The Bowden principle

The Bowden tube lets you reduce the moving mass of the extruder and thus allowing faster controlled motion, less shaking of your machine, less energy use and importantly: faster printing! Normally the mechanism that drives the filament into the hot end (where it melts) is directly on top of the extruder. This creates problems of balance and oscillations with faster motion which you can see in your printing results and hear and feel when your machine is shaking.

If the filament drive mechanism is placed on a non-moving part of the 3D printer, it can be pushed into a tube. PTFE (Teflon™) is useful because it is slippery: it has little friction with the plastic. This limits wear and loss of energy. The tube's other end is connected to the extruder's hot-end.

The concept of using a Bowden cable as guide was suggested and pioneered by Ed Sells.

Benefits

The lighter the extruder is, the quicker you can move the toolhead(s), e.g. when you're not extruding. The machine will need less current to run the motors and it reduces stringing when not extruding. Even more so, it reduces the moving mass of the X-axis so much that a much simpler and lighter Cartesian bot is possible. The steel rods wouldn't necessarily be needed, allowing a much larger ratio of self-replication. The Bowden cable itself could be printed in several modules that snap together. This guide could be lined with telfon-tape (available in every hardware store) that can be replaced when worn.

 

Drawback

The Bowden cable system has one major drawback: Hysteresis. The plastic filament will compress in any extruder, but putting pressure on such a long length of filament will multiply the effects of this compression, leading to springiness. The flexibility of the PFTE tube exacerbates this problem.

It is potentially possible to control this problem, perhaps with an encoder just above the hot end. Software might also be able to reduce this problem, but would require (maybe lengthy) calibration.

A stepper-based extruder is required if no encoder is used.

Bowden hints and tips

  • Gives you slightly less control over how much thermoplastics are output where, but:
  • It decouples the extruder drive mechanism from the moving mass in the printer.
  • By doing this it greatly reduces the mass, allowing much faster motion and less oscillations at the surface of the objects' exteriors.
  • It also allows you to use a decent plastic driving motor or more 'space consuming' complex gearing arrangement. This makes sure that you can not only speed up motion, but also output more plastics. So this is especially a good way towards faster printing.
  • It can help make printing slightly more reliable. If the nozzle orifice is jammed for just a short while (e.g. too close to a part of the object that curled up a little bit), without the Bowden extruder the drive mechanism will have stripped the filament and not recover because it loses grip when it has stripped it too much. With the Bowden extruder, short blockages are not causing failure of the build. This is useful when you're just starting with printing, because you may have some problems getting large objects to stick to the platform very well.
  • Reversing the extruder motor very quickly allows you to have less oozing. The beneficial effect of reversing is more pronounced for the Bowden cable setups than for regular extruders.
  • Fast changes in Z-height are helpful if you don't want to get a small seam where it changes layers. So make sure your bot can go fast in that direction too, or optimize it to have zero oozing.
  • The Bowden extruder is not helpful if you have a fixed printing head (or moving in Z-only) and a XY-moving platform.

Content

  • 1m PTFE Bowden tube OD 4mm, ID 2mm (for 1.7mm filament)
  • 2pcs Push-in fitting M8x1.0mm

 

  • All items are shipped from our local shop in Denmark, Copenhagen.
  • For Standard shipping we use Danish Postal Services (untracked) or FedEx International Economy (Tracked).
  • All orders will be processed within 1 workday of payment. Delivery confirmation will be sent to you via email, once your order is processed.
  • We are not responsible for service transit time. This information is provided by the shipping carrier and excludes weekends and holidays. Note that transit times may vary, particularly during peak periods.
  • Local pickups are not allowed, for eBay customers. Use our webshop at reprap.me if you wish to pick up your order locally.
  • Please allow sufficient time for delivery and contact us if you don't receive your package after 30 days and before 60 days. We can't refund if you haven't contacted us within 60 days.

 

Destination Shipping method Speed in average
Inside European Union FedEx 3-5 days
Inside European Union Danish Postal Services 4-20 days
Outside European Union FedEx 4-7 days + Custom
Outside European Union Danish Postal Services 5-30 days + Custom
  • International Buyers – Please Note:
    Import duties, taxes, and charges are not included in the item price or shipping cost. These charges are the buyer's responsibility.
    Please check with your country's customs office to determine what these additional costs will be prior to bidding or buying.
  • We accept PayPal only.
  • All major credit cards are accepted through our secure payment processor PayPal.
  • Payment must be received within 7 days of auction closing.
  • If you have bought multiple items from us, you can send us one payment for all the items instead of paying for them individually. When you click the Pay Now button, eBay will automatically determine if there are other items you have won or purchased from us and will combine them for your review. 
  • If this item is defective upon receipt, customer has up to 14 days from date of receipt for exchange of a replacement or asking for a refund. 
  • We greatly appreciate your POSITIVE feedback. Please do NOT leave negative feedback without asking for help.
  • Our aim is to provide Top Level Customer Service, so we will try our best to solve any problem.
  • Please DON’T leave negative or neutral feedback if you haven’t received item in 30 days, we usually ship your items within the same day of the order, but sometimes the postal services will be very slow or a package will be lost.
  • If you have any questions, please feel free to email our service specialists 24/7. We will reply you ASAP. If no response within 1 workday, please check the spamfilter. Or you can call us Monday - Friday, 9am - 4pm CET.

RepRap ApS /DK35387366
Bibliotekvej 55A
2650 Hvidovre, Copenhagen
Denmark

Email: info@reprap.me
Phone: +45 484 23232 (Monday - Friday, 9am - 4pm CET)