Mendel materials procurement
So what do you need and where do you get the parts?
Part quantities and suggested suppliers are in the Mendel assembly data sheet.
From the BOM you'll see that you need to get hold of about 10 different types of materials. Before you buy anything, here is some important information you should know, including a cost breakdown at the end:
All bar is ø 8 mm diameter. Generally you can survive just fine on “Bright Zinc Plated" (BZP). BZP is better than 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 Mendel assembly data sheet for the number of 1m lengths needed.
Mendel does not impart big loads on any of the bearings, therefore high specification bearings are not at all needed. Get the cheapest ones you can.
Make sure you get a Contitech 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 Mendel assembly data sheet for the belt specifications.
Belt need to be split to a width of 5mm. This can be achieved using the Belt splitter jig (two reprapped parts).
The extruder design is frequently updated: check the Mendel extruder page for the latest procurement/preparation documentation.
Cheap BZP parts are fine.
Mendel uses two different types of nut: nylock and standard. As an alternative to nylocks, however, you may prefer to use standard nuts and use a thread locker compound, for example brand name LocTite 243, and apply a small amount where ever a nyloc is called for. A thread locker is a compound that sets in the absence of air.
Mendel has been designed to cater for either NEMA 17 or NEMA 14 specification stepper motors. Buy whichever is easier and cheaper for you. 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.
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, which are easy to cut with ordinary scissors...
You need to get hold of a set of reprapped parts. Many people will be upgrading to Mendel from RepRap Version I "Darwin". Darwin can print all Mendel's parts. So can all the commercial RepRap-derived machines available from the suppliers on the Get-a-RepRap-Kit page. There is a page on the RepRap forums where people offer reprapped parts for sale, and another forum page where people post wanted notices. Finally, if you know someone with a RepRap who could print the parts for you, offer them some beer...
- Part files for the cartesian robot are available here.
- Part files for the Mendel extruder are available here.
Check the thumbnail for a visual glossary of all the RP parts.
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 or saws 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 (i.e. threaded rod) is M8. BZP is fine. It is best to buy in 1m lengths and then cut to size. See the Mendel assembly data sheet for required lengths.
Note the cost analysis below is old. Check the Mendel assembly data sheet for cheaper costing data.
|Cost type||UK estimate||Notes|
|Motors||£51.66||Assumes 4x NEMA 17s (www.motioncontrolproducts.co.uk) +delivery|
|PCB/Electronics||£110.00||Zach\'s Gen3 electronics|
|Thin sheet||£0.00||Beer can|
|RP||£20.00||Assumes no commission|
|Total||£309.33 + Motor delivery|
This needs updating!/|\
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