Show all posts by user
@ruevs:
Does the current Marlin firmware move the same speed regardless of the print head position?
You can check it by moving in one line (one g-command) from tower near to the tower base to the other side of the base. Does the print head have the same speed during the whole length of the move?
by
hercek
-
Delta Machines
Some people prefer magnetic joints because they disconnect when the print head hits something. I doubt it is an advantage. My printer just skips steps when the print head hits something. If I'm nearby I stop the print. Otherwise it would continue badly. Waste of filament but not a big deal. It happened to me a few times when a corner of a printed ABS part pealed off.
At least I do not need to re
by
hercek
-
Delta Machines
Well, there are 6 pieces in the $5 pack. That makes it $10 per one 3d printer. Plus shipping. Not too bad.
If you are in US, I bet you can find some US based ball joints which have good quality.
If it is only about replacing the print head then magnetic joints do not make much difference. My head is screwed to the platform (to which the ball joints are screwed). It is not a problem to replace th
by
hercek
-
Delta Machines
I tried only one kind: MP-Jet. I got a reference from a friend that they are good. I bought about 5 packs of them and the quality was consistent.
See:
If you would buy exactly the kind posted in the link then make sure you tighten them well. Catch the thick neck (just next to the M3 thread in thin pointed players. Press the players hard and tighten hard. Take care so that the players do not slip
by
hercek
-
Delta Machines
Quotegambrose
I think another issue I had was that the steel housing needs to be very close to the ball to at all effective.
Yes, at best, the housing should touch the ball the same way as the cup touches the ball.
You can try to get some really thin cylindrical magnets (check what thin strong magnets are available) so that together with the housing it still does not have big diameter compared t
by
hercek
-
Delta Machines
The ball joints in the video SUCK BIG TIME!!!
I'm no fan of magnetic joints (they are too heavy and weak) but compared to the ball joint in the video I would rather take magnetic joints which suck a bit less :-D
Get ball joints which are sold already assembled and which are tight. If there is some local shop for RC model planes or even better RC model helicopters then get the ball joints in the
by
hercek
-
Delta Machines
Definition: Iron housing for the magnet is the iron part in which the magent is inserted (it is the bottom cylindrical black part on your drawing). Iron cup for the iron ball is the black iron part on your drawing which is between the ball and the magnet. This part should be fixed to the magnet and slip over the ball.
Something like your hand-drawing may work well. You just need to optimize the f
by
hercek
-
Delta Machines
I used marlin few years ago. I use repetier now.
The main reason for the switch was that at that time marlin applied the speed from g-code to tower carriages. This led to smaller print head speed when the printer was printing at the edge of the bed compared to the speed when printing at the middle. Repetier correctly applies the speed to the print head.
Does the latest marlin still apply the sp
by
hercek
-
Delta Machines
QuoteMKSAA soft iron housing plus a soft iron cup.
Soft iron housing looks like the best idea. This should completely close the magnetic circuit. It should hold pretty well.
I would be a bit careful with the soft iron cup part if the housing is already present. The reason is so that the magnetic circuit is not shorted through the cup to the housing (without entering the ball). The goal is to have
by
hercek
-
Delta Machines
@frankvdh: I would not try option 3.
I would try these two options(magnets in red, iron in white):
by
hercek
-
Delta Machines
You need to consider a steel core belt like a consumable but if you want to print quickly you may prefer steel to glass:
See:
by
hercek
-
Delta Machines
Quotefrankvdh
Ferrite should provide a much stronger attraction than iron?
No, ferrite would be worse than iron. Relative permeability of ferrite is around 650. Iron has it at 5000. Ferrites are used because of their low losses when magnetic field is changing. But there are no significant magnetic field changes in a delta printer since the speeds are only in the range of 20 cm/s ... which is "no
by
hercek
-
Delta Machines
If it is only protective layer and the inner core is straight and tightly packed then it may work. But the inner fibers will not be packed tightly enough ... probably.
The other option which may work is if the strands are only twisted.
You need to test it first regardless how the string is made.
Take about 2 m of the string and hang about 5 kg on it. This is so that the string stretches to its
by
hercek
-
Delta Machines
There are way too many kinds of PE (polyethylene). Young's modulus (E) can be as low as 1 GPa for the weaker types.
Spectra has more versions:
Spectra 900: E=66-73GPa; Spectra 1000: E=98-113GPa; Spectra 2000: E=113-124GPa
Kevlar has more versions too:
Kevlar 49: E=154 GPa; Kevlar 29: E=61 GPa, ...
Aramid seems to be some version of Kevlar.
Glass: 50 - 90 GPa
Steel: about 200 GPa.
There are big
by
hercek
-
Delta Machines
Of course you can bent it. But the important thing is that a diagonal rod is loaded only in the direction of the axe along its length (if your ball joints are free to move). Try to bend your rods by pressing them from their ends. Use force only in the direction of the axe along the rod length. Notice that the forces exerted by the printer on your diagonal rods are in the range of 7 N.
