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Da Vinci Jr - Best way of securing print to print bed

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  • #26
    Beerwise, I replied to this from my tablet last night but it doesn't seem to have turned up. Not the first time that's happened from the tablet, but if a similar response appears from me you will know why.

    I assume you're referring to the glass full-contact on the heated print bed, held in place with clips. Yeah, you can do that. It's a method that's pretty much gone out of fashion now. Things change incrementally as people find new and better ways to do things.

    Glass and aluminium have different coefficients of thermal expansion, so any attempt to fix them together (clips etc) is risky. Gino pads are grippy but not adhesive, so the glass is free to "float" as it expands/contracts according to its own physical properties. Over the years many people using clips had the experience of seeing their glass crack or chip, and those stories soon spread through the various 3D printer communities.

    Here is a shot of my own Wanhao Duplicator i3 showing the Gino pads in place, and then hidden by the mirror glass.

    Click image for larger version

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    You really don't need to start digging into the physics of thermal properties of matter. The arrangement illustrated has been widely adopted because it works excellently and is extremely convenient in every respect. Many people who have used more than the four Gino pads have found no advantage in heat distribution, and usually discover that some of the pads don't touch the glass at all. Don't forget that the main purpose of using glass is to get a "perfectly" flat surface. Your print bed is almost certainly not nearly as flat -- in fact after some use (repeated expansion/contraction) it's almost guaranteed to have distortions. Thus it doesn't matter how many Gino pads you spread around, some of them will not be touching the glass.

    Those pads that are touching the glass not only distribute the heat very efficiently, but provide the added advantage of helping to prevent vibration in the metal bed from spreading to the glass.

    As to glass type...

    I've been in discussions with people who get foaming-at-the-mouth rabid with any suggestion that you can use any glass other than borosilicate. There is often a lot of waffling on about Pyrex, borosilicate, rates of thermal expansion, and so on, and it's usually a load of uninformed crap. There was a point in time when things got quite messy in the world of these specialist glasses (https://en.wikipedia.org/wiki/Pyrex) which confused the issue somewhat. Anyway, I'm not getting into one of those discussions now, I'll just say this: there is a heap of evidence that much glass sold as borosilicate isn't borosilicate. That's point #1.

    Next is the overwhelming evidence that plain glass is just fine; used day in and day out by thousands and thousands of people. One US professional I know buys window glass off-cuts from his local hardware store and cuts them to size himself to suit the various sized beds on the 20+ 3D printers he usually has on the go at any one time.

    Yes, a lot of people use 3 mm plain glass, but my personal preference is for 4 mm mirror glass. I have a large Glass & Mirror company nearby so it was no trouble for me to get a sheet of mirror glass 213 mm x 213 mm, with the corners bevelled off. That is the exact size of my heated aluminium plate, which has a bolt head in each corner.

    But as always, I can only tell you what I do. You are completely free to go your own way. No advantage to me either way.
    Last edited by AnonyMouse; 03-25-2016, 02:17 AM.

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    • #27
      Good write up, thanks AnonyMouse. I been thinking using mirror too. A good friend of mine ran a glass business for 30 years and according to him most of of the problems with glass cracking is due to hitting the edge of it. The clips do not have enough strength or grip to worry about thermal expansion, chances are the edge of the clip nicked the edge of the glass just right. Anyhow that is a moot point. More importantly since I have lots of thermal pads, what size of pads are you using on the standard print bed? Going to give it a shot.

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      • #28
        nevermind
        I can see I pissed you off already
        Thanksalot for the negative feedback.
        jheez
        Last edited by sdtag; 03-26-2016, 03:49 PM.

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        • #29
          I'd Like to share my experience.

          I jumped right in and started using my Da Vinci printer...nothing wrong with that. Like many users it seems the #1 problem is getting the ABS to adhere to the heated bed. I searched the net and collated many options...Also started spending money on some suggestions. I found what works for me perfectly, no glue, no hair spray, just by calibrating the bed properly and printing directly onto the heated glass bed.

