HoloPiBot #5 : Some Movement Has Been Achieved

RE: HoloPiBot #5 : Some Movement Has Been Achieved

balearicdynamics — Tue, 30 Apr 2019 04:28:49 GMT

Dubbie, sounds going well. As far as I view in the video, my only worry is that the 3D printed supports maybe too weak when the entire system is rotating. Did you consider this? Just a warning as the point of view of your shooting gives few details on the support structure and robustness.

Instead, about the problems with acrylic, you are not new. I can say that also when you are on a perfectly flat surface the risk of breaking diminish only a few. Then, if the drill rotation is too high the alternative is to melt the hole (that tend to block the drill tool and acrylic crash [View:/resized-image/__size/16x16/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-33cd933d-9fb2-46f1-9862-0c34b32e6ba1/contentimage_5F00_2516.png:16:16] )

I have solved the problem of acrylic using Perspex, that is a special kind of acrylic with better characteristics. It is not difficult to laser cut but I never had problems on cutting it with different kind of saws as well as making holes. I have also used in a lot of occasions to mill is and always had very good results. The difference is that this acrylic polymer tends to melt less, make very small scrap easy to remove and after a few try you can find the right drill rotation speed to optimize the result.

I buy Perspex from Kitronik.co.uk they have plenty of colors and different thickness at a very reasonable price.

Enrico

RE: HoloPiBot #5 : Some Movement Has Been Achieved

three-phase — Mon, 29 Apr 2019 19:17:14 GMT

Nice update, do you have smaller diameter wheels you could try to increase the torque?

Kind regards.

RE: HoloPiBot #5 : Some Movement Has Been Achieved

shabaz — Mon, 29 Apr 2019 17:58:35 GMT

Hi Dubbie,

This is great to see it all coming along! That's very cool that you've got steering capability on that front wheel.

Drilling near to the narrow areas like where you've got the cutout is always hard : (

Sometimes I give up, and use ABS sheet. If the motors are not getting hot, it's (possibly) ok to just increase the voltage to them, see if that improves things.

RE: HoloPiBot #5 : Some Movement Has Been Achieved

14rhb — Mon, 29 Apr 2019 17:16:51 GMT

Hi Dubbie,

Nice updates, thanks. When I saw your robot with motors I thought, "great, I'll be able to read Dubbie's blog and see where I went wrong with my r2b4" but I'm sorry to hear you too have suffered from low torque steppers. I have little I can add to help you as I never got the expected torque from my motors either, however [mention:b0bc65b9ecdc4307bd967592f00e340a:e9ed411860ed4f2ba0265705b8793d05] made some really useful points about the high frequency pulses and the coil inductance meaning full coil current (and hence torque) was never achieved....something I need to take another look at.

When I've cut acrylic before I use water as a coolant/lubricant to get a better cut, which might help, and I always drill through into some scrap wood.

Rod

RE: HoloPiBot #5 : Some Movement Has Been Achieved

genebren — Mon, 29 Apr 2019 16:22:52 GMT

Dubbie,

Yeah, acrylic is very brittle. There are some special drill bits for drilling into plastic, but even with these it is easy to crack it while drilling. Coming along nicely!

Gene