In response to a recent blog entry, I got this series of questions...
Mauricio
How many clamps are needed to hold a specific tool? Which is the correct distance between clamps? Is there an order or sequencing to tightening the bolts?
My Response
When asked 'How many clamps should I use?' one plant manager I know likes to respond with 'As many as you can'. In reality, each clamping system, mold base, and platen is different. When discussing standard adjustable height mold clamps, I prefer to use six clamps per half on smaller molds, and as many as a dozen for larger molds. In general, the spacing of the clamps are usually dictated by the platen hole location and rail size.
When tightening the bolts, I recommend using an alternating pattern which alternates back and forth as well as up and down. For example, when using a four clamp setup, starting with the top right hand corner, you would tighten in this order:
└ Top Right
┐ Bottom Left (diagonally across)
┌ Bottom Right (across)
┘ Top Left (diagonally across)
The intent is to balance the force being applied to the mold base to prevent any uneven stress on the mold base or platen.
Additional Thoughts
Ultimately, the more clamps that you use, the less stress that is applied to any specific clamp point. This will increase the life of the clamps, and help prevent damage to the platen holes.
-Andy
Andy,
First let me say that this blog page is a great service to Molders. Secondly, you had a great booth at NPE, it was nice to visit and chat.
I was going to ask what constitutes a big and small mold, but that is subjective and and, of course, common sense must be used.
I must ask about '6 clamps per small mold' though.
Do you mean 6 per mold half? If there were 6 per mold then 3 per half would be odd and hard to do.
Keep blogging and keep on Molding!
brent
Thank you for the compliments Brent,
Regarding the number of clamps: Yes, I was referring to 6 per half. I will update the main entry to reflect this.
Regarding the mold size: Yes, this is subjective with respect to both mold weight and equipment condition. For example, someone using a new machine with new clamps and a shiny new mold may get away with fewer clamps... adversely, someone with a deep mold base on a worn-out platen may want to add a larger clamping plate to the mold to get some additional support. For these reasons... I always err on the side of caution.
-Andy
Yes, deep drawn parts pose more of a challenge, especially multi cavity hot runner tools that could lose a cavity and over-pack. You need plenty of clamps in this case, or you could pull a mold half off the platen.
Keep on molding!
brent
Very good point Brent,
This just supports the fact that you cannot have too much support.
I have worked with many companies who actually specify their molds to be build with over-sized clamping plates just to ensure they have enough space for clamping.
-Andy