Prusa i3 Build

I have a Huxley and a home built Prusa both circa 2012-13. I have only ever used Kapton tape with both and whilst in the early days used to change it, the current tape has been on several years. So still on first reel of tape. I use Acetone to clean the beds, in the form of Boots or Tesco ( no connection) nail polish remover. Used PLA and ABS in various forms on the Prusa and yield improved with use of a full 10mm brim to no failures. Was going to upgrade to glass, but the brim technique seems to do the trick. However having two plates would make sense if you wanted to continuously run a machine.

For levelling have just run a single layer and measured when cooled and adjusted to suit.

The quality and "alloying" of the filament will make a considerable difference to the performance. The colouring pigment and flow modifiers will yield different properties just as carbon and other additives do for steel. So may be worth trying different sources/brands.

You have to be careful with nail polish remover, it often has oil added to help prevent the nails being damaged by the acetone.

Ian S C

Yes read the label, the "cheaper" removers seem to be neater without the oils. Probably the conditioners got more additives.

I keep meaning to bulk buy acetone and use most of it with some mineral oil as WD40 substitute.

Re levelling. As engineers is there a reason you don't use a DTI, in some specially printed holder perhaps, to measure the variations?

Several people are mentioning they have a Prusa with or without heated bed etc but I see a huge number of mfrs on the web with an equally wide range of prices so perhaps more specific details would be appropriate when mentioning a factor that would be mfr dependent.

I was thinking of doing that. But unless it is a permanent fitting you still need to set the initial gap.

The problem is any permanently fitted probe mustn't extend below the nozzle, which is why you can get inductive sensors to do the job.

Neil

Some beds are sprung mounted? so if using a DTI you may be measuring to a deflected point, rather than the operating position. If you extrude material and measure you are measuring the real situation.

Have to explain please, further why a inductive mounted sensor, which would not extend beyond nozzle would not work?

Even the sprung beds are rigid enough for a DTI, they have to hold level with the weight of a print on top.

I was saying inductive sensors will do the job. Marlin firmware has auto levelling code that can be enabled.

Neil

This makes me feel very old! - what will you use it for when it is made?

Norman

I got into computers with the Altair - mid 70's. The most common question I got at the time was "yes, but what can you use it for?"

At the time just the fun was enough to satisfy. The uses came along later. The first really useful program I found was a mortgage amortization program that let you do "what-if" scenarios. It was a complete eye-opener, let me pay off my house mortgage in 6 years and saved me more money than every computer I've had since.

I tried regular feeler blades at first but found they were a bit short in my case. Switching to the long Starrett ones was much better.

Norman, pity you didn't come along to the last Exeter DEMS meeting as someone was showing some pieces he had made. Brackets for something not the usual star wars figures and printed on a Prusa too. Someone else brought along a Stuart compound so we should have challenged him to make a printed one.

edit - looks like a printed D10 has already been done.

Edited By Bazyle on 24/04/2017 18:44:34

Ah it's not the computer side of things that fazes me - I was in early - my introduction to them was writing simple Basic programs and submitting them on line to a computer bureau in New York! It all went on from there and computers have become firmly lodged in all aspects of life. I accept it all but I don't find it fun anymore - out in my workshop though twiddling handles and making swarf - now that IS fun. ( I do have a computer out there too - useful for reference but NOT connected to the machines. I want the fun of turning those handles myself!)

Norman

It doesn't replace the metal mangling, but it complements it.

It's incredibly easy to make useful bits and pieces, especially now I have sussed how to print usable threads.

I could do a list, but...

How about some of these Neil?

Dave

If you are buying acetone in bulk you may have to be careful, someone might start asking questions, I believe it is used in the manufacture of some kinds of illicit drugs. You might even have to sign for it, or be an approved company.

Ian S C

Terrorists also use aceton if I'm not mistaken...

Neil, can you reveal how you are modeling the threads please and what thread type? This is a subject that has come up on 3D printing forums and often causes difficulties. There are several people who have tackled this on Thingyverse with what looks like good results. Are you using one of these?

Paul

That hoary chestnut!

3D printing lets you print those ready assembled

Neil

I did it the simplest way possible in Turbocad:

Hollow cylinder at the outer diameter of the thread, centres at 0,0,0

Measured thread pitch at 1.7mm for two threads, so 0.85mm

Created an equilateral triangle 0.85mm on each side and placed it where I wanted the thread to be.

'Span' it into a torus centred on 0,0.

Changed properties so the spin had pitch 0.85mm and 10 turns clockwise.

Enlarged the spin by 0.4mm in diameter (on the second run after I found the original thread was too tight).

Placed the spin at the right z-height in the cylinder, duplicated it and put the copy at the other end.

Cropped both ends of the cylinder to length.

Saved as STL and printed at 0.15mm layer height.

0.2mm a side seems to be about right to allow for over-extrusion of the thread, its appearance is a two to three-layer continuous spiral.

It engages nicely (although it is easy to cross-thread) and seems to be more than strong enough for the light duty required.

I made an external 0.75mm thread for a t-mount adaptor the same way. I have done it up and undone several times and it doesn't seem to have degraded noticeably.

I think the secret is to accept that things like tip and root radii are meaningless at small pitches, and adjust the diameter to provide the required fit, using a 60-degree equilateral; triangle ensures that it will approximate to a metric thread, which is all you need.

Acetone is a commonly used solvent in organic chemistry and has a multitude of uses. It is also used as a solvent in other industries. One might just as well say that alcohol can be used in making drugs or explosives - or even water.

Here you can buy acetone in litre bottles in any supermarket.

Russell