DIY Build of Aluminium CNC Wood Router without Workshop & Tools

[WandrinAndy]

If you're buying the Hiwin rails new then there's no need to get 20mm for this size machine - 15mm is perfectly good for the vast majority of CNC routers. This could help with making the Z-axis more compact.

Thanks Jonathan... Pics really help visualise things... Looks to me like those mounts are milled down to about 3mm? Have you noticed you're missing a bolt in pic-1... or is that one an optional extra... Lol

I've drawn my pics with 20mm rails because I had already created them as components under Sketchup, but am seeing more and more comments stating that 15mm is plenty good and that would save some dosh, and might bring Z 2mm nearer to Y.

But, I am a wee bit worried about aligning 15mm rails on this particular profile as the slot itself is 10mm wide and then there is a wee surface rebate on each side of the slot, that looks to be about 1mm, which makes a total gap of 12mm resulting in the rail only being supported by 1.5mm on each side! So am thinking that 20mm would better... supported by 4mm on each side?

[Jonathan]

Looks to me like those mounts are milled down to about 3mm? Have you noticed you're missing a bolt in pic-1... or is that one an optional extra... Lol

Yes something like that... you don't need much thickness if there's plenty of material around the motor mount surface to stop it bending. I missed two screws in that picture as it was just a test fit.

I've drawn my pics with 20mm rails because I had already created them as components under Sketchup, but am seeing more and more comments stating that 15mm is plenty good and that would save some dosh, and might bring Z 2mm nearer to Y.

The drawings are available from the Hiwin website by the way...
You can also get Z closer to Y by milling pockets in the Z-plates for the rails and blocks. That's required anyway if the plate isn't nice and flat...

But, I am a wee bit worried about aligning 15mm rails on this particular profile as the slot itself is 10mm wide and then there is a wee surface rebate on each side of the slot, that looks to be about 1mm, which makes a total gap of 12mm resulting in the rail only being supported by 1.5mm on each side! So am thinking that 20mm would better... supported by 4mm on each side?

Ahh didn't notice that. With either size rail I would prefer to see them mounted on a strip of aluminium and have that bolted to the aluminium extrusion to spread the load. Hiwin 20mm linear guides are 36mm tall and the 15mm variety are 24mm tall, so if you mount the 15mm rails on a 12mm thick strip the rest of the drawing stays the same. In addition this maintains a good spacing between the 4 blocks which is necessary for good rigidity.

[WandrinAndy]

With either size rail I would prefer to see them mounted on a strip of aluminium and have that bolted to the aluminium extrusion to spread the load. Hiwin 20mm linear guides are 36mm tall and the 15mm variety are 24mm tall, so if you mount the 15mm rails on a 12mm thick strip the rest of the drawing stays the same. In addition this maintains a good spacing between the 4 blocks which is necessary for good rigidity.

The Hiwin pdf I downloaded from Zapp about a week ago gives the height from bottom of rail to top of block as: HGH20CA = 30 and HGH15CA as 28, so much of a muchness. Are you figures for a different model or have I cocked up?

Yep, I will also need some milling done in the Z/Y plates.

[Jonathan]

The Hiwin pdf I downloaded from Zapp about a week ago gives the height from bottom of rail to top of block as: HGH20CA = 30 and HGH15CA as 28, so much of a muchness. Are you figures for a different model or have I cocked up?

Edit, sorry I accidently looked at the dimensions for HGL and completely misread the table. You are correct.
Page 6.

[WandrinAndy]

Edit, sorry I accidently looked at the dimensions for HGL and completely misread the table. You are correct.
Page 6.

Ok, that looks like the same doc but I'm taking the specs from page 6 for Model Series HGH (Square type) which is what Zapp is advertising on their website currently, whereas your page 5 is for model series HGL (Square type3) whatever type3 means... Maybe low "profile"... Why oh why can't things be simple...

[Jonathan]

Ok, that looks like the same doc but I'm taking the specs from page 6 for Model Series HGH (Square type) which is what Zapp is advertising on their website currently, whereas your page 5 is for model series HGL (Square type3) whatever type3 means... Maybe low "profile"... Why oh why can't things be simple...

It is simple - if you get 15mm HGH from Zapp it's 28mm. If you get 20mm HGH it's 30mm.
Sorry for causing the confusion...

[WandrinAndy]

No probsh... My confusion was caused by me not realising the blocks come in that many different models.

Two quick questions please.... I'm considering again how prone the ballscrews and profile-rails are to contamination from chips etc. particularly on the X-Axis.

I'm guessing it might be prudent to get the optional bearing-block scrapers fitted to protect the seals on the X-axis, but that the other axes are far enough removed from the cutting point to not be too much of a worry?

Let's say I am machining small alu parts... would this be best done at the BF end for better accessibility and to reduce contamination, or best at the BK end that is closer to the motor?

Thanks,
Andy