Monday, September 28, 2009

Bertha cuts her own T slot work clamping base

Using the Dremel Key hole router bit 655 not quite its intended use but it works well once I figured out that 10mm a min was the best speed for a 7mm deep cut and almost the slowest speed on the look alike avoided MDF burning smell. so it takes 30Min's per slot to cut there are 19 slots ie every 20mm. I also learn a little G code in the process.

The process has identified that I forgot to put the collar back on the X axis drive shaft when I added the two extra runner on the X axis. Oops so there was a 2mm difference between the start point of the first X T slot to the start of the last X T slot. As the Slots are only for Clamping stuff down is no big problem tho.

The bigger problems are:-

Finding a reliable way to set spindle speed on the look alike.

Finding a way to stop the filters blocking on the hover when cutting MDF.

Modifications required:

Fit the Collar on the X axis.

Upgrade Y and Z Axis's to have motor couplers, bearings and collars like X instead of Plastic tube and tie wraps... Coupling... Thou neither the Y or Z axis had any measurable error like the X had.. the solution for X is more mechanically stable thou..

An electronic switch to turn the spindle on and off.

An electronic switch to turn the hover on and off.

Maybe make some kind of spindle speed detector to have complete control of spindle speed.

Wednesday, September 16, 2009

A busy weekend in Gloucester making a Double door frame and fitting new hard wood doors to my Mom's house. So not much rep rapping or CNC~ing etc.. Any way here is a quick up date on Bertha and Big Bertha the projects.. Some brief details on the Big Bertha project blog. Slightly earlier than anticipated due to the success of Bertha.

Also last weekend I added the 2 extra runners on the X and Y axis of Bertha.

Bertha completed over 110,000 lines of G code using the pic to G code function of EMC2 I made the mistake of clicking on invert image so I stopped the G code some 120,000 lines early. lessons learnt dont make the first real job for your CNC a big one a 9.4 MB Gcode file is > 200,000 lines of Gcode set the feed rate higher than 120mm a min and a cut of depth 0.1mm.

So the carve a logo exercise ended up as one long soak test.
Great result though Bertha did not fall apart it did not lose position and the low cost look like a Dremel did not fail. Other lessons learnt you need a fan for the X Axis motor or run it at < 2A. An aborted Bodge It Logo around 100mm x 73 mm~ 3-4mm deep. Note the invert function takes the regular G code and reverses the code order not a good idea as it re cuts seach layer.

Oh and not forgetting the picture of the Wind and Solar powered speed caution signs seen on roads around Gloucester.

Thursday, September 3, 2009

I love it when a plan comes together!

Things arrive from around the world together amazing!!!.

To see more go here:-

The deliverys arrive.. pictures of the bits.

Pictures of the rebuilt Bertha now as a CNC

A work in progreess with axis transion speeds of > 30mm /s

I'm working on making the as yet unsupported trapezoidal spindle drive shaft to make it so that its supported with bearings, this will allow a much higher axis transition speed. I'm also will be improving the rigidity of the Y axis by adding two more 8mm y Axis slide bars the beauty of using the nylon blocks as the mounting method has saved around £70 the cost of a traditional CNC slide system.

Here is a picture of the first test routing performed.. using a cone shaped dremel bit no 125

I am still having intermitent problems with the Z Axis home opto sensor despite ex-changing the sensor for another one and changing the parallel printer port input pin from 12 to 13, using USB double screend cable and adding high and low value capacitanc to the 5v supply pins on the Opto sensor PCB.
I have also reduced the length of the sensor cable run that is spiro wraped with the stepper and dremel power cables. curently run out of ideas to solve the problem.
Correction its a Dremel look alike from Aldi.. I do have a puka Dremel as well as several other imitations. I also have a giant 700W dremel type tool from the B&Q P Pro range this will be used on Big Bertha .. Yes a 700w with a small collete pin chuck just like a dremel.

More pictures of Bertha and its insides on the BodgeITQuickTools blog.

Ps Midge just asked why I didnt sand the test piece to make it look better. It is as it is off of Bertha.. I didnt use a small dremel 105 engraving bit as I did not know if Bertha would work hence it is a rough cut in the beach ply that is 0.02mm deep (If my stepper configuration settings are correct ) I dont know the speed of the cutting either but it was finished /done in less than 2 min.