To support the headed bed and/or print bed from the y-axis and the bed frame – all Prusa 3D printers, including the P3Steel use a combination of bolts, washers and nuts on each corner – fastening the bed to the y-axis frame. This will make the bed and frame as one with no movement or adjustment. To allow movement in the bed and to give you manual adjustment, as well as vibration dampening – these M3 bolts are fastened with large springs. The springs act against the bed and frame and give it the tension, but allow for minor adjustment to level the bed independently at each coder.
Toolson’s edition of the P3Steel does away with these springs and opts for a novel (genius) solution of using silicone dampeners. These dampeners give the required space between the bed and frame, act as vibration dampeners, and also allow for minor adjustment via an M3 bolt which threads through the middle.
This post will show you the process of making the silicone dampener and is a great example of how 3D printing can be used to make an end product which is NOT 3D printed.
The Dampeners Mould
You can find Toolson’s design at Thingiverse – http://www.thingiverse.com/thing:1306605. It’s a two part model with the main part and a “lid” which screws on and allows you to get at your finished moulds once they are complete.
After printing the parts you need to secure them together with some long M3 bolts and nuts. The mould is secured with the four corner bolts and the middle edge one. And then there are four additional M3 bolts which go through the mould and will help cast the “hole” in the parts for the final M3 bolts to go through. Once you are at this stage, you are ready to case your moulds using silicone. Toolson goes into detail about what he used on his make. However, here in the UK I was finding it difficult to find a two part heat resistant silicone product… so I experimented….
Bathroom Silicone Sealant
My first test was with normal “bathroom” silicone sealant. I though – “hey, it’s silicone, it’s rated to be fairly heat resistant and it is rubbery when set, i’ll give it a try”. Turns out it shrinks a lot when curing and also tends to only cure on the outside areas which are in contact with air. Ideal for beading a bath with a thin line, but building up a large amount in a hole is basically like squeezing it back into the tube!! After taking the top off after a couple of days watching the front wall cave in it was not even set. I left it out to set so I could pull it out, but no – it sticks well too!
Below you can see my attempts of removing the silicone sealant. After some picking and hacking I gave up and just printed a new base mould. That is why you may see slight colour differences in the pictures and YouTube video linked below – the first was grey, the second black. Why spend hours cleaning out a mould when you can print one in the same time?! 👌
Silicone Moulding Paste
After that mess I thought i would try with some modelling silicone – the type you cast with etc. After looking in my local HobbyCraft I found some stiffer modelling silicone paste which is designed to be a little more rigid that traditional casting silicone. It’s called Siligum Moulding Paste and you can find this stuff on Amazon here – http://amzn.to/2eZbZt9 if there’s no HobbyCraft near you.
You mix the two pastes together like any other two part component and the chemical reaction starts – you have a few minutes to play with it before it sets like rubber and stays like that.
It was a case of pushing the paste down into the holes and trying to get rid of any air pockets. I decided to do two at first just to test it, so that’s why there’s only two seen below. Keep pressing and pushing to get all air that you can out and then level off the top… minutes later it should have cured and set.
I think I left it to fully cure for an hour, but the packet does say ready in 5 minutes. After “some time” I took off the lid and pulled out the M3 bolts. The parts just popped out with a leverage, they were not stuck in any way, just needed encouraging out.
They turned out great and are nice and stiff, but with a little bounce to them. They also seemed quite solid too and not brittle at all. The packaging states that moulds are good for fifty castings, so I suspect this is fifty pushes and pulls of the mould to break out the plaster or whatever it is you have cast, before it starts to break down and fail somehow? We’re not using these as moulds, so I think they will last a long time, heat and vibration pending… watch this space!
I’m going to leave this post here and call it a day. The next post will be installing these silicone dampeners onto the print bed, along with the bed itself and all that entails. For a sneak peak of this, and to see how the mould was made – check out my YouTube video below, and don’t forget to subscribe to my channel and like the video if you can!! 👍