Sunday, 16 January 2011

What has changed?

I have finally got back to 3d printing after 2 years - changing jobs (new school) new qualifications (sailing instructor) and life with two teenagers and a wife.

When I was last printing there was 1 major issue extruder jamming which drove me crazy and I could not get a consistent fix despite following others ideas so this time I have bought a makerbot extruder and hot end and I am having no problems at all. The key I am sure is the Teflon tube inside the barrel, I have now run my machine for 20 hours with no jams at all.(Not definitive proof but a good indication)

The other differences I have noticed from 2 years ago are:-

Kapon tape

What great stuff it sticks all manner of hot things together.

Heated beds
These seem all the rage so I built one using nichrome wire a glass heatproof mat and power it from a car battery charger with no heat control. It works OK ish but I now need to control the temperature and make the temperature spread more evenly so I will probably move to the power resistor and metal solution that others use. I have tried the blue tape to get a bond to the bed with little success (using ABS) and kapon tape (with little success) and have resorted back to evostick and this works OK.


Obtaining parts is much easier now with EBAY and many small suppliers setting up.

I am currently printing a mendel as I believe having two machines is vital so that when one breaks down you can make bits for the old one and it would be nice to have a standard machine to compare my work to.

Good to be back

Sunday, 14 June 2009

Its given birth(Nearly)

After a long absence with no posting I have been busy designing and printing a reprap. I nearly went for a Darwin but having tried to build the original it was fiddly to set up and had a lot of complicated parts which I struggles to separate from the source forge AOI file.

At the same time I discovered that school had a site licence for Solidworks so I thought give it a go build a simple threaded rod 3 axis machine the same as I have at the moment.

I also decided to minimise the different parts. Currently it has

Printed parts
Nema 23 motor holder
Bearing slides
threaded rod bearing block
threaded nut holder

And other parts

MDF20 mm
8mm threaded rod (stainless)
8mm bar
skate bearings
rubber pipe(motor to rod coupling)
Plus various nuts and bolts
In the picture you can see the Z and Y axis. The Y axis is a little big and is not MDF but an old shelf that was lying around.
I have stolen eD's idea about using the skate bearings as bearings for the slides. That works well- (Thanks eD if you read this)
Both the axes move smoothly and I have run the Z axis for 2 hours backwards and forwards to see what fell off (and nothing did)
I tried to make a printed motor to rod coupling but nothing I made had as good a characteristics as the rubber pipe.
I have been improving the quality of the printing in the manufacture of all the components. The Biggest is the Nema 23 motor mount at 8cm X10cm X 4cm. I found that if you make it too thick (1cm) then it tends to delaminate so I redesigned to to 5mm thick and added webs to it and it is now really sturdy. Warping was not a major issue- I am now extruding onto a glass chopping board(Robert Dyas 5 pounds) coated in evostick.

I also found that the accuracy was pretty good. I designed the bearing holes at 22mm diameter and then all I had to do was tap the bearings in with a rubber mallet with no preparation at all. The same for ineserting the long nut (studding connector) that runs on the threaded rod - just tap in .

My major issue was with some ABS I bought which varied in diameter causing many jams. I gave up in the end and bought some from Bits from Bytes and had no trouble at all, but it is very expensive. I would hope to pay 20 pounds for a reel soon.

Anyway next steps make the x axis, the extruder and double my production capability.

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 .