People have experimented with a variety of build surfaces on which to print ABS plastic such as MDF, acrylic, painters tape and sandpaper. One of best materials to use was found to be a high temperature Polyimide (Kapton) film while it is being heated to around 100°C. So, for my first build surface I decided to fabricate one with this polyimide film.
Polyimide (Kapton) Film Build Surface
This build surface is simply a .125 inch (3.18 mm) aluminum plate with through holes for eight mounting screws. You can see the adhesive backed polyimide film is not one entire sheet as the largest size I could find it in was 1 x 1 foot (30.5 x 30.5 cm), so I had to cut a few sheets up into sections.
Polyimide (Kapton) Build Base mounted on the Build Plate
Build surfaces mount to the build base plate (the one with the heaters mounted on it) with eight screws, so they can easily be swapped out to experiment with another build surface. For example I have found, as others have, that the polyimide film does tend to wear out over time as the plastic will fail to stick. The next build surface I am working on, will be made of PET film which can be wiped down with acetone if it begins to wear. It is also much less expensive than polyimide film.
Due to the very large size of the heated build base, some analysis needed to be done. This was to ensure that the target temperature could be held across the plate and that it could be done with optimal cost-effectiveness.
The simplest way to heat a plate this large would be to buy one or two large rectangular flexible heaters (backed with high temperature pressure sensitive adhesive). The problem is, heaters that large get very expensive when trying to cover such a large area. So a solution that is less expensive and offers better heating coverage, would be to buy many smaller heaters. Their placement is then critical.
Thermal FEA of the Build Base
The above image is the result of a fairly coarse meshed Finite Element Analysis (FEA) on the build plate with the heaters in the final chosen placement. Different sizes and placements of heaters were tested and it was deiced to use eight, 1″ x 12″ flexible heaters with a pressure sensitive adhesive backing. At a target temperature of 100°C, the plate achieves approximately a 5.5°C spread across the plate, which is quite acceptable considering the high temperatures.
Underside of the Build Base During Heater Assembly
The above image is the underside of the build plate with the eight flexible heaters mounted in position. These heaters will pump 480W into the build plate. For now, the entire plate is heated no matter what size part is printed. On my to-do list is a zoned heating system which would only heat the part of the plate that is needed, in order to save energy.
Thermocouple and Cable Managment
Here you can see the cable management of all the wires and the thermocouple held mostly down with kapton tape. The J-type thermocouple is glued with high temperature epoxy to the plate for more accurate temperature response.
ULTEM Insulator Plate
To help prevent the high temperatures of the plate from heating the rest of the machine, a plate made of ULTEM is used as a thermal insulator between the build base and Y axis block. This is important because the linear ball bearings are rated to a maximum temperature of 70°C.
It is very important to lubricate the moving components of the machine in order to reduce wear and extend part life. Especially since I am using Delrin anti-backlash lead nuts which exert a constant back pressure on the threads of the steel ACME lead screw. This is a high wear area so I have lubricated all of the lead screws with a high temperature synthetic grease. Having the lead screws black oxide coated does help reduce friction slightly, but I would still recommend lubricating the lead screws with grease to get the most out of the components.
Lubricating the X and Y Axes
Here you can see the red-ish purple high temperature synthetic grease on the lead screws of the X and Y axes. Also, it is important to lubricate the linear ball bearing slides as well. The linear ball bearing blocks feature brass grease nipples which make lubricating them simple by allowing you to inject grease directly into the caged ball bearings.
Lubricating the Z Axis
Here the Z axis is lubricated in the same manner as the other axes.
