Considerations when upgrading your WorkBee CNC to linear rails & blocks

First of all credit where credit is due:

Mark Carew, of OpenBuilds, inventor / designer of V-Slot system - Marks innovative concept has enabled massive worldwide take up of the concept.

Ryan Lock, designer of the first 'real' OX CNC and then the worldwide best seller the WorkBee CNC, Ryan deserves massive credit for what was at the time of incepetion a ground breaking V-Slot design.

Kudos to both for allowing people like us to stand on their shoulders. 

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However, there are a couple of parts on the WorkBee, and the Sphinx and the OX, and the LEAD CNC and all other known openbuilds CNC kits that are weak.... and no matter what you do to improve your kit if you keep these parts you are wasting your time and money upgrading.

1. The lead nuts.

Teeny tiny thin lead nuts believe it or not, is the number one weakness. These standard thin 8mm lead nuts are the main cause of chatter and poor cuts. They are simply too small and too thin for the job of CNC machining. The lead nuts are without doubt your number one frustration giver for poor performance and poor cuts, So called 'experts' who give regular advice on upgrading OB (openbuilds) kits fail constantly to mention upgrading the lead nuts. This was our number one consideration!

2. The 8mm leadscrews 

Especially on C-Beam over 750mm. The screws are too thin on anything over 750mm, again causing chatter, and whip. The whip can be eliminated by putting a Torsion bearing onto each end of the screw but that does not change the fact that they are 8mm diameter. 

If you seriously want to upgrade and you want to leave these two items in place then sadly you re missing the point of upgrading. There is NO point upgrading your kit if you leave these first two items in place.

3. The wheels

The wheels are great, no matter what some people think, the concept is brilliant and has allowed people all over the world to buy CNC kits at a lower cost than would have been possible with traditional linear motion. Mark Carew, the owner of Openbuilds came up with the idea of a combined wheel / rail linear motion system that used a rail system with a V in every slot and I am an absolute fan of the concept. Some readers may remember earlier versions of this concept used on other systems, but the OB kits are stronger than all of the other variations that use this concept.

 

BUT... wheels wear out, they need to be checked and adjusted regularly and they are generally a pain to work with, from excess time to assemble to having to adjust the eccentric nuts on EVERY wheel set to get the correct trim to having to take a whole wheel set apart when needing to replace just one wheel... a pain. And lastly the bolts on the wheel sets are M5, which is 5mm diameter which again is just TOO thin for CNC work. The bolts are fine on low force cuts but on high force cuts the bolts will feel the strain.

4. The Spindle placement is front loaded which means it is not balanced in line with the Y gantries, this leads to making the X c-beam easy to twist. Anything that helps to reduce the distance between the spindle and the X axis is good! For our use on this kit we remove the Openbuilds front X plate and the Z plate. This reduces the spindle position by 12mm, not a lot but something.... (some upgrades from other suppliers increase this distance making the upgrade worse and twist worse)

So, having read all of that what do you need to do to really upgrade your kit?

Recommendations, in order of preference!

1. Bin the tiny lead nuts and change those for these . There is work to do to allow these to fit onto your current kit but the difference will be massive. If this is of interest to you then send an email to admin@roboteer.co.uk asking for more details, but basically our lead nuts push the gantries out 7.5mm from where they currently are and that gap has to be compensated for.

2. Bin the 8mm leadscrews, change them for T12 (12mm) leadscrews, the difference seems to be only 4mm but that small change makes an enormous amount of difference. 12mm lead screws are far more rigid meaning less whip. Torsion bearings will still be needed on long lengths such as over 1000mm but the cost of those is minimal and the addition of torsion bearings is recommended so you can move your X/Z gantry faster when not cutting, for instance when moving from cut to cut. This drastically reduces your overall machining time.

3. Bin the wheels, NOT necessarily. If you change your M5 bolts to 8mm bolts (you will need 8mm spacers, eccentrics, shims and so on as well) then again you will see a massive change in rigidity and stability for your kit. We use this concept on our CNCGear gantries as well as T12 lead nuts and our smaller kits so as long as you use Polyurethane wheels you will get better performance from your machine and some longevity but... not as much as if you DO bin the wheels...

4. Fit Linear rails and guides, which is the traditional method of linear motion on CNC kits. This is without a doubt the very best way in combination with recommendations 1 and 2 to supercharge your machine accuracy. However, if this is your decided route then the only reason to continue using V-Slot or in particular C-Beam V-Slot is to utilise the space inside the C-Beam. If as some people do you decide to fit 16mm or larger diameter lead screws then you cannot use that space, The lead nut will not fit, so there is absolutely no reason to use V-Slot at this stage, get a different kit, use traditional 40x80 profiles which are inherently stronger anyway.

Downside; linear rails are expensive because they take a very, very long time to machine / produce so labour costs and machining costs push up the price. Although the rails and guides are not as expensive as they once were. For instance the upgrade kit shown below with full XYZ upgrade consists of;

8pcs 15mm x 1495mm rail
2pcs 16mm x 245mm rail
18pcs 15mm guides
the total price is 568usd, including shipping to USA (at the time of writing)

This would be for a 1500 x 1500mm machine and that price is just for the rails, the price does not cover the costs of the bolts and t-nuts to secure the linear rails to the C-Beam, nor the M4 x 8mm bolts to secure the guides to the linear plates.

But, a very large portion of this cost is shipping which has more than doubled since this time last year because of Coronavirus. The cost of shipping is around a third of the total price currently and this cost is expected to rise further over the coming months especially on the run up to Christmas.

This brings us to our upgrade kit. Exclusive to us because we designed it and we have it manufactured for us and we believe it to be the best workbee upgrade kit available.

 

Why?

 

  • 1. Keep your current workbee plates, no need to fit new plates, if you want to change your workbee plates as well then quite simply you probably need a new machine / kit. (We can help in that regard so email us on admin@roboteer.co.uk if that is what you want to do... you might really want to consider looking at something like this Titan Gambit)

  • 2. Simplistic design concept, low cost linear rail plates.

  • 3. Very easy assembly

  • 4. Reinforced rigidity built in, machine harder, faster and deeper, make your production process easier and more accurate.

  • 5. Anti-Twist C-Beam linear plate built in. We supply the anti-twist plates, you supply the C-Beam.

 

 

 

 

 

workbee%20linear%20upgrade_edited.jpg
  • Black Plates - Original workbee plates (not all are used)

  • Purple Plates - Y Gantry linear plates x 4

  • Blue Plates - Z gantry linear plate x 1

  • Green Plates - X gantry linear plates x 2

  • Copper Plate(s) - Anti-Twist linear plate(s) 2nd is optional