          As for the calibration, the method suggested by XYZprinting is to complicated...Chuck Hellebuyck has a method of evaluating the printing quality URL: https://www.youtube.com/watch?v=xpe0wOxHHnY Not bad, but for my bad eyesight not feasible. As a metrologist my experience tells me using a thickness gauge is the way to go, and 0,2 mm is a good height. It so happens that two layers of paper is about 0,2 mm thick. Take a look at this: https://www.youtube.com/watch?v=C4S1QLRO6dg

          After this simple calibration, I run the XYZprinting calibration as a check, and it showed 235 all round...and I'm getting perfect prints, by using a clean glass bed, no glue, no tape, no special plate...make sure the bed is clean...

          The thing is, if you move your printer, you should check the calibration again...even if you turn it though 90 degrees...

          I hope this help someone...

          I

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          • #30
            but how do you secure the glass to the bed? That mousey guy used pads and had an air gap between the glass and the bed. I said that couldn't work and he blasted me for it. nice guy. Now I ignore him.
            I have also resorted to using a feeler gauge because 1. I think it's more accurate and 2. my built in calibration routine fails every time. I have moved on.
            Basically I was just curious how to attach a sheet of glass to the bed. clips? I assume it needs contact all the way across, not an air gap.
            I am pretty happy with my gecko plate. I was researching glass just in case.

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            • #31
              Originally posted by sdtag View Post
              That mousey guy used pads and had an air gap between the glass and the bed. I said that couldn't work and he blasted me for it. nice guy. Now I ignore him.
              Oh my, you poor little flower. Some imagined slight has you all in a tither.

              You haven't pissed me off Shirley, I couldn't give a rats arse what you do or believe. The longer you substitute mindless argument for practical research the longer it will take you to establish a method that works for you.

              You think you are the first know-all I've come across who thinks his kindergarten physics trumps the actual experiences of tens of thousands of 3D printer users with years of experience? My method may or may not be the absolute best for you and your equipment, but it will definitely work if you try it.

              Oh, but you'll never find out will you? Instead of making progress you'll still be waffling on about air gaps.

              Tell you what, why don't you really put me in my place by not believing anything I say. That'll learn me! Arrgggg ... I'm feeling the pain already.

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              • #32
                Originally posted by Ian@XYZ View Post
                I'd Like to share my experience.

                I jumped right in and started using my Da Vinci printer...nothing wrong with that. Like many users it seems the #1 problem is getting the ABS to adhere to the heated bed. I searched the net and collated many options...Also started spending money on some suggestions. I found what works for me perfectly, no glue, no hair spray, just by calibrating the bed properly and printing directly onto the heated glass bed.

                As for the calibration, the method suggested by XYZprinting is to complicated...Chuck Hellebuyck has a method of evaluating the printing quality URL: https://www.youtube.com/watch?v=xpe0wOxHHnY Not bad, but for my bad eyesight not feasible. As a metrologist my experience tells me using a thickness gauge is the way to go, and 0,2 mm is a good height. It so happens that two layers of paper is about 0,2 mm thick. Take a look at this: https://www.youtube.com/watch?v=C4S1QLRO6dg

                After this simple calibration, I run the XYZprinting calibration as a check, and it showed 235 all round...and I'm getting perfect prints, by using a clean glass bed, no glue, no tape, no special plate...make sure the bed is clean...

                The thing is, if you move your printer, you should check the calibration again...even if you turn it though 90 degrees...

                I hope this help someone...

                I
                Interesting, I've never heard of anyone having good results with all different size print jobs just on plain glass untreated. Have you had the same experience with prints of both large and small surface area, short and tall heights?

                What bed temp are you using for your ABS jobs?

                I find an index card much easier to use than a feeler gauge, but if the card is not there when I need it I just grab a piece of printer paper. Either way I set the height to the point where I can just barely feel the slightest resistance as I slide the paper/card under the nozzle. Obviously there's a very tiny acceptable range there.

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