Finishing the surface of 3D Models

Over Christmas I had 3D printed a clock frame for my granddaughter’s birthday.   The size ended up being three separate prints which I later glued together.  All three prints were done ‘face down’ on the Sindoh bed and all printed on a raft.   Once the raft had been removed the finish was not very elegant as it showed the striations of the raft on what would be the viewed surface.   The print was in PLA and I initially did some tests on scrap prints to see if I could rub a surface down.   This was not an ideal approach and I was not too keen to start on the clock in this manner.

Next idea was to use Gorilla twin pack glue cut with Meths.   This created a very runny adhesive mix that could be brushed onto the surface of the print.  Surprisingly enough despite being ‘modified’ the glue went off and was quite hard to the touch.   It did not rub down all that well.

Reading up on the net there is a product called XTC-3D which is made just for this purpose.   It is expensive but does stretch a long way in use.  It is a twin pack mix in 2:1 ratio and once mixed it has a setting time of around 20 minutes so you need to get your act together and be well prepared. The makers recommend using a wide foam brush to apply the compound.   This was quite good in that it ‘scraped’ across the tops of the striations and the filler settled like levelling compound does on a floor.

I left it to harden off overnight and then rubbed down wet with 400 grit paper on a flat surface.   This kept the dust damped. The finish was excellent.   I then undercoated and glossed with acrylic spray paint.

The final clock frame looked very good with no obvious signs of the printing artefacts.  While pricey, I would recommend the XTC-3D product for this purpose.

Similar or related subjects : –

Another Haimer tip bites the dust or at least the mill bed

When I was at NYC CNC I saw that John was selling posters as shown below.

I didn’t realise the significance until I started doing CNC …..

I had been doing OK on breakages of late then like buses, two came along at once.  One was excusable (to my conscience) but the second was a disaster always likely to happen.

I had the Haimer held in a collet in the Myford VMB manual mill.  This means you need both hands occupied to contra rotate the collet and spindle when locking and unlocking.   I just overdid the realise pressure and the Haimer dropped out onto the mill bed.  Crunch, expletives, gloom, expense.  The tips are not cheap at GBP20+ each but Amazon do sell them.

There is the same issue to a lesser extent on the Tormach when releasing the power drawbar even though you are holding the Haimer the sudden momentum of the drop from the collet can sometimes catch you out if the mill table is close.

While discussing my gloom with a friend he suggested putting some sort of protection around the tip when loading and unloading from the spindle.   The Haimer is not an ideal shape for gripping something along these lines given its curved surfaces.  However after some thought a solution was found.   I drew a simple cylinder in Fusion that was 40mm long, 38mm OD and 32mm ID and 3D printed it.  Note these dimensions are for the Haimer FH 3D Taster version.

The cylinder sits over the probe and rests on the outer rim of the tip mounting.  The 32mm ID is just tight enough to squeeze the Haimer rubber gasket and so hold the tube in place.

Not only is this useful for mounting and dismounting the Haimer but it also works as a general protect guard when not in use.

Similar or related subjects : –

FlatCAM Update and experimental copper cutting

I’m quite pleased with progress converting GSpark PCB gerber files to CNC with FlatCAM.   The conversion process is straightforward and the resulting GCode looks OK.

I have tried cutting copper using the cutters I have to hand but quickly realised I need to get some much finer ones in carbide.  My tests with modified dental burrs does not work or at least not for very long before the burr goes blunt and the cut width degrades.

I have ordered some 10 degree included angle 0.1mm wide cutters but they won’t be here until February.

The picture shows two runs.   The left hand run used 30 degree cone shaped burr and the right hand run used a modified teardrop burr.   The initial cut on both was where the stars are.

The left hand cut left severe copper burrs which were easily removed using a scalpel blade flat to the surface of the board.

The right hand side was clean of all burrs but gradually degraded in quality as the cutter became blunt.

The teardrop burr was ground to half diameter in an attempt simulate a more normal engraving cutter profile.  I must have drawn the temper in the grinding process.

More experimentation needed once the better cutters arrive.

Similar or related subjects : –

Welding and being well and FlatCAM

Welding Course

Despite being laid low with flu since New Year I’ve attended two of the evening welding classes much to the contrary advice from my wife.  With hindsight she was right – I should not have gone the first night such was my state of health.

The focus so far has been on MIG welding and I am slowly getting the feel of things.  Too many variables to start with what with power, angle of attack, closeness to the job and of course wire feed rate.

How anyone did welding without the modern auto dimming helmets astonishes me.   They are amazing.

Not much else to report given the state of health but clearly I have now started to creep back into the workshop so health and state of mind must be improving.  Made a note in the diary to get a Flu Jab next year.

FlatCAM

Anyway more interesting stuff – my friend has asked if I can mill a prototype printed circuit board on the Tormach for him.   My initial thoughts were to bring the design into Fusion and do the CAM there.   However a conversation with a friend in Namibia lead me to FlatCAM which is a wonderful little program.   It takes the Gerber files from the PCB design package and converts them to GCode.   It is simple to use and produces nice code listings.   It gives you options to add your own GCode initialisation strings.    There are a few YouTube videos out there if you are interested.

More results to report when we have milled some copper.

Similar or related subjects : –

Heading home from France and Welding Course

Well we came out for the New Year to France with lots of jobs to do and both ended up totally incapacitated with flu.  Not felt so miserable in a long time and now totally weak and wobbly.

We did manage to get the new office sorted and it’s nice to sit here working in it.

We have decided to leave early and stay overnight near Tours on the run to the ferry.  The prospect of the normal 7 hour drive in one hit did not appeal to either of us.

You know what, if you are going to be ill, it is best done at your home with your own bed and I am really looking forward to unlocking the front door on Tuesday.

Wednesday night looms exciting however as my mate and I have registered on a 21 hour introduction to Welding Course over the next 7 weeks.  Got to get back on my feet ready for that.   Hopefully some new skills to be added to my very mature CV …

Similar or related subjects : –