Cheap Science

I’m not dead…just busy

I’ve been back at uni for the last couple of weeks and I’m doing my dissertation this year so I’ve been pretty busy and haven’t had the chance to update this. Anyway I finished my second machine which I call the PLA machine for obvious reasons and here it is:

I tired to make everything as neat as possible and I think it turned out OK. So some key features with this machine:

• LM8UU Linear Bearings throughout
• T2.5 Pitch Belts with Machined Aluminium Pulleys
• J-Head MKII 0.5mm Nozzle
• 9-47 Gear Ratio on the extruder

I’ve been experimenting with it for the few weeks I had before uni started and here’s a few things I’ve learned (with the obvious caveat that this stuff is true for my machine/extruder/plastic combination):

Okay so I’ve read that two bed surface materials are good for PLA, blue painters tape (masking tape) and a heated bed at 60 degrees.

Lets talk heated bed first: I found that PLA will stick to a heated bed (at 60 degrees) fine for a while but for certain objects (tall or large flat objects) it’s unreliable. I’ve had objects coming unstuck half way through pretty much ruining the print. So I tired upping the temp to 90-100 degrees and this seemed to work better but I still got a lot of corner lifting.

Masking tape: this is by far the better option for me anyway I found adhesion to be a lot more consistent no corner lifting or objects getting unstuck.

Now I’m still playing around with different types of tape I’ve used super cheap tesco masking tape which is OK but not great and I’ve used crazy heavy duty masking tape which I got from my hardware store (the blue stuff) which sticks insanely well but that means when you pull objects off the bed you invariably rip  some of the tape off with it.

If I can find something that falls between the two extremes I’ll really be cooking!

In other news I picked up a RAMPS 1.4 kit for my ABS machine from http://www.reprapworld.com/ (which I highly recommend: good prices and fast delivery). Here it is:

I got the DIY kit cause it’s cheaper and apparently I’m a masochist…I will say this while it is possible to put the board together with no hot plate/reflow soldering oven it’s but no means easy. I managed with a soldering iron, flux, tweezers and a magnifying glass but it was a painful process. So unless you’re particularly adventurous get the pre-soldered kit!

I’m still waiting for my Arcol Hot-End for my ABS machine so when that arrives I’ll post another update!

Reducing friction

The linear bearings I ordered finally arrived so I set about installing them (I’ve taken this machine apart so many times now I could probably do it blindfolded).

So here’s some pictures of my handy-work (I took the pictures on my second machine which is under construction, so it’s easier to see)

X-axis (using Greg Frost’s LM8UU X carriage: http://www.thingiverse.com/thing:9869)

The Y-axis (using xnarnon’s snap in holders: http://www.thingiverse.com/thing:10287) just bolted onto the bottom plate.

Now for the Z-axis Prusa has released an LM8UU variant of the standard Prusa design which use push-fit holders for the X-axis smooth rods. This means that the X-axis smooth rods have to be cut to the correct length which, given my wonky hacksaw and terrible cutting skills might not turn out so well. So I used Prusa’s snap fit X-ends for the motor side (http://www.thingiverse.com/thing:9936), because I like the design of the new X motor mount:

and I used DXBLouie’s design for the idler end (http://www.thingiverse.com/thing:9862):

Oh and a quick tip you really need a heat gun for this, you have to heat up all the plastic parts to make the bearings fit otherwise you’re more than likely going to break one of the plastic parts.

So what’s the verdict is it worth the £15-20 to get the linear bearings, hell yes! They significantly reduce friction on all three axes compared to the PLA bushings and they will hopefully last a lot longer.

One final thing I found that there was still quite a bit of friction on the X and Y axes when I put the belts back on. I traced this to the mudguard washers used for the standard belt guides:

Even if you loosen the two nuts holding it together the belt still tends to rub against either side. So the solution is to print a few bearing guides: http://www.thingiverse.com/thing:503. 

They are really great it uses less parts (no need for load of washers), and they work phenomenally well. I installed them on both the X and Y axis and now with the linear bearings everything is ridiculously smooth. 

Back in business

I gave up on my mendel-parts extruder, I tried a few thing to stop the leak but nothing worked. Luckily I had an old Makerbot MK4 nozzle lying around, all it needed was an M6 nut and it fit the mendel-parts PEEK mounting bracket I was already using. 

At least the mendel-parts nozzle lasted long enough for me to print all the parts for my second printer, I’ve managed to get the frame together today:

I still haven’t squared everything I just wanted to get the frame together for now. I still have to get some steppers, belts and electronics so it’ll be a while. I’ve been shopping around and it seems that Zapp Automation is a good place to get cheap steppers. And like the RAMPS 1.4 kits at RepRapWorld plus they have a nice selection of ABS and PLA. 

It’s leaking!

I’ve been printing quite a lot lately and the first signs of the wear have started to creep in. As you can see my hot end is leaking! 

I’m using a Mendel-Parts v5 hot end which uses a threaded PTFE insulator which screws into the brass nozzle. You can just make out a few blobs of ABS at the beginning of the threads (apologies for the quality my phone isn’t the best camera). 

I’ve heard of this happening to other people and I have been meaning to add a heatsink and/or cooling fan to help keep the insulator cool but haven’t gotten around to it. I’ve already printed up a 40 mm fan mount for my lm8uu x carriage http://www.thingiverse.com/thing:10767 so I’ll be adding that once my bearings arrive.

I’m not sure if that will solve the leaking issue, the threaded end of the PTFE insulator is really the weak point of this design and I think the guys at mendel-parts got rid of it in newer versions.