End User advice wanted! Makerfarm Pegasus 12 Build

[uncle_bob]

Hi

On a lot of the early machines, holding a "zero bed" was a real pain. Some of that was related to the materials being used in the printers themselves. Some of it was process induced. The "old way" to run a glass plate machine was to swap plates with each print. You let the part cool down on the plate while you printed on a new one. Turns out that the thickness and flatness of cheap glass isn't all that terrific. The "new way" is to just leave the same piece of glass in place all the time. Let the part cool down on the printer. Pop it off the glass and move on. It might add a couple of minutes to a print that takes a half hour to do. If you go back a couple of years, you will find a bunch of posts from a guy named Bob talking about the need for auto bed leveling. Obviously my view has changed as printers have gotten better and we've learned things.

Bob

[longjohn119]

Hi

There was a question here about bed leveling and then it went away ... hmmm ...

Manual bed leveling seems to work very well on this machine. Servo bed leveling has issues with servos and temperature. Inductive bed leveling zeros to the pc board under the glass. Either way, the automatic approach has issues on a "stock" machine. I suppose you could glue tin foil to the back of the glass ... sounds like a pain ...

Bob

I'm using an 8mm inductive probe on a Pegasus 10 and it works great. It senses the PSB at about 5mm which leaves me about 3mm clearance between the probe and the print surface. Once I got the offset tweaked it
s been spot on ever since (about 3 weeks) A 4mm probe isn't going to work without some more metal below it.

Has anyone seen Prusa's new ABL setup that also measures and compensates for any skew in the x/y axises?

[uncle_bob]

If you are using an inductive system the results are totally dependent on how well the glass follows the PCB. SInce this is totally random it's not generally a good way to go.

Bed sensing / compensation for X and Y is not normally done on a machine like this. A one or two mm offset is lost in the > 300 mm travel available. All an X or Y error does is to bump the start point of the print by the (minor) error.

[microjedi]

I am so close to ordering one of these but I keep chickening out. I go from wanting a simple, smaller, pre-built one, back to this one. I guess my inexperience is to blame. Mono price has there mini and the Wanhao clone for $199 and $349 respectively. But then I think that this 12" Pegasus is all I would ever need. Maybe I should just bite the bullet and jump right in with this one. Any other news out there who bought this one?

MODERATOR NOTE: Post late in appearing due to delay in obtaining moderator approval

[longjohn119]

If you are using an inductive system the results are totally dependent on how well the glass follows the PCB. SInce this is totally random it's not generally a good way to go.

Bed sensing / compensation for X and Y is not normally done on a machine like this. A one or two mm offset is lost in the > 300 mm travel available. All an X or Y error does is to bump the start point of the print by the (minor) error.

I've been using an 8mm inductive probe for over 3 weeks without a single bad first layer (other than some minor ABS warp unrelated to layer height) ... That's about a spool of ABS and two spools or more of PLA. A 4mm won't cut it but an 8mm leaves me about 3mm above the top of a print with a -0.65 offset. It senses at roughly 5-5.5 mm from the top of the PCB (Hardware store glass about 2.3 mm thick) I'm also using the bed extenders (Pegasus 10) that I modified for 10mm clearance below the PCB with 2 pieces of 5mm cork with a channel cut out for the thermistor and wires and the PCB heater sits right on top so it doesn't sag in the middle. That stabilizes the pcb and keeps it flat and (gently) pushed up against the glass (10" x 11 1/4"). I also have 0,0 in the front left corner of the bed like my other 2 printers which necessitates the use of Safe Homing. As soon as I put the X gantry on I knew I wasn't going to like it set up that way so I flipped the gantry which was easy as pie since the metal ends are symmetrical. It would have been too counterintuitive (for me) for troubleshooting and set up which I did from scratch with a fresh copy of Marlin (stable) from Github and the latest version of Slic3r rather than the technologically outdated version provided. For me there was no way to have a 2 fan print cooling assembly and a servo type mount for ABL

The bottom line really is you need to support the PCB heater to keep it flat anyway if you want it to heat the glass bed properly and you don't want to give up bed space to side clips which still doesn't work as well as support in the center. Of course doing it the way I did necessitates ABL since the bed is no longer adjustable. My other printer with ABL has an MK3 aluminum heater and the 4mm probe works fine there

[uncle_bob]

Hi

As soon as you try to put the pcb on something firm enough to keep it flat, you either bow it upwards or you suck enough heat out of it to mess up the thermal performance. The real answer is to go to an aluminum heat bed with a silicone heater if you want to use inductive bed leveling.

Bob

[longjohn119]

Hi

As soon as you try to put the pcb on something firm enough to keep it flat, you either bow it upwards or you suck enough heat out of it to mess up the thermal performance. The real answer is to go to an aluminum heat bed with a silicone heater if you want to use inductive bed leveling.

Bob

Gee I guess someone forgot to tell my unit that because it's been working flawlessly for 3 straight weeks and I print constantly. I also have no problem running the bed at 115 C which is as high as I've needed it to go. I also ditched the relay for a SSR and went back to PID regulation because bang-bang sucks for anything with a short (less than several minutes) on/off cycle. I could really notice it during the first 2-3 layers using a translucent red PLA (Ingeo 4048D based) and you could see from the color changes from dark to lighter and back to dark synchronized to the clicking of the relay leaving a 45 degree 'zebra stripes' pattern on the print. It wasn't noticeable that much in the finished print but it was definitely a clue heat regulation sucked and there was constant expansion and contraction going on but the SSR and PID control cleared that up. I kind of figured going in that I wasn't going to like the bang-bang controlled bed

An aluminum bed and a good silicon heater are a better solution whether you use ABL or not ...... but it also adds costs and weight. This works for me, I'm happy with it for now. Granted what works on a 10 may not work on a 12", I opted for the 10 because 12" bed at only 12v is really pushing the limits

[uncle_bob]

Well my printer works perfectly with no ABL and no PWM ( it is PID all the time).

It it is not very hard to get one of these working....