After a miserable day with my cnc machine, trying to trouble shoot an issue that I`m now fairly certain lies with a totally randomly faulty TB6560 driver (sometimes works and sometimes doesn`t!!), I decided to end with some positivity and show you my drag engraver.
When I first thought about homebrew cnc I never thought I could do fine detailed line and text work and presumed it would be only good enough for cutting mdf into rough shapes! However, I read on the net about drag engraving where the spindle doesn`t spin and you simply drag a diamond across the top layer and "scratch" the surface. I didn`t have much faith but I found a few simple ideas on the net and thought I`d have a go at making one.
The commerical ones are very expensive and start with the smallest shank of 12mm. My er16 spindle can only take 10mm max and although adapters are available, I read that if your spindle can`t handle 12mm, it is likely the bearings will not be beefy enough to withstand the sideways cutting forces of dragging the tool across the work surface. Sounded sensible to me and with my little home made brushless dc motor spindle, didn`t want to risk it.
No worries anyway, since I`m making it, I`ll just make a massive body - this is actually a massive advantage as my spindle bracket is 43mm, so making a body of 43mm means I can just drop the drag engraver straight in place of the spindle!
I turned the outer body to 43mm, reamed a 12mm bore. Used 12mm silver steel which I reamed 1/4" to fit the diamond tool (this needs turning a little deeper so less is held out the top). The 12mm silver steel slots in the centre bore...ideally to a shoulder. I didn`t do this and ended up turning a little face cap and holding it on with 3 screws (can be made out in the first photo). A spring sits on top with a little brass spring stopper and then a rear end cap screws on that with an M8 thread and bolt to apply and adjust pressure onto the spring (M8 bolt needs replacing with a nice little thumb screw asap)
I`m very chuffed with the results. Setting the pressure depth and spring took a lot of scrap test efforts but got something I`m happy with.
Here I`ve attempted to fill cut, so the diamond drag engraver sweeps across in many steps to fill the letters. All was going well until my double sided tape gave way!
Talking of which...is double sided tape definately the way to go and I just need to pay more for some decent stuff or is there a better way? Also, I know double sided tape is a method used by lots of you, but how do you go about getting your bed all nice and clean again after sticking something down to it???
Chris
