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


  1. Drilling concentric holes is easier if you rotate the work (i.e. the bolt) and keep the drill still. This is what happens in a lathe.
    There's a way do do it with an electric drill here:

    Good luck mate! Nice work.

  2. Not exactly related to this post but...

    I recently built a EMC controlled miniature mill. After reading some RepRap sites I really want to started printing plastic right now. the XYZ are driven by stepper + ball screw so is a bit slow 15mm/s compared to timing belt driving, but I hope that shouldn't be an issue?

    Assume I could wipe the electronics and software, Besides the XYZ the only piece missing would be the extruder - yet the most critical part that I don't think I could make it by myself - I don't even have a proper drill stand or G-Clamp, so forget about the afghan lathe. I'm a CS grad and Mechanics is really new to me.

    I think I will start by paying the machine shop to get the nozzle and PTFE thermal block, following the design of the Thermoplast Extruder Version 2.0. For other mount I could just mill from the scrap aluminum around.

    Before starting, I would like to know if the Extruder v2 design is stable enough? Was there a forum or talk page or mailing list discussing this? The RepRap main site and Nophead's blog are basically the only large source of information I have found over the net...
    Any hints that you can give me for converting my desktop mill to a RapStart?

  3. Sanghvi Techno Products offers PTFE Bush, PTFE Rod from India.