The only w
by
hercek
-
Delta Machines
QuoteDjDemonD
I have linear rails on the XL, gates belts 6mm 2gt, Haydn rods 360mm 6mm diameter, smart effector and carriages. Its a 2040 frame with robot digg corners. So it has to be the belts, or the carbon rods.
If your Ø 6 mm diagonal (carbon) rods do not have any noticeable play at the joints and the joints move easily then your diagonal rods are not a problem.
by
hercek
-
Delta Machines
Acceleration is more important than speed when considering ringing.
Ringing depends about linearly on acceleration. The more acceleration the more ringing.
Speed only needs to be above some minimum for ringing to appear. After that minimum the ringing does not really depend on speed.
Your lead screw delta probably will not be able to achieve high enough accelerations (a probably not even speed)
by
hercek
-
Delta Machines
dc42: Ok, I defined holding torque as torque needed to hold the given microstep position.
Vigilant: That's why I said one needs also high holding torque and recommended to increase stepper motor current to the maximum allowed. If the maximum acceleration set in firmware does not need more (micro-step adjusted) holding torque than the motor can provide then the motor will ring at most one micro-s
by
hercek
-
Delta Machines
Young's modulus of spectra is about 120 GPa. Steel is 200 GPa. Glass is about 70 GPa. Spectra cable needs to be 1.3 times thicker to stretch the same as a steel cable. My steel core belts have steel cross-section area of 0.22 mm². Your Spectra cable would need cross-section area at least 0.37 mm² (diameter 0.7 mm) to be comparable to my steel core belt.
Anyway you can almost halve the belt stret
by
hercek
-
Delta Machines
Quotedc42
0.9deg motors are better than 1.8deg motors here, because for the same holding torque they are twice as stiff as 1.8deg motors. In practice 0.9deg motors usually have a little less holding torque than similar 1.8deg motors, so the gain isn't quite double.
I agree. Both Nema17 and Nema23 used in the analyzes were 0.9°. Micro-stepping decreases the holding torque very badly so it is bett
by
hercek
-
Delta Machines
I was thinking about a design using Ø 1.6 mm steel cable instead of belts to minimize ringing. Drums would be used to drive the cable (similar like spectra string kosel). Ø 16 mm smooth rods instead of linear rails.
I probably never get to build this but here are some estimates of different error kinds for such a printer when using Nema17 motor (42 Ncm): target acceleration: 7.3 m/s² microstep le
by
hercek
-
Delta Machines
Solid or hollow: If you have two rods with the same mass and length then the hollow rod will be stronger than solid one. Prefer rods with wall thickness around 0.5, at most 1 mm.
by
hercek
-
Delta Machines
Diagonal rods are loaded mostly in the direction of their axe. If the ball joints move freely it is unlikely that rods would cause ringing. I use Ø 5 mm rods and they seem to be strong enough.
Belts, motors (small static moment at higher microstepping), or smooth rods are more likely cause of ringing.
by
hercek
-
Delta Machines
Diagonal rod length and steps per mm must precise. You can calibrate the rest.
If your machine can achieve very low angles (<10°) of diagonal rod to the bed and hotend can go beyond of the triangle connecting virtual tower positions then you can calibrate also the diagonal rod length. These low angles would not be useful for printing (because of high stepper speed requirement), but they would
by
hercek
-
Delta Machines
Maybe a pulley is not centered on its shaft.
by
hercek
-
Delta Machines
Just lower segments per second to some value in the range 80 - 100.
LCD can be a hog of MCU power too. If you have LCD and printer shutters sometimes then try to lower LCD refresh rate. Or try to disable it temporarily to see whether it causes problems.
How quickly an extruder can feed plastic is unrelated to segments per second setting. That is a feature of your extruder and its stepper driver
by
hercek
-
Delta Machines
That being said it is great to eliminate delta segmentation errors. It is just not really needed. There are other much bigger problems at high speeds; and therefore with high accelerations because increasing speed without increasing acceleration does not make much sense. And at low speeds segments per second can be really low.
by
hercek
-
Delta Machines
Delta segmentation is not a big issue (at least if you do not use LCD). I run my printer at 120 mm/s printing speed and 250 mm/s non-printing moves often and never found artifacts I could attribute to delta segmentation. Here are examples of delta segmentation error at 120 mm/s and segments per second equal 80.
marlin:
repetier:
If you already have 8-bit electronics then there is not much reaso
by
hercek
-
Delta Machines
I think a delta printer is for two kinds of users: those who like the funny way delta moves when it prints, users needing high printing speed (and high acceleration); in such a case: you do not want small diagonal rod angles with bed because of the chart I posted before you want short steel core belts (despite steel core lasting less than glass core) at least Ø 12 mm smooth rods (if you use the c
by
hercek
-
Delta Machines
QuoteDjDemonD
I'd disagree, if I plot a 3D graph with width along x, height along y and print volume along z, there should emerge a cluster around the optimum.
I'd prefer to do this mathematically but I'm not how I'd go about it.
You do not need to. The extreme case gives you result which is not useful.
If you allow your diagonal rods to go horizontal and your diagonal rods cannot move behind car
by
hercek
-
Delta Machines