View Full Version : Here I go again.

Bush Flyer
28-09-2014, 04:22 PM
It's has been about one year and five month since I started a build on this forum for a CNC router, now it's been finished for a good while now, and it's a lot better than I thought possible, it has also been a lot of ups and downs right from about the first post when I was told to scrap my design ( I nearly scrapped it altogether ) but I did start again and I'm very pleased how it has turnout, also when I set my budget for the build I added my usually 30% for the things I never thought of. Well it cost a lot more than I thought. But now I cannot believe but I going to start a new build this time for a CNC CO2 40 watt laser. Now I have only done some sketches no CAD. Drawings, but I do have a question ? Before I start drawing in CAD.
I was having a look at some CNC lasers online, and I noticed that on the gantry I could only see one linear guide rail HGR type, and the laser head is bolted on to the bearing through a plate. Now the reason I'm asking is I need to cut down the weight of the gantry as I have been thinking of designing mine with two SBR12 rails and three lumps of 10mm aluminium bolted on to the four pillow blocks, then the laser head is bolted to that. The main concern is the weight of all this flying about when raster engraving, this is why I am asking, is having one linear guide rail of the HGR type be OK or do you need two, and if you only need one should it be a HGR15 or HGR20 or what size would you use, it would be 700mm length?
Once I start to draw it up in CAD I will start another build on the machine building thread. Mike.

Robin Hewitt
28-09-2014, 08:49 PM
I want to rework my laser to cut Perspex in bigger sheet sizes.

I'm thinking smallest HiWin rail for the X with the laser tube bolted over the top and aiming down in to a slot with some black sand at the bottom.

For the Y, some means to grip the sheet and move it a reasonable distance while holding it square.

Fast X for engraving, relatively slow Y for cutting.

This makes the machine a lot smaller and simplifies everything apart from the Y.

Unless someone has is a positively brill solution to the Y :very_drunk:

28-09-2014, 09:11 PM
Robin, would it make more sense to swap the axes, i.e.

For the X, some means to grip the sheet and move it a reasonable distance while holding it square.
Fast Y for engraving, relatively slow Y for cutting.

That way the material could move 'through' the machine in the X direction

Robin Hewitt
29-09-2014, 10:57 AM
X,Y? Y,X? I think we are agreeing. For the purposes of exploring this design concept let us assume the head moves quick the material moves slow.

But how to hold the sheet without making the machine enormous when unloaded.

Right now the picture in my head is deliciously compact, borderline bijou :smug:

29-09-2014, 11:40 AM
I'm only guessing here as I can't fully visualize the set up but what about friction rollers, think 'old fashioned washing mangle', the roller could be driven by a stepper motor or have an encoder fitted to measure the material position. There would need to be mechanical guides to stop the material skewing.

Robin Hewitt
30-09-2014, 10:15 AM
It is tricky. If you add mechanical guides you are depending on the sheet being square sided. Rollers mean wasted margins.

Perhaps some kind of frame that you attach to the sheet end before feeding it in to the cutter?

Limiting the head movement to one narrow axis solves all kinds of problems with space, mirrors, air connects, beam catching, smoke clearance, no honeycomb required. Dreamy.