Hello,

This probably is a dumb question... I have purchased a kit for Mendel Prusa i3. I'm almost done with the build - what's left is the electronics and heated plate, and extruder (some parts were missing in the kit so I am waiting for the parts).

The kit does not include a glass pane, but the build instruction mentions that I need to get one, which I did. However, I can't find any further instructions on how/where to use this glass pane. I searched the forum and other postings a little bit, and it seems like the glass plate goes on top of the heated plate. Is that right? If so, I guess the purpose of doing this is to prevent the printed shape from sticking to the heated plate (and ruining it). Am I correct?

But then again, I also saw postings from some people having a problem with making the heated plate hot enough. If getting heated plate hot is a bit of challenge as it is, I would think putting a glass on top of it won't help the case - I believe the glass is a poor heat conductor.

Having said that, now I am not sure if it really is supposed to go to top of the plate (so the printed shape will be sitting on it), or if it actually need to under the plate - to provide some insulation at the bottom and direct the heat to the top side.

Yet again, if it's the latter, then why bother using a glass plate instead of other insulator material? Because the heated plate gets pretty hot and not many other materials can withstand such heat while providing good insulation???

Thank you.

Yes, the glass goes on top of the heated bed. If you are having issues getting up to temp then you need to install some sort of insulator under neath your headed bed. I have heard of people using sheet cork as well as 100% wool felt. You'll want to read up on heated beds and part adhesion there are various methods and opinions. Glass is just one of them and I believe is the most common. There are variants about what to put on the glass to get parts to stick. (Sorry can find the entery I read on reprap.org.) I have found that a cold bed with blue tape on the glass works great for PLA prints. Other say hair spray on the heated glass for both PLA and ABS. For ABS you always need the heated glass. Some say ABS juice (search wiki) is the best. Others say kapton tape on glass with hot bed is best for ABS. Others say you should use another material besides glass. Read up, experiment, and see what works for you.

appdev007,

Thank you for your reply.

Yes... I actually read more about the glass and heated bed thingy, and to my surprise I realized the challenge is to make the shape stick to the plate, not to take it off the plate. Well, the reason I assumed we are trying to prevent the shape from sticking to the plate was... well, simply because the glass is so slick.

I wonder why glass is the most commonly used material... If the glass is used because it can withstand the heat, well, I wonder why we are not using some sort of metal plate? Hmm.. well, I guess you are right. I should read more to learn from other people's failure/success and also experiment with different materials myself.... once I have my 3D printer built that is. LOL

Thank you.

Glass is used because it is made perfectly flat and does not bend and because PLA sticks to it when hot and releases when cool.

---

[www.hydraraptor.blogspot.com]

Yamster, welcome to the 3D printing world. We do lots of experimentation and what works for some doen't work for others, so I'm glad to hear you are willing to experiment. Be sure to not experiment with large parts when trying out new bed surfaces. You will wind up wasting too much plastic. And do be aware there are surfaces that you can't get parts off of.

Have fun and good luck.

(P.S. When nophead tells you something take note. He knows his stuff!)

In terms of just the bed ( you need to calibrate everything first (with firmware), before doing your firsts prints), I used a mirror from the hardware store cut into a shape to fit on my bed. I don't know if you already have a build plate to put the heater board + glass ontop, but here's a picture of how I have my bed right now.

When using a heater plate, If you can get some 100% wool (felt works great), cut a piece to go underneath the heater plate and glass.
For my setup this helps to insulate the heat from going to my wood and plastic parts below.

Insulation is really important, even if you have a metal moving plate below, since you want to focus the heat to the glass itself.

Hope this helps you in some way

Just a side note on insulating the underside of the heated bed.

I simply folded some aluminium foil to double it up and slid it under the heated bed. It is held by the same bulldog paperclips that are also holding the glass to the heat element/PCB. Make sure the foil does not find the solder points on any electrical connections....

Quick, and it radically reduced warm up time, and increased max. temp.

I should also add, some people have several glass plates, that way you can take on off the printer, let it cool off to the side and start printing again on another glass plate.

---

Yvan

Singularity Machine