I saw those in another thread. I think losing 1.5cm of space is not an issue for me with 55x75cm workspace at the moment and it is a lot cheaper than printing a whole new core. Plus less shouting at the kids if they go near it while printing a core.
Did anyone else try those modified clamps?
/edit: @vicious1 You didn’t seem too happy with the modified clamps because of the missing Y clamp. Do you see the possibility of altering the Y clamp the same way the others have been altered as a quick and dirty fix for those who don’t want to reprint the core?
Yeah - I just checked the PLA leftovers, and I don’t have anything at all left for sticking to my color combo, not for a new print, nor only the clamps. Well well - function over beauty!! Would the modified clamps provide the same mechanical precision in the end product?? (other than loosing 15mm)
I have got like, 10g left. -_- So either I print them red like the core or I’ll wait for my filament to arrive. I ordered black, yellow and white. I could add some white for the Schneewittchen theme. My daughter criticized me anyway because only the table was white.
I am going to try and figure that out. It is not an easy cut and without the actual build here I can not be sure it is correct. So I have to wait and finish the “C” version and see how it differs. I am not sure that will even work for smaller parts.
Several hundred posts above I posted that I started the Primo F update with printing one of the trucks.
The second part I printed was the core and the result was quite bad, small layer shifts and a bad impression in general.
I thought of reprinting immediately but I decided to print the remainig parts first and had hope the core is functionally fine.
But I was not happy at all, because the new machine should not only work fine but also look nice.
I suffered from bad print quality since some time, but not always. Means sometimes it is quite decent, sometimes bad.
More or less by accident I found out that it was due to the use of OctoPrint.
But not OctoPrint was to blame, but me using it on a Raspberry Pi 1. I had it at hand and at the time, when I wanted to give OctoPrint a try, I found no posts or something that this is not a good idea.
Now I know better…
After printing the core I installed an additional plugin to OctoPrint (DisplayLayerProgress) that led to printing in slow motion.
After seeing the calibration cube below, it was obvious even to me that something went terribly wrong…
In fact the Raspberry Pi 1 is too slow to feed the printer with commands fast enough.
Now that I found it out myself I find posts telling NOT to use OctpPrint on a Raspberry Pi 1 everywhere.
Again, not Octoprint is to blame, but me.
The remaing parts I printed directly from the SD card.
I also had the problem several other people reported that the bearing of the core clamp was not touching the tube.
I had to tighten the bolt real hard to remove any play. But the range to correct squareness is very limited, basically not existing.
Anyhow I could setup my MPCNC Primo completely and it moved for the first time today.
The bottomline of all this is to say thank you to Ryan to give me good reason to reprint the core.
(And I mean it, no sarcasm this time!)
It is good that a solution is found that avoids having to try tweaked parts of any kind.
The table is 110x90 cm.
Although the tubes are stainless steel 25mm with 2mm walls you can really feel the flex. I did not expect that initially. And the tubes really bend down when the Burly gantry moved. So I decided do add supports at least for the longer tubes.
I noticed that the bolt (and nut) are rotating from vibration. Does this just need a little tightening? The bearing does not rotate with z rods, rotates freely
What is your specific tube length for the x-sides?
Do you think the flex is really noticable when the machine is operating? I’m planning to have a long x, the outer sides 1124mm, with 2mm thick walls. Could I ask you for a favor?? I’m going to assemble tomorrow, but wonder if you could do a small test? I don’t want supports, so I’d rather reduce the x if necessary. If you run the gantry from side to side in the x-direction, would the gantry sag when you are in the middle, closer to the bed?
Edit: shoot… I’ll assemble it with the current length and see how it goes. If the sag is noticeable and impacting the functionality, I’ll simply shrink it. Right now the table is sized to this specific length, with two ledges under the feet in the y direction.
Yup, they should all be in contact, with equal tension. Test by spinning with your fingers, all 4 should be in contact and take a little force to rotate.
It shows a flex of only 0.1 mm which is very nice.
I cannot tell what the flex was on my Burly build, but maybe it is reduced now to to better, larger clambing by the corners.
And now I remember that the main reason to add the support (and on my Burly I only had it at the front tube) was to compensate for a sligthly hanging tube even without a force. Might also have been a bent tube.
Unfortunately my current measurement does not show this. Need to measure again…tomorrow.
I wish you as much fun assembling the MPCNC as I had.
Thanks for your replies! @lars33 let’s say I had slight bend on my tubes, wouldn’t it be perfect to let it point upwards? I’m afraid I have a slight bend caused by driving home with the 4m long pipe on the car roof, and seeing it wobble all the way home…
If it happens I can’t either see nor measure it. You can always switch to a smaller build, cutting tubes is possible, making them longer isn’t. Have a good night.
I again made some measurements to get an impression about the sag in the static situation, with the gantry sitting in 0/0 position.
My measurements show that the tube is very uneven. From left to right it differs max. 0.2mm.
And no distinct drop in the middle I would say.
But I am also not very confident in the measurements as I use my wooden base as the reference.
I also rotated the smaller y-axis tube (980mm length) and the measurements while rotating differed up to 0.3mm.
Not sure if the tube is bend completely or if the tube is uneven simply.
Overall I am satisfied with the results.
I would start without mid span support and just get an impression how it behaves.
Something you should not do if you want to be fair to your machine:
Lean yourself onto the tube and say: “Hey, see, it is flexing. This machine is bad.”
(You should also not let anybody else do that)
I thought of moving to solid stainless rods that have a given tolerance (h9) when updating, but the price is 50 to 60€ per meter.
I leave it for later…
Thank you again, this is very informative! I have also noticed that the pipes are quite uneven. A friend of mine who is an engineer in mechanical drawing says that I shouldn’t worry to much about these variances, since it’s not going to be used for high demanding precision mechanics. I guess he is right
Advice taken with gratitude, I could’ve easily tried something similar! (and it wouldn’t be smart, since I have quite a lot of tonnage to help me…)
I’m afraid I have a slight bend caused by driving home with the 4m long pipe on the car roof, and seeing it wobble all the way home…
Have a good night.