dimensioned rods

If this hypothesis is repeatable by multiple users then it moves up to a theory.

There are no "facts" here.

 

Because when you buy 8mm rods that you hope are perfect you'll see nearly the same thing. A slight variation depending on your measurement point, but with a caliper you won't see the kind of precision to actually know how inaccurate your rods are.

Measurement error is a real thing.

 

Taking just one measurement in one location isnt a good representation of the rod diameter either. You need to take multiple measurements along the rod and at different orientations around the circumference of the rod, then find the average diameter. It may be closer to 8mm than you think.

 

I guess I should apologize as I stand corrected. They are in fact 5/16" smooth rods, direct from the source.