I have been experiencing intermittent issues when drilling. I share the experience here to help others avoid the same issues or offer some tips to explain what is wrong.
Some of the cuts I am doing are two-sided. I use MeshCAM to create the toolpaths which has a two sided cut ("flip job") option. To achieve this, I first drill two holes centered on the Y axis of the stock towards the ends I then fit 4 mm registration dowels to aid precise placement when the stock is flipped over front to back along the Y axis on completion of milling the top side. The stock is attached securely to a 12 mm MDF spoil board with double sided carpet tape positioned to avoid the drilling region.
Last week I successfully milled a small oak insert for my guitar design from 19 mm thick European oak. I set up the job with two 4 mm wide supports located at the top of the geometry.
My parameters are summarised as follows:
- 4 mm solid carbide four flute end mill
- Plunge speed 90 mm/min.
- Retract speed 120 mm/min.
- 5,000 rpm rotation speed (25% on Stepcraft HF500 control unit, i.e. slowest possible speed).
The drill process I use is to drill at successively deeper 5 mm depths with full retracts each time, so:
0.1 to 5 mm at 90 mm/min.
Full retract at 120 mm/min.
0.1 to 10 mm at 90 mm/min.
Full retract at 120 mm/min.
Final drill is 5 mm into the MDF spoil board so 24 mm depth in total.
On my third attempt to cut a revised design block, the bit stalled, caused the two halves of spindle body to unscrew from each other and caused a failure of the power supply in the Stepcraft HF control box (the second failure since I have had the machine in operation). This will be returned to the supplier for a replacement Kress spindle and refund of the difference. The Stepcraft spindle system does not appear to have any thermal or current overload protection, either via user replaceable fast rupture fuse or user resettable relay. This is unacceptable on any spindle, let alone an outfit costing £500. Thanks once again to Rory for a fantastic response.
My MDF is flat and secured across the entire area with double sided carpet tape.
The machine is perfectly mechanically tuned.
The router bit is relatively new and not blunt (still cuts my skin if I'm not careful).
The failures cause a small amount of looseness to appear in the XZ module which then requires some more mechanical tuning. I dismantled the XZ module and extrusions yesterday to rectify a faulty limit switch (see previous post). When I reassembled it there was no looseness so no lasting damage or movement had been done.
Going forward, I will check the vertical level of the Z extrusion relative to the bed in case it is trying to drill at a slight angle.
Other than that, I conclude that the HF spindle system is not suitable for vertical drilling, even using relatively conservative parameters.
Doug