Mendel materials procurement
Check the assembly data sheet for the Bill of Materials (BOM).
From the BOM you'll see that you need to get hold of ~10 different types of materials. Here are some essential notes before you buy each type:
All bar is ø 8 mm diameter. Generally you can survive just fine on “Bright Zinc Plated" (BZP). BZP is better over Bright Mild Steel (BMS) as BMS will rust unless coated with oil. A2 steel will feel nicer and be straighter, but is more expensive. It is best to buy in 1m lengths and then cut to size. See the assembly data sheet for the number of 1m lengths needed.
Mendel does not impart a big load on any of the bearings, therefore high specification bearings are not at all needed. Get the cheapest ones you can.
Make sure you get CONTI SYNCHROFLEX tooth profile, or an equivalent which allows enough room for chunky teeth. For example, HTD (round profile) does not allow enough room for teeth on a tight diameter.
RepRap attempts to print its own parts wherever possible. This includes toothed drive pulleys. 5 mm pitch (or imperial equivalent XL pitch, 0.2") belts have been investigated because at the time of research a 5 mm pitch was the most achievable to print. See the assembly data sheet for the belt specifications.
Belt widths need to be cut down to 5mm. This can be achieved using the Belt splitter jig (two RP’d parts).
The extruder design is frequently updated: check the Mendel extruder page for the latest procurement/preparation documentation.
Cheap BZP parts are fine.
Mendel has been designed to cater for NEMA 17 and NEMA 14 specification stepper motors. If going for the smaller NEMA 14 motors, aim for the high torque option. You need approximately 1400 g.cm of holding torque or more to be safe.
You’ll need a fully assembled electronics kit (the assembly directions here support Generation 3 electronics).
This is needed for the optoswitch flags. Thickness must be less than 2 mm. You will need a minimum total area of 8 cm x 5 cm. Material must be opaque to infra-red light (the optoswitch uses IR light). Material must be pliable (easy to bend into shape). Aluminium sheet is good. Some New Zealanders have been known to use beer cans.
You need to get hold of a set of printed parts.
- Part files for the cartesian bot are available here.
- Part files for the Mendel extruder are available here.
- Part files for the belt splitter jig are available here.
A small list of commercial Rapid Prototyping Services is here, but be warned, RP bureaus generally charge extortionate rates.
Sheet must range between 4 mm - 6 mm thickness. You will need a minimum total area of 42 cm x 40 cm. Your sheet must be flat as this is what you’ll be printing on! MDF (Medium Density Fibre Board) is definitely best as it laser cuts easily and is usually very flat. It is also cheap. Plywood is a good option if you require extra strength in your machine, but is harder to work with, either with a saw or a laser cutter. If using polymer make sure it is flat. Cast polymer is the flattest, but may not laser cut as well as extruded polymer. However, extruded polymer is typically not flat. When storing sheets always store them face down on a flat surface. Stacking them at an angle on their side will ruin their flatness.
All studding is M8. BZP is fine. It is best to buy in 1m lengths and then cut to size. See the data sheet for required lengths.
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