Tuesday, 7 April 2009

At the end of 4 days

Well 4 days solidly working on stuff. My family think I am mad and have not seen me apart from meal times. Still I have made some progress. The picture shows the screwable jewelry box bottom made with ABS. Unfortunately I did not lift the nozzle away at the end hence the blob at the back. Still I am pleased with it.

What have I found out?
1. It takes a lot of force to push the filament through the nozzle and my steppers only just have enough torque to drive ABS through.
2. PLA cannot be driven through my design of extruder as it buckles. There may be more to play with here as I think I may have had the temperature too high causing too much friction in the delivery tube.
3. I cannot get enough torque or friction to drive HDPE through the nozzle.
4. When designing something take time to check it as printing takes a long time and is frustrating when you get it wrong.
5. 3D designing is hard it is better to sketch it out in pencil before starting using a programme.
6. Solidworks is an excellent programme easy to use and the dimensioning facility is really easy to use- I am glad that I can use my school's educational site licence as it is much too expensive to buy.
7.Putting plugs on everything saves hours. I have just discovered railway modelling plugs cheap and easy to use.
8 Thermistors are very delicate and difficult to attach to the nozzle. They work well until you remove a nozzle and then they break easily.
9 Warping is an issue
10 The machine is very reliable, no breakdowns, repeatable movements. The threaded rods and long bolts have now probably in excess of 40 hours run time and no failures
11 Drilling a hole in a threaded rod so that it is concentric is very very difficult.

What am I going to do
1. Go to Wales for 3 days and speak to the family!
2. Try putting a thermistor in a drilled out bolt so that it can be removed/replaced easily without damage. Screw it into place on the brass bar.
3 Buy higher torque stepper motors
4. Modify the pinch wheel extruder block design for the 4th time and get it right this time
5 Blag an old oven to see if extruding at a higher ambient temperature stops warping
6. Use the pinch wheel extruder to try and extrude solder, I can melt it and I can move it through the extruder. Can I combine the two?
7. Do some experiments on how strong the bond is in the first layer and the board/plate that it is made from.
8. Try and increase the speed of the machine above 800 mm/s- M8 rods instead of m6, change the stepper driver settings.;
9. Try and find the optimum settings for starting and stopping.
10. Go back to the original screw drive design and see how well that woprks with stepppers, the new nozzle andPLA/HDPE

Saturday, 4 April 2009

Pinch wheel extruder 2

Here is my attempt at a bigger pinch wheel extruder based on Adrian's design. It took about 6 hours to print and had no breakdowns.

The only problems with it (appart from my design flaws- holes in the wrong place was the warping.
I am going to apply heat today using a hairdryer to see if this fixes teh problem and I have also had the evostick curing last night as older evostick seems to grip better.

Better stepper mounting bracket

Here is my next attempt at the stepper mounting bracket. This is much stronger, there is very little warping however as can be seen from the second picture the small holes are not as well defined.

I will experiment with the skeinforge carve preferences to improve the hole quality.

The better warping is due to thinner layers and applying a heat gun to the first two layers to ensure that they stuck. (Ithink!)

First useable part.

My Y axis vibrates like crazy so I designed this mounting block to test out the quality of all my new settings. The whole part is much more sturdy and flat. The only problem was my base plate moved half way through giving an off set. Still I will bolt this on today and reduce the noise/vibration.


Fed up with poor quality I decided to fix all the annoying bits that kept dropping off and then work out the ideal settings (Also to move the whole lot back into the garage to keep the family happy.
The main fixes were to secure the extruder to the machine much more securely. To get the maximum travel on the z axis. To get the feed so that it was consistent using the small screw eyes from B and Q and to tidy up all the wiring. This worked well.
I also changed the acceleration settings on the stepper so that they were on the maximum (increased from 30 mm/s/s to about 600mm/s/s) This has made a massive difference to the quality although I would like more)
I then checked the temperature that the plastic was being extruded at as it comes out of the nozzle and adjusted this to 235 degrees as this seems to be the preferred temperature for ABS.
I then made a series of Nophead's hearts using from left to right 0.7, 0.6 0.55 0.5 and 0.45 settings on the carve layer thickness. The best by far is 0.5 so my settings now are 800 mm/s, 235 degrees0.6 welding tip nozzle .

Adrian's pinch wheel extruder

Here is my attempt at Adrian's pinch wheel extruder. It has worked reasonably well but I

am still not happy with the overall quality but there is very little warping for some reason. Unfortunately I do not have a stepper to fit it to try out! If anyone wants it I will stick it in the post to you!(And it is not to a great standard!)

Weak stepper mount

Here is an attempt of a stepper mount to replace the B and Q brackets I am currently using.
The mounting face plate worked really well and has only a little warping (I am still using Evostick on a glass chopping board as the base)

The bit out to the left in the picture built as a tower however is very weak and would never be strong enough to mount a stepper on. There must have been a blockage in the extruder 2/3 of the way up the tower as there is a fault there.

Big Extruder

Here is my attempt at the biggest object that I have made. Not a great success!
It is about 20 cm long and 8cm tall designed to have a stepper one end and a tube through the middle.
It warped and the darker discolouring at the bottom is where I used a hot air gun to flatten it!
It is made with ABS
I had my whole extruder assembly come loose in the last part hebce the unfinished flattened top.
Also It lacks strength as the layers are not close enough together.