Mendel materials procurement

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Mendel Build Documentation

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 bill of materials (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:

This "Mendel materials procurement" page assumes you want to build a Mendel, and can get hold of a set of reprapped Mendel parts (perhaps produced on an identical Mendel, or on a Darwin, or on one of the RepStraps machines out there). If you can't get hold of a set of reprapped Mendel parts, or you want to build some other RepRap variant, skip this page and go to the PartsSupplies page.


main article: smooth rod

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. Aluminium is not recommended because it will bow, and wear easily as the bearings pass over it. It is much easier to cut, however. 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.

Bearings and Belts

Mendel does not impart big loads on any of the bearings, therefore high specification bearings are not needed. Get the cheapest ones you can.

You need:

  • 48 of 624ZZ
  • 2 of 608ZZ

It is possible to get Mendel Bearing Kits from some suppliers and these are almost always the cheapest way to get what you need.

Extruder 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 wherever 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. You need approximately 1400 of holding torque or more to be safe. Buy whichever is easier and cheaper for you. There is a Mendel Stepping Motors page listing suppliers at that link.


You’ll need a fully assembled electronics kit (the assembly directions are here). You can buy these ready assembled, or as a kit that you can solder up yourself.

Thin sheet

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 also not be reflective (like a shiney tin can) - covering the end with tape or a thin layer of paint is ok. 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... Cutting up a tin can yields a much stiffer endflag.

Reprapped parts

Mendel's reprapped parts

You need to get hold of a set of reprapped parts. If you have access to a RepRap Mendel, then the RFO files for all the parts for one RepRap Mendel are in the download at mendel/mechanics/RFO-files. Simply load them up, compute GCodes from them, and reprap them. The total elapsed time that the machine has to run to do the printing is almost exactly two days.

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...

  • Solid model files for the printed parts of the cartesian robot are available individually, or as a GNU tarball.
  • Solid model files for the printed parts of the Mendel extruder are available here.

Check the thumbnail for a visual glossary of all the RP parts.

Reprapped parts glossary. Please note there are two parts on here called y-bearing-180_0off.par and y-bearing-360_0off.par that you don't need any copies of.

A small list of commercial Rapid Prototyping Services is here, but be warned, RP bureaux generally charge extortionate rates.

Some extra info about how many of what you should print, and how long it will take here: Mendel parts more info

Thick Sheet

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. Mendel uses a screw-drive to control the z-axis, so be sure that the studding rotates freely within an M8 nut. BZP is fine, galvanized steel can be too tight and cause the axis to jam. It is best to buy in 1m lengths and then cut to size. See the Mendel assembly data sheet for required lengths.

With lengths specified in mm, Mendel studding can be cut from 8 rods as follows:

side stud + J2 + side stud
1) 370 + 234 + 370, remainder=26

side stud + J3 + top stud
2) 370 + 157 + 440, remainder=33

bottom + side + bottom
3) 294 + 370 + 294, remainder=42

bottom + side + bottom    
4) 294 + 370 + 294, remainder=42

lead screw + J1 + lead screw
5) 330 + 290 + 330, remainder=50

long z base + top stud
6) 418 + 440, remainder=142

side stud + long z base
7) 370 + 418, remainder=212

short z base + short z base
8) 355 + 355, remainder=290


Note the cost analysis below is old. Check the Mendel assembly data sheet for cheaper costing data.

Cost type UK estimate Notes
Bar £11.19 RS
Bearings £31.20 RS
Belt £23.33 RS
Extruder parts £15.00 Estimate
Fasteners £22.09 Orbital Fasteners
Motors £51.66 Assumes 4x NEMA 17s ( +delivery
PCB/Electronics £110.00 Zach\'s Gen3 electronics
Thin sheet £0.00 Beer can
RP £20.00 Assumes no commission
Thick sheet £20.00 Estimate
Studding £4.86 Orbital Fasteners
Total £309.33 + Motor delivery


This needs updating!/|\


Revised Costing

Cost type UK estimate Notes
Bar £11.19 RS
Bearings £17.95 Mendel Bearing Kits
Belt £14.79 Camiel
Extruder parts £30.00 Estimate
Fasteners £18.63 + £7.95 Orbital Fasteners + Shipping
Motors £40.89 Assumes 4x NEMA 17s

SY42STH47-1684B Camiel Motor kit

PCB/Electronics £113 + £10 Camiel's Gen6 electronics + Shipping
RP £95.00 RepRap Ltd.
Thick & Thin sheet £51.34 Camiel Sheet kit
Studding £6.66 Orbital Fasteners
Total £396.45

Back to Mendel mechanical construction root.