three-point vs four-point mounting for MK2 heated bed
Posted by jamesshuang
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three-point vs four-point mounting for MK2 heated bed February 19, 2014 02:14AM |
Registered: 10 years ago Posts: 57 |
Hey guys,
Just a word of caution for anyone using 3-point bed mounting with a moving y-axis printer. I printed an adapter to use 3-point bed mounting for an MK2 heated bed on my Prusa i3. It does make leveling the bed easier, but It's been destroying my print quality. I noticed how much the corners were wobbling during fast y-axis moves. This was the source of all the weird backlash wobbles I started seeing on all the corners.
So, moral of the story -- if your bed moves around, use all 4 corners to mount it!
Just a word of caution for anyone using 3-point bed mounting with a moving y-axis printer. I printed an adapter to use 3-point bed mounting for an MK2 heated bed on my Prusa i3. It does make leveling the bed easier, but It's been destroying my print quality. I noticed how much the corners were wobbling during fast y-axis moves. This was the source of all the weird backlash wobbles I started seeing on all the corners.
So, moral of the story -- if your bed moves around, use all 4 corners to mount it!
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Re: three-point vs four-point mounting for MK2 heated bed February 19, 2014 09:11AM |
Registered: 10 years ago Posts: 241 |
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Re: three-point vs four-point mounting for MK2 heated bed February 19, 2014 11:06AM |
Registered: 10 years ago Posts: 553 |
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Re: three-point vs four-point mounting for MK2 heated bed February 19, 2014 12:01PM |
Registered: 10 years ago Posts: 57 |
I had a stack of corkboard / MK2 / glass plate all sandwiched together. The natural springiness of this stack was the problem -- it wasn't well supported enough at the corners and wobble during quick moves. I wouldn't want another heavy plate on the y axis considering there's already so much mass there.
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Re: three-point vs four-point mounting for MK2 heated bed February 19, 2014 01:22PM |
Registered: 10 years ago Posts: 241 |
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Re: three-point vs four-point mounting for MK2 heated bed February 19, 2014 02:35PM |
Registered: 10 years ago Posts: 553 |
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KingRahl
Corkboard?!! That sounds waaay too soft and flexible. If you had your bolts going through it, then no wonder you were getting movement. Try a thin sheet of plywood or MDF.
The cork was likely just an insulator against the pcb, if you mount it solidly with bolts there is no reason to stuff plywood or mdf right against the pcb other than insulation. My pcb floats 3-4mm above the Y frame on 4 bolts but it is solid at all mounting points and I have never had movement.
Edited 1 time(s). Last edit at 02/19/2014 02:35PM by tjb1.
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Re: three-point vs four-point mounting for MK2 heated bed February 19, 2014 03:57PM |
Registered: 10 years ago Posts: 241 |
So your bolts connecting to the Y-frame are leading directly to the Heatbed holes? I guess it depends on the Y-carriage design you are using.
The 3 bolt method is not for the 4 PCB holes. It is for a stabilizing plate/board under your PCB. 2 on one side and the third in the middle of the opposite side. You wouldn't drill a hole through the middle of the PCB heatbed edge to get that 3rd hole (I hope).
The 3 bolt method is not for the 4 PCB holes. It is for a stabilizing plate/board under your PCB. 2 on one side and the third in the middle of the opposite side. You wouldn't drill a hole through the middle of the PCB heatbed edge to get that 3rd hole (I hope).
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Re: three-point vs four-point mounting for MK2 heated bed February 19, 2014 04:54PM |
Registered: 10 years ago Posts: 57 |
This was all on a Prusa i3 laser cut version, which has that "frog" plate on the y axis. See here: [secure.flickr.com]
There was no center hole on the plate, so I printed a strip that extends across the two legs to have a middle hole. The corkboard under the heatbed was only for insulation -- the MK2 floats over the top of the plate on spring-loaded bolts. In any case, don't do that! Use all 4 bolts for maximal rigidity.
There was no center hole on the plate, so I printed a strip that extends across the two legs to have a middle hole. The corkboard under the heatbed was only for insulation -- the MK2 floats over the top of the plate on spring-loaded bolts. In any case, don't do that! Use all 4 bolts for maximal rigidity.
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Re: three-point vs four-point mounting for MK2 heated bed February 19, 2014 05:08PM |
Registered: 10 years ago Posts: 241 |
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Re: three-point vs four-point mounting for MK2 heated bed February 19, 2014 07:17PM |
Registered: 13 years ago Posts: 1,780 |
Please note that if you rigidly mount the heated PCB that it's not free to slide laterally, then the board will buckle up or down instead as it expands when it heats up. The best approach is to use a M3 screws or equivalent so that there's some clearance for expansion and not to tighten the screw or nut so that the board can slide. I actually have the mounting screws for my Mk1 upside down with the head under the y carriage plate. One nut is used to hold the screw tight on the cariage plate and another is used to adjust the height of the bed.
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Re: three-point vs four-point mounting for MK2 heated bed February 20, 2014 08:23AM |
Registered: 10 years ago Posts: 553 |
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KingRahl
So your bolts connecting to the Y-frame are leading directly to the Heatbed holes? I guess it depends on the Y-carriage design you are using.
The 3 bolt method is not for the 4 PCB holes. It is for a stabilizing plate/board under your PCB. 2 on one side and the third in the middle of the opposite side. You wouldn't drill a hole through the middle of the PCB heatbed edge to get that 3rd hole (I hope).
What? The MK2 beds have 3 hole mounting, one side will have 3 holes along it (this is including the one centered) so you can mount on a 3 point plane or use the 4 corners for 4 point. The hole in the middle of the board is to allow a thermistor to get closer to the surface from what I have been told.
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Re: three-point vs four-point mounting for MK2 heated bed February 20, 2014 09:08AM |
Registered: 10 years ago Posts: 241 |
I have about 6 MK2 heatbeds (this one says Manufactured by Avanti Circuits). Not one of them has a third hole, on any edge. I guess it depends on where you ordered yours from. Mine have the four corner holes, 1 center thermistor hole, 2 holes for the wire, and 6 smaller holes in between for resistor and LEDs. My traces go along the edges and around the mounting holes. No room to drill.
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Re: three-point vs four-point mounting for MK2 heated bed February 20, 2014 11:43AM |
Registered: 11 years ago Posts: 195 |
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Re: three-point vs four-point mounting for MK2 heated bed February 20, 2014 01:19PM |
Registered: 10 years ago Posts: 553 |
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KingRahl
I have about 6 MK2 heatbeds (this one says Manufactured by Avanti Circuits). Not one of them has a third hole, on any edge. I guess it depends on where you ordered yours from. Mine have the four corner holes, 1 center thermistor hole, 2 holes for the wire, and 6 smaller holes in between for resistor and LEDs. My traces go along the edges and around the mounting holes. No room to drill.
Sorry, it is MK2a and MK2b. I didn't realize there was a MK2 also.
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Re: three-point vs four-point mounting for MK2 heated bed February 20, 2014 07:13PM |
Registered: 10 years ago Posts: 241 |
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