After nearly 2 years (maybe more) Scrappy (sorry Tweakie......... ) has cut for the first time. OK it was only a 50mm square out of 4mm plywood, but we did it and it cut it nicely, square and true, not bad for a complete novice.
As his name suggests, Scrappy is made out of scrap bits off old machines from work, with a few parts made by a local machine shop. He has a Kress FME 1050 machine head and the drivers are off an old labelling machine, modified to run off a PC via a breakout board (a UC100 motion controller is in the post) to improve the steppers performance, cutting footprint is not huge but it should suffice X = 360, Y = 390 and Z = 120.
I now have to work on a simple but effective method of clamping/securing sheets of plywood to the bed after I have given the bed a skim when my larger end mills arrive. I couldn't take a video of the first cut as my hands were busy hovering over the E-stop and main isolator just in case!!!!!!
I have noticed though that on start up the Y axis ticks and moves a step, this is caused by the breakout boards on board relay clicking in and out for a few minutes??? (cheapo Chinese unit, my fault I know), after a few minutes that stops and the Y axis is silent, also when jogging the X axis I can hear it ticking during its movement, this seems to only happen when its jogging and no other time. Teething problems associated with cheap and untested units, hopefully I shall be investing in some proper microstepper drives from CNC4YOU in the not to distant future as I can only full step at the moment and Scrappy becomes very, very noisy when the Y axis is slowing down to negotiate a curve.
Apart from these minor faults we are up and running, I shall try to get some video of Scrappy in full motion soon, thanks for your help in getting me this far.

Stewart

Excellent work Stew - I look forward to watching the video's.

Tweakie.

Here is a short vid of Scrappy in action, my CNC skills are better than my video skills...................well I'll let you decide.

https://www.youtube.com/watch?v=hgf9EgPQxNU

I did make a cock up and forgot to set the correct safe pass height, so adjusted and restarted. It came out pretty nicely and now have to mount it on SCRAPPY.

Stewart

10 out of 10 for Scrappy in action. 

Tweakie

Thanks Tweakie, a lot of what I have learnt has come from your website, so I doff my cap to you Sir.

Stewart.......................and Scrappy

Good morning all,

Scrappy has completed his first mission and done it very well indeed, I am proud of him and myself for what we have achieved, considering my experience!!!!!

Anywho, scrappy has a few flaws and it has caused a few concerns. Firstly I have found a huge amount of 'slop' if I push the z axis motor when in home position, nearly 3mm of movement is there!!!!!! Now this is down to cheap glacier bushes, so the movement is going to be present in all slides

To this end I have decided to build a Mk2 version of Scrappy, this time with more experience and knowledge I can make a more accurate and better version.

Leadscrews changed from threaded rod to ballscrews. All glacier bushed replaced with linear ball bearings, all steppers upgraded to 4Nm models, all drives repalced with microsteppers drives and motion controller.  Frame, carriage, end plates all to be CNC milled at local engineering firm for high accuracy.

3D view of Scrappy Mk2............................600mm x 400mm cutting area with +100mm Z axis clearance

Hi Stew,

Just my opinion...
Looking at your .pdf you must use fully supported rails (unless they are upwards of 25mm diameter) otherwise you will regret the flex. Ballscrews are good but remember that they can backfeed particularly on the Z axis so if the motor is disabled a brake can be useful.

I look forward to seeing Scrappy MkII. 

Tweakie.

Thanks for the input Tweakie

The rails are 20mm dia on all axis, would just one supported rail on the Y axis suffice if it is 25mm dia? It would mean a bit of reconfiguring, but better to do it now than later in the project.

Thanks for the input Tweakie

The rails are 20mm dia on all axis, would just one supported rail on the Y axis suffice if it is 25mm dia? It would mean a bit of reconfiguring, but better to do it now than later in the project.

I honestly don't know for sure but I would bet money that one fully supported rail each side would perform better than 2 unsupported rails each side for the Y axis. The X axis would IMO still need two fully supported rails.

Tweakie.

Thanks Tweakie

Off to do more Cad